Podcasts about Cytoskeleton

Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2023.07.15.549141v1?rss=1 Authors: Polino, A. J., Ng, X. W., Rooks, R., Piston, D. W. Abstract: Just under the plasma membrane of most animal cells lies a dense meshwork of actin filaments called the cortical cytoskeleton. In insulin-secreting pancreatic beta cells, a longstanding model posits that the cortical actin layer primarily acts to restrict access of insulin granules to the plasma membrane. Here we test this model and find that stimulating beta cells with pro-secretory stimuli (glucose and/or KCl) has little impact on the cortical actin layer. Chemical perturbations of actin polymerization, by either disrupting or enhancing filamentation, dramatically enhances glucose-stimulated insulin secretion. We find that this enhancement does not correlate with the state of the cortical actin layer, suggesting filament disruptors act on insulin secretion independently of the cortical cytoskeleton. Copy rights belong to original authors. Visit the link for more info Podcast created by Paper Player, LLC

Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2023.07.12.548547v1?rss=1 Authors: Prislusky, M. I. A., Lam, J. G., Ruiz Contreras, V., Ng, M., Chamberlain, M., Fields, M., Zhang, X., Amer, A., Seveau, S. M. Abstract: Mammalian cells are frequently exposed to mechanical and biochemical stresses resulting in plasma membrane injuries. Repair mechanisms rapidly reseal the plasma membrane to restore homeostasis and prevent cell death. In the present work, a silencing RNA (siRNA) screen was performed to uncover the plasma membrane repair mechanisms of cells injured by the bacterial pore-forming toxin listeriolysin O (LLO). The screen identified a novel role for the septin cytoskeleton in mediating plasma membrane repair. Upon cell injury, the septin cytoskeleton partially dissociates from actin stress fibers and remodels with cortical F-actin and myosin-II to form loop (and ring)-like domains that protrude from the cell surface. These domains strictly colocalize with the calcium-dependent phospholipid-binding protein, annexin A2 (ANXA2). Importantly, formation of the SEPT/F-actin/ANXA2 domains are dependent on SEPT7 expression and is functionally correlated with the plasma membrane repair efficiency. Our studies open new research avenues by identifying a novel role for the septin cytoskeleton in remodeling the plasma membrane for its repair. Copy rights belong to original authors. Visit the link for more info Podcast created by Paper Player, LLC

Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2023.06.26.546585v1?rss=1 Authors: Wu, H., Zhou, L.-Y., Jin, C.-X., Wang, W.-X., Song, L., Shin, J.-B., Du, T.-T. Abstract: The MRTF-SRF pathway has been extensively studied for its crucial role in driving the expression of a large number of genes involved in actin cytoskeleton of various cell types. However, the specific contribution of MRTF-SRF in hair cells remains unknown. In this study, we showed that hair cell-specific deletion of Srf or Mrtfb, but not Mrtfa, leads to similar defects in the development of stereocilia dimensions and the maintenance of cuticular plate integrity. We used FACS-based hair cell RNA-seq analysis to investigate the mechanistic underpinnings of the changes observed in Srf and Mrtfb mutants, respectively. Interestingly, the transcriptome analysis revealed distinct profiles of genes regulated by Srf and Mrtfb, suggesting different transcriptional regulation mechanisms of actin cytoskeleton activities mediated by Srf and Mrtfb. Exogenous delivery of calponin 2 using Adeno-associated virus transduction in Srf mutants partially rescued the impairments of stereocilia dimensions and the F-actin intensity of cuticular plate, suggesting the involvement of Cnn2, as an Srf downstream target, in regulating the hair bundle morphology and cuticular plate actin cytoskeleton organization. Our study uncovers, for the first time, the unexpected differential transcriptional regulation of actin cytoskeleton mediated by Srf and Mrtfb in hair cells, and also demonstrates the critical role of SRF-CNN2 in modulating actin dynamics of the stereocilia and cuticular plate, providing new insights into the molecular mechanism underlying hair cell development and maintenance. Copy rights belong to original authors. Visit the link for more info Podcast created by Paper Player, LLC

Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2023.04.20.537668v1?rss=1 Authors: Tatickova, M., Trebichalska, Z., Kyjovska, D., Otevrel, P., Kloudova, S., Holubcova, Z. Abstract: Egg quality is a limiting factor of female fertility and assisted reproductive technology (ART) success. Oocytes recovered from hyperstimulated ovaries often display morphological anomalies suspected to compromise their fertilization and developmental potential. Knowledge of (ab)normal oocytes intracellular organization is vital to establish reliable criteria for morphological evaluation of oocytes intended for in vitro fertilization (IVF). Here, we investigated the fine morphology of 22 dysmorphic IVF oocytes exhibiting different types of cytoplasmic irregularities, namely (1) refractile bodies, (2) centrally-located cytoplasmic granularity (CLCG), (3) smooth endoplasmic reticulum (SER) disc, and (4) vacuoles. Transmission electron microscopy (TEM) revealed the structural basis of these aberrations and indicated that the underlying cause of two of the studied morphotypes was inordinate organelle clustering. To address the mechanism required for accurate organelle positioning, we used cytoskeleton-targeting chemical compounds and performed a series of inhibition experiments involving a total of 133 human oocytes maturing in vitro. Fluorescence and electron microscopy showed that disruption of actin, not microtubules, led to the aggregation of subcellular structures resembling the morphological pattern seen in abnormal oocytes. These results imply that actin serves as a regulator of organelle distribution during human oocyte maturation. The ultrastructural analogy between dysmorphic eggs retrieved in IVF cycles and oocytes, in which actin network integrity was perturbed, suggests that dysfunction of the actin cytoskeleton might be implicated in generating common cytoplasmic aberrations. Knowledge of human oocytes inner workings and the origin of morphological abnormalities is a step forward to more objective egg quality assessment in clinical practice. SUMMARY SENTENCEUltrastructural analysis of eggs exhibiting cytoplasmic abnormalities combined with inhibition experiments indicates that dysfunction of the actin network might be involved in the development of oocyte dysmorphisms. Copy rights belong to original authors. Visit the link for more info Podcast created by Paper Player, LLC

Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2023.03.29.534821v1?rss=1 Authors: Green, M., Domingos, H. A., Ouzounidis, V., Finlayson, C., Prevo, B., Cheerambathur, D. K. Abstract: Precise control of dendrite branching is essential for the formation of neural circuits, yet the mechanisms that regulate this process remain poorly understood. Here we show that the kinetochore protein KNL-1, known for its role in chromosome-microtubule coupling during mitosis, together with its binding partners, the KMN network, regulate dendritic branching in the C. elegans mechanosensory neuron, PVD, in a cell division independent manner. Neuron-specific degradation of KNL-1 results in excess dendrite branching and fusion events, predisposes PVD to age-dependent degeneration, and impairs animal sensory behavior. Surprisingly, these effects are not attributable to mis-regulation of the microtubule cytoskeleton. Instead, KNL-1 degradation alters the dynamics of F-actin, an established driver of dendrite branching. Epistasis analysis shows that KNL-1 counters the activity of the RacGEF TIAM-1, a downstream effector of dendrite guidance receptors. These findings establish that the microtubule coupling KMN network promotes dendrite branching by regulating the actin cytoskeleton and provide insight into how the cytoskeleton shapes dendritic architecture. Copy rights belong to original authors. Visit the link for more info Podcast created by Paper Player, LLC

Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2023.03.29.534729v1?rss=1 Authors: Brooks, J. W., Tillu, V., Verma, S., Collins, B. M., Parton, R. G., Yap, A. S. Abstract: As physical barriers, epithelia must preserve their integrity when challenged by mechanical stresses. Cell-cell junctions linked to the cortical cytoskeleton play key roles in this process, often with mechanotransduction mechanisms that reinforce tissues. Caveolae are mechanosensitive organelles that buffer tension via disassembly. Loss of caveolae, through caveolin-1 or cavin1 depletion, causes activation of PtdIns(4, 5)P2 signalling, recruitment of FMNL2 formin, and enhanced cortical actin assembly. How this equates to physiological responses in epithelial cells containing endogenous caveolae is unknown. Here we examined the effect of mechanically-inducing acute disassembly of caveolae in epithelia. We show that perturbation of caveolae, through direct mechanical stress, reinforces the actin cortex at adherens junctions. Increasing interactions with membrane lipids by introducing multiple phosphatidylserine-binding undecad cavin1 (UC1) repeat domains into cavin1 rendered caveolae more stable to mechanical stimuli. This molecular stabilization blocked cortical reinforcement in response to mechanical stress. Cortical reinforcement elicited by the mechanically-induced disassembly of caveolae increased epithelial resilience against tensile stresses. These findings identify the actin cortex as a target of caveola mechanotransduction that contributes to epithelial integrity. Copy rights belong to original authors. Visit the link for more info Podcast created by Paper Player, LLC

Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2023.03.06.531372v1?rss=1 Authors: Gurley, N., Szymanski, R., Dowen, R. H., Butcher, T. A., Ishiyama, N., Peifer, M. Abstract: One central question for cell and developmental biologists is defining how epithelial cells can change shape and move during embryonic development without tearing tissues apart. This requires robust yet dynamic connections of cells to one another, via the cell-cell adherens junction, and of junctions to the actin and myosin cytoskeleton, which generates force. The last decade revealed that these connections involve a multivalent network of proteins, rather than a simple linear pathway. We focus on Drosophila Canoe, homolog of mammalian Afadin, as a model for defining the underlying mechanisms. Canoe and Afadin are complex, multidomain proteins that share multiple domains with defined and undefined binding partners. Both also share a long carboxy-terminal intrinsically disordered region (IDR), whose function is less well defined. IDRs are found in many proteins assembled into large multiprotein complexes. We have combined bioinformatic analysis and the use of a series of canoe mutants with early stop codons to explore the evolution and function of the IDR. Our bioinformatic analysis reveals that the IDRs of Canoe and Afadin differ dramatically in sequence and sequence properties. When we looked over shorter evolutionary time scales, we identified multiple conserved motifs. Some of these are predicted by AlphaFold to be alpha-helical, and two correspond to known protein interaction sites for alpha-catenin and F-actin. We next identified the lesions in a series of eighteen canoe mutants, which have early stop codons across the entire protein coding sequence. Analysis of their phenotypes are consistent with the idea that the IDR, including its C-terminal conserved motifs, are important for protein function. These data provide the foundation for further analysis of IDR function. Copy rights belong to original authors. Visit the link for more info Podcast created by Paper Player, LLC

Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2023.02.10.527989v1?rss=1 Authors: Carvalho, N. D., Rofatto, H. K., Villar, K. S., Magnelli, R. F., Mendonca, R. Z. Abstract: Brazil has a very large biological variety, which is an almost inexhaustible source of substances of pharmacological and biotechnological interest. Several studies have demonstrated the presence of bioactive peptides in insect hemolymph and their potential use as therapeutic agents. However, few data are available regarding molecules extracted from insects with anti-apoptotic action. The objective of this work was to identify and isolate proteins from the hemolymph of caterpillars of the Megalopygidae family with pharmacological and biotechnological interest. Two species of this family were studied, Podalia sp and Megalopyge albicolis. Cytotoxicity tests on Vero and Sf-9 cells revealed that the hemolymph of both caterpillars were cytotoxic only at concentrations greater than 5%v/v. In the anti-apoptotic activity assays, it was verified that the supplementation of cell cultures with only 1% of hemolymph v/v is sufficient to inhibit cell death by apoptosis induced by different inducers such as terbutyl, actinomycin D, hydrogen peroxide or even by nutrient depletion. For this study, cells were staining with trypan blue, crystal violet and fluorescent markers to cytoskeleton (actin and tubulin), mitochondria membrane electric potential (JC-1) and apoptosis marker (acridine orange and ethidium). The protein responsible for anti-apoptotic action was isolated through gel filtration chromatography, using an AKTA purifier high-resolution liquid chromatography system. The hemolymph was fractionated into 3 pools for Podalia sp and 6 pools for M. abicolis. In the antiapoptotic tests, semi purified hemolymph from both caterpillars showed anti-apoptotic effect in VERO and SF-9 cells, pre-treated with only 1% v/v of hemolymph and induced to death by different and apoptotic inductors. Was observed that the molecule with anti-apoptotic effect are present in pool 3 in both hemolymphs. This protector effect blocked and attenuated the disruption of the cytoskeleton (actin filaments), being that the protective effect also was observed on the integrity of the mitochondrial membrane of SF-9 cells pre-treated with both hemolymphs and treated with the apoptosis inducer Terbutil at concentrations of 25 to 100uM. Copy rights belong to original authors. Visit the link for more info Podcast created by Paper Player, LLC

Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2023.02.06.526840v1?rss=1 Authors: Rivera Alvarez, J., Asselin, L., Tilly, P., Benoit, R., Batisse, C., Richert, L., Batisse, J., Morlet, B., Levet, F., Schwaller, N., Mely, Y., Ruff, M., Reymann, A.-C., GODIN, J. D. Abstract: Completion of neuronal migration is critical for brain development. Kif21b is a plus-end directed kinesin motor protein that promotes intracellular transport and controls microtubule dynamics in neurons. Here we report a physiological function of Kif21b during radial migration of projection neurons in the mouse developing cortex. In vivo analysis in mouse and live imaging on cultured slices demonstrate that Kif21b regulates the radial glia-guided locomotion of new-born neurons independently of its motility on microtubules. Unexpectedly we show that Kif21b directly binds and regulates the actin cytoskeleton both in vitro and in vivo in migratory neurons. We establish that Kif21b-mediated regulation of actin cytoskeleton dynamics influences branching and nucleokinesis during neuronal locomotion. Altogether, our results reveal atypical roles of Kif21b on the actin cytoskeleton during migration of cortical projection neurons. Copy rights belong to original authors. Visit the link for more info Podcast created by Paper Player, LLC

Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2023.01.12.523772v1?rss=1 Authors: Polinski, P., Miret-Cuesta, M., Zamora-Moratalla, A., Mantica, F., Cantero-Recasens, G., Normanno, D., Iniguez-Rabago, L., Morenilla-Palao, C., Ordono, P., Bonnal, S., Gomez-Riera, R., De Lagran, M. M., Fernandez-Blanco, A., Rodriguez-Marin, C., Permanyer, J., Folsz, O., Sierra, C., Legutko, D., Wojnacki, J., Musoles-Lleo, J. L., Herrera, E., Dierssen, M., Irimia, M. Abstract: Actin cytoskeleton dynamics is crucial for neurogenesis and neuronal function. Precise quantitative and qualitative regulation of actin polymerization is achieved by multiple actin-binding proteins, among which formins are particularly versatile. Here, we investigate how neuronal-specific splicing expands formin's functional diversity in the brain. We uncovered a highly conserved microexon in DAAM1, whose inclusion extends the linker region of the FH2 domain and leads to remarkable changes in actin polymerization rates and structure. Microexon deletion causes neuritogenesis defects and increased calcium influx in in vitro differentiated neurons, and mice carrying this deletion exhibit deficient memory formation. These memory defects were associated with higher activity of DAAM1's interactor RhoA, increased ARC protein levels, postsynaptic deficiencies, fewer dendritic spines and impaired long-term potentiation. In summary, precise post-transcriptional regulation of DAAM1's FH2 domain is a novel mechanism for modulating actin dynamics in neurons and is essential for proper brain function. Copy rights belong to original authors. Visit the link for more info Podcast created by Paper Player, LLC

Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2023.01.09.523364v1?rss=1 Authors: Albright, A. R., Angeles-Albores, D., Marshall, W. F. Abstract: Cells have complex and beautiful structures that are important for their function, but understanding the molecular mechanisms that produce these structures is a challenging problem due to the gap in size scales between molecular interactions and cellular structures. The giant ciliate Stentor coeruleus is a unicellular model organism whose large size, reproducible structure, and ability to heal wounds and regenerate has historically allowed the formation of structure in a single cell to be addressed using methods of experimental embryology. Such studies have shown that specific cellular structures, such as the oral apparatus, always form in specific regions of the cell, which raises the question of what is the source of positional information within this organism? By analogy with embryonic development, in which localized mRNA is often used to mark position, we asked whether position along the anterior-posterior axis of Stentor might be marked by specific regionalized mRNAs. By physically bisecting cells and using single-cell RNAseq analysis on each half, we were able to identify sets of messages enriched in either the anterior or posterior half. We repeated this analysis in cells in which a set of longitudinal microtubule bundles running down the whole length of the cell, known as KM-fibers, were disrupted by RNAi of beta tubulin. We found that many messages either lost their regionalized distribution , or else switched to an opposite distribution, such that anterior-enriched messages in control became posterior-enriched in the RNAi cells, or vice versa. This study indicates that mRNA can be regionalized within a single giant cell, and that microtubules may play a role, possibly by serving as tracks for movement of the messages. This study also illustrates a strategy for subcellular spatial genomics based on physical dissection, allowing the high throughput and sensitivity of sequencing technology to be brought to bear as a rapid, low cost alternative to current fluorescence imaging based methods. Copy rights belong to original authors. Visit the link for more info Podcast created by Paper Player, LLC

Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2022.12.16.520837v1?rss=1 Authors: Niu, J., Wang, X., Zhao, W., Wang, Y., Qin, Y., Huang, X., Xue, B., Li, C., Sun, Y. Abstract: The trans-luminal LINC (Linker of Nucleoskeleton and Cytoskeleton) complex plays a central role in nuclear mechanotransduction by coupling the nucleus with cytoskeleton. High spatial density and active dynamics of LINC complex have hindered its precise characterization for the understanding of underlying mechanisms how the linkages sense and respond to mechanical stimuli. In this study, we focus on SUN2, a core component of LINC complex interconnecting the nuclear lamina and actin cytoskeleton and apply single molecule super-resolution imaging to reveal how SUN2 responds to actomyosin contractility. Using stochastic optical reconstruction microscopy (STORM), we quantitated the distribution pattern and density of SUN2 on the basal nuclear membrane. We found that SUN2 undergoes bidirectional translocation between ER and nuclear membrane in response to actomyosin contractility, suggesting that dynamic constrained force on SUN2 is required for its proper distribution. Furthermore, single molecule imaging unveils interesting dynamics of SUN2 molecules that are regulated by both actomyosin contractility and laminA/C network, whereas SUN2 oligomeric states are not affected by actomyosin contractility. Lastly, the mechanical response of SUN2 to actomyosin contractility was found to regulate expression of mechano-sensitive genes located in lamina-associated domains (LADs) and perinuclear heterochromatin. Taken together, our results reveal how SUN2 responds to mechanical cues at the single-molecule level, providing new insights into the mechanism of nuclear mechanotransduction. Copy rights belong to original authors. Visit the link for more info Podcast created by Paper Player, LLC

Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2022.11.02.514829v1?rss=1 Authors: Skorentseva, K. V., Bolshakov, F. V., Saidova, A. A., Lavrov, A. I. Abstract: The crucial step in any regeneration process is epithelization, i.e. the restoration of epithelium structural and functional integrity. Epithelialization requires cytoskeletal rearrangements, primarily of actin filaments and microtubules. Sponges (phylum Porifera) are early branching metazoans with pronounced regenerative abilities. Calcareous sponges have a unique step during regeneration: formation of a temporary structure, regenerative membrane which initially covers a wound. It forms due to the morphallactic rearrangements of exo- and choanoderm epithelial-like layers. The current study quantitatively evaluates morphological changes and characterises underlying actin cytoskeleton rearrangements during regenerative membrane formation in asconoid calcareous sponge Leucosolenia variabilis, through a combination of time-lapse imaging, immunocytochemistry, and confocal laser scanning microscopy. Regenerative membrane formation has non-linear stochastic dynamics with numerous fluctuations. The pinacocytes at the leading edge of regenerative membrane form a contractile actomyosin cable. Regenerative membrane formation either depend on its contraction or being coordinated through it. The cell morphology changes significantly during regenerative membrane formation. Exopinacocytes flatten, their area increases, while circularity decreases. Choanocytes transdifferentiate into endopinacocytes, losing microvilli collar and flagellum. Their area increases and circularity decreases. Subsequent redifferentiation of endopinacocytes into choanocytes is accompanied by inverse changes in cell morphology. All transformations are based on actin filament rearrangements similar to those characteristic of higher metazoans. Altogether, we provide here a qualitative and quantitative description of cell transformations during reparative epithelial morphogenesis in a calcareous sponge. Summary statementFirst detailed description of actin cytoskeleton rearrangements during wound healing in calcareous sponge. Purse-string mechanism presumably involved. Cytoskeletal rearrangements resemble those characteristic of Eumetazoans. Copy rights belong to original authors. Visit the link for more info Podcast created by Paper Player, LLC

Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2022.10.31.514622v1?rss=1 Authors: Tombesi, G., Chen, C., Favetta, G., Plotegher, N., Sevegnani, M., Marte, A., Battisti, I., Civiero, L., Onofri, F., Piccoli, G., Arrigoni, G., Manzoni, C., Parisiadou, L., Greggio, E. Abstract: Dendritic spines, small protrusions of the dendrites, constitute the postsynaptic compartment of excitatory synapses. Filamentous actin is the major cytoskeletal constituent of dendritic spines, whose dynamic nature allows them to plastically remodel their shape and volume in response to stimuli. Notably, dendritic spine abnormalities are linked to a number of neurological and neurodegenerative disorders. Here, we show that the Parkinson disease (PD)-associated kinase LRRK2 participates in spine remodeling processing by binding a panel of actin-related proteins enriched in postsynaptic compartments. Phosphorylation of LRRK2 Ser935, which controls LRRK2 subcellular localization, rapidly increases upon brain-derived neurotrophic factor (BDNF) stimulation of differentiated SH-SY5Y cells and primary mouse neurons. Affinity-purification coupled with mass spectrometry (AP-MS/MS) analysis revealed that LRRK2 interactome is significantly reshaped upon BDNF stimulation, with an interconnected network of actin cytoskeleton-associated proteins increasing their binding to LRRK2. Accordingly, Lrrk2 knockout primary neurons exhibit impaired response to BDNF-induced spinogenesis and TrkB signaling. In vivo, one-month old Lrrk2 knockout mice exhibit defects in spine maturation, a phenotype that disappears with age. Finally, by comparing the phosphoproteomes of Lrrk2 wild-type versus Lrrk2 G2019S PD mutant synaptosomes, we found that the differentially phosphorylated proteins are enriched in categories related to postsynaptic structural organization. Taken together, our study discloses a critical function of LRRK2 in shaping dendritic spine morphology during development and defines a mechanistic role of the kinase in postsynaptic actin-cytoskeletal dynamics. Copy rights belong to original authors. Visit the link for more info Podcast created by Paper Player, LLC

Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2022.10.30.514432v1?rss=1 Authors: Fradet, A., Fitzgerald, J. Abstract: Mutations in INPPL1, the gene coding for SH2 Domain-Containing Inositol 5'-Phosphatase 2 (SHIP2), cause Opsismodysplasia, a severe chondrodysplasia characterized by delayed bone maturation. The mechanism by which the loss of an inositol phosphatase causes a major skeletal developmental defect is unclear. To investigate the role of SHIP2 in mineralization, the INPPL1 gene was deleted in vitro in chondrocyte and osteoblast differentiation models and the effect of the loss of SHIP2 on cell differentiation, subsequent mineralization, and on actin cytoskeleton formation was investigated. The loss of SHIP2 does not impact differentiation but, consistent with the disease phenotype, induces a significant reduction in extracellular matrix mineralization in both cell types. Absence of SHIP2 also altered the actin cytoskeleton to increase cell adhesion and focal adhesion formation. Furthermore, inhibition of actin polymerization in SHIP2-deficient cells rescued the mineralization phenotype. RhoA/ROCK, Cdc42 and Rac1 are the three main RhoGTPases responsible for actin cytoskeleton regulation in bone cells. Specific inhibitors of these RhoGTPases were used to determine the pathways involved in SHIP2-mediated mineralization. Since only the ROCK pathway inhibitor rescued the mineralization phenotype, it is concluded that SHIP2 regulates actin cytoskeleton remodeling and consequently extracellular matrix mineralization by inhibiting the RhoA/ROCK pathway. Copy rights belong to original authors. Visit the link for more info Podcast created by Paper Player, LLC

Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2022.09.21.508765v1?rss=1 Authors: Iram, T., Garcia, M. A., Amand, J., Kaur, A., Iyer, M., Lam, M., Ambiel, N., Keller, A., Wyss-Coray, T., Kern, F., Zuchero, J. B. Abstract: Myelination of neuronal axons is essential for nervous system development. Myelination requires dramatic cytoskeletal dynamics in oligodendrocytes, but how actin is regulated during myelination is poorly understood. We recently identified serum response factor (SRF), a transcription factor known to regulate expression of actin and actin regulators in other cell types, as a critical driver of myelination in the aged brain. Yet, a major gap remains in understanding the fundamental role of SRF in oligodendrocyte lineage cells. Here we show that SRF is required cell autonomously in oligodendrocytes for myelination during development. Combining ChIP-seq with RNA-seq identifies SRF-target genes in OPCs and oligodendrocytes that include actin and other key cytoskeletal genes. Accordingly, SRF knockout oligodendrocytes exhibit dramatically reduced actin filament levels early in differentiation, consistent with its role in actin-dependent myelin sheath initiation. Together, our findings identify SRF as a transcriptional regulator that controls the expression of cytoskeletal genes required in oligodendrocytes for myelination. This study identifies a novel pathway regulating oligodendrocyte biology with high relevance to brain development, aging, and disease. Copy rights belong to original authors. Visit the link for more info Podcast created by PaperPlayer

Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2022.09.13.507749v1?rss=1 Authors: Velazquez Sanchez, C., Muresan, L., Belin, D. Abstract: Some compulsive disorders have been considered to stem from the loss of control over coping strategies, such as displacement. However, the cellular mechanisms involved in the acquisition of coping behaviors and their ensuing compulsive manifestation in vulnerable individuals have not been elucidated. Considering the role of the locus coeruleus (LC) noradrenaline dependent system in stress and related excessive behaviors, we hypothesised that neuroplastic changes in the LC may be involved in the acquisition of an adjunctive polydipsic water drinking, a prototypical displacement behavior, and the subsequent development of compulsion in vulnerable individuals. Thus, male Sprague Dawley rats were characterised for their tendency, or not, to develop compulsive polydipsic drinking in a schedule-induced polydipsia (SIP) procedure before their fresh brains were harvested. A new quantification tool for RNAscope assays revealed that the development of compulsive adjunctive behavior was associated with a low mRNA copy number of the plasticity marker Arc in the LC which appeared to be driven by specific adaptations in an ensemble of tyrosine hydroxylase (TH)+, zif268- neurons. This ensemble was specifically engaged by the expression of compulsive adjunctive behavior, not by stress, because its functional recruitment was not observed in individuals that no longer had access to the water bottle before sacrifice while it consistently correlated with the levels of polydipsic water drinking only when it had become compulsive. Together these findings suggest that downregulation of Arc mRNA levels in a population of a TH+zif268- LC neurons represents a signature of the tendency to develop compulsive coping behaviors. Copy rights belong to original authors. Visit the link for more info Podcast created by PaperPlayer

Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2022.09.07.507048v1?rss=1 Authors: Coakley, S., Bonacossa-Pereira, I., Hilliard, M. A. Abstract: Spectrins are highly conserved molecules that form a distinct membrane associated periodic scaffold within axons thought to provide mechanical resilience. In C. elegans, UNC-70/{beta}-Spectrin also functions outside the nervous system, within the epidermis, to maintain the integrity of sensory neurons. The precise molecular organization and cellular mechanisms that mediate this protection are unknown. Here, using 3D-structured illumination microscopy, we show that within the epidermis spectrins form a crescent-shaped scaffold with a periodicity of ~ 200 nm that embraces adjacent axons. This epidermal spectrin scaffold is induced by developing axons and reformed during axonal regeneration, and creates a molecular imprint of the adjacent nervous system. Disruption of this epidermal scaffold causes widespread axonal damage in sensory and motor neurons. These findings reveal the existence of a distinct and periodic spectrin framework within the epidermis that is molded by the developing nervous system and is necessary to protect it from mechanical damage. Copy rights belong to original authors. Visit the link for more info Podcast created by PaperPlayer

Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2022.09.07.506915v1?rss=1 Authors: Puri, D., Samaddar, S., Banerjee, S., Ghosh-Roy, A. Abstract: Regulation of microtubule cytoskeleton is fundamental for the development and maintenance of neuronal architecture. Recent studies have shown that regulated RNA processing is also critical for the establishment and maintenance of neural circuits. In a genetic screen using mechanosensory neurons of C. elegans, we identified a mutation in muscleblind-1 as a suppressor of loss of kinesin-13 family microtubule destabilizing factor klp-7. Muscleblind-1(MBL-1) is an RNA-binding protein that regulates the splicing, localization, and stability of RNA. We found that mbl-1 is required cell-autonomously for axon growth and synapse formation in the posterior lateral microtubule (PLM) neuron. Loss of mbl-1 affects stability and plus-end-out organization of microtubules in the anterior process of PLM. These defects are also accompanied by abnormal axonal transport of the synaptic protein RAB-3 and loss of gentle touch sensation in mbl-1 mutant. Our data showed that mbl-1 is genetically epistatic to mec-7 ({beta}-tubulin) and mec-12 (-tubulin) for axon growth. The immunoprecipitation of MBL-1 pulls down the mec-7, mec-12, and sad-1 mRNAs. Additionally, the mbl-1 mutants show a reduction in the level and stability of mec-7 and mec-12 transcripts. Independently, mbl-1 is epistatic to sad-1 for synapse formation. Our work elucidated a previously unknown link between RNA binding protein and cytoskeletal machinery for the development and maintenance of the nervous system. Copy rights belong to original authors. Visit the link for more info Podcast created by PaperPlayer

In this episode of the Jack Westin MCAT Podcast, Phil Hawkins, Lead Instructor and Director of MCAT Prep and Harvard Medical Student Azaii Calderón Muñiz discuss the cytoskeleton. You will learn a few ways that the AAMC will test your knowledge on test day and how you can best prepare for the MCAT. About Jack Westin - The team at Jack Westin is dedicated to a single goal: giving students the highest quality learning resources. Jack Westin understands that students can't crush the MCAT without the perfect blend of critical thinking and fundamental science knowledge. To this end, Jack Westin is dedicated to providing students with cutting edge comprehensive tools, courses, and practice materials. The Jack Westin MCAT science and CARS courses, taught by the world's best and most engaging MCAT instructors, are designed to do more than just teach students the MCAT—it supercharges studying and encourages lifelong learning. Want to learn more? Shoot us a text at 415-805-6292 Free Resources: https://jackwestin.com Live Education Sessions: https://jackwestin.com/sessions Courses: https://jackwestin.com/courses Tutoring: https://jackwestin.com/tutoring Follow Us On Instagram: https://www.instagram.com/jackwestinmcat

In this episode, I speak with Prachee Avasthi. Prachee is an Associate Professor of Biochemistry and Cell Biology at Dartmouth University, and her lab broadly studies cytoskeletal assembly. Prachee is also spearheading efforts to improve the academic publishing system in the life sciences.  (00:34) -- how Prachee got interested in cytoskeletal assembly (2:37) -- algae as a model system (6:31) -- evaluating tradeoffs in model systems (9:45) -- general scientific lessons in genetics and cell biology (15:26) -- issues with the academic publishing system (17:44) -- ASAPbio (21:00) -- rise of preprints  (24:45) -- open reviews (29:02) -- crowd sourced peer review (32:48) -- need for journals 

Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2020.09.11.293589v1?rss=1 Authors: Emond, M. R., Biswas, S., Morrow, M. L., Jontes, J. Abstract: Protocadherin-19 belongs to the cadherin family of cell surface receptors and has been shown to play essential roles in the development of the vertebrate nervous system. Mutations in human Protocadherin-19 (PCDH19) lead to PCDH19 Female-limited epilepsy (PCDH19 FLE) in humans, characterized by the early onset of epileptic seizures in children and a range of cognitive and behavioral problems in adults. Despite being considered the second most prevalent gene in epilepsy, very little is known about the intercellular pathways in which it participates. In order to characterize the protein complexes within which Pcdh19 functions, we generated Pcdh19-BioID fusion proteins and utilized proximity-dependent biotinylation to identify neighboring proteins. Proteomic identification and analysis revealed that the Pcdh19 interactome is enriched in proteins that regulate Rho family GTPases, microtubule binding proteins and proteins that regulate cell divisions. We cloned the centrosomal protein Nedd1 and the RacGEF Dock7 and verified their interactions with Pcdh19 in vitro. Our findings provide the first comprehensive insights into the interactome of Pcdh19, and provide a platform for future investigations into the cellular and molecular biology of this protein critical to the proper development of the nervous system. Copy rights belong to original authors. Visit the link for more info

Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2020.08.28.272435v1?rss=1 Authors: Balakrishnan, S., Raju, S. R., Barua, A., Ananthasuresh, G. K. Abstract: Tension in actin cytoskeleton regulates many cellular processes and nuclear morphology. Here, we demonstrate a simple computational method for estimating actin cytoskeletal tension from nucleus shape. We first note that mechanics-based modeling defines a relationship among the volume, surface area, and projected area of the nucleus and hence a specific surface in the three-parameter space of the aforementioned geometric quantities. Data of nuclei from multiple cell types lie on such a surface. Furthermore, nuclei from a given cell population lie on a straight line on the surface. The location and orientation of the line varies with cell type. By using a mechanical model, we present two non-dimensional parameters, namely, the flatness and stretch indicators, which serve as curvilinear coordinates on the surface. Flatness indicator defines the extent of nuclear flattening due to actin cytoskeletal tension and the stretch indicator captures the effect of the elastic modulus of the nuclear envelope. We validate our assertions by modulating the actin cytoskeletal tension using three independent mechanisms: (i) direct downregulation by Cytochalasin D, (ii) indirect upregulation using Nocodazole, and (iii) mechanical stimulation by varying substrate stiffness. We also infer that the flatness indicator is equivalent to the ratio of the height to diameter of the nucleus and is related to the Vogel number. By using this geometric insight, we validate the predictions of our model with data from many previous studies. Finally, we present an analytical formula and a correlation for estimating actin cytoskeletal tension from nuclear projected area and volume. Copy rights belong to original authors. Visit the link for more info

Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2020.08.27.268318v1?rss=1 Authors: Stein, D. B., De Canio, G., Lauga, E., Shelley, M. J., Goldstein, R. E. Abstract: In the cellular phenomena of cytoplasmic streaming, molecular motors carrying cargo along a network of microtubules entrain the surrounding fluid. The piconewton forces produced by individual motors are sufficient to deform long microtubules, as are the collective fluid flows generated by many moving motors. Studies of streaming during oocyte development in the fruit fly D. melanogaster have shown a transition from a spatially-disordered cytoskeleton, supporting flows with only short-ranged correlations, to an ordered state with a cell-spanning vortical flow. To test the hypothesis that this transition is driven by fluid-structure interactions we study a discrete-filament model and a coarse-grained continuum theory for motors moving on a deformable cytoskeleton, both of which are shown to exhibit a swirling instability to spontaneous large-scale rotational motion, as observed. Copy rights belong to original authors. Visit the link for more info

Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2020.05.12.092148v1?rss=1 Authors: Wang, J., Jiang, J., Yang, X., Wang, L., Xiao, B. Abstract: The mechanically activated Piezo channel plays a versatile role in conferring mechanosensitivity to various cell types. However, how it incorporates its intrinsic mechanosensitivity and cellular components to effectively sense long-range mechanical perturbation across a cell remains elusive. Here we show that Piezo1 is biochemically and functionally tethered to the actin cytoskeleton via the E-cadherin-{beta}-catenin mechanotransduction complex, whose perturbation significantly impairs Piezo1-mediated responses. Mechanistically, the adhesive extracellular domain of E-cadherin interacts with the cap domain of Piezo1 that controls the transmembrane gate, while its cytosolic tail might interact with the cytosolic domains of Piezo1 that are in close proximity to its intracellular gates, allowing a direct focus of adhesion-cytoskeleton-transmitted force for gating. Specific disruption of the intermolecular interactions prevents cytoskeleton-dependent gating of Piezo1. Thus, we propose a force-from-filament model to complement the previously suggested force-from-lipids model for mechanogating of Piezo channels, enabling them to serve as versatile and tunable mechanotransducers. Copy rights belong to original authors. Visit the link for more info

Your heart beats over 100,000 times a day and over 2 billion times a lifetime. The heart keeps up with wear and tear because it has a strong yet flexible cytoskeleton, the 'framework' of the cell. But what happens when the cytoskeleton malfunctions, and more importantly, how do we fix it? On this episode of Beyond the Abstract, Derek and Ellen chat with cell biologist and PhD candidate Brittany MacTaggart about alterations that happen to the cytoskeleton during heart failure and how these changes affect how the heart functions. Chen et al. Suppression of detyrosinated microtubules improves cardiomyocyte function in human heart failure. Nature Medicine, 2018. 24(8); 1225-1233. PMID: 29892068.

The TWiV team covers outbreaks of eastern equine encephalitis virus in the US and poliovirus in the Philippines, and explain how a chemokine induced by HIV-1 infection helps release more virus particles from cells. Hosts: Vincent Racaniello, Dickson Despommier, Alan Dove, Rich Condit, Kathy Spindler, and Brianne Barker Subscribe (free): iTunes, Google Podcasts, RSS, email Become a patron of TWiV! Links for this episode Poliomyelitis returns to the Philippines (Mashable, virology blog) EEE in the USA (Am J Trop Med Hyg) Chemokine helps HIV-1 release (eLIFE) Image credit Letters read on TWiV 567 Timestamps by Jolene. Thanks! Weekly Science Picks Brianne - History of infectious disease before/after vaccines Alan - NIH Ham Radio Club Rich - Renewable jet fuel from air Dickson - Newly Discovered Comet Is Likely Interstellar Visitor Kathy - How professors spend their time Vincent - Non-polio enterovirus surveillance network Listener Picks Alexey - Periodic Table Podcasts and Videos Intro music is by Ronald Jenkees. Send your virology questions and comments to twiv@microbe.tv

The TWiV team covers outbreaks of eastern equine encephalitis virus in the US and poliovirus in the Philippines, and explain how a chemokine induced by HIV-1 infection helps release more virus particles from cells. Hosts: Vincent Racaniello, Dickson Despommier, Alan Dove, Rich Condit, Kathy Spindler, and Brianne Barker Subscribe (free): iTunes, Google Podcasts, RSS, email Become a patron of TWiV! Links for this episode Poliomyelitis returns to the Philippines (Mashable, virology blog) EEE in the USA (Am J Trop Med Hyg) Chemokine helps HIV-1 release (eLIFE) Image credit Letters read on TWiV 567 Timestamps by Jolene. Thanks! Weekly Science Picks Brianne - History of infectious disease before/after vaccines Alan - NIH Ham Radio Club Rich - Renewable jet fuel from air Dickson - Newly Discovered Comet Is Likely Interstellar Visitor Kathy - How professors spend their time Vincent - Non-polio enterovirus surveillance network Listener Picks Alexey - Periodic Table Podcasts and Videos Intro music is by Ronald Jenkees. Send your virology questions and comments to twiv@microbe.tv

Host Kevin Patton discusses the many ways case studies can be used in teaching, why they enhance learning, and where to find them. Also, updates in factors underlying left-handedness, functional maps of the brain, and reversing biological age, plus some tips on responding to student questions. 00:44 | Left-handedness 02:54 | Responding to Students 22:30 | Sponsored by HAPS 22:59 | Mapping Brain Functions 26:55 | Sponsored by AAA 27:14 | Reversing Age 30:32 | Sponsored by HAPI Online Graduate Program 31:18 | Case Studies in Teaching A&P 47:59 | Staying Connected If you cannot see or activate the audio player click here. Questions & Feedback: 1-833-LION-DEN (1-833-546-6336) Follow The A&P Professor on Twitter, Facebook, Blogger, Nuzzel, Tumblr, or Instagram!   If the left half of the brain controls the right half of the body then only left handed people are in their right mind. (W.C. Fields)   1 | Left-Handedness 2 minutes A new report suggests that left-handedness, which one in ten of us exhibit, is partially influenced by genes. One effect of these genes is to change the structure of our body cells' cytoskeleton. Of course, a lot more work has to be done. By left-handers and right-handers alike. Left-handed DNA found - and it changes brain structure (brief summary article) my-ap.us/2AfTLAQ Handedness, language areas and neuropsychiatric diseases: insights from brain imaging and genetics (research article) my-ap.us/2AbWACQ     2 | Responding to Students 19.5 minutes Half of students don't read the syllabus, don't read directions, don't listen to us—which can produce some frustrations when they reach out to us with questions that they already have the answer for. Somewhere nearby them. Kevin gives some tips on how to to handle these with grace and ease (taking barely any time or effort), as well as advice on heading them off before they are asked. The Syllabus Episode | Bonus | Episode 24 Connecting in The Distance Course Special | Episode 50 TextExpander (software to cut and paste automatically) theapprofessor.org/textexpander Google forms (software to make inquiry forms for students that require them to give specifics about their question) my-ap.us/2AfzbQU     3 | Sponsored by HAPS 0.5 minutes The Human Anatomy & Physiology Society (HAPS) is a sponsor of this podcast.  You can help appreciate their support by clicking the link below and checking out the many resources and benefits found there. There are a bunch of 1-day regional workshops scattered all over the continent. There's probably one near you coming up this year (or next)! Anatomy & Physiology Society  theAPprofessor.org/haps     4 | Mapping Brain Functions 4 minutes We've all see various functional maps of the human brain. But once you get down to the smaller regions, or parcels, it gets weird. Beyond a certain resolution, things are very flexible. Because functions of tiny parcels vary with the state of that region of the brain in any given moment, we will probably not be able to produce a high-resolution functional map of the brain—even for any one individual. There is no single functional atlas even for a single individual: Parcellation of the human brain is state dependent (research article) my-ap.us/2Aighc0 Brodmann areas (maps and explanation) my-ap.us/2Qc2COA     5 | Sponsored by AAA 0.5 minutes A searchable transcript for this episode, as well as the captioned audiogram of this episode, are sponsored by the American Association for Anatomy (AAA) at anatomy.org. Searchable transcript Captioned audiogram      6 | Reversing Age 3.5 minutes Can biological age be reversed? Some research in a small group of older men suggest it may be possible. Using a cocktail of common drugs, their epigenomes showed a younger biological age. Hmm. First hint that body's ‘biological age' can be reversed (brief summary from Nature) my-ap.us/2Ad78BR Reversal of epigenetic aging and immunosenescent trends in humans (research article from Aging Cell) my-ap.us/2AfUmCA   7 | Sponsored by HAPI Online Graduate Program 1 minute The Master of Science in Human Anatomy & Physiology Instruction—the MS-HAPI—is a graduate program for A&P teachers. A combination of science courses (enough to qualify you to teach at the college level) and courses in contemporary instructional practice, this program helps you power up  your teaching. Kevin Patton is a faculty member in this program. Check it out! nycc.edu/hapi     8 | Case Studies in Teaching Anatomy & Physiology 16.5 minutes In this discussion, Kevin defines what a case study is, described some different sorts of case studies, explains why case studies are such a powerful learning experience, and give sources for peer-reviewed, classroom-tested case studies for A&P. And a few odd and creative ideas, one from listener Christy Pitts, thrown in as a bonus! We're all about bonuses here. Bloom's taxonomy my-ap.us/2ZWfLjt Fink's taxonomy of significant learning my-ap.us/2Q4IQEN National Center for Case Study Teaching in Science my-ap.us/ScienceCases Grumpy Old Man: Hypercalcemia and the Parathyroid Gland (this case study & others by Sheri L. Boyce) my-ap.us/2ZUWAq3 Life Science Teaching Resource Community my-ap.us/LifeSciTRC   If the hyperlinks here are not active, go to TAPPradio.org to find the episode page. More details at the episode page. Transcript available at the script page. Listen to any episode on your Alexa device. Need help accessing resources locked behind a paywall? Check out this advice from Episode 32 to get what you need! https://youtu.be/JU_l76JGwVw?t=440   Sponsors   Transcript and captions for this episode are supported by the  American Association for Anatomy. anatomy.org     The Human Anatomy & Physiology Society  also provides marketing support for this podcast.  theAPprofessor.org/haps     Distribution of this episode is supported by  NYCC's online graduate program in  Human Anatomy & Physiology Instruction (HAPI)  nycc.edu/hapi   Clicking on sponsor links  helps let them know you appreciate their support of this podcast!   Referrals also help defray podcasting expenses.  Amazon TextExpander Snagit & Camtasia The A&P Professor Logo Items   Follow The A&P Professor on  Twitter, Facebook, Blogger, Nuzzel, Tumblr, or Instagram!   The A&P Professor® and Lion Den® are registered trademarks of Lion Den Inc. (Kevin Patton)  

Professor Eva Nogales started her career in a time where barely any women were seen in science departments. In college, she skipped biology to focus on physics, relying on her high-school knowledge of the former to shape her career as a biophysicist. Now, she’s using her understanding of the microtubules in our cells for improving disease management, including slowing the uncontrollable growth of cancer. This niche understanding of our cell behaviour at the molecular level is already improving the lives of humans everywhere, and the technique used by Professor Nogales called “cryo-EM” is taking the world of structural biology by storm. She recently visited the University of Melbourne to receive the 2019 Grimwade Medal, and to deliver the oration titled: Visualising the molecular dance at the heart of human gene expression. Episode recorded: February 14, 2019.Interviewer: Steve Grimwade.Producer and editor: Chris Hatzis.Co-production: Silvi Vann-Wall and Dr Andi Horvath.Banner: Berkeley Lab.

Weinstein & Sumeracki join Kevin for a conversation about their new book that explores how learning science can help us teach more effectively & help our students learn more effectively. And a brief update on how myosin-actin interactions in the RBC cytoskeleton help regulate cell shape and deformability. 0:59 | New discovery about the shape of red blood cells 4:54 | Featured: Chat with the authors of a new book about how we learn If you cannot see or activate the audio player click here. Questions & Feedback: 1-833-LION-DEN (1-833-546-6336) Follow The A&P Professor on Twitter, Facebook, Blogger, Nuzzel, Tumblr, or Instagram!   "Educational practice does not, for the most part, rely on research findings. Instead, there's a preference for relying on our intuitions about what's best for learning. But relying on intuition may be a bad idea for teachers and learners alike." Yana Weinstein & Megan Sumeracki in Understanding How We Learn: A Visual Guide   1 | Regulation of Red Blood Cell Shape 4 minutes Recent evidence points to a myosin-actin interaction in  the cytoskeleton connected to the plasma membrane as a key mechanism for regulating RBC deformability. Thus that old myosin-actin attraction learned while exploring muscle contraction accomplishes important tasks in other parts of the body, too! Healthy red blood cells owe their shape to muscle-like structures (brief synopsis) Myosin IIA interacts with the spectrin-actin membrane skeleton to control red blood cell membrane curvature and deformability (research article)   2 | Understanding How We Learn: A Visual Guide 23 minutes Dr. Yana Weinstein and Dr. Megan Sumeracki join Kevin for an informative chat about their new book Understanding How We Learn: A Visual Guide. These learning scientists explain how A&P professors can use the six strategies for learning in their courses to help students learn. Understanding How We Learn: A Visual Guide (the book; multiple formats available) Featured in The A&P Professor Book Club learningscientists.org (the website for The Learning Scientists; links to blog, podcast, videos, downloadable resources; good link to share with your A&P students) @AceThatTest (follow The Learning Scientists on Twitter) Related resources from The A&P Professor Episode 1: Spaced Retrieval Practice (the pilot episode of this podcast explored Kevin's experience with combining spacing and retrieval practice (discussed by Weinstein & Sumeracki in today's chat). Episode 7: Teaching for Long Term Learning Seminar: Long Term Learning | Five Strategies for Teaching A&P Please call in with your reactions, questions for the authors, comments, and ideas for implementing the tips in this book: 1-833-LION-DEN or 1-833-546-6336 podcast@theAPprofessor.org Here's an example of a visual chapter preview mentioned in the interview. Sample from Understanding How We Learn: A Visual Guide If the hyperlinks here are not active or images do not appear, go to TAPPradio.org to find the episode page. More details at the episode page. Transcript available at the script page. Listen to any episode on your Alexa device. Join The A&P Professor social network: Blog Twitter @theAPprofessor Facebook theAPprofessor Instagram theAPprofessor YouTube Amazon referrals help defray podcasting expenses.  

Dia1-dependent adhesions help epithelia branch out The actin cytoskeleton and its regulators play key roles in the maturation and stabilization of focal adhesions but how adhesion maturation affects tissue morphogenesis is largely unknown. Fessenden et al. reveal that the actin-nucleating formin protein Dia1 promotes branching morphogenesis by stabilizing adhesions that are required for epithelial tissues to initiate invasion. This biosights episode presents the paper by Fessenden et al. from the April 2nd, 2018, issue of the Journal of Cell Biology and includes an interview with the paper's senior author, Margaret Gardel (University of Chicago). Produced by Caitlin Sedwick and Ben Short. See the associated paper in JCB for details on the funding provided to support this original research. Subscribe to biosights via iTunes or RSS View biosights archive The Rockefeller University Press biosights@rockefeller.edu

Myosins team up to help secretory granules integrate Actomyosin contractility drives a variety of membrane remodeling events, including the integration of secretory granules into the apical plasma membrane after exocytosis. By visualizing granule integration in the salivary glands of live mice, Milberg et al. reveal that myosin IIA and myosin IIB act at different stages of the process and that the activation and assembly of these myosin isoforms into contractile filaments is regulated by the F-actin scaffold, which assembles on secretory granules and recruits myosin light chain kinase. This biosights episode presents the paper by Milberg et al. from the July 3rd, 2017, issue of The Journal of Cell Biology and includes an interview with the paper's senior author, Roberto Weigert (National Institutes of Health, Bethesda, MD). Produced by Caitlin Sedwick and Ben Short. See the associated paper in JCB for details on the funding provided to support this original research. Subscribe to biosights via iTunes or RSS View biosights archive The Rockefeller University Press biosights@rockefeller.edu

Vincent visits the laboratories of Kit and Joseph Pogliano on the campus of the University of California, San Diego, where he learns about their work on the bacterial cytoskeleton, sporulation, and the effects of antibiotics on bacterial cells. Visit microbeworld.org/mwv for complete shownotes including links mentioned in this episode.

Vincent visits the laboratories of Kit and Joseph Pogliano on the campus of the University of California, San Diego, where he learns about their work on the bacterial cytoskeleton, sporulation, and the effects of antibiotics on bacterial cells. Visit microbeworld.org/mwv for complete shownotes including links mentioned in this episode.

Vincent visits the laboratories of Kit and Joseph Pogliano on the campus of the University of California, San Diego, where he learns about their work on the bacterial cytoskeleton, sporulation, and the effects of antibiotics on bacterial cells. Visit microbeworld.org/twim for complete shownotes including the special video version of this episode. Thanks for listening and watching!

Birkbeck Inaugural Lecture - 1 June 2015 Professor Carolyn Moores - Professor of Structural Biology Just as our bodies have a skeleton providing support and strength, so also do the cells of our bodies; this framework is called cytoskeleton, and it is involved in many cell functions - movement, definition of architecture, and multiplication. My research team studies the three-dimensional shape of the cytoskeleton (called microtubules) using an electron microscope, a powerful tool ideally suited to visualising these nano (very tiny) structures. My talk, for a general audience, will describe some of our recent discoveries that shed light on how healthy cells work, but also how mulfunctions of the cytoskeleton cause disease. For more information about Birkbeck's Department of Biological Sciences - www.bbk.ac.uk/biology Professor Carolyn Moores - http://www.bbk.ac.uk/biology/our-staff/academic/carolyn-moores

Formin' actin at adherens junctions Actin assembly promotes the formation of intercellular adherens junctions, but the role of actin-nucleating formin proteins in this process remains unclear. Grikscheit et al. reveal that, in breast epithelial cells cultured in 3D, the formin FMNL2 stimulates junctional actin assembly downstream of the small GTPase Rac1. This biosights episode presents the paper by Grikscheit et al. from the May 11, 2015, issue of The Journal of Cell Biology and includes an interview with the paper's senior author, Robert Grosse (University of Marburg, Marburg, Germany). Produced by Caitlin Sedwick and Ben Short. See the associated paper in JCB for details on the funding provided to support this original research. Subscribe to biosights via iTunes or RSS View biosights archive The Rockefeller University Press biosights@rockefeller.edu

James Martin explains how the transcriptional coactivator Yap promotes migration of cardiomyocytes to the site of injury during heart regeneration.

The cytoskeleton in most eukaryotes consists of actin filaments, intermediate filaments, microtubules and specific associated proteins. It determines the shape and the polarity of a cell and is inevitable for the coordination of cell movement. The regulation of this complex structure requires a highly organised and specialised signalling network. Ste20-like kinases and the regulator protein Mo25 (Morula protein 25) are part of this signalling network. The main objective of this work was the functional characterisation of the regulator protein Mo25 and the Ste20-like kinases Fray1, Fray2 (Frayed kinase 1/2) and DstC (Dictyostelium serine threonine kinase C) in the amoeba Dictyostelium discoideum (D. discoideum). An additional project was to map and characterise the actin and actin related genes in the genome of the fresh water foraminifer Reticulomyxa filosa (R. filosa). Mo25 is a highly conserved 40 kDa scaffolding protein with a 60% identity from amoeba to man. The disruption of the mo25 gene in D. discoideum results in very large, multinucleated cells which are unable to complete cytokinesis. Growth as well as development is severely delayed in the Mo25-minus strain. Furthermore, in phototaxis assays performed with multicellular aggregates (slugs), the Mo25-minus slugs were unable to migrate towards the light source. These findings imply that Mo25 plays an important role in cytokinesis, growth and cell polarity. We could link the Ste 20-like kinase SvkA (severin kinase), a homolog of the human Mst3, Mst4 (Mammalian Ste20-like kinase 3/4) and Ysk1/Sok1 (Yeast Sps1/Ste20-related kinase 1, Suppressor of Kinase 1) kinases to Mo25 as a binding partner. To further elucidate the interaction of Mo25 with SvkA as well as their role in cytokinesis or polarity signalling, we generated a series of GFP–Mo25 rescue constructs with distinct point mutations in protein-protein interaction surfaces and transformed these into the Mo25-minus background. The kinase domains of the Ste20-like kinases, Fray1 and Fray2 in D. discoideum are highly homologous to the catalytic domains of OSR1 (Oxidative stress response kinase 1) and SPAK (Ste20/SPS1-related proline-alanine-rich protein kinase) in humans and Frayed in fruit fly. Here, we generated the knockout clones Fray1-minus, Fray2-minus, and the double knockout Fray2Fray1-minus in D. discoideum. In developmental studies, Fray2-minus did not show an altered phenotype, whereas Fray1-minus and Fray2Fray1-minus developed slightly slower into fruiting bodies. When grown in shaking culture, Fray1-minus and Fray2Fray1-minus showed a reduced growth rate compared to Fray2-minus and the wild type. In addition, by using a GFP-Trap resin we identified a binding partner of Fray1, a yet unknown protein that we named FRIP (Fray Interacting Protein). FRIP mainly consists of a CBS (Cystathionine beta synthase) domain pair and is 30% identical to the gamma subunit of the AMPK (5‘ adenosine mono phosphate-activated protein kinase) complex in D. discoideum. The Ste20-like kinase DstC has been described to be a regulator of the actin driven process of phagocytosis. The catalytic domain of DstC is most similar to the mammalian kinase Mst2 (Mammalian Ste20-like kinase 2) and Hippo (“Hippopotamus”-like phenotype) of D. melanogaster. We could map the sorting signal that localises DstC to phagocytic cups and acidic vesicles to about 90 amino acids. Here we present an array of distinct point mutations for the identification of the exact localisation signal. R. filosa is a fresh water protist which belongs to the the group of Foraminifera within the Rhizaria. The R. filosa genome is the first foraminiferal and only the second rhizarian genome to be deciphered. In this bioinformatics project, we could identify, map and characterise four new actin genes in addition to the already known actin and about 40 genes that code for potential actin related proteins of seven different protein classes.

José María González-Granado, Francisco Sánchez-Madrid, and Vicente Andrés have found that a component of the nuclear skeleton modulates signaling through immunological synapses.

Targeting the cytoskeleton (CSK) of cancer cells offers a valuable strategy in cancer therapy. Whereas drugs which address microtubule CSK such as vinca alkaloids or taxanes are well established in the clinic, compounds binding to the actin CSK are still far away from their therapeutical application. One reason might be the lacking knowledge on their mode of cytotoxicity and moreover their tumor specific mechanism of action. We used the myxobacterial compound Chondramide as a tool to first elucidate the mechanisms of cytotoxicity by actin targeting in different breast cancer cells, namely MCF7 and MDA-MB-231. Chondramide inhibits actin filament assembly and dynamics shown by a fluorescence-based analysis (FRAP) in whole cells and leads to apoptosis characterized by phosphatidylserine exposure, release of cytochrome C from mitochondria and finally activation of caspases (-9 and -3). Detailed analysis revealed, that Chondramide induces apoptosis by enhancing the occurrence of mitochondrial permeability transition (MPT). Known MPT-modulators were found to be affected by Chondramide: Hexokinase II (HkII) bound to the voltage dependent anion channel (VDAC) translocated from the outer mitochondrial membrane to the cytosol and the proapoptotic protein Bad was recruited to the mitochondria. Importantly, PKCε, a prosurvival serine/threonine kinase possessing an actin-binding site and known to regulate the HkII/VDAC interaction as well as Bad phosphoylation was identified as the link between actin CSK and apoptosis induction. PKCε which was found overexpressed in breast cancer cells accumulated in actin bundles induced by Chondramide and lost its activity. The second goal of our work was to inform on a potential tumor specific action of actin binding agents such as Chondramide. As the nontumor breast epithelial cell line MCF-10A in fact shows resistance to Chondramide induced apoptosis and notably express very low level of PKCε we claim that trapping PKCε via Chondramide induced actin hyperpolymerization displays tumor cell specificity. Our work provides a link between targeting the ubiquitously occurring actin CSK and selective inhibition of pro-tumorigenic PKCε, thus setting the stage for actin-stabilizing agents as innovative cancer drugs. This is moreover supported by the in vivo efficacy of Chondramide triggered by abrogation of PKCε signaling shown in a xenograft breast cancer model. For the actin targeting compound Doliculide we could show that Doliculide impairs the dynamics of the actin CSK similar to Chondramide. Moreover, it reduces the proliferation rate and migration of cancer cells and also leads to the induction of apoptosis, thus Doliculide is also an interesting lead structure for further preclinical investigations.

Hosts: Vincent Racaniello, Alan Dove, Kathy Spindler, and Ashlee Bennett Vincent, Alan, Kathy, and Ashlee discuss fomites in physicians offices, plant virus factories involved in aphid transmission, and clues from the bat genome about flight and immunity. Links for this episode How viruses cause disease (Coursera) How clean is your iPad (Which?) Meeting announcement: From emerging to pandemic viruses CaMV virus factories involved in aphid transmission (J Virol) Caulimovirus (ViralZone) CaMV responds instantly to vector (eLIFE) Aphid acquiring CaMV (J Virol) Bat genomes, flight, and immunity (Science) Letters read on TWiV 268 Weekly Science Picks Kathy - Jean-Luc Doumont (slides, communicating science, website, Scitable)Alan - Wireless thermometerVincent - LORiOLA viral necklaces Listener Pick of the Week Jessica - Knit icosahedronRobert - Practical computing for biologists by Haddock and DunnStephen - Fourteen years of US weather (YouTube) Send your virology questions and comments (email or mp3 file) to twiv@twiv.tv

All living cells are made up of protein molecules - but how do they organise themselves into structures? Plus bee sex, tough mice, and a happily married gene of the month. Like this podcast? Please help us by supporting the Naked Scientists

A framework for understanding muscle microtubules The microtubules of skeletal muscle fibers are arranged into an orthogonal grid, but how this network is formed is unknown. Oddoux et al. reveal that the network is built by dynamic microtubules nucleated from Golgi elements. This biosights episode presents the paper by Oddoux et al. from the October 28, 2013, issue of The Journal of Cell Biology and includes an interview with senior author Evelyn Ralston (NIH, Bethesda, MD). Produced by Caitlin Sedwick and Ben Short. See the associated paper in JCB for details on the funding provided to support this original research. Subscribe to biosights via iTunes or RSS View biosights archive The Rockefeller University Press biosights@rockefeller.edu

The nodal network In addition to specialized actin structures such as lamellipodia and stress fibers, cells are thought to contain a contractile actomyosin matrix that maintains cell shape. Luo et al. describe the organization and dynamics of an actomyosin network that may fulfill this function. This network is formed by actin nodes that contain the formin DAAM1 and the crosslinker filamin A, and that are connected to each other by myosin II. This biosights episode presents the paper by Luo et al. from the September 30, 2013, issue of The Journal of Cell Biology and includes an interview with corresponding author Alexander Bershadsky (Weizmann Institute, Israel, and Mechanobiology Institute, National University of Singapore). Produced by Caitlin Sedwick and Ben Short. See the associated paper in JCB for details on the funding provided to support this original research. Subscribe to biosights via iTunes or RSS View biosights archive The Rockefeller University Press biosights@rockefeller.edu

Actin is one of the most abundant proteins in eukaryotic cells and regulation of the microfilament system is crucial for a wide range of cellular functions including cell shape, cell motility, cell division and membrane dynamics. The aim of this thesis was (1) to gain a better understanding of the function of distinct actin binding domains in the regulation of the actin cytoskeleton and (2) to elucidate the role of actin variants. WH2 domains (WH2, Wiskott-Aldrich syndrome protein homology 2) are ubiquitous multifunctional regulators of actin dynamics. The protein Spire contains four central WH2 domains A-B-C-D with about 20 amino acids each and the cyclase-associated protein CAP2 contains only one WH2 domain. Under certain conditions, they can (1) nucleate actin polymerization, (2) disintegrate actin filaments and (3) sequester actin monomers. Here, the influence of selected Drosophila melanogaster Spire-WH2 and Mus musculus CAP2-WH2 domain constructs on actin dynamics was tested in vitro. To act as a filament nucleator, at least two WH2 domains are required, and nucleation of actin polymerization was only observed at substoichiometric concentrations of WH2 domains over actin. At higher concentrations, the sequestering activity of WH2 domains takes over. Preformed and purified SpireWH2-actin complexes act as extremely efficient nuclei for actin polymerization, even at superstoichiometric WH2 concentrations, under which free WH2 domains would sequester actin. All analyzed constructs, including these with only a single WH2 domain, sequester actin as well as they can disrupt filaments. This latter and most peculiar behavior of WH2 domains was observed in fluorometric, viscometric and TIRF assays. The WH2 domains seem to have such a high affinity for actin that they can forcefully sequester monomers even from filaments and filament bundles, thus breaking the whole structures. Taken together, the data clearly show that SpireWH2-actin complexes are the intermediates that account for the observed nucleating activity, whereas free WH2 domains can disrupt filaments and filament bundles within seconds, again underlining the intrinsic versatility of this regulator of actin dynamics. These data have been confirmed by crystallography in collaboration with the groups of Prof. Dr. Tad Holak and Prof. Dr. Robert Huber (Martinsried, Germany). Besides the well-studied conventional actins many organisms harbor actin variants with unknown function. The model organism Dictyostelium discoideum comprises an actinome of a total of 41 actins, actin isoforms and actin-related proteins. Among them is filactin, a highly conserved actin with an elongated N-terminus. The 105 kDa protein has a distinct domain organization and homologs of this protein are present in other Dictyosteliidae and in some pathogenic Entamoebae. Here, the functions of filactin were studied in vivo and in vitro. Immunofluorescence studies in D. discoideum localize endogenous and GFP-filactin in the cytoplasm at vesicle-like structures and in cortical regions of the cell. A most peculiar behavior is the stress-induced appearance of full length filactin in nuclear actin rods. To perform in vitro analyses recombinant filactin was expressed in Sf9 cells. Fluorescence studies with the filactin actin domain suggest that it interferes with actin polymerization by sequestering G-actin or even capping filaments. Gel filtration assays propose a tetrameric structure of full length filactin. Protein interaction studies suggest that filactin is involved in the ESCRT (endosomal sorting complexes required for transport) pathway which is responsible for multivesicular body formation. The data on filactin suggest that only the conventional actins are the backbone for the microfilamentous system whereas less related actin isoforms have highly specific and perhaps cytoskeleton-independent subcellular functions.

The peptidoglycan cell wall (CW) and the actin-like MreB cytoskeleton are the majordeterminants of cell morphology in non-spherical bacteria. Bacillus subtilis is a rod-shaped Grampositive bacterium that has three MreB isoforms: MreB, Mbl (MreB–like) and MreBH (MreBHomologue). Over the last decade, all three proteins were reported to localize in dynamic filamentous helical structures running the length of the cells underneath the membrane. This helical pattern led to a model where the extended MreB structures act as scaffolds to position CW-synthesizing machineries along sidewalls. However, the dynamic relationship between the MreB cytoskeleton and CW elongation complexes remained to be elucidated. Here we describe the characterization of the dynamics of the three MreB isoforms, CW synthesis and elongation complexes in live Bacillus subtilis cells at high spatial and temporal resolution. Using total internal reflection fluorescence microscopy (TIRFM) we found that MreB, Mbl and MreBH actually do not assemble into an extended helical structure but instead into discrete patches that move processively along peripheral tracks perpendicular to the long axis of the cell. We found similar patch localization and dynamics for several morphogenetic factors and CW-synthesizing enzymes including MreD, MreC, RodA, PbpH and PBP2a. Furthermore, using fluorescent recovery after photobleaching (FRAP), we showed that treadmilling of MreB filaments does not drive patch motility, as expected from the structural homology to actin. Blocking CW synthesis with antibiotics that target different steps of the peptidoglycan biosynthetic pathway stopped MreB patches motion, suggesting that CW synthesis is the driving force of patch motility. On the basis of these findings, we proposed a new model for MreB fuction in which MreB polymers restrict and orient patch motility to ensure controlled lateral CW expansion, thereby maintaining cell shape. To further investigate the molecular mechanism underlying MreB action, we next performed a site-directed mutagenesis analysis. Alanine substitutions of three charged amino 2 acids of MreB generated a B. subtilis strain with cell shape and growth defects. TIRFM analysis revealed that the mutated MreB protein displayed wild-type localization and dynamics, suggesting that it is still associated to the CW elongation machinery but might be defective in an interaction important for MreB morphogenetic function. Thus, this mutant appears as as a good candidate to start characterizing the interactions between the three MreB isoforms and components involved in CW elongation. It might also help to understand the function of components of theCWsynthetic complexes, and how they are coordinated to achieve efficient CW synthesis. Finally, to investigate how the integrity of the CW is maintained, we studied the localization and dynamics of the LiaIH-system, which i s t he t arget o f L iaRS, a t wo-component system involved in cell envelope stress response. We found that under stress conditions, when liaI and LiaH genes are expressed, the proteins form static complexes that coat the cell membrane. LiaI is required for the even distribution of the LiaH in the membrane. Taken together, these data suggest that LiaIH complexes may protect the cell from CW damage. Taken together, the findings described in this thesis provide valuable insights into the understanding of CW synthesis in B. subtilis, which may open new perspectives for the design of novel antimicrobial agents.

Hosts: Vincent Racaniello, Rich Condit, Alan Dove, and Kathy Spindler The TWiV four discuss an mRNA-based influenza vaccine, and a phage tubulin that forms a filamentous array in the host cell that is needed for positioning viral DNA. Links for this episode: mRNA vaccine against influenza (Nat Biotech) Phage tubulin assembles dynamic filaments (Cell) Viral skeleton (The Scientist) Not unorganized bags of enzymes (TWiM 28) Bacterial cytoskeleton (FEMS Micro Rev) Triangulation number (jpg) Letters read on TWiV 211 Weekly Science Picks Rich - Ocean Global Shark TrackerAlan - The Field Book ProjectKathy - How to manipulate an army of zombiesVincent - Science sculpture Listener Pick of the Week Stephen - WEHI.TV Send your virology questions and comments (email or mp3 file) to twiv@twiv.tv

Angiogenesis requires coordinated changes in cell shape of endothelial cells (ECs), orchestrated by the actin cytoskeleton. The mechanisms that regulate this rearrangement in vivo are poorly understood - largely because of the difficulty to visualize filamentous actin (F-actin) structures with sufficient resolution. Here, we use transgenic mice expressing Lifeact-EGFP to visualize F-actin in ECs. We show that in the retina, Lifeact-EGFP expression is largely restricted to ECs allowing detailed visualization of F-actin in ECs in situ. Lifeact-EGFP labels actin associated with cell-cell junctions, apical and basal membranes and highlights actin-based structures such as filopodia and stress fiber-like cytoplasmic bundles. We also show that in the skin and the skeletal muscle, Lifeact-EGFP is highly expressed in vascular mural cells (vMCs), enabling vMC imaging. In summary, our results indicate that the Lifeact-EGFP transgenic mouse in combination with the postnatal retinal angiogenic model constitutes an excellent system for vascular cell biology research. Our approach is ideally suited to address structural and mechanistic details of angiogenic processes, such as endothelial tip cell migration and fusion, EC polarization or lumen formation.

Drugs that reduce microtubule density or prevent the production of reactive oxygen species in skeletal muscle might slow the progression of Duchenne muscular dystrophy.

Mon, 16 Jul 2012 12:00:00 +0100 https://edoc.ub.uni-muenchen.de/15331/ https://edoc.ub.uni-muenchen.de/15331/1/Katzmann_Emanuel.pdf Katzmann, Emanuel

Fibroblasts moving across two-dimensional surfaces form lamellipodial protrusions at their leading edge, but how cells move through three-dimensional environments is less well understood. Petrie et al. reveal that, depending on the strength of intracellular RhoA signaling and on the elastic properties of the extracellular matrix, fibroblasts can migrate through 3D environments using either lamellipodia or blunt, cylindrical protrusions called lobopodia. This biosights episode presents the paper by Petrie et al. from the April 30, 2012, issue of The Journal of Cell Biology and includes an interview with first author Ryan Petrie (NIH, Bethesda, MD). Produced by Caitlin Sedwick and Ben Short. See the associated paper in JCB for details on the funding provided to support this original research. Subscribe to biosights via iTunes or RSS View biosights archive The Rockefeller University Press biosights@rockefeller.edu

Vincent, Michael, and Elio review how competition within a host drives virulence of Streptococcus pneumoniae, and the expanding universe of the bacterial cytoskeleton.

T cells require the septin family of GTP-binding proteins to maintain the integrity of their plasma membranes as they invade through tissues. Gilden et al. reveal that septins function by assembling on membrane blebs to retract them back into shape. This biosights episode presents the paper by Gilden et al. from the January 9, 2012, issue of the Journal of Cell Biology and includes an interview with senior author Max Krummel (University of California, San Francisco). Produced by Caitlin Sedwick and Ben Short. See the associated paper in JCB for details on the funding provided to support this original research.   Subscribe to biosights via iTunes or RSS View biosights archive The Rockefeller University Press biosights@rockefeller.edu

This unit explains the function of the cytoskeleton and its role in controlling transport of vesicles between different subcellular compartments. This study unit is just one of many that can be found on LearningSpace, part of OpenLearn, a collection of open educational resources from The Open University. Published in ePub 2.0.1 format, some feature such as audio, video and linked PDF are not supported by all ePub readers.

Individual cells must quickly repair any disruptions to their plasma membrane. Abreu-Blanco et al. describe how early Drosophila embryos remodel their membranes and cytoskeleton to seal cell surface wounds. This biosights episode presents the paper by Abreu-Blanco et al. from the May 2, 2011 issue of The Journal of Cell Biology, and includes an interview with senior author Susan Parkhurst (Fred Hutchinson Cancer Research Center, Seattle, WA). Produced by Caitlin Sedwick and Ben Short. Subscribe to biosights via iTunes or RSS View biosights archive The Rockefeller University Press biosights@rockefeller.edu

Enhanced Audio PodcastAired date: 3/22/2010 12:00:00 PM Eastern Time

Enhanced Video PodcastAired date: 3/22/2010 12:00:00 PM Eastern Time

Fri, 22 Jan 2010 12:00:00 +0100 https://edoc.ub.uni-muenchen.de/11082/ https://edoc.ub.uni-muenchen.de/11082/1/Batsios_Petros.pdf Batsios, Petros

Filamin and Cortexillin are F-actin crosslinking proteins in Dictyostelium discoideum allowing actin filaments to form three-dimensional networks. GAPA, an IQGAP related protein, is required for cytokinesis and localizes to the cleavage furrow during cytokinesis. Here we describe a novel interaction with Filamin which is required for cytokinesis and regulation of the F-actin content. The interaction occurs through the actin binding domain of Filamin and the GRD domain of GAPA. A similar interaction takes place with Cortexillin I. We further report that Filamin associates with Rac1a implying that filamin might act as a scaffold for small GTPases. Filamin and activated Rac associate with GAPA to regulate actin remodelling. Overexpression of filamin and GAPA in the various strains suggests that GAPA regulates the actin cytoskeleton through interaction with Filamin and that it controls cytokinesis through association with Filamin and Cortexillin.

In this month's biosights, we profile Elaine Fuchs, whose 30 years of research on mammalian skin development has recently been honored with the National Medal of Science and the 2009 L'Oréal-UNESCO award for Women in Science. The video includes excerpts from an interview with Dr. Fuchs, and was produced by Eun Choi and Ben Short.   Subscribe to biosights via iTunes or RSS View biosights archive The Rockefeller University Press biosights@rockefeller.edu

If you experience any technical difficulties with this video or would like to make an accessibility-related request, please send a message to digicomm@uchicago.edu. Margaret Gardel, Ph.D., Assistant Professor in Physics, is a 2007 recipient of the NIH Director's Pioneer award, along with four others from The University of Chicago. Fundamentally interdisciplinary, Gardel's research straddles both the physical and biological sciences by exploring disease on a molecular level. Gardel explains how the physical structure of cells may yield clues to advanced treatments for cancer and other diseases.

If you experience any technical difficulties with this video or would like to make an accessibility-related request, please send a message to digicomm@uchicago.edu. Margaret Gardel, Ph.D., Assistant Professor in Physics, is a 2007 recipient of the NIH Director's Pioneer award, along with four others from The University of Chicago. Fundamentally interdisciplinary, Gardel's research straddles both the physical and biological sciences by exploring disease on a molecular level. Gardel explains how the physical structure of cells may yield clues to advanced treatments for cancer and other diseases.

This presentation examines the behavior of Candida albicans and Saccharomyces cerevisiae. In particular, there is a focus on the actin modelling dynamics of each organism.

This presentation discusses tissue stiffness and how cells react to this type of stress. In addition, the effects of gels on cell signaling are also examined.

This talk examines the strength of actin networks as a function of physical properties, such as myosin concentration and rupture events.

Enhanced Video PodcastAired date: 3/18/2009 3:00:00 PM Eastern Time

Enhanced Audio PodcastAired date: 3/18/2009 3:00:00 PM Eastern Time

Professor Peter Chantler describes the protein structures that make up the skeleton of living cells and how they ingeniously combine to provide the means for movement of structures at the cellular and sub-cellular level.

Inhalational anthrax is an acute infectious disease caused by exposure of the lungs to B. anthracis spores. Alveolar macrophages engulf spores causing them to germinate to the vegetative form of B. anthracis, which secretes edema toxin (ET)and lethal toxin (LT). The pathogenesis of inhalational anthrax is characterized by flu-like symptoms, respiratory distress, meningitis and shock, which is fatal in almost all cases. The mechanism behind the respiratory distress is not well understood. Therefore, our goal was to determine the effects of lethal toxin in the human lung epithelium. To study alterations in a more physiological setting, we developed a differentiated, polarized lung epithelial system. Lethal toxin exposure disrupted the lung barrier function and wound healing. Assembly defects of junction proteins and additional multicellular junction sites resulted in a higher permeability. Pretreatment with keratinocyte growth factor (KGF) and dexamethasone increased the viability, resulting in the rescue of the permeability changes. Upon LT treatment, a more rigid cytoskeleton was observed, evidenced by enhanced actin stress fiber formations and tubulin stabilization. Cytoskeleton and adhesion alterations prevented the epithelial cells from polarization, directed migration, and wound healing. The MAPK pathway and Cdc42 activity might be partially responsible for these motility defects. Lethal toxin is known to induce rapid cell death in murine macrophages. In contrast, human epithelial cells are more resistant to the cytotoxic effect of LT. By following the growth of epithelial cells after LT treatment, we observed inhibited cell proliferation due to a cell cycle arrest in the G1 phase. Surprisingly, biotinylated lethal factor did not induce cytotoxicity in murine macrophages. This is not due to an internalization or proteolytic activity defect; instead changes in the mitochondrial potential and proteasome activity were observed. Biotinylated LT did not reduce proteasome activity as seen in LT treated cells and caused hypopolarization of the mitochondria. However, it is possible that biotinylation of lethal toxin could prevent interaction of LT with proteins that induce cell death. The major challenge for anthrax treatment is to find a treatment, which can act faster, is easy to use and can bring patient out of the dangerous physiological state in late pathogenesis. Our study has implications in saving the viability and barrier function of lung epithelial cells. One can devise better dosage and delivery of KGF and dexamethasone as treatment modality for post anthrax exposure to reduce respiratory distress. Furthermore, overcoming the cell cycle arrest by the development of a drug would reduce the damage of lung epithelial cells and induce proliferation. The discovery that biotinylated LT is non-toxic to murine macrophages could revolutionize treatment of anthrax infection. Exploring the types of posttranslational modifications of LT that decrease toxicity and finding the mechanism behind it might, lead to therapies that directly counteract the effects of the lethal toxin in vivo.

Lecture 27: Kaplan continues his discussion of signal transduction, the role of signals in cell migration, and the ability of cells to see which direction to move.

Lecture 26: Kaplan talks about properties of signaling modules and different kinds of membrane receptors that interpret signals from outside the cell.

Lecture 25: This class is a wrap-up of cell division and checkpoints in the regulatory cycle, and introduction to how cells interpret various biochemical signals.

Lecture 24: Students learn more about cell division, and introduction to cell checkpoints along the regulatory cycle.

Review for Midterm 2: This covers protein trafficking, the cytoskeleton and cell division.

Lecture 20: Kaplan wraps up of the cytoskeleton, relation of microtubles to cell motility, introduction to cell division.