Podcasts about Integrin

Send us a text | PINERIES | ANOTHRIC | CARYOTIN | PROTAMIN | MINATORY | VANITORY | RUTILANT | BANNEROL | BARONNES | BUTANONE NANOTUBE | OBTURATE TABOURET | ORDNANCE  | NORMANDE | FONTANEL | SONARMEN MONERANS | TAUTOMER | PENTOSAN | RESORCIN | STENOTIC TONETICS | TOREUTIC | WORRITED | FISTNOTE | TOWNSITE | ALIGHTED GILTHEAD | SOMEDEAL | GERARDIA | RETIARII | NORTENOS NETROOTS | BIENNEALE | DECENNIA ENNEADIC | CEDARIER | RINGLETY | TUBENOSE | DUECENTO | ENSORCEL | UDOMETER | FELSTONE | TRUELOVE | ROCAILLE | TEOCALLI | SCARIOSE | AQUATONE | INTEGRIN | AMBERINA | THERIACA | CAVATINE | VICARATE | APHANITE | RABIETIC | HIERATIC | VINIFERA | LONGHAIR | LAAGERED | STEALAGE | ATENOLOL | ANTEVERT | AGIOTAGE | UTILIDOR | ENGENIOUS | HALIDOME | EPISOMAL | DOORCASE | HORDEOLA | TOOLHEAD | LATEWOOD | STOMODEA | SEAFLOOR | SALEROOM | AUTOSOME | CORODIES | ECLOSION | OINOMELS SIMOLEON | OTIOSELY | NICOTINE COTININE | ULTRARED | LUTENIST UNSILENT

Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2023.07.28.550203v1?rss=1 Authors: Chen, T., Huertas Fernandez-Espartero, C., Illand, A., Tsai, C.-T., Yang, Y., Klapholz, B., Jouchet, P., Fabre, M., Rossier, O., Cui, B., Leveque-Fort, S., Brown, N. H., Giannone, G. Abstract: Morphogenesis requires building stable macromolecular structures from highly dynamic proteins. Muscles are anchored by long-lasting integrin adhesions to resist contractile force. However, the mechanisms governing integrin diffusion, immobilization, and activation within developing tissue remain elusive. Here, we show that actin polymerisation-driven membrane protrusions form nanotopographies resulting in strong adhesions in the Drosophila muscle attachment site. With super-resolution microscopy and single protein tracking, we show that integrins assemble invadosomes-like adhesive belts around Arp2/3-dependent actin protrusions, which promotes enhanced integrin molecular immobilization and confinement in diffusion traps. Actin filaments also display restricted motion and confinement, indicating strong mechanical connection with integrins. Using isolated muscle cells, we show that substrate nanotopography, instead of rigidity, drives adhesion maturation by regulating actin protrusion, integrin diffusion and immobilization. These results point to the existence of a molecular clutch in developing tissue required for the formation of stable adhesions and highlight the importance of geometrical information in cellular and tissue morphogenesis. 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/2023.07.09.545606v1?rss=1 Authors: Aristizabal-Ramirez, I., Dragich, A. K., Giese, A. P. J., Zuluaga-Osorio, K. S., Watkins, J., Davies, G. K., Hadi, S. E., Riazuddin, S., Vander Kooi, C. W., Ahmed, Z. M., Frolenkov, G. I. Abstract: Calcium and Integrin-Binding Protein 2 (CIB2) is an essential subunit of the mechano-electrical transduction (MET) complex in mammalian auditory hair cells. CIB2 binds to MET channel subunits TMC1/2 and is required for their transport and/or retention at the tips of mechanosensory stereocilia. Since genetic ablation of CIB2 results in complete loss of MET currents, the exact role of CIB2 in the MET complex remains elusive. Here, we generated a new mouse strain with deafness-causing p.R186W mutation in Cib2 and recorded small but still measurable MET currents in the cochlear outer hair cells at postnatal days 4-8. We found that p.R186W mutation results in increase of the resting open probability of MET channels, steeper MET current dependence on hair bundle deflection (I-X curve), loss of fast adaptation, and increased leftward shifts of I-X curves upon hair cell depolarization. Combined with AlphaFold2 prediction that p.R186W disrupts one of the multiple interacting sites between CIB2 and TMC1/2, our data suggest that CIB2 mechanically constrains TMC1/2 conformations to ensure proper force sensitivity and dynamic range of the MET channels. Using a custom piezo-driven stiff probe deflecting the hair bundles in less than 10 s, we also found that p.R186W mutation slows down the activation of MET channels. This phenomenon, however, is unlikely to be the direct effect on MET channels, since we also observed p.R186W-evoked disruption of the electron-dense material at the tips of mechanotransducing stereocilia and the loss of membrane-shaping BAIAP2L2 protein from the same location. We concluded that p.R186W mutation in CIB2 disrupts force sensitivity of the MET channels and force transmission to these channels. 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/2023.05.02.539023v1?rss=1 Authors: Zhang, H., Zhu, D. S., Zhu, J. Abstract: 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/2023.03.24.534172v1?rss=1 Authors: Stepankova, K., Smejkalova, B., Machova Urdzikova, L., Havelikova, K., Verhaagen, J., deWinter, F., Herynek, V., Kwok, J. C. F., Fawcett, J. C. F., Jendelova, P. Abstract: Sensory axons cut within the spinal cord do not regenerate spontaneously. This failure is due in part to absence of an appropriate adhesion molecule on sensory axons, able to interact with the CNS environment. Previous work has shown that transduction of sensory neurons with 9 integrin, which combines with endogenous {beta}1 as 9{beta}1 together with the integrin activator kindlin-1 enables regeneration of sensory axons from a dorsal root crush to the brainstem. The integrin provides an adhesion molecule that recognizes Tenascin-C (which is upregulated in damaged spinal cord) and signals to upregulate the regeneration-associated gene programme. Regeneration from sensory neurons transduced with 9 integrin and kindlin-1 was examined after C4 and after T10 dorsal column lesions with C6,7 and L4,5 sensory ganglia injected with AAV1 vectors. In 9 integrin and kindlin-1 treated animals sensory axons regenerated through tenascin-C-expressing connective tissue strands and bridges across the lesion then re-entered CNS tissue. Many axons regenerated rostrally to the level of the medulla but were excluded from the sensory nuclei. Regenerated axons were seen particularly at the white matter/grey matter boundary in the dorsal cord. Many branches into the dorsal horn were seen tipped with synaptic swellings. Stimulation of the sciatic nerve led to many neurons rostral to the injury being activated to express cFos. Behavioural recovery was seen in heat and pressure sensation and tape removal. Treatment of sensory neurons with 9 integrin and kindlin-1 therefore enables partial reconstruction of the spinal sensory 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/2023.03.13.532433v1?rss=1 Authors: Ly, M., Schimmer, C., Hawkins, R., Rothenberg, K., Fernandez-Gonzalez, R. Abstract: Embryos have a remarkable ability to repair wounds rapidly, with no inflammation or scarring. Embryonic wound healing is driven by the collective movement of the surrounding cells to seal the lesion. During embryonic wound closure, the cells adjacent to the wound polarize the cytoskeletal protein actin and the molecular motor non-muscle myosin II, which accumulate at the wound edge forming a supracellular cable around the wound. Adherens junction proteins including E-cadherin are internalized from the interface with the lesion and localize to former tricellular junctions at the wound margin, in a process necessary for cytoskeletal polarity. Using quantitative live microscopy, we found that the cells adjacent to wounds in the Drosophila epidermis also polarized Talin, a core component of cell-extracellular matrix (ECM) adhesions that links integrins to the actin cytoskeleton. Integrin knock-down and inhibition of integrin binding delayed wound closure and were associated with a reduction in actin levels around the wound. Additionally, disrupting integrins caused a defect in E-cadherin reinforcement at tricellular junctions along the wound edge, suggesting crosstalk between integrin-based and cadherin-based adhesions. Together, our results show that cell-ECM adhesion contributes to embryonic wound repair and reveal an interplay between cell-cell and cell-ECM adhesion in the collective cell movements that drive rapid wound healing. 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/2023.01.26.525744v1?rss=1 Authors: Baade, T., Michaelis, M., Prestel, A., Paone, C., Klishin, N., Scheinost, L., Nedielkov, R., Hauck, C. R., Moller, H. M. Abstract: Integrins are fundamental for cell adhesion and the formation of focal adhesions (FA). Accordingly, these receptors guide embryonic development, tissue maintenance and haemostasis, but are also involved in cancer invasion and metastasis. A detailed understanding of the molecular interactions that drive integrin activation, focal adhesion assembly, and downstream signalling cascades is critical. Here, we reveal a direct association of paxillin, a marker protein of focal adhesion sites, with the cytoplasmic tails of the integrin {beta}1 and {beta}3 subunits. The binding interface resides in paxillin's LIM3 domain, where based on the NMR structure and functional analyses a flexible, seven amino acid loop engages the unstructured part of the integrin cytoplasmic tail. Genetic manipulation of the involved residues in either paxillin or integrin {beta}3 compromises cell adhesion and motility. This direct interaction between paxillin and the integrin cytoplasmic domain identifies an alternative, kindlin-independent mode of integrin outside-in signalling particularly important for integrin {beta}3 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/2023.01.25.525562v1?rss=1 Authors: de la Fuente, A. G., Dittmer, M., Heesbeen, E., de la Vega-Gallardo, N., White, J. A., Young, A., Mayne, K., Falconer, J., McMurran, C. E., Innayatulah, M., Tiwari, V., Penalva, R., Ingram, R. J., Dombrowski, Y., Fitzgerald, D. C. Abstract: Myelin regeneration (remyelination) is essential to prevent neurodegeneration in demyelinating diseases such as Multiple Sclerosis but its efficiency declines with age. Regulatory T cells (Treg) recently emerged as critical players in tissue regeneration, including remyelination. However, the effect of ageing on Treg-mediated regenerative processes is poorly understood. Here, we show that expansion of aged Treg does not rescue age-associated remyelination impairment due to an intrinsically diminished capacity of aged Treg to promote oligodendrocyte differentiation and myelination. This decline in regenerative Treg functions can be rescued by a young environment. We identified Melanoma Cell Adhesion Molecule 1 (MCAM1) and Integrin alpha 2 (ITGA2) as novel candidates of Treg-mediated oligodendrocyte differentiation that decrease with age. Our findings demonstrate that ageing limits the neuroregenerative capacity of Treg, likely limiting their remyelinating therapeutic potential in aged patients and describe two novel mechanisms implicated in Treg-driven remyelination that may be targetable to overcome this limitation. 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/2022.12.19.521109v1?rss=1 Authors: Kumar, S., Stainer, A., Dubrulle, J., Simpkins, C., Cooper, J. Abstract: Integrins link the cytoskeleton to the extracellular matrix for cell movement. Integrin ligation stimulates tyrosine phosphorylation of integrin-associated proteins but the role of phosphorylation signaling in regulating integrin-cytoskeletal linkages and assembly of focal adhesions is unclear. Using spreading or migrating epithelial cells, we provide evidence that phosphorylated Cas (p130Cas, BCAR1), its binding partner, Crk, and inactive focal adhesion kinase (FAK) cluster together with inactive integrins at the cell periphery at sites that develop into focal adhesions containing F-actin, active integrins, active FAK and mechanosensing proteins such as vinculin and talin. Cas, Crk, Src family kinases (SFK) and Rac1 are required for focal adhesion formation and cell spreading, while vinculin is not needed for Cas clustering. Furthermore, Rac1 provides positive feedback onto Cas through reactive oxygen, opposed by negative feedback from the ubiquitin proteasome system. The results suggest that phosphorylation signaling precedes and regulates mechanosensing during focal adhesion formation. 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/2022.12.17.520852v1?rss=1 Authors: Wang, B., Liang, P., Wu, Y., Zheng, S., Zhang, J., Yang, S., Wang, J., Ma, S., Zhang, M., Gu, Z., Liu, Q., Jiang, W., Xing, Q. Abstract: Focal adhesions (FAs) are transmembrane protein assemblies mediating cell-matrix connection. Tools to manipulate the compositionally intricate and dynamic FAs are currently limited, rendering many fundamental hypotheses untestable. Although protein liquid-liquid phase separation (LLPS) has been tied to the organization and dynamics of FAs, the underlying mechanisms remain unclear. Here, we experimentally tune the LLPS of PXN/Paxillin, an essential scaffold protein of FAs, by utilizing light-inducible Cry2 system. In addition to nucleating FA components, light-triggered PXN LLPS potently activates integrin signaling and subsequently accelerates cell spreading. PXN favors homotypic interaction-driven LLPS in vitro. In cells, PXN condensates are associated with plasma membrane, and modulated by actomyosin contraction and client proteins of FAs. Interestingly, non-specific weak inter-molecular interactions, together with specific molecular interactions, underlie the multicomponent condensation of PXN, and are efficient to promote FA assembly and integrin signaling. Thus, our data establish an active role of PXN phase transition into a condensed membrane-associated compartment in promoting assembly/maturation of FAs. 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/2022.10.12.511145v1?rss=1 Authors: Goudswaard, L. J., Williams, C. M., Khalil, J., Burley, K. L., Hamilton, F., Arnold, D., Milne, A., Lewis, P. A., Heesom, K. J., Mundell, S. J., Davidson, A. D., Poole, A. W., Hers, I. Abstract: BackgroundPatients with coronavirus disease-19 (COVID-19) are at increased risk of thrombosis, which is associated with altered platelet function and coagulopathy, contributing to excess mortality. ObjectivesWe aimed to characterise the mechanism of altered platelet function in COVID-19 patients. MethodsThe platelet proteome, platelet functional responses and platelet-neutrophil aggregates were compared between patients hospitalised with COVID-19 and healthy control subjects using Tandem Mass Tag (TMT) proteomic analysis, Western blotting and flow cytometry. ResultsCOVID-19 patients showed a different profile of platelet protein expression (858 altered out of 5773 quantified). Levels of COVID-19 plasma markers were enhanced in COVID-19 platelets. Gene ontology (GO) pathway analysis demonstrated that levels of granule secretory proteins were raised, whereas some platelet activation proteins, such as the thrombopoietin receptor and PKC, were lowered. Basally, COVID-19 platelets showed enhanced phosphatidylserine (PS) exposure, with unaltered integrin IIb{beta}3 activation and P-selectin expression. Agonist-stimulated integrin IIb{beta}3 activation and PS exposure, but not P-selectin expression, were significantly decreased in COVID-19 patients. COVID-19 patients had high levels of platelet-neutrophil aggregates, even under basal conditions, compared to controls. This interaction was disrupted by blocking P-selectin, demonstrating that platelet P-selectin is critical for the interaction. ConclusionsOverall, our data suggests the presence of two platelet populations in patients with COVID-19: one with circulating platelets with an altered proteome and reduced functional responses and another with P-selectin expressing neutrophil-associated platelets. Platelet driven thromboinflammation may therefore be one of the key factors enhancing the risk of thrombosis in COVID-19 patients. Essentials- COVID-19 patient platelet function and platelet proteins were compared with healthy controls - Proteomic analysis of platelets indicated that COVID-19 decreased platelet activation proteins - Agonist induced PS exposure and integrin IIb{beta}3 activation were impaired in COVID-19 - COVID-19 led to maximal levels of P-selectin dependent platelet-neutrophil aggregates Copy rights belong to original authors. Visit the link for more info Podcast created by Paper Player, LLC

This week, please join authors Svati Shah and Senthil Selvaraj as well as Guest Editor and Editorialist Manuel Mayr as they discuss the article "Metabolomic Profiling of the Effects of Dapagliflozin in Heart Failure With Reduced Ejection Fraction: DEFINE-HF" and the editorial "SGLT2 Inhibitors in Heart Failure: Targeted Metabolomics and Energetic Metabolism." Dr. Carolyn Lam: Welcome to Circulation On Run, your weekly podcast summary and backstage pass to the journal and its editors. We're your co-hosts, I'm Dr. Carolyn Lam, Associate Editor from the National Heart Center and Duke National University of Singapore. Dr. Greg Hundley: And I'm Dr. Greg Hundley, Associate Editor, Director of the Pauley Heart Center at VCU Health Richmond, Virginia. Dr. Carolyn Lam: In today's feature paper, we will be talking about the metabolomic profiling of the effects of dapagliflozin in heart failure, and this is from the DEFINE-HF trial. It's just such a cool paper with a lot of insights you have to hear from the authors. But, before we get there, let's talk about some of the other papers in today's issue. Shall we, Greg? Dr. Greg Hundley: You bet, Carolyn. Well, how about if I go first? Dr. Carolyn Lam: Please. Dr. Greg Hundley: Thank you, Carolyn. My first paper comes to us from Professor Paulus Kirchhof from the Universitäres Herzzentrum in Hamburg. Carolyn, in the randomized EAST-AFNET 4 study, so the early treatment of atrial fibrillation for stroke prevention, these trial investigators demonstrated that systematic initiation of early rhythm control reduced adverse cardiovascular outcomes in patients with recently diagnosed atrial fibrillation and stroke risk factors. However, the effectiveness and safety of early rhythm control in patients with multiple cardiovascular comorbidities is not known. Carolyn, in this study, it was a prespecified sub-analysis of the EAST-AFNET 4 trial and it compared the effectiveness and safety of early rhythm control with usual care stratified into patients with high CHA2DS2-VASc scores of greater than or equal to 4. Dr. Carolyn Lam: Nice. Okay. Important question, what did they find? Dr. Greg Hundley: Right, Carolyn. Quite a bit of data in this study, so let's walk through it carefully. First, in regards to the study population, the EAST-AFNET 4 randomized 1093 patients with CHA2DS2-VASc scores of greater than or equal to 4, these were predominantly women, 61% female, and then also 1,696 patients with CHA2DS2-VASc of less than four, and these were predominantly men, so only 37% women. Now let's get to the date. Early rhythm control reduced the composite primary efficacy outcome of cardiovascular death, stroke, or hospitalization for worsening heart failure or for acute coronary syndrome in patients with high CHA2DS2-VASc scores of greater than 4, but not in patients with CHA2DS2-VASc scores of less than 4. Second, now Carolyn, the primary safety outcome, so death, stroke, or serious adverse events of rhythm control therapy, was not different between study groups in patients with high CHA2DS2-VASc scores of greater than 4, but occurred more often in patients with low CHA2DS2-VASc scores randomized to early rhythm control. Now Carolyn, life threatening events or death were not different between the groups. When female sex was ignored for the creation of high and lower groups, the interaction P was not significant for the primary efficacy outcome, but remained significant for the primary safety outcome. Dr. Carolyn Lam: Oh, you are right. A lot of interesting data here. What's a take home message? Dr. Greg Hundley: Right, Carolyn. So the take home message is the following. Patients with recently diagnosed atrial fibrillation and multiple cardiovascular comorbidities should be considered to have priority access to early rhythm control to reduce cardiovascular outcomes, and a specific trial of early rhythm control in these patients is really needed as a next step. Dr. Carolyn Lam: Oh, thank you, Greg. The next paper focuses on arrhythmogenic right ventricular cardiomyopathy, which we know is characterized by a high propensity to life threatening arrhythmias and progressive loss of heart muscle. More than 40% of reported genetic variants linked to arrhythmogenic right ventricular cardiomyopathy, or ARVC, reside in a gene called plakophilin-2, or PKP2. In today's paper, Dr. Delmar and Lundby from NYU Grossman School of Medicine and University of Copenhagen, respectively, and their colleagues, described a comprehensive characterization of the ARVC molecular landscape using a multidisciplinary approach including human samples from ARVC patients with PKP2 mutations and left ventricular ejection fraction above 45%, as well as PKP2-deficient murine and human induced pluripotent stem cell-derived cardiomyocytes. They studied all of these with comprehensive proteomics and functional analysis. Dr. Greg Hundley: Wow, Carolyn, another great study in circulation combining both preclinical murine models as well as data from human subjects. So, what did they find? Dr. Carolyn Lam: Precisely, Greg. Here's what they found. Loss of nuclear envelope integrity and subsequent DNA damage is a key substrate in the molecular pathology of AR VC. The authors further showed transcriptional down regulation of proteins of the electron transcript chain as an early event in the molecular pathophysiology of the disease prior to an ejection fraction falling below 45%. This associates with increased oxidant production, with the clinical message being, therefore, that the authors propose therapies that limit oxidant formation may be a possible intervention to restrict DNA damage in ARVC. Dr. Greg Hundley: Very nice, Carolyn. Okay, our next paper comes from Dr. Donald Lloyd-Jones from Northwestern University, the Feinberg School of Medicine. Carolyn, you can tell the change in inflection of my voice because it's time for another Carolyn's quiz. Carolyn, open-ended question. Can you remind us of life's essential eight? Dr. Carolyn Lam: Oh boy, Greg. It's like asking me to name the dwarfs. I know I'm going to forget one, but here you go. Diet, exercise, cholesterol, weight, smoking, sugar must be there, diabetes, blood pressure. You see, I got seven. What's the eighth? Dr. Greg Hundley: Yeah. Remember seven dwarfs, Sleepy. Dr. Carolyn Lam: Sleep. Dr. Greg Hundley: Very good. Great job, Carolyn. Dr. Carolyn Lam: Thank you. Dr. Greg Hundley: Recently, the American Heart Association recently published an updated algorithm for quantifying cardiovascular health, the Life's Essential 8 score. In this study, the investigative team quantified US levels of cardiovascular health using the new score. They included non-pregnant, non-institutionalized individuals aged 2 through 79 years who were free of cardiovascular disease from the National Health and Nutrition Examination Surveys that were conducted between 2013 and 2018. Now, for all participants, they calculated the overall cardiovascular health score, and it ranged from 0, which is really low, to 100, which is the highest, as well as the score for each component. And Carolyn, yes, you are very close. Remember the eight? Diet, physical activity, nicotine exposure, sleep duration, body mass index, blood lipids, blood glucose, and blood pressure, and they used published American Heart Association definitions of these. The cardiovascular health scores were assessed across strata of age, sex, race, ethnicity, family income, and depression. Dr. Carolyn Lam: Okay, Greg. What did they find? Dr. Greg Hundley: Right, Carolyn. There were 23,400 plus participants, representing 201,728,000 adults and 74 million children. The overall mean cardiovascular health score was 64.7 among adults using all eight metrics, and it was 65.5 for the three metrics available of diet, physical activity, and BMI among the children and adolescents that were aged 2 through 19 years. Now, for the adults there were significant differences in mean cardiovascular health scores by sex, age, and racial ethnic group. Mean scores were lowest for diet, physical activity, and the BMI metrics. There were large differences in mean scores across demographic groups for diet, nicotine exposure, blood glucose, and blood pressure. In children, diet scores were low, 40.6, and were progressively lower in higher age groups. Large differences were also noted in mean physical activity and BMI by sociodemographic group. Carolyn, this study basically identifies wide ranges of scores across multiple domains of the essential eight, and thus, this new Life's Essential 8 score helps identify large group and individual differences in cardiovascular health. Additionally, overall, cardiovascular health in the US population remains well below optimal levels, and there are both broad and targeted opportunities to monitor, preserve, and improve cardiovascular health across the life course in both individuals, as well as the population at large. Dr. Carolyn Lam: Wow. Thanks, Greg. Truly really interesting. Everyone's going to have to pick up that paper and all the other papers in this issue, because there's also an In Depth paper by Dr. Whelton on “Harmonization of the ACC/AHA and ESC/ESH Blood Pressure Hypertension Guidelines, Comparisons, Reflections, and Recommendations. There's a Research Letter by Dr. Munshi on the accurate classification of cardiomyopathy etiology by chromatin accessibility. Dr. Greg Hundley: Carolyn, I have got to report an exchange of letters from Professor Sun and Weng regarding the article, “Legumain Is an Endogenous Modulator of Integrin αvβ3 Triggering Vascular Degeneration, Dissection, and Rupture.” And then Carolyn, lastly, there's a Perspective piece from Professor Vidal-Petiot entitled, “Thresholds for Hypertension Definition, Treatment Initiation, and Treatment Targets: Recent Guidelines at a Glance.” Well, Carolyn, how about we get on to that feature discussion? Dr. Carolyn Lam: Yes, let's go Greg. Wow, we have a star stud cast for today's feature discussion, and on a star studied topic, if I may. It's on the SGLT2 inhibitors, this time in the DEFINE-HF study and really going into the mechanism of action of SGLT2 inhibitors. Now, that's one question I personally get all the time. How do these things work? Today's paper brings us one step closer, for sure, in the understanding. I'm so grateful to have the first author, Dr. Senthil Selvaraj from University of Pennsylvania, as well as the corresponding author of the paper, Dr. Svati Shah, associate editor, as well as the corresponding author from Duke Molecular Physiology Institute. We also have Dr. Manuel Mayr who was both the guest editor and editorialist for this paper, and Dr. Mayr is from Kings College London, British Heart Foundation Center. Welcome, everyone. Senthil, get us started here. The DEFINE-HF study, just a quick summary, what that was about and then what you did, what you found. Dr. Senthil Selvaraj: Absolutely. Good morning, everyone, or maybe good evening for your time, Carolyn, but we were very excited about this study and the ability to do targeted metabolomic profiling in DEFINE. This audience is well familiar with the fact that SGLT2 inhibitors are foundational therapy in heart failure reduced ejection fraction, and the interesting thing is, despite a lot of literature, we still don't know why. Whether it relates to change in inflammation or endothelial function, but given the mechanism of action, metabolism is sort of at its core. So in this study we sought to identify metabolic pathways that were associated with dapagliflozin treatment using this targeted metabolomics platform in which we assayed 63 metabolites, acylcarnitine, which are markers of fatty acid oxidation, several amino acids, and ketone-related metabolites. To do this, we studied 234 participants from DEFINE, which is a 12-week placebo-controlled trial of dapagliflozin in this population, and we perform principal components analysis for dimensionality reduction techniques. In this study, briefly we found that, first, our principal components analysis yielded 13 different factors that accounted for the substantial proportion in the variation of the data, and that two in particular, ketone-related metabolites and short acylcarnitines in factor 6, as well as medium-chain acylcarnitines in factor 7 were differentially associated with dapagliflozin treatment. Specifically, there were increases in several ketone-related metabolites and short acylcarnitines, as well as several medium-chain acylcarnitines, really speaking to, potentially, changes in fatty acid as well as ketone biology with dapagliflozin treatment. The second aim of our study was to look at changes in metabolites and changes in endpoint studying DEFINE, which included NT-proBNP as well as KCCQ scores. We found that dicarboxylate long-chain acylcarnitines and aromatic amino acids really related to worsening heart failure endpoints there. So, a lot to impact, a lot that we found, and appreciative about the opportunity. Dr. Carolyn Lam: Oh, wow. Thank you so much for that amazing summary. Svati, I've heard you speak so many times on metabolomics on our calls, but this is really so important. First, I think the question is, congratulations for thinking ahead of time to collect the samples and to do all of this. Congratulations on that. Could I ask if you went in with any specific hypothesis or were you surprised by these findings, Svati? Dr. Svati Shah: Yeah, Carolyn, thank you so much. It was such a pleasure to work with Senthil on this and I really want to highlight what an incredible early career investigator he is. He's really going to set the metabolism world on fire. I also wanted to say thank you to the PI of the clinical trial, the parent clinical trial DEFINE-HF Mikhail Kosiborod, who did the really hard work of collecting the samples along with the clinical trial itself. To me, what's really cool is to be able to take a clinical trial like this with really important clinical outcomes well adjudicated and to be able to dig into the mechanism at a metabolic level of what might be going on with SGLT2 inhibitors. Going into this, Carolyn, we suspected that ketone-related biology was at play. There have been studies in other populations, non-HFrEF populations, that have shown that SGLT2 inhibitors have what appears to be beneficial impacts on ketone biology and induced ketosis. So, going into this, we suspected that this ketone pathway was going to come up. I think what's exciting is, not only did we find that the ketone pathway was differential modified by dapagliflozin, but that it wasn't at the level of severe ketosis that we would be concerned about. And then secondly, we found pathways of fatty acid oxidation. Some related to the effects of the medication and some related to changes in functional outcome. So it really enhanced beyond what we already knew about ketone biology, expanded our understanding of potential mechanisms of SGLT2 inhibitors, and expanded this into the HFrEF space, Carolyn. Dr. Carolyn Lam: Oh, that's so nice. I'm bursting with questions, but I really, really have to ask Dr. Manuel Mayr, first, could you put these findings into context for us and tell us what they mean clinically? Dr. Manuel Mayr: Yeah, Carolyn. First of all, I want to join you in congratulating the authors to this important study. As Svati mentioned, previous studies have reported effects of SGLT2 inhibitors on ketone bodies, but the present study really adds to the literature because it uses the state of the art metabolomic techniques. It uses a technique called mass spectrometry, but they also have a rating of, I think, in total, 63 metabolites in over 200 patients. Mass spectrometry is becoming increasingly important for cardiovascular precision medicine because we can use it in clinical trials to provide an unbiased assessment of metabolites and proteins. So it's a very versatile technology. I think this study really adds to the rapidly growing literature that SGLT2 inhibition is a principle of unloading the failing heart from metabolic stress. Dr. Carolyn Lam: Wow, I really like that and your editorial is just beautiful. I love that you say, "After the serendipitous findings of improved heart failure outcomes with SGLT2 inhibitors, mechanisms were postulated, but studies, such as the one we're discussing, are needed to really uncover what's the real thing." Now, I know this may sound really oversimplified and so on, but I'd really love for Senthil or Svati to just bear with me as I ask, what are you going to say to people who go, "Okay, then we should just be downing ketones," Or, "We should be Working on the fatty acid parts of it," Or taking conclusions like that. What would you say to something like that? Dr. Senthil Selvaraj: I'm happy to go first. It's a really wonderful question and I do think that this study raises the question of whether we should be exogenously increasing ketone levels to provide some sort of benefit. I would say the jury's still out there. I think it's a hot topic right now. But there are also differences between how we raise key tone levels, whether you do that endogenously in the body, or whether you give something like a ketone supplement, so exogenous ketone supplementation. And I think that there are completely different physiologies there. So more to come. I think there are a lot of studies in this space. The ketogenic diet is something that I'm often asked as well, whether that might provide benefit to heart failure. There are a lot of ways that I can, but one thing that we need to be mindful of is the fact that it will reduce glycogen stores as well, which may impact exercise capacity. So, we need more data. I would say the other thing that we found in our studies, while they were increased in ketone levels and markers of fatty acid oxidation with dapagliflozin treatment, we aren't necessarily sure that those mediate the benefits of SGLT2 inhibitors. DEFINE has important clinically relevant endpoints, but it is not an event-based trial. And so we don't know and we can't link the changes in metabolites with changes in outcomes quite yet. Dr. Svati Shah: Carolyn, just to add to the wonderful response that Senthil just gave, I think we do have to be careful. We don't know whether these are direct effects of SGLT2 inhibitors or whether these are related to the caloric loss that we know happens with these medications. I think it's important to point out that we're looking in the blood, we don't actually know what's happening at the tissue level, so we do have to be a little bit careful. We have made inferences that this is reporting on substrate fuel selection in the heart, but we also suspect that skeletal muscle and other organs are heavily involved in some of the pathways we're seeing. So I just wanted to make those important caveat to the epidemiologic work that we do. Dr. Carolyn Lam: And those are so important, so thank you Senthil and Svati. Manuel, I'd love to invite your thoughts because you did sort of point out some of these points in your editorial. Could you maybe discuss a bit of those and raise any questions, perhaps? Dr. Manuel Mayr: Yes. I think Svati and Senthil have nicely mentioned already that these measurements are performed in plasma. So the changes in plasma could be due to, for example, increased production in the liver due to decreased consumption in other tissues. So I guess the next step would be, and I would be really interested on what the authors want to pursue, is to provide direct evidence for the energetic hypothesis, that really the heart is consuming these keto bodies and what type of measurements could be performed to provide direct evidence in humans for these metabolic hypothesis. Dr. Senthil Selvaraj: That's a really great question, Manuel. There was a really nice study that was published about a year or two ago in Science in which the authors did coronary sinus sampling. So really to get arterial venous gradients, measure substances in the arterial system as well as the coronary sinus venous system and get extraction. I think that that study would be very interesting to understand. You take patients on SGLT2 inhibitors, those who are not, and to understand what is the heart chewing on. Obviously more invasive than some other approaches, but other studies that I think would be really interesting in those space would be flux studies and stable isotope studies. Again, as Svati really nicely mentioned, these are systemic physiology snapshots whenever we do less localized techniques like that, but they're still very important because heart failure is a systemic process. Dr. Carolyn Lam: Anything to add, Svati? Dr. Svati Shah: No, I think you said it beautifully. I'll just say on the sort of epidemiologic side, to be able to link this to harder outcomes, DEFINE-HF wasn't really designed to be able to do that. So as we expand our understanding of SGLT2 inhibitors, understand different populations, and to link these pathways to more objective outcomes, I think, will be really useful, also. Dr. Carolyn Lam: Indeed. Manual, in your editorial, you actually discuss some of your own work, which may be the ones that Senthil is actually talking about. What is your view? Dr. Manuel Mayr: Well, I think I'm very excited that beyond fatty acid metabolism and glucose metabolism, ketones have extracted increasing attention. Ketone body metabolism, I think, has long been underappreciated. We still need to understand to what extent it really acts as a fuel and that it can help to overcome the energy deficit that creates heart failure. I think, as mentioned by Svati and Senthil, we need more studies in this area, and of course other trials are ongoing where they're going to measure, for example, the phosphocreatine to ATP ratio by using phosphor-NMR spectroscopy. So we get direct evidence whether there really is an energetic improvement upon SGLT2 inhibition. I think this will be studies to look forward to and to add to the growing literature that metabolism is important as a therapeutic target for heart failure. Dr. Carolyn Lam: Oh, such exciting times. You mentioned the EMPA-VISION trial in your editorial. I think I'm trying to tell everybody, you have to pick up the paper and the editorial. You're going to learn so much. This is so cool. Thank you so, so much all of you for being on this podcast, for sharing your thoughts. I'm sure everyone has learned a lot and enjoyed it just as I have. On behalf of Greg and I, thank you for being here, thank you for joining us today, and don't forget to tune in again next week. Thank you. Dr. Greg Hundley: This program is copyright of the American Heart Association 2022. The opinions expressed by speakers in this podcast are their own and not necessarily those of the editors or of the American Heart Association. For more, please visit ahajournals.org.

Compared to other interventions used in training cyclists (e.g. HIIT, heat acclimation, altitude training) eccentric cycling doesn’t have a lot of notoriety. In fact, this might be the first time you’ve ever heard of it. But just because eccentric cycling isn’t popular, doesn’t mean it can’t potentially benefit the performance of cyclists. In this episode we talk with eccentric cycling expert Dr. Georgios Mavropalias and explore what eccentric cycling is, its known benefits, whether or not it can improve cycling performance, and how to potentially apply it to your training program. Is eccentric cycling the next big intervention for cyclists? Time will tell. But it’s probably not a bad idea to get insight on it now so you can be keeping an eye on it for the future. Don’t forget, TCPCP listeners get an exclusive 20% discount off the InfoCrank Road or the InfoCrank Track (and any accessories!). Simply use the discount code performance20 at checkout on the InfoCrank website (www.infocrank.cc). This deal ends on 30-Sep-2022, so don’t hesitate to get yourself the most accurate power meter on the market and show support for the show! Guest panelist:Georgios Mavropalias, Ph.D.Staff PageResearchgateLinkedInTwitter: @x_centrik Episode References:Comparison between high- and low-intensity eccentric cycling of equal mechanical work for muscle damage and the repeated bout effect Increases in Integrin–ILK–RICTOR–Akt Proteins, Muscle Mass, and Strength after Eccentric Cycling Training Eccentric cycling does not improve cycling performance in amateur cyclists This is a listener supported podcast, and we would be stoked if you supported us by becoming a member of The Cycling Performance Club! With your backing we can continue our mission to deliver the best in cycling performance knowledge and practical advice to you and the greater cycling community. Support The Club by clicking here! Co-hosts:Jason Boynton, Ph.D.boyntoncoaching.com Cyrus Monkcyclistscientist.com Producer & co-host:Damian Rusesemiprocycling.com Website:

Compared to other interventions used in training cyclists (e.g. HIIT, heat acclimation, altitude training) eccentric cycling doesn’t have a lot of notoriety. In fact, this might be the first time you’ve ever heard of it. But just because eccentric cycling isn’t popular, doesn’t mean it can’t potentially benefit the performance of cyclists. In this episode we talk with eccentric cycling expert Dr. Georgios Mavropalias and explore what eccentric cycling is, its known benefits, whether or not it can improve cycling performance, and how to potentially apply it to your training program. Is eccentric cycling the next big intervention for cyclists? Time will tell. But it’s probably not a bad idea to get insight on it now so you can be keeping an eye on it for the future. Don’t forget, TCPCP listeners get an exclusive 20% discount off the InfoCrank Road or the InfoCrank Track (and any accessories!). Simply use the discount code performance20 at checkout on the InfoCrank website (www.infocrank.cc). This deal ends on 30-Sep-2022, so don’t hesitate to get yourself the most accurate power meter on the market and show support for the show! Guest panelist:Georgios Mavropalias, Ph.D.Staff PageResearchgateLinkedInTwitter: @x_centrik Episode References:Comparison between high- and low-intensity eccentric cycling of equal mechanical work for muscle damage and the repeated bout effect Increases in Integrin–ILK–RICTOR–Akt Proteins, Muscle Mass, and Strength after Eccentric Cycling Training Eccentric cycling does not improve cycling performance in amateur cyclists This is a listener supported podcast, and we would be stoked if you supported us by becoming a member of The Cycling Performance Club! With your backing we can continue our mission to deliver the best in cycling performance knowledge and practical advice to you and the greater cycling community. Support The Club by clicking here! Co-hosts:Jason Boynton, Ph.D.boyntoncoaching.com Cyrus Monkcyclistscientist.com Producer & co-host:Damian Rusesemiprocycling.com Website:

In this podcast, expert clinicians discuss the latest updates on anti-integrin therapy and S1P receptor modulators in IBD management.

In this podcast, expert clinicians will discuss new evidence on investigational agents, the anti-integrin and S1P-1 receptor modulators, that are in late-stage development for treating moderate to severe CD.

Commentary by Dr. Douglas Mann

Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2020.10.25.353904v1?rss=1 Authors: Li, F., Park, T. H., Sankin, G., Gilchrist, C., Liao, D., Chan, C. U., Mao, Z., Hoffman, B. D., Zhong, P. Abstract: Ultrasound or shockwave-induced cavitation is used therapeutically to stimulate neural and muscle tissue, but the mechanisms underlying this mechanotransduction are unclear. Intracellular calcium signaling is one of the earliest events in mechanotransduction. In this study, we investigate the mechanism of calcium signaling in individual HEK293T cells stimulated by single cavitation bubbles. Calcium responses are rare at cell-bubble distance that avoids membrane poration, even with overexpression of the mechanosensitive ion channel Piezo1, but could be increased in frequency to 42% of cells by attaching RGD beads to the apical surface of the cells. By using Piezo1 knockout and Piezo1-expressing cells, integrin-blocking antibodies, and inhibitors of P2X ion channels, key molecular players are identified in the RGD bead-enhanced calcium response: increased integrin ligation by substrate ECM triggers ATP release and activation of P2X-but not Piezo1-ion channels. These molecular players have not been examined previously in cavitation-induced calcium signaling. The resultant calcium influx causes dynamic changes in cell spread area. This approach to eliciting a calcium response with cavitation microbubbles without cell injury, and the uncovered mechanotransduction mechanism by which increased integrin-ligation mediates ATP release and calcium signaling will inform new strategies to stimulate tissues with ultrasound and shockwaves. Copy rights belong to original authors. Visit the link for more info

Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2020.10.06.327742v1?rss=1 Authors: Kliche, J., Ali, M., Ivarsson, Y. Abstract: The spike protein of the SARS-CoV-2 interacts with angiotensin converting enzyme 2 (ACE2) and enters the host cell by receptor-mediated endocytosis. Concomitantly, evidence is pointing to the involvement of additional host cell receptors, such as integrins. The cytoplasmic tails of ACE2 and integrin beta3 contain a plethora of predicted binding motifs. Here, we confirm the functionality of some of these motifs through affinity measurements. The class I PDZ binding motif in the ACE2 cytoplasmic tail binds the first PDZ domain of the scaffold protein NHERF3. The clathrin-adaptor subunit AP2 Mu2 interacts with an endocytic motif in the ACE2 with low affinity and the interaction is abolished by phosphorylation of Tyr781. Furthermore, the C-terminal region of integrin beta3 contains a LC3-interacting region, and its interaction with ATG8 domains is enhanced by phosphorylation. Together, our data provides possible molecular links between host cell receptors and endocytosis and autophagy Copy rights belong to original authors. Visit the link for more info

Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2020.06.26.133553v1?rss=1 Authors: Heller, J. P., Heintz, T. G., Kwok, J. C., Martin, K. R., Fawcett, J. W. Abstract: Retinal pigment epithelial (RPE) cells have been used in disease modelling and transplantation studies in retinal diseases. Several types of RPE cells have been trialed, ranging from primary cells and immortalized cell lines to stem cell-derived RPE cells. During aging and in disease, the extracellular environment of the RPE cells changes, interfering with RPE cell adhesion. We hypothesize that this could be a key problem in transplantation studies that have reported lack of adhesion and survival of the transplanted RPE cells. Integrins are essential for the proper function of the RPE, mediating adhesion to Bruch's membrane, and the binding and subsequent phagocytosis of photoreceptor outer segments. Variability that has been found in clinical trials might be due to the variability of cell types used and their expression profiles of surface molecules. Here, we set out to analyze integrin expression in primary rat RPE cells and in the human cell line ARPE-19 using immunochemistry. We found that both cell types express integrins to varying degrees. After long-term culturing, ARPE-19 cells resemble mature RPE cells, and increase integrin expression. We hence argue that it is important to test the properties of these cells prior to transplantation to avoid failure of adhesion and to facilitate correct function. Copy rights belong to original authors. Visit the link for more info

Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2020.05.07.082453v1?rss=1 Authors: Mossink, B., van Rhijn, J.-R., Wang, S., van Hugte, E., Linda, K., Bak, J., Verboven, A. H., Selten, M., Anania, A., Jansen, S., Keller, J. M., Klein Gunnewiek, T., Schoenmaker, C., Oudakker, A., Frega, M., van Bokhoven, H., Schubert, D., Nadif Kasri, N. Abstract: Activity in the healthy brain relies on concerted interplay of excitation (E) and inhibition (I) via balanced synaptic communication between glutamatergic and GABAergic neurons. A growing number of studies imply that disruption of this E/I balance is a commonality in many brain disorders, however, obtaining mechanistic insight into these disruptions, with translational value for the human patient, has typically been hampered by methodological limitations. Cadherin-13 (CDH13) has strongly been associated to attention-deficit/hyperactivity disorder and comorbid disorders such as autism and schizophrenia. CDH13 localises at inhibitory presynapses, specifically of parvalbumin (PV) and somatostatin (SST) expressing GABAergic neurons. However, the mechanism by which CDH13 regulates the function of inhibitory synapses in human neurons remains unknown. Starting from human induced pluripotent stem cells, we established a robust method to generate a homogenous population of SST and PV expressing GABAergic neurons (iGABA) in vitro, and co-cultured these with glutamatergic neurons at defined E/I ratios on micro-electrode arrays. We identified functional network parameters that are most reliably affected by GABAergic modulation as such, and through alterations of E/I balance by reduced expression of CDH13 in iGABAs. We found that CDH13-deficiency in iGABAs decreased E/I balance by means of increased inhibition. Moreover, CDH13 interacts with Integrin-{beta}1 and Integrin-{beta}3, which play opposite roles in the regulation of inhibitory synaptic strength via this interaction. Taken together, this model allows for standardized investigation of the E/I balance in a human neuronal background and can be deployed to dissect the cell-type specific contribution of disease genes to the E/I balance. Copy rights belong to original authors. Visit the link for more info

Guests: Baruch Kuppermann, MD, PhD Chair, Department of Ophthalmology UC Irvine Irvine, CA Theo Seiler, MD, PhD Head, Institute for Refractive and Ophthalmic Surgery Zurich, Switzerland

Allegro Ophthalmics’ executive team boasts a successful pedigree that began with starting ISTA and taking it public. Now, Vicken Karageozian, MD, president and CMO, says the company is six months away from receiving results from Phase II trials. Hear how the firm has advanced this promising new drug without venture capital.

Host: Vincent Racaniello Guests: Ruth Jarrett, Glen Nemerow, and Esther Schnettler At the Glasgow Science Festival microTALKS, Vincent speaks with Ruth, Glen, and Esther about their research on viruses and Hodgkin lymphoma, adenovirus structure and entry into cells, and interactions between arthropod borne viruses and their hosts. Links for this episode Glasgow Science Festival microTALKS Hodgkin lymphoma (Histopath) HHV-6 and Hodgkin lymphoma (PLoS One) Adenovirus entry (PLoS Path) Adenovirus membrane penetration (Virology) Mosquito pathways that limit CHIK replication (PLoS Negl Trop Dis) Tick antiviral RNAi (Nucl Acids Res) Video of this episode - view at YouTube Send your virology questions and comments (email or mp3 file) to twiv@twiv.tv

Thu, 30 Oct 2014 12:00:00 +0100 https://edoc.ub.uni-muenchen.de/18364/ https://edoc.ub.uni-muenchen.de/18364/1/Widmaier_Moritz.pdf Widmaier, Sven Moritz ddc:540, ddc:500, Fakultät für Chemie und Pharm

Tue, 13 May 2014 12:00:00 +0100 https://edoc.ub.uni-muenchen.de/17670/ https://edoc.ub.uni-muenchen.de/17670/1/Hermann_Michaela-Rosemarie.pdf Hermann, Michaela-Rosemarie

Tue, 3 Dec 2013 12:00:00 +0100 https://edoc.ub.uni-muenchen.de/16656/ https://edoc.ub.uni-muenchen.de/16656/1/Rohwedder_Ina.pdf Rohwedder, Ina ddc:540, ddc:500, Fakultät für Chemie und Pharmazie

Integrins are ubiquitously expressed adhesion receptors with important functions in cellular adhesion, proliferation, migration and signaling. These functions are determined by integrin trafficking through endosomal compartments and receptor affinity regulation. In this thesis, we identified the distal NxxY motif of the β1 integrin cytoplasmic tail as a molecular switch modulating a spatiotemporally controlled binding of two FERM-domain proteins in different cellular compartments. Kindlins mediate integrin activation at the plasma membrane and they dislodge upon internalization. In the endosomal compartment, the free cytoplasmic domain is subsequently bound by sorting nexin 17 (SNX17) to inhibit integrin degradation. We identified SNX17 as a new β1 integrin adaptor protein, which uses the kindlin-binding site in endosomal compartments to stabilize integrins and to promote their recycling back to the plasma membrane.

Dr. Louise Rodino-Klapac Discusses Alpha 7 Integrin As A Therapeutic Approach to Muscular Dystrophy Guest: Louise Rodino-Klapac, PhD, principal investigator, Center for Gene Therapy, The Research Institute at Nationwide Children’s Hospital. Access an abstract of this month’s featured research article: AAV-mediated Overexpression of Human a7 Integrin Leads to Histological and Functional Improvement in Dystrophic Mice. Mol Ther. 2013 Mar;21(3):520-5. doi: 10.1038/mt.2012.281. Epub 2013 Jan 15.

Dr. Louise Rodino-Klapac Discusses Alpha 7 Integrin As A Therapeutic Approach to Muscular Dystrophy Guest: Louise Rodino-Klapac, PhD, principal investigator, Center for Gene Therapy, The Research Institute at Nationwide Children’s Hospital. Access an abstract of this month’s featured research article: AAV-mediated Overexpression of Human a7 Integrin Leads to Histological and Functional Improvement in Dystrophic Mice. Mol Ther. 2013 Mar;21(3):520-5. doi: 10.1038/mt.2012.281. Epub 2013 Jan 15.

Sat, 9 Feb 2013 12:00:00 +0100 https://edoc.ub.uni-muenchen.de/15563/ https://edoc.ub.uni-muenchen.de/15563/1/Brunner_Eva_Dorothea.pdf Brunner, Eva Dorothea

Thu, 24 Jan 2013 12:00:00 +0100 https://edoc.ub.uni-muenchen.de/15294/ https://edoc.ub.uni-muenchen.de/15294/1/Frick_Alexandra.pdf Frick, Alexandra ddc:610, ddc:600,

Integrins constitute an important class of cell adhesion receptors, as they bidirectionally transduce information between the cytoplasm of biological cells and the surrounding extracellular matrix. By means of atomic force microscopy, spectroscopic measurements of the specific interactions of integrins with their corresponding ligands were performed. Basically, these experiments allow deep insights into cellular signal transduction, but despite sophisticated vibration isolation systems the acquired data exhibit very low signal-to-noise ratios that impair an accurate analysis. This drawback was overcome by a novel post-processing algorithm, which significantly reduces the noise and thus improves the signal-to-noise ratio. Thereby, previously invisible signal features can be revealed. Another important task when evaluating this kind of experiments is the identification of steplike transitions corresponding to unbinding events between the receptor-ligand bonds. To this end, a technique has been developed that can be adjusted to detect very low or narrow steps even if they are smooth and hidden by noise. By applying the noise reduction algorithm to force spectroscopy data obtained with living T lymphocytes, the onset force required for the extraction of a membrane tether could be observed for the first time. Using the step detection method, strong evidence of sub-10-pN steps was found. Moreover, it was shown that the chemokine SDF-1α leads to a strengthening of individual bonds between VLA-4, one type of integrins primarily involved in the early stages of chemokine-induced lymphocyte adhesion, and its ligand VCAM-1. The adhesion strengthening is accompanied by a stiffening of the integrins’ environment. It is independent of an intracellular binding site of VLA-4 to talin, the major intracellular factor involved in integrin affinity modulation. Further, the functional role of the integrin trans-membrane domains in receptor-ligand interactions was explored by analyzing the effects of two mutations of the integrin αvβ3 on cellular adhesion: a chimera encompassing the strongly dimerizing trans-membrane domain of glycophorin A and a point mutation known to induce trans-membrane domain dissociation. The results show that both constructs provoke strong cell adhesion. They correspond well to a three-state model of integrin activation. A resting state is activated by intracellular ligands to an intermediate state without trans-membrane domain separation. The dimerizing chimera mimics the intermediate state, which strengthens cellular adhesion.

Thu, 5 Jul 2012 12:00:00 +0100 https://edoc.ub.uni-muenchen.de/16020/ https://edoc.ub.uni-muenchen.de/16020/1/Radovanac_Korana.pdf Radovanac, Korana ddc:540, ddc:500, Fakultät für Chemie und Pharmazie

One of the most important hormones in the human stomach is the peptide gastrin. It is mainly required for the regulation of gastric pH but is also involved in growth and differentiation of gastric epithelial cells. In Helicobacter pylori infected patients, gastrin secretion can be upregulated by the pathogen, resulting in hypergastrinaemia. H pylori induced hypergastrinaemia is described as being a major risk factor for the development of gastric adenocarcinoma.

Guido Serini,University of Torino, Medical School, Cell Adhesion Dynamics, Turin, ITALY speaks on "Regulation of integrin adhesion receptors by conformation and traffic: implications for tumor angiogenesis". This seminar has been recorded by ICGEB Trieste

Activating integrin signaling may be an effective strategy for developing therapeutics to reduce leukocyte recruitment during inflammation.

Eine zunehmende Zahl von Daten aus der Fachliteratur weist immer deutlicher darauf hin, dass Tumor- und Stammzellen trotz aller funktionellen Unterschiede, wie beispielsweise der Destruktion von gesundem Gewebe bzw. Regeneration von zerstörtem Gewebe, offensichtlich wesentliche Gemeinsamkeiten aufzeigen, insbesondere hinsichtlich der molekularen Mechanismen, die z.B. den zellulären Prozessen Differenzierung/Transformation, Zellalterung, Apoptose und Migration/Invasion zugrunde liegen. Im Gegensatz zur Situation bei Tumorzellen ist die Rolle lysosomaler Cysteinproteasen in humanen mesenchymalen Stammzellen (hMSC) bei diesen Prozessen jedoch noch weitgehend unbekannt und sollte daher im Rahmen dieser Arbeit genauer definiert werden. So konnten wir erstmals nachweisen, dass lysosomale Cysteinproteasen sowohl in hMSC exprimiert als auch während deren Kultivierung sezerniert werden. Von den elf bekannten humanen lysosomalen Cystein¬proteasen (Cathepsine) wurden vor allem Cathepsin B und Cathepsin K durch extrazelluläre Matrix (EZM)-Proteine, insbesondere durch Vitronektin, in ihrer Expression beeinflusst und zeigten eine kontinuierliche Erhöhung der Expression im Verlauf von 21 Tagen. Eine vermehrte Sekretion nach Vitronektinstimulation wurde proteinche-misch bei Cathepsin B und X nachgewiesen. Im Gegensatz dazu hatten Stimulationen mit Kollagen I und Laminin keinen signifikanten Einfluss auf die Expression bzw. Freisetzung dieser Proteasen. Weitere Untersuchungen ergaben, dass das Adhäsions-/Migrationsverhalten der hMSC durch EZM-Proteine vor allem über deren Wechselwirkung mit Adhäsionsmolekülen (Integrinen) beeinflusst wird. Zudem kann auch Procathepsin X in Abhängigkeit von Integrin αvβ3 an hMSC binden. Durch die Interaktionen der hMSC mit EZM-Proteinen sowie mit Procathepsin X wird eine Reihe von Signaltransduktionswegen, darunter der ERK-Signalweg, aktiviert. In Transmigrationsversuchen mit Cathepsin X-defizienten hMSC wurde zudem nachgewiesen, dass Procathepsin X – im Gegensatz zur Konstellation bei Tumorzellen – keine bedeutende Rolle bei der Migration der hMSC spielt. Es kann daher davon ausgegangen werden, dass gegen dieses Enzym gerichtete Tumortherapiestrategien nur geringe (oder gar keine) Auswirkungen auf Stammzell-Mobilisation/Migration haben. Die im Rahmen dieser Arbeit erhobenen in vitro-Daten zeigen somit neue Erkenntnisse bezüglich der Regulation lysosomaler Cysteinproteasen durch extrazelluläre Matrixproteine in hMSC und stellen daher eine gute Basis für weitere in vitro- bzw. auch in vivo-Evaluierungen dar.

Background/Aims: Laminar shear stress is an important stimulus in the endothelium-dependent control of vascular tone and of vascular remodeling processes. Based on previous studies demonstrating integrin-mediated release of fibroblast growth factor 2 (FGF-2), we investigated whether shear stress-induced integrin activation requires the involvement of an extracellular protease. Methods: Cultured porcine aortic endothelial cells (PAEC) were exposed to laminar shear stress (16 dyn/cm(2)), whereas static cells served as controls. Results: Exposure of PAEC to shear stress led to an increased activity of a protease in supernatants. This protease could be characterized as elastase but was different from neutrophil and pancreatic elastases. The enhanced activity was accompanied by the activation of integrin alpha(v)beta(3) and p38 MAPK, and followed by an increased FGF-2 concentration in the supernatant. Pretreatment with inhibitors of either elastase or integrin alpha(v)beta(3) resulted in a reduction of FGF-2 release. The observed effects of shear stress on integrin alpha(v)beta(3) and p38 MAPK activation, as well as on FGF-2 release could be mimicked by application of pancreatic elastase to static endothelial cells. Conclusion: By inducing the release of an endothelial elastase, shear stress induces an integrin-dependent release of FGF-2 from endothelial cells. Copyright (C) 2011 S. Karger AG, Basel

Targeting interactions between HLA-I and the integrin beta4 subunit is a potential strategy for preventing transplant rejection.

Fri, 12 Mar 2010 12:00:00 +0100 https://edoc.ub.uni-muenchen.de/11382/ https://edoc.ub.uni-muenchen.de/11382/1/Hennig_Theres.pdf Hennig, Theres ddc:540, dd

Thu, 4 Mar 2010 12:00:00 +0100 https://edoc.ub.uni-muenchen.de/11688/ https://edoc.ub.uni-muenchen.de/11688/1/Lange_Anika.pdf Lange, Anika ddc:540, ddc:500, Fakultät für Chemie un

Thu, 28 Jan 2010 12:00:00 +0100 https://edoc.ub.uni-muenchen.de/11407/ https://edoc.ub.uni-muenchen.de/11407/1/Stieger_Sabine_H.pdf Stieger, Sabine Hariett

Translocation of the Helicobacter pylori (Hp) cytotoxin-associated gene A (CagA) effector protein via the cag-Type IV Secretion System (T4SS) into host cells is a major risk factor for severe gastric diseases, including gastric cancer. However, the mechanism of translocation and the requirements from the host cell for that event are not well understood. The T4SS consists of inner- and outer membrane-spanning Cag protein complexes and a surface-located pilus. Previously an arginine-glycine-aspartate (RGD)-dependent typical integrin/ligand type interaction of CagL with alpha5beta1 integrin was reported to be essential for CagA translocation. Here we report a specific binding of the T4SS-pilus-associated components CagY and the effector protein CagA to the host cell beta1 Integrin receptor. Surface plasmon resonance measurements revealed that CagA binding to alpha5beta1 integrin is rather strong (dissociation constant, K(D) of 0.15 nM), in comparison to the reported RGD-dependent integrin/fibronectin interaction (K(D) of 15 nM). For CagA translocation the extracellular part of the beta1 integrin subunit is necessary, but not its cytoplasmic domain, nor downstream signalling via integrin-linked kinase. A set of beta1 integrin-specific monoclonal antibodies directed against various defined beta1 integrin epitopes, such as the PSI, the I-like, the EGF or the beta-tail domain, were unable to interfere with CagA translocation. However, a specific antibody (9EG7), which stabilises the open active conformation of beta1 integrin heterodimers, efficiently blocked CagA translocation. Our data support a novel model in which the cag-T4SS exploits the beta1 integrin receptor by an RGD-independent interaction that involves a conformational switch from the open (extended) to the closed (bent) conformation, to initiate effector protein translocation.

Die Charakterisierung und Kultivierung von Tumorzelllinien mit Hilfe einer zweidimensionalen (2D) Zellkultur gilt als Standardmethode in der Zellbiologie. Dreidimensionale (3D) Modelle gewinnen jedoch immer mehr an Bedeutung, da sie die Tumorbiologie in Bezug auf physiologisch relevante Zusammenhänge bei der Tumorentstehung und –progression besser abbilden als eine herkömmliche 2D-Kultur. Die auf poly-HEMA beschichteten Zellkulturplatten induzierten multizellulären Tumorspheroide reflektieren die Morphologie von avaskularen Tumoren und Mikrometastasen. In der vorliegenden Arbeit werden anhand von HER2-überexprimierenden Tumorzelllinien die Unterschiede der HER2-Signalaktivierung und –weiterleitung in 2D- und 3D-Kultur umfassend beschrieben. In 3D-Kultur konnte ohne Zugabe von zusätzlichen Wachstumsfaktoren eine stärkere HER2-Phosphorylierung beobachtet werden. Bei der Brusttumorlinie SKBR-3 bildet HER2 in 2D-Kultur bevorzugt Heterodimere mit HER3, wohingegen in Spheroiden HER2-Homodimere vorliegen. Diese Homodimere lokalisieren in lipidreichen Mikrodomänen und begünstigen die Aktivierung des Ras-MAPK-Wegs, der die Proliferation der Tumorzellen reguliert. Mit Hilfe des therapeutischen Antikörpers Trastuzumab, der spezifisch für HER2 ist, kann die Proliferation der Zellen und die Phosphorylierung von HER2 im 3D-System besser inhibiert werden. Zusätzlich konnte in 3D eine Herunterregulierung des HER2/HER3 assoziierten PI3K-Akt-Signalwegs nachgewiesen werden. Bei SKBR-3 war in 3D-Kultur neben der stärkeren Phosphorylierung von MAPK auch die Aktivierung der Integrin 4/Rac1/PAK2-Signalkaskade zu beobachten. Des Weiteren wurde im Rahmen dieser Arbeit in 3D-Kultur die Zelllinie SKBR-3 HR generiert, die resistent gegen die Behandlung mit Trastuzumab ist. Die Charakterisierung dieser Linie zeigte eine verstärkte Expression von DARPP-32 und eine gesteigerte HER2/HER3-Heterodimerbildung, gefolgt von einer Hochregulierung des PI3K-Akt-Wegs. Das Gen für DARPP-32 liegt im ERBB2-Amplikon und liegt bei vielen Brusttumorproben und –zelllinien amplifiziert vor. Es konnte gezeigt werden, dass die induzierte Resistenz reversibel ist und die erneut Trastuzumab responsiven Zellen eine schwächere Expression von DARPP-32 aufwiesen, gefolgt von einer reduzierten Aktphosphorylierung. Die Ergebnisse dieser Arbeit weisen darauf hin, dass das beschriebene 3D-Modell einige in vivo Aspekte des HER2-Signalmusters besser reflektiert und deshalb als Basis für die weitere Aufklärung des Wirkmechanismus von Trastuzumab dienen kann. Außerdem kann dieses 3D-System zur Identifizierung von neuen Zielmolekülen herangezogen werden um Therapiestrategien zu entwickeln, welche eine Behandlung der HER2-positiven Patientenpopulation erlaubt, die bisher nur suboptimal auf die Behandlung mit Trastuzumab angesprochen haben.

Fri, 29 May 2009 12:00:00 +0100 https://edoc.ub.uni-muenchen.de/11960/ https://edoc.ub.uni-muenchen.de/11960/1/Raducanu_Aurelia.pdf Raducanu, Aurelia ddc:540, ddc:500, Fakultät für Chemie und Pharmazie

Thu, 28 May 2009 12:00:00 +0100 https://edoc.ub.uni-muenchen.de/10659/ https://edoc.ub.uni-muenchen.de/10659/1/Jimenez_Soto_Luisa_Fernanda.pdf Jimenez Soto, Luisa Fernanda ddc:61

Atheromatöse Plaques sind vulnerabel, und deren Ruptur kann die Bildung gefäßverschließender plättchen- und fibrinreicher Thromben induzieren, welche akute Myokardinfarkte und ischämische Schlaganfälle verursachen können. Bisher geht man davon aus, dass der Plaque-„tissue factor“ als Aktivator der extrinsischen Blutgerinnung und Stimulator der Thrombin-vermittelten Plättchenaktivierung und Aggregation die bedeutendste prothrombogene Substanz atheromatöser Läsionen darstellt. Zu Beginn dieser Arbeit war nicht geklärt, ob und wie das lipidreiche atherosklerotische Plaquematerial auch direkt mit den Thrombozyten im Blut interagieren und auf diese Weise die Bildung eines gefäßverschließenden Plättchenthrombus induzieren kann. Die atheromatösen Läsionen von mehr als 60 verschiedenen Patienten mit Karotisstenose wurden mittels Endarterektomie isoliert und Kollagen Typ I- und Kollagen Typ III-positive, morphologisch äußerst heterogene Strukturen in den Plaques identifiziert, welche direkt die Adhäsion, Sekretion und Aggregation von Plättchen in Puffer, Plasma und Blut stimulierten. Darüber hinaus lösten die Plaques auch die Bildung von Thrombozyten-Monozyten-Aggregaten sowie eine plättchenbeschleunigte Fibrinbildung und Gerinnung aus. Unter arteriellen Flussbedingungen induzierten die kollagenpositiven Komponenten des Plaquematerials die Adhäsion, das Ausbreiten und die Aggregatbildung der Thrombozyten. Die Plaque-stimulierte Plättchenaggregatbildung erfolgte sehr rasch (< 5 min) und wurde in Hirudin-antikoaguliertem Blut beobachtet, was darauf schließen lässt, dass diese direkt und unabhängig von der Plaque-„tissue factor“-vermittelten Koagulation erfolgte und sehr wahrscheinlich für die initiale und schnelle Thrombusbildung nach einer Plaqueruptur in vivo von Bedeutung ist. Sowohl die Ergebnisse mit humanen, als auch mit murinen Blutplättchen wiesen auf eine essentielle Rolle morphologisch diverser Kollagen Typ I- und Kollagen Typ III-positiver Plaquestrukturen und des thrombozytären Kollagenrezeptors GPVI bei der durch atheromatöse Läsionen stimulierten Plättchenformveränderung, Adhäsion, Ausbreitung, Sekretion und Aggregation im statischen System und unter arteriellen Flussbedingungen hin. Der zweite bedeutende thrombozytäre Kollagenrezeptor, das Integrin α2β1, schien hingegen nicht an der durch die atheromatösen Läsionen hervorgerufenen Plättchenadhäsion und Aggregation im statischen System und unter Fluss beteiligt zu sein. Diese Beobachtungen führten zur Annahme, dass die Verabreichung von z. B. spezifischen anti-GPVI-Antikörpern oder löslichem GPVI-Protein, welche die Interaktion des thrombozytären GPVI-Rezeptors mit dessen Liganden im Plaquegewebe (Kollagen Typ I/Typ III) inhibieren, viel versprechende neue und effektive antithrombotische Strategien zur frühen Prävention kardio- und cerebrovaskulärer Gefäßverschlüsse darstellen könnten. Der thrombozytäre VWF-Rezeptor GPIbα war weder im gerührten System, noch unter Fluss mit niedrigeren Scherraten von 500 s-1 von Bedeutung für die durch atheromatöse Plaques induzierte Plättchenaggregation im Blut. Unter arteriellen Flussbedingungen mit höheren Scherraten von 1500 s-1 allerdings resultierte die Blockade von GPIbα in einer starken Reduktion (77±5%) der Plaque-stimulierten Thrombozytenadhäsion und Aggregatbildung. Dies lässt darauf schließen, dass unter diesen Strömungebedingungen auch die Interaktion des VWF mit dem Plättchen-GPIbα-Rezeptor eine wichtige Rolle für die Thrombusbildung nach Plaqueruptur spielt. Sowohl die ADP-Rezeptor-Antagonisten MRS2179 (P2Y1-Antagonist) und AR-C69931MX (P2Y12-Antagonist), als auch Aspirin® konnten die Plaque-vermittelte Thrombozytenaggregation in gerührtem PRP und Blut signifikant verringern, wobei die Kombination aller drei Plättchenhemmer am effektivsten wirkte und die Plaque-induzierte Aggregation vollständig inhibierte. Unter arteriellem Fluss (Scherraten: 1500 s-1) wirkten MRS1279, AR-C69931MX sowie deren Kombination allerdings deutlich weniger effizient als im statischen System und reduzierten die Plaque-stimulierte Plättchenaggregatbildung nur um 35±14%, 32±13% und 58±12%. Überraschender Weise führte die Zugabe von Aspirin® unter Fluss zu keiner signifikanten Reduktion der Plaque-induzierten Thrombozytenaggregatbildung. Diese Ergebnisse lassen vermuten, dass ADP-Rezeptor-Antagonisten sowie Aspirin® die Bildung eines gefäßverschließenden Thrombus nach Plaqueruptur eher ineffizient hemmen dürften. Die atheromatösen Plaquehomogenate verschiedener Patienten wiesen unterschiedliche thrombozytenaktivierende Eigenschaften auf, welche weder auf deren variierenden Gehalt an löslichem Kollagen, noch auf die unterschiedliche Morphologie der Kollagen Typ I- und Kollagen Typ III-positiven Plaquekomponenten zurückgeführt werden konnte. Weiterhin verhielt sich sowohl fibrilläres als auch lösliches Kollagen Typ I und Kollagen Typ III anders als das Plaquematerial bezüglich der Plättchenaggregation im PRP. Die Bindung des thrombozytären GPVI-Rezeptors an das Plaquematerial stellte die Voraussetzung für die Plättchenaktivierung der Plaques dar, wobei jedoch keine eindeutige positive Korrelation zwischen der GPVI-Bindung und der Aktivität der atheromatösen Läsionen verschiedener Patienten hergestellt werden konnte. Der Grund für die unterschiedliche Thrombozytenaktivierung induziert durch das Plaquematerial verschiedener Patienten bleibt letztlich also unklar. Die weitere Erforschung möglicher Ursachen für die unterschiedlichen plättchenaktivierenden Eigenschaften der lipidreichen atheromatösen Läsionen verschiedener Patienten stellt eine interessante und vor allem klinisch relevante zukünftige Fragestellung dar.

Fri, 25 Jul 2008 12:00:00 +0100 https://edoc.ub.uni-muenchen.de/9597/ https://edoc.ub.uni-muenchen.de/9597/1/Schmitz_Julia.pdf Schmitz, Julia ddc:530, ddc:500, Fakultät für Physik

The extracellular matrix (ECM) provides the structural frame for the development of tissues and organs. The ECM is bound by numerous membranous matrix-adhesion molecules and thereby triggers intracellular signals that control various cellular functions such as survival, polarity, proliferation and differentiation. Integrins represent an important family of ECM adhesion molecules which link the ECM with the intracellular actin-cytoskeleton. Integrin mediated adhesion structures also serve as important signaling platforms, although the integrin itself does not harbors any catalytic domains. Therefore integrin signaling depends on the recruitment of a number of cytoplasmic proteins that directly or indirectly bind to the short cytoplasmic integrin tails. During my PhD thesis I worked on three of these molecules, ILK, Kindlins and Palladin, and used the mouse as a model system to address their in vivo function. First, I investigated the role of integrin-linked kinase (ILK) in skeletal muscle. Loss of ILK expression in mice leads to peri-implantation lethality due to a cell polarization defect of the early embryo and abnormal actin accumulations. Studies in Caenorhabditis elegans and Drosophila melanogaster revealed an essential function for ILK in the attachment of actin filaments to the membrane of muscle cells and lack of ILK expression results in early lethality during embryogenesis. We generated mice with a skeletal muscle-restricted deletion of ILK that developed a mild, but progressive muscular dystrophy. This phenotype is predominantly restricted to myotendinous junctions (MTJs). Ultrastructural analyses showed muscle cell detachment from the basement membranes, and an accumulation of extracellular matrix. Endurance exercise training enhances the defect leading to disturbed subsarcolemmal myofiber architecture and an abrogation of the phosphorylation of Ser473 as well as Thr308 of protein kinase B (PKB)/Akt. The reduction in PKB/Akt activation is accompanied by an impaired insulin-like growth factor 1 receptor (IGF-1R) activation. Second, I studied the expression and in vivo function of a further integrin- and actin- associated protein, palladin. Palladin belongs to the palladin/myotilin/myopalladin protein family. Palladin represents a phosphoprotein which plays an important role in cell adhesion and motility. Initially, I characterized the gene structure and the expression pattern of palladin. The palladin gene spans about 400 kb, with 25 exons and 3 alternative promoters resulting in at least three different isoforms (200 kDa, 140 kDa and 90-92 kDa) in mice. Using RT-PCR and in situ hybridizations of embryonic and adult tissues, I could show that the 200kDa isoform is predominantly expressed in heart and skeletal muscle. In contrast, the 140kDa isoform is expressed in various tissues and represents the major palladin isoform of the brain. The 90-92 kDa isoform is almost ubiquitously expressed with highest levels in tissues rich in smooth muscle, like bladder, uterus, small intestine and colon. The expression of the 200kDa isoform was characterized in more detail with a polyclonal antibody showing that this isoform localizes to the Z-discs of heart and skeletal muscle cells. In vitro differentiation experiments with a mouse myoblast cell line revealed an induction of the 200kDa isoform during myoblast fusion and differentiation suggesting that the biggest palladin isoform may serve as a molecular scaffold during myogenesis. Third, I specifically inactivated the largest palladin isoform in mice. Lack of the 200 kDa palladin isoform has no impact on the development, viability and fertility of mice. However ultrastructural analyses by transmission electron microscopy (TEM) showed a mild cardiac myopathy due to disintegration of myofibrils. In collaboration with the group of Olli Carpén, we generated palladin 200 kDa isoform/ myotilin double knockout mice. Myotilin is also expressed in heart and skeletal muscle. Ablation of both myotilin and palladin 200 kDa isoform in mouse revealed in addition to the mild cardiac myopathy a structural and functional impairment of skeletal muscle. Finally, I was also involved in the characterization of the expression and subcellular localization of a novel family of integrin associated proteins: the Kindlins. The Kindlin family consists of three members, Kindlin-1, -2 and -3. Mutations in Kindlin-1 cause a human disease, called Kindler Syndrome, which represents a skin blistering disease affecting the actin cytoskeleton of basal keratinocytes. Kindlin gene expression was first analyzed at the mRNA level by RT-PCR and Northern Blot studies. In situ hybridizations showed that Kindlin-1 is preferentially expressed in epithelia. Kindlin-2 is expressed in all tissues with highest levels in striated and smooth muscle cells. While both localize to integrin-mediated adhesion sites in cultured keratinocytes Kindlin-2, but not Kindlin-1, colocalizes with E-cadherin to cell-cell contacts in differentiated keratinocytes. In contrast, Kindlin-3 expression is restricted to hematopoietic cells. Using a Kindlin-3-specific antiserum and an EGFP-tagged Kindlin-3 construct, we could show that Kindlin-3 is present in podosomes, which are specialized adhesion structures of hematopoietic cells.

Thu, 29 May 2008 12:00:00 +0100 https://edoc.ub.uni-muenchen.de/8607/ https://edoc.ub.uni-muenchen.de/8607/1/Then_Cornelia.pdf Then, Cornelia

Fri, 9 May 2008 12:00:00 +0100 https://edoc.ub.uni-muenchen.de/12502/ https://edoc.ub.uni-muenchen.de/12502/1/Lorenz-Baath_Katrin.pdf Lorenz-Baath, Katrin ddc:540, ddc:500, F

Cathepsine sind lysosomale Cysteinproteasen, die neben der allgemeinen Proteindegradation in Lysosomen auch spezifische Funktionen ausüben, die eine limitierte Proteolyse erfordern. Zudem werden Cathepsine sezerniert, weshalb man sie auch im Extrazellulärraum findet, wo sie ebenfalls an verschiedenen biologischen Vorgängen, wie etwa der Zellmigration/Invasion, teilnehmen. Über Cathepsin X, einen relativ neu entdeckten Vertreter dieser Proteinklasse, war zu Beginn der Promotionsarbeit noch wenig bekannt. Die Struktur und das Aktivitätsprofil konnten zwar bereits gelöst werden, über mögliche (patho-)physiologische Funktionen gab es jedoch noch keine Erkenntnisse. Das Hauptziel meiner Untersuchungen war daher, mittels geeigneter Methoden nähere Aufschlüsse über die Rolle von Cathepsin X oder seiner Proform innerhalb und außerhalb der Zelle zu erlangen. Dies sollte vorwiegend durch die Analyse der Expression und Sekretion dieser Protease, sowie durch das Auffinden von Interaktionspartnern erfolgen. Wie sich in Vorversuchen zeigte, wird Cathepsin X in humanen Leukozyten unterschiedlich stark exprimiert. Da eine hohe Expression insbesondere in Monozyten vorlag, wurde für weitere Analysen das Zellmodell THP-1 eingesetzt, das auch für die Differenzierung zu Makrophagen-ähnlichen Zellen durch Stimulation mit Phorbol-12-Myristat-13-Acetat (PMA) oder all-trans Retinsäure (ATRA) verwendet werden kann. Interessanterweise zeigten diese Agenzien unterschiedliche Auswirkungen auf die Expression und Sekretion von Cathepsin X. So wurde mit PMA eine starke intra- und extrazelluläre Erhöhung der Protease verzeichnet, während mit ATRA das Gegenteil der Fall war. Da eine differenzielle Expression von Cathepsin X in Leukozyten auf eine mögliche Funktion in der Entzündungsantwort hindeutet, schien eine Untersuchung der Wirkung von proinflammatorischen Zytokinen und extrazellulären Matrix (EZM)-Proteinen sinnvoll, weil diese Faktoren ebenfalls die Sekretion von Proteasen beeinflussen können. Die untersuchten Zytokine hatten allerdings keinen Effekt auf die Sekretion von Cathepsin X aus THP-1-Zellen, wohingegen mit dem EZM-Protein Vitronektin eine Verdopplung der Cathepsin-X-Konzentration im Medium beobachtet wurde. In diesem Kontext konnte nachgewiesen werden, dass Vitronektin durch die Interaktion mit dem Zelloberflächenrezeptor Integrin avb3 den Sekretionsapparat der Zelle beeinflusst, wobei offensichtlich das Sequenzmotiv Arginin-Glyzin-Aspartat (RGD), welches in Vitronektin enthalten ist, für diesen Vorgang entscheidend ist. Neben Cathepsin X wurde auch für die Cathepsine B und L eine erhöhte Freisetzung nach Inkubation mit Vitronektin gemessen, was zeigt, dass dieser durch das EZM-Protein ausgelöste Mechanismus nicht auf Cathepsin X beschränkt ist. Umgekehrt ließ sich in einem weiteren Zellmodell (HUVEC) durch den Einsatz von „small-interfering RNA“ (siRNA) die Expression von Cathepsin X erniedrigen, was zu einer verminderten Migration der HUVEC in einem Invasionsversuch führte. Dies deutet auf eine Funktion von Cathepsin X in der Zellmotilität hin. Weil Cathepsin X, ähnlich wie Vitronektin, ein exponiertes RGD-Motiv in seiner Proregion aufweist, sollte nun eine mögliche Interaktion mit Integrinen untersucht werden. Tatsächlich ließ sich eine RGD-abhängige Interaktion von Procathepsin X mit dem Integrin avb3 zeigen. Somit werden in dieser Arbeit zwei wesentliche neue Aspekte in der Regulation der Sekretion und seiner Beteiligung an Migrationsvorgängen gezeigt, wobei die Interaktion von Procathepsin X mit dem Integrin avb3 eine besondere Rolle zu spielen scheint. Ob diese beiden Vorgänge miteinander gekoppelt sind, konnte mit den bisherigen Ergebnissen noch nicht bewiesen werden. Insgesamt deuten die Ergebnisse jedoch darauf hin, dass extrazelluläres (Pro)Cathepsin X neben seiner Rolle als Protease auch nicht-proteolytische Funktionen, beispielsweise als Ligand bestimmter Zelloberflächenstrukturen ausüben kann. Dieser Aspekt könnte im Hinblick auf eine therapeutische Inhibition von Angiogenese und Metastasierung von Tumorzellen durch Antikörper gegen Cathepsin X und/oder Integrine von großem Nutzen sein.

Thu, 24 Apr 2008 12:00:00 +0100 https://edoc.ub.uni-muenchen.de/9971/ https://edoc.ub.uni-muenchen.de/9971/1/Bauer_Martina.pdf Bauer, Martina ddc:540, ddc:5

Zelladhäsion wird durch definierte Erkennungsepitope der extrazellulären Matrixproteine vermittelt. Diese werden durch Plasmamembranproteine erkannt und gebunden. Unter den Zelladhäsionsrezeptoren dominieren Integrine. Im Mittelpunkt dieser Arbeit stand die Entwicklung eines Modellsystems, das eine detaillierte Untersuchung von Zell-Oberflächen-Interaktionensprozessen ermöglicht.

Wed, 28 Mar 2007 12:00:00 +0100 https://edoc.ub.uni-muenchen.de/13466/ https://edoc.ub.uni-muenchen.de/13466/1/Grashoff_Carsten.pdf Grashoff, Carsten ddc:540, ddc:500, Fakultät für Chemie und Pharmazie

Tumorendothelmarker (TEM) 5 gehört zu den Adhäsions-G-Protein-gekoppelten Rezeptoren und wird in Endothelzellen während der physiologischen Angiogenese und Tumorangiogenese exprimiert. Bisher wurden noch kein Ligand und keine Funktion von TEM5 beschrieben. In dieser Arbeit wurde gezeigt, dass TEM5 in Endothelzellen während der In Vitro-Angiogenese intrazellulär an einer konservierten Proteolysestelle (GPS) gespalten wird. Diese Proteolyse führte einerseits zur Translokation der nicht-kovalent verbunden TEM5-Fragmente an die Zelloberfläche und andererseits zur Freisetzung von löslichem TEM5 (sTEM5). Bindungsstudien haben ergeben, dass sTEM5 mit verschiedenen Glykosaminoglykanen interagiert. Sequenzanalysen und funktionelle und biochemische Studien haben gezeigt, dass sTEM5 eine kryptische RGD-Bindungsstelle für Integrin alpha(v)beta(3) enthält. Matrixmetalloprotease 9-prozessiertes, jedoch nicht unprozessiertes, sTEM5 vermittelte Endothelzelladhäsion durch direkte Interaktion mit Integrin alpha(v)beta(3). Die Interaktion von immobilisiertem proteolytisch prozessierten sTEM5 mit Integrin alpha(v)beta(3) vermittelte Überleben von Wachstumsfaktor-deprivierten Endothelzellen. Die Ergebnisse dieser Arbeit führen zu der Schlußfolgerung, dass sTEM5 während der Angiogenese von Endothelzellen freigesetzt wird und an Glykosaminoglykane in der extrazellulären Matrix und auf der Oberfläche von Zellen bindet. Proteolytische Prozessierung von sTEM5 führt zur Freilegung seines RGD-Motivs und vermittelt Überleben von Endothelzellen durch die Interaktion mit Integrin alpha(v)beta(3).

Alterations in glomerular podocyte cell-cell and cell-matrix contacts are key events in progressive glomerular failure. Integrin-linked kinase (ILK) has been implicated in podocyte cell matrix interaction and is induced in proteinuria. To evaluate ILK function in vivo, mice with a Cre-mediated podocyte-specific ILK inactivation were generated. These animals appeared normal at birth, but developed progressive focal segmental glomerulosclerosis and died in terminal renal failure. The first ultrastructural lesion seen at onset of albuminuria are glomerular basement membrane (GBM) alterations with a significant increase in true harmonic mean GBM thickness. Podocyte foot processes effacement and loss of slit diaphragm followed with progression to unselective proteinuria. No significant reduction of slit-membrane molecules (podocin and nephrin), key GBM components (fibronectin, laminins and collagen IV isoforms) or podocyte integrins could be observed at onset of proteinuria. However, alpha3-integrins were relocalized into a granular pattern along the GBM, consistent with altered integrin mediated matrix assembly in ILK-deficient podocytes. As the increased GBM thickness precedes structural podocyte lesions and key components of the GBM were expressed at comparable levels to controls, our data imply an essential role of ILK for the close interconnection of GBM structure and podocyte function.

Cell migration plays a central role in the development and maintenance of multicellular organisms. It involves regulated cell adhesion, mediated by integrins, and polarized changes of the cytoskeleton, controlled by Rho GTPases such as Cdc42. Aim of this study was to investigate the role of integrins and Cdc42 in cell migration and in particular the cross-talk between these molecules. In addition, the structure–function relationship of beta1 integrin in mediating migration associated events was studied. To test whether Cdc42 is essential for directed cell migration in mammalian cells and to investigate the cross-talks between integrin and Cdc42 mediated signalling, fibroblastoid cell lines lacking a functional Cdc42 gene were established and analyzed in wound closure assays. Contrary to the expectations, we could show that Cdc42 is neither required for integrin activation nor for integrin mediated protrusion formation. Moreover, Cdc42 has no significant influence on the speed of directed migration. However, it contributes to the directionality of migration and to the re-orientation of the Golgi apparatus into the direction of migration by a mechanism independent of Gsk3beta phosphorylation. Furthermore, we demonstrated that Cdc42 controls cell morphology, quite likely by regulating Rac1 activity. Expression of dominant negative Cdc42 (dnCdc42) in Cdc42-null cells revealed that dnCdc42 non-specifically inhibits other Rho GTPases besides Cdc42, since it aggravates the impairments observed in Cdc42-null cells, resulting in strongly reduced directed migration, severely reduced single cell directionality, and complete loss of Golgi polarization and of directionality of protrusion formation towards the wound. Beta1 integrins were previously shown to activate Cdc42 in response to wounding and thus to regulate the directionality of migration. We demonstrated now, that fourfold reduction of beta1 integrin expression in keratinocytes in vivo did not impair wound healing. However, keratinocyte stem cells with normal levels of beta1 integrin had a competitive advantage over the hypomorphic cells and expanded steadily in the skin of mice harbouring both cell types in the epidermis. Finally, we analysed the importance of specific amino acids of the intracellular domain of beta1 integrin in keratinocytes in vivo by generating 8 mice strains which in skin express only point or deletion mutants of beta1 integrin. Our data are for the most part strikingly different from previous results obtained in vitro and significantly revise proposed models for the role of serine and tyrosine phosphorylation and the function of a salt bridge between the integrin beta subunits and the integrin alpha tails.

Thu, 20 Mar 2003 12:00:00 +0100 https://edoc.ub.uni-muenchen.de/881/ https://edoc.ub.uni-muenchen.de/881/1/Unschuld_Paul_G.pdf Unschuld, Paul Gerson ddc