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Drs. Mehdi Mollapour, Jennifer Heritz, and Sarah Backe from SUNY Upstate Medical University (Syracuse, NY) discuss a review they co-authored that was published by Oncotarget in Volume 15, entitled, “Molecular chaperones: Guardians of tumor suppressor stability and function.” DOI - https://doi.org/10.18632/oncotarget.28653 Correspondence to - Mehdi Mollapour - mollapom@upstate.edu Video interview - https://www.youtube.com/watch?v=vEHmyemWgNo Video transcript - https://www.oncotarget.net/2024/10/24/behind-the-study-molecular-chaperones-tumor-suppressor-stability/ Abstract The term ‘tumor suppressor' describes a widely diverse set of genes that are generally involved in the suppression of metastasis, but lead to tumorigenesis upon loss-of-function mutations. Despite the protein products of tumor suppressors exhibiting drastically different structures and functions, many share a common regulatory mechanism—they are molecular chaperone ‘clients'. Clients of molecular chaperones depend on an intracellular network of chaperones and co-chaperones to maintain stability. Mutations of tumor suppressors that disrupt proper chaperoning prevent the cell from maintaining sufficient protein levels for physiological function. This review discusses the role of the molecular chaperones Hsp70 and Hsp90 in maintaining the stability and functional integrity of tumor suppressors. The contribution of cochaperones prefoldin, HOP, Aha1, p23, FNIP1/2 and Tsc1 as well as the chaperonin TRiC to tumor suppressor stability is also discussed. Genes implicated in renal cell carcinoma development—VHL, TSC1/2, and FLCN—will be used as examples to explore this concept, as well as how pathogenic mutations of tumor suppressors cause disease by disrupting protein chaperoning, maturation, and function. Sign up for free Altmetric alerts about this article: https://oncotarget.altmetric.com/details/email_updates?id=10.18632%2Foncotarget.28653 Subscribe for free publication alerts from Oncotarget: https://www.oncotarget.com/subscribe/ Keywords - cancer, molecular chaperone, tumor suppressor, renal cell carcinoma, Birt-Hogg-Dubé (BHD) syndrome, TSC syndrome About Oncotarget Oncotarget (a primarily oncology-focused, peer-reviewed, open access journal) aims to maximize research impact through insightful peer-review; eliminate borders between specialties by linking different fields of oncology, cancer research and biomedical sciences; and foster application of basic and clinical science. Oncotarget is indexed and archived by PubMed/Medline, PubMed Central, Scopus, EMBASE, META (Chan Zuckerberg Initiative) (2018-2022), and Dimensions (Digital Science). To learn more about Oncotarget, please visit https://www.oncotarget.com and connect with us: Facebook - https://www.facebook.com/Oncotarget/ X - https://twitter.com/oncotarget Instagram - https://www.instagram.com/oncotargetjrnl/ YouTube - https://www.youtube.com/@OncotargetJournal LinkedIn - https://www.linkedin.com/company/oncotarget Pinterest - https://www.pinterest.com/oncotarget/ Reddit - https://www.reddit.com/user/Oncotarget/ Spotify - https://open.spotify.com/show/0gRwT6BqYWJzxzmjPJwtVh MEDIA@IMPACTJOURNALS.COM
BUFFALO, NY- October 16, 2024 – A new #review was #published in Oncotarget's Volume 15 on October 1, 2024, entitled, “Molecular chaperones: Guardians of tumor suppressor stability and function.” As highlighted in the abstract of this paper, "tumor suppressor" describes a diverse set of genes typically involved in suppressing metastasis, but which can lead to tumorigenesis when loss-of-function mutations occur. Despite the varied structures and functions of tumor suppressor proteins, many share a common regulatory mechanism—they are "clients" of molecular chaperones, and they rely on an intracellular network of chaperones and co-chaperones to maintain their stability. Mutations in tumor suppressors that disrupt proper chaperoning prevent cells from maintaining sufficient protein levels for normal physiological function. In their review, researchers Jennifer A. Heritz, Sarah J. Backe, and Mehdi Mollapour from SUNY Upstate Medical University and New York VA Health Care in Syracuse, New York, discuss the role of molecular chaperones Hsp70 and Hsp90 in maintaining the stability and functional integrity of tumor suppressors. They also detail the contributions of co-chaperones prefoldin, HOP, Aha1, p23, FNIP1/2, and Tsc1, as well as the chaperonin TRiC, to tumor suppressor stability. “Overall, it is clear that oncogenesis can result from the dysregulation of tumor suppressor stabilization by chaperones.” DOI - https://doi.org/10.18632/oncotarget.28653 Correspondence to - Mehdi Mollapour - mollapom@upstate.edu Video short - https://www.youtube.com/watch?v=V5OFjeqaH3A Sign up for free Altmetric alerts about this article: https://oncotarget.altmetric.com/details/email_updates?id=10.18632%2Foncotarget.28653 Subscribe for free publication alerts from Oncotarget: https://www.oncotarget.com/subscribe/ Keywords - cancer, molecular chaperone, tumor suppressor, renal cell carcinoma, Birt-Hogg-Dubé (BHD) syndrome, TSC syndrome About Oncotarget Oncotarget (a primarily oncology-focused, peer-reviewed, open access journal) aims to maximize research impact through insightful peer-review; eliminate borders between specialties by linking different fields of oncology, cancer research and biomedical sciences; and foster application of basic and clinical science. Oncotarget is indexed and archived by PubMed/Medline, PubMed Central, Scopus, EMBASE, META (Chan Zuckerberg Initiative) (2018-2022), and Dimensions (Digital Science). To learn more about Oncotarget, please visit https://www.oncotarget.com and connect with us: Facebook - https://www.facebook.com/Oncotarget/ X - https://twitter.com/oncotarget Instagram - https://www.instagram.com/oncotargetjrnl/ YouTube - https://www.youtube.com/@OncotargetJournal LinkedIn - https://www.linkedin.com/company/oncotarget Pinterest - https://www.pinterest.com/oncotarget/ Reddit - https://www.reddit.com/user/Oncotarget/ Spotify - https://open.spotify.com/show/0gRwT6BqYWJzxzmjPJwtVh MEDIA@IMPACTJOURNALS.COM
BUFFALO, NY- July 10, 2024 – A new #research paper was #published in Aging (listed by MEDLINE/PubMed as "Aging (Albany NY)" and "Aging-US" by Web of Science) Volume 16, Issue 12, entitled, “Aging exacerbates oxidative stress and liver fibrosis in an animal model of Down Syndrome.” Down Syndrome (DS) is a common genetic disorder characterized by an extra copy of chromosome 21, leading to dysregulation of various metabolic pathways. Oxidative stress in DS is associated with neurodevelopmental defects, neuronal dysfunction, and a dementia onset resembling Alzheimer's disease. Additionally, chronic oxidative stress contributes to cardiovascular diseases and certain cancers prevalent in DS individuals. In this new study, researchers Sebastiano Giallongo, Jessica Ferrigno, Rosario Caltabiano, Giuseppe Broggi, Amer M. Alanazi, Alfio Distefano, Emanuela Tropea, Antonella Tramutola, Marzia Perluigi, Giovanni Li Volti, Eugenio Barone, and Ignazio Alberto Barbagallo from the University of Catania, King Saud University, and Sapienza University of Rome investigated the impact of aging on oxidative stress and liver fibrosis using a DS murine model (Ts2Cje mice). “Our results show that DS mice show increased liver oxidative stress and impaired antioxidant defenses, as evidenced by reduced glutathione levels and increased lipid peroxidation.” DS liver exhibited an altered inflammatory response and mitochondrial fitness as the researchers showed by assaying the expression of HMOX1, CLPP, and the heat shock proteins Hsp90 and Hsp60. DS liver also displayed dysregulated lipid metabolism, indicated by altered expression of PPARα, PPARγ, FATP5, and CTP2. Consistently, these changes might contribute to non-alcoholic fatty liver disease development, a condition characterized by liver fat accumulation. Consistently, histological analysis of DS liver revealed increased fibrosis and steatosis, as showed by Col1a1 increased expression, indicative of potential progression to liver cirrhosis. Therefore, their findings suggest an increased risk of liver pathologies in DS individuals, particularly when combined with the higher prevalence of obesity and metabolic dysfunctions in DS patients. “These results shed a light on the liver's role in DS-associated pathologies and suggest potential therapeutic strategies targeting oxidative stress and lipid metabolism to prevent or mitigate liver-related complications in DS individuals.” DOI - https://doi.org/10.18632/aging.205970 Corresponding author - Giovanni Li Volti - livolti@unict.it Video short - https://www.youtube.com/watch?v=8GlAruy0xfk Sign up for free Altmetric alerts about this article - https://aging.altmetric.com/details/email_updates?id=10.18632%2Faging.205970 Subscribe for free publication alerts from Aging - https://www.aging-us.com/subscribe-to-toc-alerts Keywords - aging, Down Syndrome, oxidative stress, liver About Aging-US The mission of the journal is to understand the mechanisms surrounding aging and age-related diseases, including cancer as the main cause of death in the modern aged population. The journal aims to promote 1) treatment of age-related diseases by slowing down aging, 2) validation of anti-aging drugs by treating age-related diseases, and 3) prevention of cancer by inhibiting aging. (Cancer and COVID-19 are age-related diseases.) Please visit our website at https://www.Aging-US.com and connect with us: Facebook - https://www.facebook.com/AgingUS/ X - https://twitter.com/AgingJrnl Instagram - https://www.instagram.com/agingjrnl/ YouTube - https://www.youtube.com/@AgingJournal LinkedIn - https://www.linkedin.com/company/aging/ Pinterest - https://www.pinterest.com/AgingUS/ Spotify - https://open.spotify.com/show/1X4HQQgegjReaf6Mozn6Mc MEDIA@IMPACTJOURNALS.COM
The long-awaited Oxide and Friends bookclub! Bryan and Adam were joined by special guest--and real life biologist--Greg Cost to discuss Philip Ball's terrific book, How Life Works: A User's Guide to the New Biology. Spoiler: Alan Turing makes a very expected appearance!In addition to Bryan Cantrill and Adam Leventhal, we were joined by special guest Greg Cost.Some of the topics we hit on, in the order that we hit them:The Turing patternRNA as a precursor to DNAXenopus frogXenobotsAnton computerBryan's reading notesCentral themesPower and limitations of metaphor – especially mechanical onesThe fundamental, diametrical opposition between life and machines. (Nature does not use simulations!)Rejecting the neo-Darwinian paradigmPassages of note:p. 91: “of the common SNPs seen in human populations, fully 62 percent are associated with height” … “the most common genomic associations for complex traits like this are in the noncoding regions” What is cognition? p. 137: “Life is, as biologist Michael Levin Jeremy Gunawardenaand philosopher Daniel Dennet have argued, ‘cognition all the way down'” AlphaFold2 p. 148 “AlphaFold does not so much solve the infamously difficult protein-folding problem as sidestep it. The algorithm makes no predictions about how a polypeptide chain folds, but simply predicts the end result based on the sequence.”p. 156: allostery refers to how a
BUFFALO, NY- March 25, 2024 – A new #research paper was #published in Oncotarget's Volume 15 on March 14, 2024, entitled, “ABT199/venetoclax synergism with thiotepa enhances the cytotoxicity of fludarabine, cladribine and busulfan in AML cells.” ABT199/venetoclax, an inhibitor of the pro-survival BCL-2 protein, has improved AML treatment. Its efficacy in hematopoietic stem cell transplantation (HSCT), when combined with other chemotherapeutic drugs, has not been thoroughly investigated. In this new study, researchers Benigno C. Valdez, Bin Yuan, David Murray, Jeremy L. Ramdial, Uday Popat, Yago Nieto, and Borje S. Andersson from The University of Texas MD Anderson Cancer Center and the University of Alberta demonstrate the synergistic cytotoxicity of ABT199/venetoclax with the DNA alkylator thiotepa (Thio) in AML cells. “The results may provide relevant information for the design of clinical trials using these drugs to circumvent recognized drug-resistance mechanisms when used as part of pre-transplant conditioning regimens for AML patients undergoing allogenic HSCT.” Cleavage of Caspase 3, PARP1 and HSP90, as well as increased Annexin V positivity, suggest potent activation of apoptosis by this two-drug combination; increased levels of γ-H2AX, P-CHK1 (S317), P-CHK2 (S19) and P-SMC1 (S957) indicate an enhanced DNA damage response. Likewise, the increased level of P-SAPK/JNK (T183/Y185) and decreased P-PI3Kp85 (Y458) suggest enhanced activation of stress signaling pathways. These molecular readouts were synergistically enhanced when ABT199/venetoclax and Thio were combined with fludarabine, cladribine and busulfan. The five-drug combination decreased the levels of BCL-2, BCL-xL and MCL-1, suggesting its potential clinical relevance in overcoming ABT199/venetoclax resistance. Moreover, this combination is active against P53-negative and FLT3-ITD-positive cell lines. Enhanced activation of apoptosis was observed in leukemia patient-derived cell samples exposed to the five-drug combination, suggesting a clinical relevance. “The results provide a rationale for clinical trials using these two- and five-drug combinations as part of a conditioning regimen for AML patients undergoing HSCT.” DOI - https://doi.org/10.18632/oncotarget.28563 Correspondence to - Benigno C. Valdez - mbalasik@yahoo.com Sign up for free Altmetric alerts about this article - https://oncotarget.altmetric.com/details/email_updates?id=10.18632%2Foncotarget.28563 Subscribe for free publication alerts from Oncotarget - https://www.oncotarget.com/subscribe/ Keywords - cancer, acute myeloid leukemia, aml, pre-transplant regimens, venetoclax, thiotepa, busulfan About Oncotarget Oncotarget (a primarily oncology-focused, peer-reviewed, open access journal) aims to maximize research impact through insightful peer-review; eliminate borders between specialties by linking different fields of oncology, cancer research and biomedical sciences; and foster application of basic and clinical science. Oncotarget is indexed and archived by PubMed/Medline, PubMed Central, Scopus, EMBASE, META (Chan Zuckerberg Initiative) (2018-2022), and Dimensions (Digital Science). To learn more about Oncotarget, please visit https://www.oncotarget.com and connect with us: Facebook - https://www.facebook.com/Oncotarget/ X - https://twitter.com/oncotarget Instagram - https://www.instagram.com/oncotargetjrnl/ YouTube - https://www.youtube.com/@OncotargetJournal LinkedIn - https://www.linkedin.com/company/oncotarget Pinterest - https://www.pinterest.com/oncotarget/ Reddit - https://www.reddit.com/user/Oncotarget/ Spotify - https://open.spotify.com/show/0gRwT6BqYWJzxzmjPJwtVh Media Contact MEDIA@IMPACTJOURNALS.COM 18009220957
In this week's episode, we discuss real-world evidence for CAR T cell therapy in older patients with diffuse large B-cell lymphoma, inhibiting endogenous anticoagulant pathways in congenital factor deficiencies, and finally targeting the HSP90 epichaperome in acute myeloid leukemia.
Jeffrey Holzbeierlein, MD - physician-in-chief of The University of Kansas Cancer Center - joins Dr. Roy Jensen in the podcast studio this week to discuss the future of cancer care and research in our region. Dr. Holzbeierlein is the William L. Valk endowed professor and chair of the Department of Urology at the University of Kansas Medical Center. He specializes in urologic cancer surgery, especially bladder, kidney, penile and testicular cancer. His research interests include Hsp90 inhibitors in bladder cancer and improving cystectomy (bladder removal) outcomes. Do you have questions about cancer? Call our Bench to Bedside Hotline at (913) 588-3880 or email us at benchtobedside@kumc.edu, and your comment or question may be shared on an upcoming episode!
Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2023.02.17.528950v1?rss=1 Authors: Gayen, N., Mitra, S., Roy, S., Mandal, A. K. Abstract: The stability and activity of CRAF kinase are stringently regulated by heat shock protein 90 (Hsp90). Hsp90-mediated client folding and maturation is governed by its co-chaperones, but their functionality in chaperoning CRAF/Raf1 kinase to accomplish signaling under physiological conditions remains poorly understood. Here, we show that Hsp70/Hsp90 organizing protein (HOP) associates with CRAF kinase for maintaining its kinase activity and facilitates the activation of the MAPK pathway. Such activation is mediated by TPR2A-2B-DP2 domain of HOP and requires efficient binding to Hsp90. Being a recruiter of Hsp90, Cdc37 is unable to supplement the function of HOP/Sti1. Downregulation of HOP/Sti1 in yeast and in vitro cell culture significantly reduces the CRAF signaling. Our data suggest that Hsp90 is recruited to CRAF in two steps, separately initiated by co-chaperones HOP and Cdc37 respectively during CRAF folding/maturation, and again upon CRAF activation mediated by HOP during MAPK signaling. Therefore, HOP is a regulator of CRAF kinase during activation of MAPK pathway and serves as a sensor of growth signaling beyond its client folding and maturation 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/2023.01.25.525547v1?rss=1 Authors: Maiti, S., Bhattacharya, K., Wider, D., Hany, D., Panasenko, O., Bernasconi, L., Hulo, N., Picard, D. Abstract: Cells are exposed to a wide variety of internal and external stresses. Whereas many studies have focused on cellular responses to acute and severe stresses, little is known about how cellular systems adapt to sublethal chronic stresses. Using mammalian cells in culture, we discovered that they adapt to chronic mild stress by increasing their size and translation, thereby scaling the amount of total protein. These adaptations render them more resilient to persistent and subsequent stresses. We demonstrate that Hsf1, well known for its role in acute stress responses, is required for the cell size increase, and that the molecular chaperone Hsp90 is essential for coupling the cell size increase to augmented translation. We term this translational reprogramming the "rewiring stress response", and propose that this protective process of chronic stress adaptation contributes to the increase in size as cells get older, and that its failure promotes aging. 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/2022.12.30.522347v1?rss=1 Authors: Biswas, P., Stuehr, D. J. Abstract: Indoleamine-2, 3-dioxygenase (IDO1) and Tryptophan-2, 3-dioxygenase (TDO) catalyze the conversion of L-tryptophan to N-formyl-kynurenine and thus play primary roles in metabolism, inflammation, and tumor immune surveillance. Because their activities depend on their heme contents which range from 30-60% heme-saturated in biological settings and go up or down in a dynamic manner, we studied how their heme levels may be impacted by nitric oxide (NO) in mammalian cells. We utilized cells expressing TDO or IDO1 either naturally or via transfection and determined their activities, heme contents, and expression levels as a function of NO exposure. We found NO has a bimodal effect: A narrow range of very low NO exposure promoted cells to allocate heme into TDO and IDO1 and boosted their activities several fold, while beyond this range the NO exposure transitioned to have a negative impact on their heme contents and activities. NO did not alter dioxygenase protein expression levels and its bimodal impact was observed when NO was released by a chemical donor or was generated naturally by immune-stimulated macrophage cells. NO-driven heme allocations to IDO1 and TDO required participation of a GAPDH-heme complex and for IDO1 required chaperone Hsp90 activity. Thus, cells can up- or down-regulate their IDO1 and TDO activities through a bimodal control of heme allocation by NO. This mechanism has important biomedical implications and helps explain why the IDO1 and TDO activities in animals go up and down in response to immune stimulation. Copy rights belong to original authors. Visit the link for more info Podcast created by Paper Player, LLC
"Wall Street doesn't believe in this target," by Dario Altieri. A scientist shares his 12-year journey that led to the discovery of a drug now in clinic. TRANSCRIPT Narrator: Wall Street Doesn't Believe in This Target by Dario C. Altieri, MD (10.1200/JCO.22.00180) March 2, 2009. Just published in the Journal of Clinical Investigation.1 And we even got the cover. Twists and turns of heat shock protein-90 (Hsp90), the chaperone, the evolutionary capacitor. Great name and important cancer target. People smiled when I talked about this at the Hsp90 conference. No, no, really there is a lot of it in mitochondria, and only in mitochondria of tumor cells. And, I don't know why, but Hsp90 drugs don't touch it: somehow, they don't get to mitochondria. So, I made my own. Took an old Hsp90 inhibitor, 17-allylamino-17-demethoxygeldanamycin and attached it to triphenylphosphonium, a carrier that basically gets anything into the mitochondria. No, of course, I didn't do the synthesis in my laboratory. What do I know about medicinal chemistry? Outsourced it. Like sneakers and sweaters. And after three months, there it was: an Hsp90 inhibitor that only goes to the mitochondria, causes aggregation of a lot of proteins, and kills tumor cells in minutes. Makes sense, right? Mitochondria must control protein folding, especially in cancer, and they do it with chaperones. Inhibit the process and tumor cells can't cope. Normal cells don't seem to mind. So, strong preclinical activity, and against a lot of different tumor types. Better than any other Hsp90 inhibitor. Good safety. Totally different mechanism of action. And even a cool name, Gamitrinib. Tired of curing mice. What if this were to work in people? Ideas are made in academia; drugs are made in companies. Okay, fine, then I'll launch a startup, spinout, whatever they are called. The (former) doctor-turned scientist now turns entrepreneur, and then captain of industry. Problem is, I am not like that. More like an (aged) boy scout. The inner soapbox says: it belongs to the American taxpayers; they funded it; it's theirs. Excellent start. What else? If doctors and scientists become businessmen (or businesswomen), who will take care of humanity and discover new things? Perfect for a campaign ad. Sold. Bring it to the patients solely from academia: no pharma, no biotech, no investors, no nothing. Soapbox meme for the day: Yes, we can. It's going to cost. So? I'll write a grant, that's what I do for a living anyway. And the fact that I know zero about drug discovery? Or drug development? Laboratory-Clinical Transition Award from the Department of Defense. Great title. Three years of funding. Perfect for me. Pass-through money, nothing for the laboratory, but it pays the bills of outsourcing. First things first. Synthesize Good Laboratory Practice (GLP) Gamitrinib. Already getting a pretty good hang on the acronyms. Hey, we made this drug lots of times before and has never taken this long. It's almost a year and counting. The Department of Defense (DoD) is on my case because I am already behind. What's going on? Yes, I understand that we don't make anything in this country anymore. New import permits that need to clear the Indian government? The what? This is just a chemical, not an international incident. Yes, I get it, nothing I can do about it. My new job is mailman. And telephone operator. Finally shipped the GLP drug for the toxicology. Two animal species, says the US Food and Drug Administration (FDA). Rats and dogs sound good to me. Should I feel sorry for the dogs? Rats not so much. But what if Gamitrinib poisons the mitochondria in the brains? Or hearts? Wait, you said it's just perfect? Animals are doing great, all of them. And no toxicity at all, like giving them…water. Wow, that's some news. Feeling quite pleased with myself. See? I said it all along: mitochondria are wired differently in cancer. That's why the drug is safe for normal tissues. Maybe I should write a review article about that. Serious boost of the citation index. I am sorry, what? Yes, of course I know that the drug is purple. Okay, you filtered it before giving it to the animals and instead of purple it turned white? And you did that to all animals. For the entire time. Oh, what do I think it means? I think it means that you filtered out the drug and we have been giving animals…water. Yes, I get it. I need a new formulation. And start over. Note to self: find a new Contract Research Organization (CRO) that doesn't give water to the animals. Formulation experts. Big pharma ex-pats who now have their own CRO. Everybody is an entrepreneur here. Is this drug oral? Nope. Is it soluble in water? Not at all. So, it's an intravenous (IV) infusion? Yes, that's what it is. Sorry, then it's not a drug. It's not? And what about things like, you know, paclitaxel or doxorubicin? Aren't they also insoluble and given IV? Last time I checked, we used them for half a century and saved millions. Oh, now we think differently? I see, Fail Fast: that's how we think now. And mine, whatever it is if it is not a drug, has already failed. Nobody likes to take risks. Soapbox meme for the day: If nobody takes risks, how do we make progress, exactly? So, maybe I am in good company: paclitaxel and doxorubicin would also Fail Fast today. It's doable. Nobody likes it but it's doable. Sterile-filter the emulsion components and then bring the particle size below 200 nm. Nice. How do I do that? With a microfluidizer. And why nobody likes it? Oh, because the microfluidizer is a dirty machine and where you make Good Manufacturing Practice is called a clean room. Impeccable logic. But a place in California may do it. For a fee, of course. Oh, and you have to buy the machine. Buy what? Or lease it, whatever. People may not like it, but the whole thing works like a charm. Except, of course, when the microfluidizer stops for no reason in the middle of the run. Media fill looks good. Drug is stable for months in the new formulation. Release testing coming together nicely. I am running out of money. Burned through not just one but two DoD grants and all my research kitty. Nothing saved for the swim back: talk about risk-taking. At least the repeat toxicology is paid for and looks good. The drug, the real thing this time, is safe. They even did ECGs on the dogs. Thank goodness I didn't have to read those, but they are normal: no QTc liability. Can't drop the ball now, but I really need money. Here is how you do it: silence the inner soapbox and enchant the big pharma suits that are coming over. Use the right words. It's not early stage anymore. Asset totally derisked. Sure it's ready for prime time. It works. I am a natural. Maybe I should have done this before. A lot of nodding around the table. The suits must be in awe with the great pharmacokinetics, long half-life, and fabulous safety. A hand goes up. I am sorry? Sales data? Sales of what? What is the unit price? No, no, no, we are not there yet. I haven't even filed an Investigational New Drug (IND) application. Something different now. Analysts who advise big-time investors. They don't wear suits. Sweaters for sure. Maybe black tees a la Steve Jobs. They like new things and totally live by risks. Sounds like my crowd. And don't forget, they can get tons of money from people who already have tons of money and want to make even more money. My crowd? Voices out of a polyphone. Yes, it is Hsp90. Yeah, the chaperone. Sure, I know, it has been around for a long time. But this is a completely new story: nobody ever tested a cancer drug that goes to a subcellular organelle: that's really where the action is. Yes, Hsp90. And mitochondria, they used to be bacteria two and a half billion years ago, but they turned out to be important in cancer. I know that too, Hsp90 drugs didn't fare well in the clinic. Lot of toxicity, basically no efficacy. Yes, very unfortunate. But this one has a completely different mechan…Sure, I would like to hear that perspective. I am sorry, did you say, Wall Street doesn't believe in this target? Triaged the first time but funded on the resubmission. Could have been worse. This one is a grant from the National Cancer Institute. And a nice award from the Gateway Foundation is coming too. Enough to pay for the clinical trial. Single site, standard phase I. Accelerated dose escalation. Up to 35 patients with advanced cancer. All comers. Drug vials ready to go. And a fantastic clinical investigator to run the trial. You really don't want me in the clinic. The only thing missing is IND approval. Right, there is that. No, not a commercial IND, investigator-initiated IND, thank you very much. The FDA people are the nicest in the world. Super-helpful, don't believe otherwise. Or maybe they just feel sorry for the clueless applicant. Thirty days to respond to the questions. Totally getting a promotion to a higher rank of telephone operator. And publisher of FDA modules. And certifier of United States Pharmacopeia (USP) . recommendations. And fixer of Chemistry, Manufacturing, and Controls deficiencies. Oh, and let's not forget the specs for polytetrafluoroethylene filters. Then the examiner mutters two words at the end of a phone call. Good luck. Then, nothing. No more questions, e-mails, or phone calls. Right on the thirty-day mark. Were you expecting this? It's a letter; it says study may proceed. What would the day look like? The first patient to be dosed. Maybe I should go to the clinic: it's in town, not far from where I am. I don't think I can pass muster as one of those confidence-inspiring docs in pharma ads. But I do well as chief executive officer. The cufflinks look good, and so do the shoes. I can impress the family. My Italian accent can pass as straight from South Philly, so I have that also going for me. And I can more than hold my own if I need to talk about Philadelphia Eagles football and worries with Jalen Hurts' arm for next season. I used to be good with my patients. Or at least I convinced myself of that. Yes, this is an experimental drug straight out of our backyard, right here in Philadelphia. No, I don't know if it will work, but I sure hope it will. And thank you, thank you so much for being part of the trial. What if I make these people even sicker than they are? I took an oath a long time ago. Anyway, I know the literature on phase I studies, chances are it just won't do anything, so nobody gets hurt and I am finally done with it. I never thought this moment would arrive. There is none of that. January 10, 2022. It's just a late-night e-mail on the anniversary of my mom passing from lung cancer. Hey, the first patient did great at the starting dose of Gamitrinib. No problem whatsoever. The next patient will now get twice the dose. I hope we get that started this month. Happy new year. And that was that. Twelve years, 10 months, and nine days from that Journal of Clinical Investigation paper.1 Affiliation: 1The Wistar Institute, Philadelphia, PA Dr. Lidia Schapira: Welcome to JCO's Cancer Stories: The Art of Oncology. I'm Lidia Schapira, Associate Editor for Art of Oncology, and Professor of Medicine at Stanford University. And I'll be the host of this show. Cancer Stories is brought to you by the ASCO Podcast Network, a collection of nine programs covering a range of educational and scientific content and offering enriching insight into the world of cancer care. You can find all of the shows including this one at podcast.asco.org. With me today is Dr. Dario Altieri, president, and CEO at the Wister Institute. We'll be discussing his Art of Oncology article: Wall Street Doesn't Believe in This Target. Our guest is a named inventor for patent number 2,699,794. Titled: Mitochondria Targeted Anti-Tumor Agents. Dario, welcome to our podcast. Dr. Dario Altieri: Thank you so much for having me, Lidia. It's a great privilege. Dr. Lidia Schapira: My first question to you and to our authors is this, people who enjoy writing are usually also readers, what are you reading now? Dr. Dario Altieri: Well, absolutely it has been a passion of mine since the floods. I am an absolute avid reader of novels, and history, in particular, contemporary history and modern history. Those are my favorite topics. Dr. Lidia Schapira: Do you read in English, Italian, or other languages? Dr. Dario Altieri: I typically read in English, even though some of the Italian literature is best read in the native tongue. And so, I am still attached to that. Dr. Lidia Schapira: You're clearly a very accomplished scientist. But tell me a little bit about your writing in this particular area in what I'll call creative nonfiction. How has this writing helped you perhaps process experiences or communicate with others? Dr. Dario Atieri: It has been, it's been a passion of mine for a very long time, I think. In finishing up college, of course, my major was contemporary literature and philosophy. The question was whether to continue on in a classic literature career or go to medical school, probably the wrong choice was made. But it has remained with me for a very long time, and it's a form of expression that I truly enjoy. In writing, this particular contribution was a bit transformative for me. It doesn't happen every time that you write a scientific article to express a little bit about yourself and your passions and dreams. Dr. Lidia Schapira: Let's talk a little bit about your passions and dreams in this article. You described an intensely personal journey of 12 years that led to the discovery or the availability of this drug now in the clinic. When did you think that you wanted to share this story with your colleagues? And tell me a little bit about the process of writing this article? Dr. Dario Altieri: It has certainly been a roller coaster experience. I would like to describe it as life-defining and life-changing. I've learned so much and so many things, not just about the process, but also a little bit about myself. I recognize reaching the clinic, especially in a phase one trial, is really just the beginning. But for me, as a basic scientist, somebody who has seen his last patient in the 13th century. As a basic scientist, that was a little bit of a milestone, and I wanted to share what it took, the experiences that I lived through, especially with our youngest colleagues, scientists, and doctors, starting their own careers in oncology, whether it's basic research, clinical research, translational research, I really don't think it matters. And so, issues of resilience, staying the course, passion, and not really giving up are the parameters that I had hoped to convey with this contribution. Dr. Lidia Schapira: In your article, I was so impressed by how you used humor, often self-deprecating humor, and the particular narrative style and writing style that you chose and defended as you were revising it. You know, this choppy phrasing, a staccato, and you said, this is what it feels like, how can I pack it into a small number of words and describe it all? Tell us a little bit about how you allowed your imagination to take over and how you found the proper voice and style for this particular narrative. Dr. Dario Altieri: Again, it's been a thrilling experience and it's been a thrilling experience to answer to the editors and the reviewers of the JCO, who provided incredible insightful comments. The challenge was, how do I tell a story without sounding obvious, fright, or expected, and more importantly, without sounding boring? And I think to paraphrase one of our reviewers about this journey. What the reviewer said, the author, that would be me, has encountered many of the absurdities of the path in drug development, something that we don't talk about too much because it's been the realm of a drug company for the longest time. And so, I wanted to try to capture that absurdity in a positive way. Things that the reviewer indicated, may be second nature to the pharmaceutical industry, but for academic investigators, that's been publicly funded for 30 years, is not second nature and is unusual, and is a world all in itself. And so, that was the impetus of trying to use literature advice on short sentences that are really intended to convey the impression of the moment that was what I tried to accomplish. Dr. Lidia Schapira: Well, you certainly picked a catchy title, and we have not published this sort of article in Art of Oncology before. For our listeners, tell us a little bit about why Wall Street doesn't care about your discovery? Dr. Dario Altieri: Unfortunately, I think, I mean, I don't know for sure. But I think that dealing with this particular molecule, heat shock protein 90 in the clinic has been difficult. Hsp90 has long been recognized as an important cancer target. There have been several generations of small molecule inhibitors that have been tested in the clinic. And unfortunately, I hope I'm not offending anybody, but unfortunately, the clinical results of those studies, and some of them moved all the way to really large phase two trials have been disappointing. And so, that is the idea that perhaps this was a dead target. And therefore, trying to leverage industry or biotechnology interest around it was quite a remarkable challenge. Dr. Lidia Schapira: What message do you want the young investigators to take away from your story in terms of the collaboration between academia where thoughts start, as you say, in your article, and all of the rest of the partners that you actually need it to bring this discovery and this idea to fruition? Dr. Dario Altieri: Lydia, this may sound trite, I really hope to convey one simple notion. It's not even a message, it's a very personal account. And that is don't give up. If you have run the controls. If you have done your experiments enough time. If you're convinced of the results, if you explore alternative explanations, and you keep coming back to the same conclusions, go for it. That has been a little bit of my own personal experience and if there are things that you don't know about, that's perfectly fine. Actually, that is the fun of the process, and the things that I didn't know about drug development, I can fill in the encyclopedia. I've learned some of them through people who have been doing this for a living, for a very long time. And that has been truly inspiring for me, a life lesson and professional lesson about how we can think of a drug target that has been discounted and remain true to the core value of strong basic research and try to advance that to the clinic, whether this will ever become something useful for our patients? I don't have the faintest idea. I certainly hope so. But that would be the experiment that is being done right now in the clinic. Dr. Lidia Schapira: In your article towards the end, you just give us two little glimpses into something that is personal and meaningful to you by telling us that there's an anniversary of a loss, the passing of your mother from cancer. Can you tell us a little bit more about that, and why you chose to put that sentence just where you did? Dr. Dario Altieri: I didn't know if anybody would have noticed, frankly, so I appreciate you bringing it up, Lidia. It's been a very personal journey for me as well. Both my parents died of lung cancer. They were a different generation. Both were heavy smokers. I remember those dates very well and I remember the void that they're passing is created. And so, I thought it was an interesting circumstance, that in fact, the first patient was enrolled in a clinical trial, the notion about that and of course, I am technically conflicted. So, I am not supposed to know anything about what is happening in the clinic. But it was interesting that the first notion about the first dosing came on that day, on January 10. Dr. Lidia Schapira: Well, I'm sure other readers will notice that too, the timing of that in the article and the fact that there was some emotion implied, I think, in how you chose to end your story by saying that this had happened in the clinic, but somehow, you were not there, that you had to be removed. Tell us a little bit more about that, about why you needed to be removed from the clinical site and why do you talk about yourself as a former doctor? In my mind, once you are you always are, but somehow you feel that you need to make the distinction. What does it all mean to you? Dr. Dario Altieri: Well, Lidia, let me just say you don't want me in the clinic right now. At 64years of age, like I said that the last patient was a very long time ago. I have to say, sometimes I miss those days, just as a personal account. I need to be removed because I'm technically conflicted on the trial, I was the IND holder, and then the FDA asked me to transfer the IND to the clinical investigator as proper because I'm not involved in patient care or research, in this particular case. And technically, because I am the inventor on a patent, I could potentially stand to benefit financially from the results of the trial, something that is certainly not on my mind, but that I have been reminded of. And so, I try to stay away as much as I can. Obviously, I think about this every day. But whatever information I can gain, that I can gather from my colleagues across town will be wonderful, but I'm not the one initiating those calls. Dr. Lidia Schapira: So back to the humorous side of your essay, you say that you've learned to be a telephone operator and a mailman, and a whole bunch of other things. Have those lessons been useful to the other aspects of your life? Or do you see that as a total waste of your time? Dr. Dario Altieri: Not at all. Not at all. I have been an incredible component and I think I was trying to be humorous and to take myself seriously, but not too seriously. But in fact, maintaining that level of interaction, particularly with aspects of the work that I've never encountered, for instance, regulatory aspects of an early-stage clinical trial with the Food and Drug Administration, that has been part of the life journey and I only have very good things to say about my experience. You know, it's been interesting, Lidia, being part of the experience of being a telephone operator and a mailman. I had this sense, and I could be completely wrong, but I had this sense that people out there want to see us taking small risks. They want to see testing new drugs, they want to see new targets being somehow examined, developed, if at all possible. I had the sense that there was support, you know, for the idea, and this was an entirely publicly funded program. I funded both the preclinical and now the clinical trial of Gamitrinib out of the American taxpayer's commitment and in many different study sections, in dealing with the FDA, in dealing with other regulatory consultants, I always get the sense people who wanted to help, then had perhaps the mindset, okay, we don't know whether this is going to work or not but let's give it a try. Let's give it a shot. It was wonderful, that was an absolutely awe-inspiring experience. Dr. Lidia Schapira: I'm glad they did and I'm glad you shared your experience with all of us. Is there something else that you'd like our listeners or your readers to know about you or this story? Dr. Dario Altieri: I just would like to say that I would do it again, 12 years, I would do every step of the way but I think I'm done. If I were to start over, I'll do it again, but I don't think I'm ready to do it again with another target. Dr. Lidia Schapira: And with that, I want to thank you and I want to thank our listeners. Until next time, thank you for listening to this JCO's Cancer Stories: The Art of Oncology podcast. If you enjoyed what you heard today, don't forget to give us a rating or review on Apple podcasts or wherever you listen. While you're there, be sure to subscribe so you never miss an episode of JCO's Cancer Stories: The Art of Oncology podcast. This is just one of many of ASCO's podcasts. You can find all of the shows at the podcast.asco.org. The purpose of this podcast is to educate and to inform. This is not a substitute for professional medical care and is not intended for use in the diagnosis or treatment of individual conditions. Guests on this podcast express their own opinions, experience, and conclusions. Guest statements on the podcast do not express the opinions of ASCO. The mention of any product or service organization activity or therapy should not be construed as an ASCO endorsement.
Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2020.11.09.374355v1?rss=1 Authors: Pearl, L. H., Pal, M., Munoz-Hernandez, H., Bjorklund, D., Zhou, L., Degliesposti, G., Skehel, J. M., Hesketh, E. L., Thompson, R. F., Llorca, O., Prodromou, C. Abstract: The R2TP (RUVBL1-RUVBL2-RPAP3-PIH1D1) complex, in collaboration with HSP90, functions as a chaperone for the assembly and stability of protein complexes, including RNA polymerases, snRNPs and PI3 kinase-like kinases (PIKK) such as TOR and SMG1. PIKK stabilisation depends on an additional complex of TELO2, TTI1 and TTI2 (TTT), whose structure and function are poorly understood. We have now determined the cryo-EM structure of the human R2TP-TTT complex that together with biochemical experiments reveals the mechanism of TOR recruitment to the R2TP-TTT chaperone. The HEAT-repeat TTT complex binds the kinase domain of TOR, without blocking its activity, and delivers TOR to the R2TP chaperone. In addition, TTT regulates the R2TP chaperone by inhibiting RUVBL1-RUVBL2 ATPase activity and by modulating the conformation and interactions of the PIH1D1 and RPAP3 components of R2TP. Together, our results show how TTT couples the recruitment of TOR to R2TP with the regulation of this chaperone system. Copy rights belong to original authors. Visit the link for more info
Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2020.11.05.370247v1?rss=1 Authors: Wang, R. Y.- R., Noddings, C. M., Kirschke, E., Myasnikov, A., Johnson, J. L., Agard, D. A. Abstract: Maintaining a healthy proteome is fundamental for organism survival. Integral to this are Hsp90 and Hsp70 molecular chaperones that together facilitate the folding, remodeling and maturation of Hsp90's many "client" proteins. The glucocorticoid receptor (GR) is a model client strictly dependent upon Hsp90/Hsp70 for activity. Chaperoning GR involves a cycle of inactivation by Hsp70, formation of an inactive GR:Hsp90:Hsp70:Hop "loading" complex, conversion to an active GR:Hsp90:p23 "maturation" complex, and subsequent GR release. Unfortunately, a molecular understanding of this intricate chaperone cycle is lacking for any client. Here, we report the cryo-EM structure of the GR loading complex, in which Hsp70 loads GR onto Hsp90, revealing the molecular basis of direct Hsp90/Hsp70 coordination. The structure reveals two Hsp70s--one delivering GR and the other scaffolding Hop. Unexpectedly, the Hop cochaperone interacts with all components of the complex including GR, poising Hsp90 for subsequent ATP hydrolysis. GR is partially unfolded and recognized via an extended binding pocket composed of Hsp90, Hsp70 and Hop, revealing the mechanism of GR loading and inactivation. Together with the GR maturation complex (Noddings et al., 2020), we present the first complete molecular mechanism of chaperone-dependent client remodeling, establishing general principles of client recognition, inhibition, transfer and activation. Copy rights belong to original authors. Visit the link for more info
Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2020.11.04.368837v1?rss=1 Authors: Liu, Y., Sun, M., Elnatan, D., Larson, A. G., Agard, D. A. Abstract: Hsp90 is a ubiquitous molecular chaperone that mediates the folding and maturation of hundreds of ''client'' proteins. Although Hsp90s generally function as homodimers, recent discoveries suggested that the mitochondrion specific Hsp90 (TRAP1) also forms functionally relevant tetramers. The structural mechanism of tetramer formation remains elusive. Here we used a combination of solution, biochemical and cryo-electron microscopy (cryo-EM) approaches to confirm that, independent of nucleotide state, a subpopulation of TRAP1 exists as tetramers. Unexpectedly, cryo-EM reveals multiple tetramer conformations having TRAP1 dimers arranged in orthogonal, parallel, or antiparallel configurations. The cryo-EM structure of one of the orthogonal tetrameric states was determined at 3.5 [A] resolution. Each of the two TRAP1 dimers is in a symmetric AMP{middle dot}PNP-bound closed state with the tetramer being stabilized through three distinct dimer-dimer interaction sites. In unique ways, each of the three TRAP1 domains contributes to tetramer formation. In addition to tetramerization via direct dimer-dimer contacts, our structure suggests that additional stabilization could come from domain swapping between the dimers. These results expand our understanding of TRAP1 biology beyond the conventional view of a functional dimer and provide a platform to further explore the function and regulation of tetrameric TRAP1 in mitochondria. Copy rights belong to original authors. Visit the link for more info
Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2020.10.27.357780v1?rss=1 Authors: Pinkerton, M., Ruetenik, A., Bazylianska, V., Nyvltova, E., Barrientos, A. Abstract: Human neurodegenerative proteinopathies are disorders associated with abnormal protein depositions in brain neurons. They include polyglutamine (polyQ) conditions such as Huntington's disease (HD) and alpha-synucleinopathies such as Parkinson's disease (PD). Overexpression of NMNAT/Nma1, an enzyme in the NAD+ biosynthetic salvage pathway, acts as a powerful suppressor of proteotoxicities in yeast, fly, and mouse models. Screens in yeast models of HD and PD in our lab allowed us to identify three additional enzymes of the same pathway that achieve similar protection against proteotoxic stress: Npt1, Pnc1, and Qns1. Here, we report that their ability to maintain proteostasis is independent of their catalytic activity. Furthermore, we show that, under proteotoxic stress, the four proteins are recruited as molecular chaperones with holdase and foldase activities. In yeast cells, the NAD+ salvage proteins act by preventing misfolding and, together with the Hsp90 chaperone, promoting the refolding of extended polyQ domains or alpha-synuclein. For Nma1, we demonstrate that its foldase activity maps to the C-terminal domain of the protein. The proteostasis activity of Nma1, Npt1, Pnc1, and Qns1 does not require cellular protein quality control systems such as the proteasome or autophagy. We conclude that the entire salvage NAD+ biosynthetic pathway links NAD+ metabolism and proteostasis and emerges as a target for therapeutics to combat age-associated neurodegenerative proteotoxicities. Our observations also illustrate the existence of an evolutionarily conserved strategy of repurposing or moonlighting housekeeping enzymes under stress conditions. Copy rights belong to original authors. Visit the link for more info
Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2020.10.06.327627v1?rss=1 Authors: Liu, Y., Elnatan, D., Sun, M., Myasnikov, A., Agard, D. Abstract: TRAP1 is a mitochondrion specific Hsp90, a ubiquitous chaperone family that mediates the folding and maturation of hundreds of 'client' proteins. Through the interaction with client proteins, TRAP1 regulates mitochondrial protein homeostasis, oxidative phosphorylation/glycolysis balance, and plays a critical role in mitochondrial dynamics and disease. However, the molecular mechanism of client protein recognition and remodeling by TRAP1 remains elusive. Here we established the succinate dehydrogenase B subunit (SdhB) from mitochondrial complex II as a client protein for TRAP1 amenable to detailed biochemical and structural investigation. SdhB accelerates the rate of TRAP1 dimer closure and ATP hydrolysis by 5-fold. Cryo-EM structures of the TRAP1:SdhB complex show TRAP1 stabilizes SdhB folding intermediates by trapping an SdhB segment in the TRAP1 lumen. Unexpectedly, client protein binding induces an asymmetric to symmetric transition in the TRAP1 closed state. Our results highlight a client binding mechanism conserved throughout Hsp90s that transcends the need for cochaperones and provide molecular insights into how TRAP1 modulates protein folding within mitochondria. Our structures also suggest a potential role for TRAP1 in Fe-S cluster biogenesis and mitochondrial protein import and will guide small molecule development for therapeutic intervention in specific TRAP1 client interactions. Copy rights belong to original authors. Visit the link for more info
Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2020.09.24.311779v1?rss=1 Authors: Jin, Y., Kotler, J. L. M., Wang, S., Huang, B., Halpin, J. C., Street, T. O. Abstract: While cytosolic Hsp70 and Hsp90 chaperones have been extensively studied, less is known about how the ER Hsp70 and Hsp90 paralogs (BiP and Grp94) recognize clients and influence their folding. Here, we examine how BiP and Grp94 influence the folding of insulin-like growth factor 2 (IGF2). Full-length proIGF2 is composed of an insulin-like hormone and an E-peptide that has sequence characteristics of an intrinsically disordered region. We find that the E-peptide region allows proIGF2 to form oligomers. BiP and Grp94 influence both the folding and the oligomerization of proIGF2. BiP and Grp94 exert a similar holdase function on proIGF2 folding by preferentially binding the proIGF2 unfolded state, rather than stabilizing specific folding intermediates and changing the proIGF2 folding process. In contrast, BiP and Grp94 exert counteracting effects on proIGF2 oligomerization. BiP suppresses proIGF2 oligomerization under both ADP and ATP conditions. Interestingly, Grp94 can enhance proIGF2 oligomerization when Grp94 adopts an open conformation (ADP conditions), but not when Grp94 is in the closed conformation (ATP conditions). We propose that BiP and Grp94 regulate the assembly of proIGF2 oligomers, and that regulated oligomerization may enable proIGF2 to be effectively packaged for export from the ER to the Golgi. Copy rights belong to original authors. Visit the link for more info
Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2020.09.23.309450v1?rss=1 Authors: Rasola, A., Laquatra, C., Sanchez-Martin, C., Minervini, G., Moroni, E., Schiavone, M., Tosatto, S. C. E., Argenton, F., Colombo, G., Bernardi, P., Masgras, I. Abstract: The mitochondrial paralog of the Hsp90 chaperone family TRAP1 is often induced in tumors, but the mechanisms controlling its expression, as well as its physiological functions remain poorly understood. Here, we find that TRAP1 is highly expressed in the early stages of Zebrafish development, and its ablation delays embryogenesis while increasing mitochondrial respiration of fish larvae. TRAP1 expression is enhanced by hypoxic conditions both in developing embryos and in cancer models of Zebrafish and mammals. The TRAP1 promoter contains evolutionary conserved hypoxic responsive elements, and HIF1alpha stabilization increases TRAP1 levels. TRAP1 inhibition by selective compounds or by genetic knock-out maintains a high level of respiration in Zebrafish embryos after exposure to hypoxia. Our data identify TRAP1 as a primary regulator of mitochondrial bioenergetics in highly proliferating cells following reductions in oxygen tension and HIF1alpha stabilization. Copy rights belong to original authors. Visit the link for more info
Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2020.09.12.294975v1?rss=1 Authors: Noddings, C. M., Wang, R. Y.-R., Agard, D. A. Abstract: Hsp90 is a conserved and essential molecular chaperone responsible for the folding and activation of hundreds of client proteins. The glucocorticoid receptor (GR) is a model client that constantly depends on Hsp90 for activity. Previously, we revealed GR ligand binding is inhibited by Hsp70 and restored by Hsp90, aided by the cochaperone p23. However, a molecular understanding of the chaperone-induced transformations that occur between the inactive Hsp70:Hsp90 client-loading complex and an activated Hsp90:p23 client-maturation complex is lacking for GR, or for any client. Here, we present a 2.56A cryo-EM structure of the GR-maturation complex (GR:Hsp90:p23), revealing that the GR ligand binding domain is, surprisingly, restored to a folded, ligand-bound conformation, while simultaneously threaded through the Hsp90 lumen. Also, unexpectedly, p23 directly stabilizes native GR using a previously uncharacterized C-terminal helix, resulting in enhanced ligand-binding. This is the highest resolution Hsp90 structure to date and the first atomic resolution structure of a client bound to Hsp90 in a native conformation, sharply contrasting with the unfolded kinase:Hsp90 structure. Thus, aided by direct cochaperone:client interactions, Hsp90 dictates client-specific folding outcomes. Together with the GR-loading complex structure (Wang et al. 2020), we present the molecular mechanism of chaperone-mediated GR remodeling, establishing the first complete chaperone cycle for any client. Copy rights belong to original authors. Visit the link for more info
In this podcast Dr Marcelo Paez-Pereda talks about his recent paper 'A C-terminal HSP90 inhibitor restores glucocorticoid sensitivity and relieves a mouse allograft model of Cushing disease.' published in Nature Medicine, February 2015.
Fakultät für Chemie und Pharmazie - Digitale Hochschulschriften der LMU - Teil 06/06
FK506 binding protein 5 (FKBP5) has been linked to stress related diseases and treatment response in depression (Binder et al., 2004). The corresponding protein FKBP51 was first identified as co-chaperone of HSP90 in a complex with steroid hormone receptors, where it diminishes hormone affinity and nuclear translocation efficiency of the receptors (Pratt and Toft, 1997; Wochnik et al., 2005). With FKBP5 transcription being induced by glucocorticoid signalling, an ultra-short feedback loop is provided for regulation and termination of GR activity. Dysregulation of this ultra-short feedback loop interferes with the stress hormone regulation and likely contributes to the association of FKBP5 with stress-related psychiatric disorders. Recently, important actions of FKBP51 beyond glucocorticoid signalling have been characterised in shaping the posttranslational regulation of certain molecular pathways in response to treatment with particular psychopharmaca (Gassen et al., 2014, 2015). As a contribution to elucidating the role of FKBP5 in stress related diseases, a two-sided approach was taken in this study by analysing the role of FKBP5 in regulation of transcription and in calibrating the responsiveness of these pathways to psychopharmacological treatment. To elucidate the transcriptional effects of FKBP5 in an unbiased approach, the expression profile of mice with deleted FKBP5 and their litter mates with functional FKBP5 were compared. A marked difference in glyoxalase-1 (GLO1) transcription was observed with higher GLO1 transcription in mice with deleted FKBP5, which was reflected by about two-fold more GLO1 protein in these mice. The efforts in deciphering the role of FKBP5 in elevation of GLO1 expression led to the identification of a duplication of the GLO1 gene inherent to mice with deleted FKBP5; this likely explains the enhanced GLO1 expression in these mice. This observation exemplifies the flanking gene problem and is a note of caution for interpreting data from conventionally generated knock-out mice. Overall, deletion of FKBP5 did not markedly change gene expression. In the second part of this thesis, the molecular effects of psychopharmacologic drugs were profiled for their dependency on FKBP51 function to modulate intracellular pathways relevant for treatment outcome in a cellular FKBP5 knockout model. For this purpose, psychopharmaca from the classes of SSRIs, SSNRIs, TCAs, atypical antidepressants, mood stabilisers, and NMDA receptor antagonists were analysed. In addition to GSK3β and AKT, which were reported to interact with and be targeted by FKBP51 recently (Gassen et al., 2015; Pei et al., 2009), ERK was identified as a novel kinase interacting with and being targeted by FKBP51 in this work. With GSK3β, AKT, and ERK, three major kinases were observed to be regulated by psychopharmaca. The effects were not homogeneous across all psychopharmaca and only loosely followed drug classes. Moreover, regulation of these kinases as well as their downstream targets was non-uniformly influenced by FKBP51. With FKBP51 being a stress induced gene, this transcriptional mechanism efficiently links the stress response to the regulation of the targets analysed in this work. Moreover, markers of autophagy, a cellular degradation process which has been linked to neurotransmission, were detected to be regulated by valproic acid (VPA), a mood stabiliser with HDAC inhibitory activity. VPA, as well as a second HDAC inhibitor butyric acid (BUT) enhanced the transcription of late and delayed autophagy markers controlled by FOXO3 signalling. Considering the versatile action of FKBP51 on targets analysed in this work, the list of proteins modulated by FKBP5 seems by far not complete. The diversity of effects evoked by different psychopharmaca hints to superimposed molecular effects underlying treatment outcome. Better understanding of pathway responsiveness could yield molecular markers for personalised medication that could be utilised to improve treatment outcome in stress related psychiatric diseases.
Neben AM2PM hörst du in HSP90 Songs von Adam Port, Bontan und Sonny Fodera. Außerdem habe ich noch ein paar House Tracks der vergangenen Folgen reingemixt, unter anderem vom City Soul Project, von Electronic Youth & Gardy sowie Harry Romero und Joeski. Den Song „AM2PM – My Feelin“ probierte ich letztes Wochenende bei einer Geburtstagsparty […] Der Beitrag HSP90 Mini-Jubiläum mit House Music von Adam Port, AM2PM, Gardy, Bontan & Sonny Fodera erschien zuerst bei Houseschuh. Verpasse keine Podcast-Folge und werde VIP-Hörer unter houseschuh.com/vip.
Heat shock protein (Hsp) 90 is a ubiquitous protein that helps other proteins to fold and stabilises a number of proteins involved in tumour growth. Dr Banjerji (Institute of Cancer Research, Sutton, United Kingdom) talks to ecancertv at TAT 2015 about his experience with Hsp90 inhibitors and the practicalities of using these drugs in the clinic.
Fakultät für Biologie - Digitale Hochschulschriften der LMU - Teil 05/06
The main function of glucocorticoids in corticotroph cells is to suppress proopiomelanocortin, the precursor of the stress hormone adrenocorticotropin (ACTH). Cushing’s disease is a rare but severe neuroendocrine condition caused by partially glucocorticoid resistant corticotroph adenomas, which consequently secrete excessive amounts of ACTH in an uncontrolled fashion. The patients suffer from chronic hypercortisolism due to excessive stimulation of the adrenal glands by ACTH to produce glucocorticoids. Impairing mutations of the glucocorticoid receptor (GR) only sporadically explain the reduced glucocorticoid sensitivity in the adenomas – the molecular mechanism behind the partial resistance is poorly understood. The function of GR depends on direct interactions with the molecular chaperone Hsp90. Both the reduction and overexpression of Hsp90 impedes GR activity in different experimental settings. Therefore, the expression of the inducible Hsp90α isoform was determined in biopsy specimens of corticotroph pituitary adenomas from patients with Cushing’s disease. Its strong overexpression compared to normal human pituitary cells paved the way to study its role in the function of corticotroph adenomas using small molecules which target Hsp90. The three distinct Hsp90 inhibitors 17–AAG, Novobiocin and Silibinin showed antiproliferative effects in AtT–20 cells through the degradation of the oncogenic client kinase Cdc2, a hallmark of pharmacologic inhibition of Hsp90. Surprisingly, only the N–terminal Hsp90 inhibitor 17–AAG caused the degradation of GR, as was reported also for other Geldanamycin–based Hsp90 inhibitors. Neither Silibinin nor the C–terminal Hsp90 inhibitor Novobiocin affected GR protein levels. These converging effects led to the assumption that both compounds bind to the same domain in Hsp90. It was shown here that Novobiocin displaces Silibinin from the C–terminal domain of Hsp90, and that these compounds dissociate mature GR from Hsp90 at the biochemical level. As a result, increased levels of mature receptor were present in the cell able to bind glucocorticoids with high affinity. This novel molecular mechanism proved to potentiate GR transcriptional activity in AtT–20 cells. The potentiation in GR activity also led to enhanced suppression of ACTH elicited by low concentrations of Dexamethasone in AtT–20 cells and in primary cultures of human corticotroph adenomas from patients with Cushing’s disease. In contrast, Silibinin did not show effects on rat normal pituitary cells. Finally, Silibinin reduced tumor growth, partially reverted hormonal alterations, and alleviated symptoms in a mouse allograft model for Cushing’s disease. These results suggest that the regulation of GR sensitivity by overexpressed Hsp90 may represent a pharmacologically reversible mechanism in the pathogenesis of this disease. Together, a proof of principle is provided that the clinically safe Hsp90 inhibitor Silibinin potentially restores glucocorticoid sensitivity in corticotroph adenomas in vitro and in vivo, and that it might be used to treat Cushing’s patients in the future.
Medizinische Fakultät - Digitale Hochschulschriften der LMU - Teil 17/19
Thu, 23 Oct 2014 12:00:00 +0100 https://edoc.ub.uni-muenchen.de/17897/ https://edoc.ub.uni-muenchen.de/17897/1/Ailer-Maerzluft_Galina.pdf Ailer-Märzluft, Galina
Dr. Edward Garon, David Geffen School of Medicine at UCLA, reviews impressive results from the GALAXY-1 trial of the heat shock protein inhibitor ganetespib combined with combined with second line docetaxel in advanced lung adenocarcinoma.
Dr. Edward Garon, David Geffen School of Medicine at UCLA, reviews impressive results from the GALAXY-1 trial of the heat shock protein inhibitor ganetespib combined with combined with second line docetaxel in advanced lung adenocarcinoma.
Dr. Edward Garon, David Geffen School of Medicine at UCLA, reviews impressive results from the GALAXY-1 trial of the heat shock protein inhibitor ganetespib combined with combined with second line docetaxel in advanced lung adenocarcinoma.
Dr. Edward Garon, David Geffen School of Medicine at UCLA, reviews impressive results from the GALAXY-1 trial of the heat shock protein inhibitor ganetespib combined with combined with second line docetaxel in advanced lung adenocarcinoma.
Dr. Edward Garon, David Geffen School of Medicine at UCLA, reviews impressive results from the GALAXY-1 trial of the heat shock protein inhibitor ganetespib combined with combined with second line docetaxel in advanced lung adenocarcinoma.
Dr. Edward Garon, David Geffen School of Medicine at UCLA, reviews impressive results from the GALAXY-1 trial of the heat shock protein inhibitor ganetespib combined with combined with second line docetaxel in advanced lung adenocarcinoma.
Medizinische Fakultät - Digitale Hochschulschriften der LMU - Teil 15/19
Neuroendocrine tumors are a heterogeneous group of malignancies with an increasing prevalence. Since there is not much progress in therapy, model systems are urgently needed. We have a CEA424-SV40 TAg transgenic mouse model which develops spontaneous tumors in the antral region of the stomach. In addition, several cell lines derived from the tumor were established. Gene expression analysis of the tumor tissue as well as cell lines revealed neuroendocrine markers. Therefore we further characterized this model with special emphasis on the cells of origin and used it for testing new targeted treatment protocols. To analyze CEA424-SV40 TAg mouse model in more detail, tumor tissue as well as the cell lines derived from the primary tumor were investigated by immunohistochemistry, immunofluorescence, western blot, and ELISA. Antibodies used were directed at SV40 TAg, Ki-67, chromogranin A, chromogranin B, secretin, H+-K+-ATPase, glucagon, and transcription factors NeuroD1 and Nkx2.2. Plasma hormone levels of serotonin and secretin were measured by ELISA. Immunostainings of SV40 TAg and Ki-67 revealed highly proliferative tumors cells. The tumors stained intensively for the neuroendocrine markers chromogranin A, chromogranin B, secretin and glucagon. The tumor tissue as well as the cell lines expressed transcription factors NeuroD and Nkx2.2, which are involved in the differentiation of the neuroendocrine lineage. Hormone levels of serotonin and secretin in the plasma of the transgenic mice were dramatically elevated when compared with normal littermates, thus supporting the neuroendocrine phenotype. As the neuroendocrine phenotype of CEA424-SV40 TAg transgenic mouse was confirmed, molecularly targeted therapies were tested in this model system both in vitro and in vivo. Cell lines were tested for drug sensitivity with mTOR inhibitors (RAD001, NVP-BEZ235), paclitaxel, E2F inhibitor, HSP90 inhibitor, and p53 stabilizer Nutlin-3a. All the drugs tested in vitro could efficiently inhibit cell proliferation in a dose dependent manner. From these drugs the mTOR inhibitor RAD001 was chosen for the in vivo experiment. Daily feeding of 10 mg/kg RAD001 inhibited the tumor development and prolonged the survival time of the CEA424-SV40 TAg transgenic mice dramatically. The effects of the RAD001 treatment on tumor cells were achieved mainly through inactivating mTOR-p70S6K and mTOR-4EBP1 signaling as proven by western blot and immunohistochemistry. Still, some cells must develop escape mechanisms, since the tumor tend to grow. To gain a better understanding of the T antigen transforming mechanisms as well as the possible escape mechanisms, some efforts were made on the tumor originating cells in the CEA424-SV40 Tag transgenic mouse model. Possible candidates for these tumor originating cells in the stomach are the newly described epithelial as well as mesenchymal stem cells. In a first attempt, the expression feature of epithelial and mesenchymal stem cell markers were analyzed. Established cell lines as well as tumor tissue from the tumor bearing mice were investigated by reverse transcription PCR (RT-PCR), immunohistochemistry, immunofluorescence, western blot, and microarray analysis. From several markers analyzed, the tumor cell lines showed a high expression level of the potential epithelial stem cell marker Bmi1 in RT-PCR and cDNA expression array. This could be further substantiated by western-blotting and immunostaining. Consequently, Bmi1 message could also be found in the growing tumors both in mRNA and protein levels. Experiments using siRNA to knock down the SV40-TAg expression showed that the Bmi1 expression went down in the cell lines thus showing the interrelationship. On the other hand, the mesenchymal stem cell marker Etv1 was also found to be expressed in the tumor tissue and cell lines derived from the tumor. More interestingly, Etv1 expression level was up-regulated over the time course of the tumor development. From these, an Etv1 positive mesenchymal cell could be a possible candidate for transformation. Since the CEA-promoter used for the generation of the T-antigen transgenic animals contains Etv1 binding sites, it is tempting to speculate, that this may drive the transcription of the T antigen. In conclusion, our data provide convincing evidence that CEA424-SV40 TAg mice are a clinically relevant model for neuroendocrine tumor. Testing of molecularly targeted therapies both in vitro and in vivo offered promising candidates for further clinical evaluation. Thus, this new model system could be of great value not only for studies on the mechanisms of how SV40 TAg induces neuroendocrine tumors but also for exploring novel targeted therapy in a preclinical setting.
Drs. Mary Pinder, Nate Pennell, and Jack West discuss the results presented at ASCO 2013 of the GALAXY-1 trial of the HSP90 inhibitor ganetespib combined with Taxotere (docetaxel) as second line therapy for advanced NSCLC.
Drs. Mary Pinder, Nate Pennell, and Jack West discuss the results presented at ASCO 2013 of the GALAXY-1 trial of the HSP90 inhibitor ganetespib combined with Taxotere (docetaxel) as second line therapy for advanced NSCLC.
Drs. Mary Pinder, Nate Pennell, and Jack West discuss the results presented at ASCO 2013 of the GALAXY-1 trial of the HSP90 inhibitor ganetespib combined with Taxotere (docetaxel) as second line therapy for advanced NSCLC.
Dr. Natasha Leighl, Princess Margaret Hospital in Toronto, Canada, describes emerging data on the efficacy of ALK inhibitors for patients with advanced NSCLC that harbors an ALK or ROS1 rearrangement.
Dr. Natasha Leighl, Princess Margaret Hospital in Toronto, Canada, describes emerging data on the efficacy of ALK inhibitors for patients with advanced NSCLC that harbors an ALK or ROS1 rearrangement.
Dr. Natasha Leighl, Princess Margaret Hospital in Toronto, Canada, describes emerging data on the efficacy of ALK inhibitors for patients with advanced NSCLC that harbors an ALK or ROS1 rearrangement.
Dr. Natasha Leighl, Princess Margaret Hospital in Toronto, Canada, describes emerging data on the efficacy of ALK inhibitors for patients with advanced NSCLC that harbors an ALK or ROS1 rearrangement.
Dr. Natasha Leighl, Princess Margaret Hospital in Toronto, Canada, describes emerging data on the efficacy of ALK inhibitors for patients with advanced NSCLC that harbors an ALK or ROS1 rearrangement.
Dr. Natasha Leighl, Princess Margaret Hospital in Toronto, Canada, describes emerging data on the efficacy of ALK inhibitors for patients with advanced NSCLC that harbors an ALK or ROS1 rearrangement.
Q and A session with Dr. Jared Weiss, Medical Oncologist at UNC-Chapel Hill, about highlights in lung cancer in 2011.
Q and A session with Dr. Jared Weiss, Medical Oncologist at UNC-Chapel Hill, about highlights in lung cancer in 2011.
Dr. Jared Weiss, Medical Oncologist at UNC-Chapel Hill, reviews lung cancer highlights in 2011, with this podcast focusing on ALK rearrangements and new molecular targets in lung cancer.
Dr. Jared Weiss, Medical Oncologist at UNC-Chapel Hill, reviews lung cancer highlights in 2011, with this podcast focusing on ALK rearrangements and new molecular targets in lung cancer.
Background: Surfactant protein C (SP-C) is important for the function of pulmonary surfactant. Heterozygous mutations in SFTPC, the gene encoding SP-C, cause sporadic and familial interstitial lung disease (ILD) in children and adults. Mutations mapping to the BRICHOS domain located within the SP-C proprotein result in perinuclear aggregation of the proprotein. In this study, we investigated the effects of the mutation A116D in the BRICHOS domain of SP-C on cellular homeostasis. We also evaluated the ability of drugs currently used in ILD therapy to counteract these effects. Methods: SP-C-A116D was expressed in MLE-12 alveolar epithelial cells. We assessed in vitro the consequences for cellular homeostasis, immune response and effects of azathioprine, hydroxychloroquine, methylprednisolone and cyclophosphamide. Results: Stable expression of SP-C-A116D in MLE-12 alveolar epithelial cells resulted in increased intracellular accumulation of proSP-C processing intermediates. SP-C-A116D expression further led to reduced cell viability and increased levels of the chaperones Hsp90, Hsp70, calreticulin and calnexin. Lipid analysis revealed decreased intracellular levels of phosphatidylcholine (PC) and increased lyso-PC levels. Treatment with methylprednisolone or hydroxychloroquine partially restored these lipid alterations. Furthermore, SP-C-A116D cells secreted soluble factors into the medium that modulated surface expression of CCR2 or CXCR1 receptors on CD4(+) lymphocytes and neutrophils, suggesting a direct paracrine effect of SP-C-A116D on neighboring cells in the alveolar space. Conclusions: We show that the A116D mutation leads to impaired processing of proSP-C in alveolar epithelial cells, alters cell viability and lipid composition, and also activates cells of the immune system. In addition, we show that some of the effects of the mutation on cellular homeostasis can be antagonized by application of pharmaceuticals commonly applied in ILD therapy. Our findings shed new light on the pathomechanisms underlying SP-C deficiency associated ILD and provide insight into the mechanisms by which drugs currently used in ILD therapy act.
Meme kanserine dair çalışması Türk basınında yer bulan Doç. Dr. Tan İnce ile araştırmaları hakkında görüştük. Doç. Dr. Tan İnce Dr. Tan İnce şu anda Miami Üniversitesi'ne bağlı Miller Tıp Fakültesi'nde Multidisipliner (Çokyaklaşımlı) Kök Hücre Enstitüsü'nde Tümör Kök Hücreleri bölümünü yönetiyor. Kendisine söyleşi için yeniden teşekkür ederiz. Notlar Dr Tan İnce ve ekibinin, bu söyleşide tartıştığımız son makalesi şu: Sandra Santagata vd., 2011. High levels of nuclear heat-shock factor 1 (HSF1) are associated with poor prognosis in breast cancer. Proceedings of the National Academy of Sciences of the United States of America 108:18378-18383. Bu makaleye dair İngilizce basın açıklamasını buradan okuyabilirsiniz. Dr İnce'nin daha önce geliştirdiği kanser hücresi kültürünün makalesi: Tan A. Ince vd., 2007. Transformation of Different Human Breast Epithelial Cell Types Leads to Distinct Tumor Phenotypes. Cancer Cell 12:160-170. HSF1'in bu makalede tartışılan rolünün tarif edildiği makale: Chengkai Dai vd., 2007. Heat Shock Factor 1 Is a Powerful Multifaceted Modifier of Carcinogenesis. Cell 130:1005-1018. Bu makale Dr İnce ile işbirligi yapan Dr Susan Lindquist ekibinin çalışmasını tarif ediyor. HSF1'in rolünü Şekil 1'deki çizimle anlatmaya çalıştım: (A) HSF1, hücre içinde ama çekirdek dışında HSP70 ve HSP90 gibi protenlerle bir arada bulunur. Bu esnada HSF1 henüz etkin değildir. Hücre çeşitli olumsuz fiziksel/kimyasal şartlar altındayken hücre içindeki elverişsiz ortam, çeşitli proteinlerin yapısal özelliklerini ve işlevlerini kaybetmesine yol açar. (B) Bu bozuk proteinlerin temizlenmesi görevi HSP70 ve HSP90 gibi proteinlere düşer. Bu sırada HSF1 bunlarla temasını kaybeder, çekirdek içine aktarılır, etkinleştirilir ve oradaki DNA'ya bağlanır. (C) HSF1, hücreye daha çok HSP70 ve HSP90 ürettirerek elverişsiz ortam ile başa çıkmasını sağlar. Bu esnada hücrenin içindeki ortamın kötüleşmesine (ya da iyileşmesine) bağlı olarak çekirdek içindeki HSF1 miktarı da artacaktır (veya azalacaktır). Şekil 1. HSF1,in hücre içindeki rolü (ölçeksiz çizilmiştir)
Dr. Ross Camidge reviews considerations of who to screen for an ALK rearrangement and additional treatment alternatives for patients with ALK-positive advanced non-small cell lung cancer.
Dr. Ross Camidge reviews considerations of who to screen for an ALK rearrangement and additional treatment alternatives for patients with ALK-positive advanced non-small cell lung cancer.
Annual reviews issue, Computational Analysis of Human Protein Interaction Networks, Proteome-wide changes induced by the HSP90 inhibitor, geldanamycin in anaplastic large cell lymphoma cells, Novel eye-specific calmodulin methylation characterized by protein mapping in Drosophila melanogaster.
Annual reviews issue, Computational Analysis of Human Protein Interaction Networks, Proteome-wide changes induced by the HSP90 inhibitor, geldanamycin in anaplastic large cell lymphoma cells, Novel eye-specific calmodulin methylation characterized by protein mapping in Drosophila melanogaster.
Fakultät für Biologie - Digitale Hochschulschriften der LMU - Teil 02/06
Precursor protein targeting toward surfaces of organelles is assisted by different cytosolic chaperones. The Toc translocon recognizes precursor proteins and facilitates their translocation across the outer envelope of chloroplasts. Toc64 is a subunit of the chloroplast protein import machinery. This work focuses on topological and functional properties of Toc64. The topological prediction of the protein by different programs revealed that Toc64 contains three transmembrane domains, which has been confirmed by the obtained biochemical an experimental results. It was demonstrated that the TPR domain of Toc64 is cytosolic exposed, whereas a second domain of about 30 kDa is exposed to the intermembrane space and protected by the chloroplast outer envelope, which is a part of the amidase and charged regions. Functional analysis demonstrated that Toc64 is a bi-functional preprotein receptor. First, the cytosolic exposed TPR is the docking site for Hsp90 bound precursor proteins. The Hsp90 is recognised by the clamp type TPR of Toc64. Hence, a novel mechanism in which chaperones are recruited for a specific targeting event by a membrane-inserted receptor is outlined. Second, the intermembrane space exposed domain allows the association of Toc64 with the Toc complex and is involved in precursor protein recognition and translocation across the intermembrane space. This domain also participates in the formation of the intermembrane space complex, which involves Toc12, isHsp70 and Tic22.
Fakultät für Chemie und Pharmazie - Digitale Hochschulschriften der LMU - Teil 01/06
Myosine sind molekulare Motoren, die an einer Vielzahl von zellulären Prozessen wie Bewegung, Zellteilung oder Polarität beteiligt sind. Ihr Grundaufbau gliedert sich in Motordomäne, Hals- und Schwanzdomäne. Der Motor interagiert ATP-abhängig mit dem Aktinzytoskelett und ist die krafterzeugende Komponente. Vergleicht man die verschiedenen Myosine miteinander, zeigt der Kopfbereich die höchste Konservierung. An den Motor schliesst sich der Halsbereich an, der die Bindestellen für regulatorische Untereinheiten wie z.B. Calmodulin beinhaltet. Der Schwanzbereich dient zum einem der Interaktion mit der transportierten Fracht und zum anderen der Dimerisierung oder Organisation in Filamente. In der Hefe Saccharomyces cerevisiae findet man fünf Myosine aus drei verschiedenen Klassen. Myo1p ist das einzige Klasse II Myosinund gehört zu den muskelähnlichen Myosinen, die sich in Filamenten organisieren. Myo2p und Myo4p gehören zu den Klasse V Myosinen und vermitteln Prozesse wie Vesikel-Transport, mRNALokalisation und Vererbung von Organellen und Endoplasmatischen Retikulum. Es wird vermutet, dass sie Dimere bilden, die als prozessive Motoren, also eigenständig, durch die Zelle wandern und so ihre Fracht an den Ort ihrer Bestimmung bringen. Myo3p und Myo5p sind in ihrer Funktion redundant und vermitteln als Klasse I Myosine die Endozytose, sowie die Integrität und Polarität des kortikalen Aktinzytoskeletts. Sie liegen als Monomere vor und interagieren über spezifische Domänen in ihren Schwanzbereich mit einer Vielzahl von Proteinen wie z.B. Verprolin oder Komponenten des Arp2/3-Komplexes. Die rekombinante Expression von Myosinen stellt sich als sehr problematisch dar, da sich die Motordomäne nicht spontan in eine funktionelle Konformation falten kann. Verschiedene Publikationen deuten daraufhin, dass für die Faltung dieser Multidomänenstruktur die UCS-Proteine notwendig sind. UCS leitet sich von den Namen der zuerst identifizierten Mitglieder ab (UNC-45 aus C. elegans, Cro1p aus P. anserina und She4p aus S. cerevisiae), welche lediglich die C-terminale UCS-Domäne gemeinsam haben. Für UNC-45 konnte bereits gezeigt werden, das es über die UCS-Domäne mit der Motordomäne von Muskelmyosin interagiert und als Chaperon dessen thermale Aggregation verhindert. Ausserdem interagiert UNC-45 über eine N-terminale TPR-Domäne mit Hsp90 und über den zentralen Bereich mit Hsp70. Im Rahmen meiner Arbeit wurde der Einfluss von She4p auf die Funktion der Myosine untersucht. Es wurde gezeigt, dass She4p über die UCS-Domäne mit der Motordomäne von Klasse I und Klasse V Myosinen interagiertund somit die Lokalisation von Myo3p, Myo4p und Myo5p ermöglicht. Mit Hilfe eines Aktin Pelleting Assays konnte gezeigt werden, dass die Misslokalisation der Klasse I Myosine im she4! Hintergrund durch einen Defekt in der Aktinbindedomäne im Motorbereich verursacht wird. Die Spezifität von She4p für verschiedene Myosinklassen spiegelt sich in der zellulären Verteilung des Proteins wieder. Das UCS-Protein wird Myo2p-abhängig in die Knospenspitze transportiert, um dort die Interaktion zwischen Klasse I Myosinen und dem Aktinzytoskelett zu vermitteln. Im Gegensatz dazu benötigt Myo4p lediglich funktionelles She4p innerhalb der Zelle, da dieses Myosin durch Mutter- und Tochterzelle wandert und somit seinen Regulator überall benötigt. Die Tatsache, ob She4p wie UNC-45 als Chaperon an der Faltung der Motordomäne beteiligt ist, ist weiterhin unklar. Es konnte jedoch in einem Pulldown Experiment und einer Immunpräzipitation eine Interaktion zwischen She4p und Hsp90 festgestellt werden. Es ist daher durchaus möglich, dass She4p als Kochaperon das Hsp90 System zum Myosin rekrutiert, damit die Motordomäne in eine funktionelle Konformation gefaltet wird. Neben der zytoplasmatischen Funktion von She4p scheint es noch eine nukleäre zu geben, da im Pulldown Experiment zahlreiche Proteine gefunden wurden, die Teil des Processosomes der kleinen ribosomalen Untereinheit sind und im Nucleolus lokalisieren. Die Funktion von She4p in diesem Prozess ist noch unbekannt.
Fakultät für Chemie und Pharmazie - Digitale Hochschulschriften der LMU - Teil 01/06
Um die Therapiemöglichkeiten bei depressiven Störungen zu verbessern, ist die Kenntnis der molekularen Grundlagen dieser Erkrankungen notwendig. Die erhöhten basalen Cortisolwerte im Serum von depressiven Patienten und die gestörte negative Rückkopplung der HPA-Achse sind Hinweise darauf, daß die Funktionsweise der Rezeptoren für Corticoide wie Cortisol eingeschränkt ist. Die vorliegende Arbeit beschäftigt sich mit den Cochaperonen für die Corticoid-Signaltransduktion, insbesondere den Immunophiline FKBP51 und FKBP52, sowie p23. Für die Immunophiline wurde entdeckt, daß für ihren Beitrag zu einer effizienten Aktivierung Corticoid-abhängiger Promotoren drei Eigenschaften von Bedeutung sind: 1. Interaktion mit Hsp90, um überhaupt den Zugang zum Heterokomplex zu erhalten, 2. Wechselwirkung mit Dynein, um den nukleären Transport der Rezeptoren zu begünstigen und 3. die Peptidyl-Prolyl-Isomerase-Aktivität. Diese Postulate gründen sich auf die folgenden experimentellen Befunde: Das Immunophilin FKBP51 reduziert als Bestandteil des Heterokomplexes mit Hsp90 und den Corticoidrezeptoren sowohl die Bindungsaffinität (Denny et al., 2000) als auch die nukleäre Translokation des Glucocorticoidrezeptors (GRs) und des Mineralocorticoidrezeptors (MRs). Im Gegensatz zu seinem Homologen FKBP52 zeigt FKBP51 nur eine geringe Interaktion mit dem Motorprotein Dynein, welches für den retrograden Transport verantwortlich ist. Durch Einführung einer Punktmutation, die die Peptidyl-Prolyl-Isomerase-Aktivität inaktiviert, konnte gezeigt werden, daß FKBP51 diese Aktivität nicht für seine inhibierende Wirkung benötigt. Im Gegensatz dazu liefert die PPIase-Aktivität von FKBP52 einen aktiven Beitrag für die Funktionalität der Corticoidrezeptoren, weil die analoge Mutation in FKBP52 zur einer Hemmung der Transaktivierung und nukleären Translokation des GRs und des MRs führt. Da diese Mutante immer noch mit Dynein interagiert, ist allein die Wechselwirkung mit diesem Motorprotein offensichtlich nicht ausreichend für die volle GR-Aktivität. Des weiteren konnte gezeigt werden, daß Polymorphismen im FKBP51-Gen nicht nur mit dem Erfolg einer Antidepressivabehandlung korrelieren, sondern auch mit den Proteinmengen von FKPB51 in Lymphozyten. Schließlich wurde die Bedeutung von p23 analysiert, einem kleinen Cochaperon von Hsp90, dem aber auch eigene Chaperonaktivität zugeschrieben wurde. Durch gezielte Mutationen im p23-Protein war es möglich, seine Chaperonaktivität getrennt von seiner Cochaperon-Funktion zu untersuchen. Dabei stellte sich heraus, daß p23 für die Hemmung der GR-abhängigen Transkription nur als Hsp90-Cochaperon fungiert, weil zwar seine Interaktion mit Hsp90 für diesen Effekt notwendig war, nicht aber seine Chaperonaktivität. Um die beschriebene nukleäre Rolle von p23, die zum Zerfall von GR-Transkriptionskomplexen führt, zu untersuchen, wurde ein konstitutiv nukleärer GR verwendet. Auch hier benötigt p23 für die Hemmung des Rezeptors seine Hsp90-Interaktion, nicht aber seine Chaperonaktivität. Diese Arbeit leistet einen Beitrag zum Verständnis der Rolle von Chaperonen in der Steroid-Signaltransduktion. Darüber hinaus wurden starke Hinweise für eine mögliche Rolle von FKBP51 bei der Depression entdeckt.
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