TFEB-driven lysosomal biogenesis is pivotal for PGC1α-dependent renal stress resistance

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Abstract

Because injured mitochondria can accelerate cell death through the elaboration of oxidative free radicals and other mediators, it is striking that proliferator gamma coactivator 1-alpha (PGC1α), a stimulator of increased mitochondrial abundance, protects stressed renal cells instead of potentiating injury. Here we report that PGC1α’s induction of lysosomes via transcription factor EB (TFEB) may be pivotal for kidney protection. CRISPR and stable gene transfer showed that PGC1α knockout tubular cells were sensitized to the genotoxic stressor cisplatin whereas transgenic cells were protected. The biosensor mtKeima unexpectedly revealed that cisplatin blunts mitophagy both in cells and mice. PGC1α not only counteracted this effect but also raised basal mitophagy, as did the downstream mediator nicotinamide adenine dinucleotide (NAD+). PGC1α did not consistently affect known autophagy pathways modulated by cisplatin. Instead RNA sequencing identified coordinated regulation of lysosomal biogenesis via TFEB. This effector pathway was sufficiently important that inhibition of TFEB or lysosomes unveiled a striking harmful effect of excess PGC1α in cells and conditional mice. These results uncover an unexpected effect of cisplatin on mitophagy and PGC1α’s exquisite reliance on lysosomes for kidney protection. Finally, the data illuminate TFEB as a novel target for renal tubular stress resistance.

Authors

Matthew R. Lynch, Mei T. Tran, Kenneth M. Ralto, Zsuzsanna K. Zsengeller, Vinod Raman, Swati S. Bhasin, Nuo Sun, Xiuying Chen, Daniel Brown, Ilsa I. Rovira, Kensei Taguchi, Craig R. Brooks, Isaac E. Stillman, Manoj K. Bhasin, Toren Finkel, Samir M. Parikh

Repression of AXL expression by AP-1/JNK blockage overcomes resistance to PI3Ka therapy

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Abstract

AXL overexpression is a common resistance mechanism to anti-cancer therapies, including the resistance to BYL719 (Alpelisib) – the p110α isoform specific inhibitor of phosphoinositide 3-kinase (PI3K) – in esophagus and head and neck squamous cell carcinoma (ESCC, HNSCC respectively). However, the mechanisms underlying AXL overexpression in resistance to BYL719 remain elusive. Here we demonstrated that the AP-1 transcription factors, c-JUN and c-FOS, regulate AXL overexpression in HNSCC and ESCC. The expression of AXL was correlated with that of c-JUN both in HNSCC patients and in HNSCC and ESCC cell lines. Silencing of c-JUN and c-FOS expression in tumor cells downregulated AXL expression and enhanced the sensitivity of human papilloma virus positive (HPVPos) and negative (HPVNeg) tumor cells to BYL719 in vitro. Blocking of the c-JUN N-terminal kinase (JNK) using SP600125 in combination with BYL719 showed a synergistic anti-proliferative effect in vitro, which was accompanied by AXL downregulation and potent inhibition of the mTOR pathway. In vivo, the BYL719–SP600125 drug combination led to the arrest of tumor growth in cell line-derived and patient-derived xenograft models, and in syngeneic head and neck murine cancer models. Collectively, our data suggests that JNK inhibition in combination with anti-PI3K therapy is a new therapeutic strategy that should be tested in HPVPos and HPVNeg HNSCC and ESCC patients.

Authors

Mai Badarni, Manu Prasad, Noa Balaban, Jonathan Zorea, Ksenia M. Yegodayev, Ben-Zion Joshua, Anat Bahat Dinur, Reidar Grénman, Barak Rotblat, Limor Cohen, Moshe Elkabets

Epigenetic loss of the endoplasmic reticulum-associated degradation inhibitor SVIP induces cancer cell metabolic reprogramming

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Abstract

The endoplasmic reticulum (ER) of cancer cells needs to adapt to the enhanced proteotoxic stress associated with the accumulation of unfolded, misfolded and transformation-associated proteins. One way by which tumors thrive in the context of ER stress is by promoting ER-Associated Degradation (ERAD), although the mechanisms are poorly understood. Here, we show that the Small p97/VCP Interacting Protein (SVIP), an endogenous inhibitor of ERAD, undergoes DNA hypermethylation-associated silencing in tumorigenesis to achieve this goal. SVIP exhibits tumor suppressor features and its recovery is associated with increased ER stress and growth inhibition. Proteomic and metabolomic analyses show that cancer cells with epigenetic loss of SVIP are depleted in mitochondrial enzymes and oxidative respiration activity. This phenotype is reverted upon SVIP restoration. The dependence of SVIP hypermethylated cancer cells on aerobic glycolysis and glucose was also associated with sensitivity to an inhibitor of the glucose transporter GLUT1. This could be relevant to the management of tumors carrying SVIP epigenetic loss, because these occur in high-risk patients who manifest poor clinical outcomes. Overall, our study provides insights into how epigenetics helps deal with ER stress and how SVIP epigenetic loss in cancer may be amenable to therapies that target glucose transporters.

Authors

Pere Llinàs-Arias, Margalida Rosselló-Tortella, Paula Lopez-Serra, Montserrat Pérez-Salvia, Fernando Setién, Silvia Marin, Juan P. Muñoz, Alexandra Junza, Jordi Capellades, Maria E. Calleja-Cervantes, Humberto J. Ferreira, Manuel Castro de Moura, Marina Srbic, Anna Martínez-Cardús, Carolina de la Torre, Alberto Villanueva, Marta Cascante, Oscar Yanes, Antonio Zorzano, Catia Moutinho, Manel Esteller

Myeloid Folliculin balances mTOR activation to maintain innate immunity homeostasis

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Abstract

The mTOR pathway is central to most cells. How mTOR is activated in macrophages and modulates macrophage physiology remain poorly understood. The tumor suppressor Folliculin (FLCN) is a GAP for RagC/D, a regulator of mTOR. We show here that LPS potently suppresses FLCN in macrophages, allowing nuclear translocation of the transcription factor TFE3, leading to lysosome biogenesis, cytokine production, and hypersensitivity to inflammatory signals. Nuclear TFE3 additionally activates a transcriptional RagD positive feedback loop that stimulates FLCN-independent canonical mTOR signaling to S6K and increases cellular proliferation. LPS thus simultaneously suppresses the TFE3 arm and activates the S6K arm of mTOR. In vivo, mice lacking myeloid FLCN reveal chronic macrophage activation, leading to profound histiocytic infiltration and tissue disruption, with hallmarks of human histiocytic syndromes like Erdheim-Chester Disease. Our data thus identify a critical FLCN-mTOR-TFE3 axis in myeloid cells, modulated by LPS, that balances mTOR activation and curbs innate immune responses.

Authors

Jia Li, Shogo Wada, Lehn K. Weaver, Chhanda Biswas, Edward M. Behrens, Zoltan Arany

Cardiac hypertrophy and arrhythmia in mice induced by a mutation in ryanodine receptor 2

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Abstract

Hypertrophic cardiomyopathy (HCM) is triggered mainly by mutations in genes encoding sarcomeric proteins, but a significant proportion of patients lack a genetic diagnosis. We identified a novel mutation in the ryanodine receptor 2, RyR2-P1124L, in a patient from a genotype-negative HCM cohort. The aim of this study was to determine whether RyR2-P1124L triggers functional and structural alterations in isolated RyR2 channels and whole hearts. We found that P1124L induces significant conformational changes in the SPRY2 domain of RyR2. Recombinant RyR2-P1124L channels displayed a cytosolic loss-of-function phenotype, which contrasted with a higher sensitivity to luminal [Ca2+], indicating a luminal gain-of-function. Homozygous mice for RyR2-P1124L showed mild cardiac hypertrophy, similar to the human patient. This phenotype, evident at 1 yr of age, was accompanied by an increase in the expression of calmodulin (CaM). P1124L mice also showed higher susceptibility to arrhythmia at 8 mo of age, before the onset of hypertrophy. RyR2-P1124L has a distinct cytosolic loss-of-function and a luminal gain-of-function phenotype. This bifunctionally-divergent behavior triggers arrhythmias and structural cardiac remodeling, and involves overexpression of calmodulin as a potential hypertrophic mediator. This study is relevant to continue elucidating the possible causes of genotype-negative HCM and the role of RyR2 in cardiac hypertrophy.

Authors

Francisco J. Alvarado, J. Martijn Bos, Zhiguang Yuchi, Carmen R. Valdivia, Jonathan J. Hernandez, Yan-Ting Zhao, Dawn S. Henderlong, Yan Chen, Talia R. Booher, Cherisse A. Marcou, Filip Van Petegem, Michael J. Ackerman, Hector H. Valdivia

Disruption of embryonic ROCK signaling reproduces the sarcomeric phenotype of hypertrophic cardiomyopathy

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Abstract

Sarcomeric disarray is a hallmark of gene mutations in patients with Hypertrophic Cardiomyopathy (HCM). However, it is unknown when detrimental sarcomeric changes first occur and whether they originate in the developing embryonic heart. Furthermore, Rho Kinase (ROCK) is a serine threonine protein kinase that is critical for regulating the function of several sarcomeric proteins and therefore, our aim was to determine if disruption of ROCK signalling during the earliest stages of heart development would disrupt the integrity of sarcomeres altering heart development and function. Using a mouse model in which the function of ROCK is specifically disrupted in embryonic cardiomyocytes we demonstrate a progressive cardiomyopathy that first appeared as sarcomeric disarray during cardiogenesis. This led to abnormalities in the structure of embryonic ventricular wall and compensatory cardiomyocyte hypertrophy during foetal development. This sarcomeric disruption and hypertrophy persisted throughout adult life, triggering left ventricular concentric hypertrophy with systolic dysfunction, and re-activation of foetal gene expression and cardiac fibrosis, all typical features of HCM. Taken together, our findings establish a novel mechanism for the developmental origin of the sarcomeric phenotype of HCM and suggest that variants in the ROCK genes or disruption of ROCK signalling could, in part, contribute to its pathogenesis.

Authors

Kate E. Bailey, Guy A. MacGowan, Simon Tual-Chalot, Lauren Phillips, Tim J. Mohun, Deborah J. Henderson, Helen M. Arthur, Simon D. Bamforth, Helen M. Phillips

Secreted cellular prion protein binds doxorubicin and correlates with anthracycline resistance in breast cancer

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Abstract

Anthracyclines are amongst the most effective chemotherapeutics ever developed, but they produce grueling side-effects, serious adverse events and resistance often develops over time. We found that these compounds can be sequestered by secreted cellular Prion protein (PrPC), blocking their cytotoxic activity. This effect was dose-dependent using either cell line-conditioned medium or human serum as a source of PrPC. Genetic depletion of PrPC or inhibition of binding via chelation of ionic copper prevented the interaction and restored cytotoxic activity. This was more pronounced for doxorubicin than its epimer, epirubicin. Investigating the relevance to breast cancer management, we found that the levels of PRNP transcript in pre-treatment tumor biopsies stratified relapse-free survival after neoadjuvant treatment with anthracyclines, particularly amongst doxorubicin-treated patients with residual disease at surgery (p=2.8E-08). These data suggest that local sequestration could mediate treatment resistance. Consistent with this, tumor cell expression of PrPC protein correlated with poorer response to doxorubicin but not epirubicin in an independent cohort analyzed by immunohistochemistry, particularly soluble isoforms released into the extracellular environment by shedding (p=0.015). These findings have important potential clinical implications for frontline regimen decision-making. We suggest there is warranted utility for prognostic PrPC/PRNP assays to guide chemo-sensitization strategies that exploit an understanding of PrPC-anthracycline-copper ion complexes.

Authors

Adrian P. Wiegmans, Jodi M. Saunus, Sunyoung Ham, Richard J. Lobb, Jamie R. Kutasovic, Andrew J. Dalley, Mariska Miranda, Caroline Atkinson, Simote T. Foliaki, Kaltin Ferguson, Colleen Niland, Cameron N. Johnstone, Victoria Lewis, Steven Collins, Sunil R. Lakhani, Fares Al-Ejeh, Andreas Möller

Targeting insulin to the liver corrects defects in glucose metabolism caused by peripheral insulin delivery

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Abstract

Peripheral hyperinsulinemia resulting from subcutaneous insulin injection is associated with metabolic defects which include abnormal glucose metabolism. The first aim of this study was to quantify the impairments in liver and muscle glucose metabolism that occur when insulin is delivered via a peripheral vein compared to when it is given through its endogenous secretory route (the hepatic portal vein) in overnight fasted conscious dogs. The second aim was to determine if peripheral delivery of a hepato-preferential insulin analog could restore the physiologic response to insulin that occurs under meal feeding conditions. This study is the first to show that hepatic glucose uptake correlates with insulin’s direct effects on the liver under hyperinsulinemic-hyperglycemic conditions. In addition, glucose uptake was equally divided between the liver and muscle when insulin was infused into the portal vein, but when it was delivered into a peripheral vein the percentage of glucose taken up by muscle was 4-times greater than that going to the liver, with liver glucose uptake being less than half of normal. These defects could not be corrected by adjusting the dose of peripheral insulin. On the other hand, hepatic and non-hepatic glucose metabolism could be fully normalized by a hepato-preferential insulin analog.

Authors

Dale S. Edgerton, Melanie Scott, Ben Farmer, Phillip E. Williams, Peter Madsen, Thomas Kjeldsen, Christian L. Brand, Christian Fledelius, Erica Nishimura, Alan D. Cherrington

Sleeve gastrectomy rapidly enhances islet function independently of body weight

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Abstract

Bariatric surgeries including vertical sleeve gastrectomy (VSG) ameliorate obesity and diabetes. Weight-loss and accompanying increases to insulin sensitivity contribute to improved glycemia after surgery, however, studies in humans also suggest weight-independent actions of bariatric procedures to lower blood glucose, possibly by improving insulin secretion. To evaluate this hypothesis, we compared VSG operated mice with pair-fed, sham-surgical controls (PF-Sham) 2 weeks after surgery. This paradigm yielded similar post-operative body weight and insulin sensitivity between VSG and calorically restricted PF-Sham animals. However, VSG improved glucose tolerance and markedly enhanced insulin secretion during oral nutrient and intraperitoneal glucose challenges compared to controls. Islets from VSG mice displayed a unique transcriptional signature enriched for genes involved in Ca2+ signaling and insulin secretion pathways. This finding suggests that bariatric surgery leads to intrinsic changes within the islet that alter function. Indeed, islets isolated from VSG mice had increased glucose-stimulated insulin secretion and a left-shifted glucose sensitivity curve compared to islets from PF-Sham mice. Isolated islets from VSG animals showed corresponding increases in the pulse duration of glucose-stimulated Ca2+ oscillations. Together these findings demonstrate a weight-independent improvement in glycemic control following VSG, which is, in part, driven by improved insulin secretion and associated with substantial changes in islet gene expression. These results support a model in which β-cells play a key role in the adaptation to bariatric surgery and the improved glucose tolerance that is typical of these procedures.

Authors

Jonathan D. Douros, Jingjing Niu, Sophia M. Sdao, Trillian Gregg, Kelsey H. Fisher-Wellman, Manish S. Bharadwaj, Anthony Molina, Ramamani Arumugam, Mackenzie D. Martin, Enrico Petretto, Matthew J. Merrins, Mark A. Herman, Jenny Tong, Jonathan E. Campbell, David D'Alessio

Stem cell-derived tissue-associated regulatory T cells suppress the activity of pathogenic cells in autoimmune diabetes

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Abstract

The auto antigen (Ag)-specific regulatory T cells (Tregs) from pluripotent stem cells (PSCs), i.e., PSC-Tregs, have the ability to suppress autoimmunity. PSC-Tregs can be programmed to be tissue-associated and to infiltrate into local inflamed tissues to suppress autoimmune responses after adoptive transfer. Nevertheless, the mechanisms by which the auto Ag-specific PSC-Tregs suppress the autoimmune response remain to be fully elucidated. In this study, we generated the functional auto Ag-specific Tregs from the induced PSC (iPSCs), i.e., iPSC-Tregs, and investigated the underlying mechanisms of autoimmunity suppression by these Tregs in a type 1 diabetes (T1D) murine model. A double transgenic (Tg) mouse model of T1D was established in F1 mice in which the first generation of RIP-mOVA Tg mice that were crossed with OT-I T cell receptor (TCR) Tg mice was challenged with vaccinia viruses expressing OVA (VACV-OVA). We show that adoptive transfer of OVA-specific iPSC-Tregs greatly suppressed autoimmunity in the animal model and prevented the insulin-secreting pancreatic β cells from destruction. Further, we demonstrate that the adoptive transfer significantly reduced the expression of ICAM-1 in the diabetic pancreas and inhibited the migration of pathogenic CD8+ T cells and the production of the pro-inflammatory IFN-γ in the pancreas. These results indicate that the stem cell-derived tissue-associated Tregs can robustly accumulate in the diabetic pancreas, and through down-regulating the expression of ICAM-1 in the local inflamed tissues and inhibiting the production of pro-inflammatory cytokine IFN-γ, suppress the migration and activity of the pathogenic immune cells that cause T1D.

Authors

Mohammad Haque, Fengyang Lei, Xiaofang Xiong, Jugal Kishore Das, Xingcong Ren, Deyu Fang, Shahram Salek-Ardakani, Jin-Ming Yang, Jianxun Song