Cell biology
Abstract
Prader-Willi syndrome (PWS) is a developmental disorder caused by loss of maternally imprinted genes on 15q11-q13, including melanoma antigen gene family member L2 (MAGEL2). The clinical phenotypes of PWS suggest impaired hypothalamic neuroendocrine function; however, the exact cellular defects are unknown. Here, we report deficits in secretory granule (SG) abundance and bioactive neuropeptide production upon loss of MAGEL2 in humans and mice. Unbiased proteomic analysis of Magel2pΔ/m+ mice revealed a reduction in components of SG in the hypothalamus that was confirmed in 2 PWS patient–derived neuronal cell models. Mechanistically, we show that proper endosomal trafficking by the MAGEL2-regulated WASH complex is required to prevent aberrant lysosomal degradation of SG proteins and reduction of mature SG abundance. Importantly, loss of MAGEL2 in mice, NGN2-induced neurons, and human patients led to reduced neuropeptide production. Thus, MAGEL2 plays an important role in hypothalamic neuroendocrine function, and cellular defects in this pathway may contribute to PWS disease etiology. Moreover, these findings suggest unanticipated approaches for therapeutic intervention.
Authors
Helen Chen, A. Kaitlyn Victor, Jonathon Klein, Klementina Fon Tacer, Derek J.C. Tai, Celine de Esch, Alexander Nuttle, Jamshid Temirov, Lisa C. Burnett, Michael Rosenbaum, Yiying Zhang, Li Ding, James J. Moresco, Jolene K. Diedrich, John R. Yates III, Heather S. Tillman, Rudolph L. Leibel, Michael E. Talkowski, Daniel D. Billadeau, Lawrence T. Reiter, Patrick Ryan Potts
Abstract
Based on its clinical benefits, Trikafta, the combination of folding correctors VX-661 (tezacaftor), VX-445 (elexacaftor), and the gating potentiator VX-770 (ivacaftor) was FDA-approved for treatment of cystic fibrosis (CF) patients carrying deletion of phenylalanine 508 (F508del) of the CF Transmembrane Conductance Regulator (CFTR) on at least one allele. Neither the mechanism of action of VX-445, nor the susceptibility of rare CF folding mutants to Trikafta are known. Here we show that in human bronchial epithelial cells, VX-445 synergistically restores F508del-CFTR processing in combination with type I or II correctors that target the nucleotide binding domain 1 (NBD1)-membrane spanning domains (MSDs) interface and NBD2, respectively, consistent with a type III corrector mechanism. This inference was supported by the VX-445 binding to and unfolding suppression of the isolated F508del-NBD1 of CFTR. The VX-661+VX-445 treatment restored F508del-CFTR chloride channel function in the presence of VX-770 to ~62% of wild-type CFTR in homozygous nasal epithelia. Substantial rescue of rare misprocessing mutations (S13F, R31C, G85E, E92K, V520F, M1101K and N1303K), confined to MSD1, MSD2, NBD1 and NBD2 of CFTR, was also observed in airway epithelia, suggesting an allosteric correction mechanism and the possible application of Trikafta for patients with rare misfolding mutants of CFTR.
Authors
Guido Veit, Ariel Roldan, Mark A. Hancock, Dillon F. Da Fonte, Haijin Xu, Maytham Hussein, Saul Frenkiel, Elias Matouk, Tony Velkov, Gergely L. Lukacs
Abstract
Actin γ 2, smooth muscle (ACTG2) R257C mutation is the most common genetic cause of visceral myopathy. Individuals with ACTG2 mutations endure prolonged hospitalizations and surgical interventions, become dependent on intravenous nutrition and bladder catheterization, and often die in childhood. Currently, we understand little about how ACTG2 mutations cause disease, and there are no mechanism-based treatments. Our goal was to characterize the effects of ACTG2R257C on actin organization and function in visceral smooth muscle cells. We overexpressed ACTG2WT or ACTG2R257C in primary human intestinal smooth muscle cells (HISMCs) and performed detailed quantitative analyses to examine effects of ACTG2R257C on (a) actin filament formation and subcellular localization, (b) actin-dependent HISMC functions, and (c) smooth muscle contractile gene expression. ACTG2R257C resulted in 41% fewer, 13% thinner, 33% shorter, and 40% less branched ACTG2 filament bundles compared with ACTG2WT. Curiously, total F-actin probed by phalloidin and a pan-actin antibody was unchanged between ACTG2WT- and ACTG2R257C-expressing HISMCs, as was ultrastructural F-actin organization. ACTG2R257C-expressing HISMCs contracted collagen gels similar to ACTG2WT-expressing HISMCs but spread 21% more and were 11% more migratory. In conclusion, ACTG2R257C profoundly affects ACTG2 filament bundle structure, without altering global actin cytoskeleton in HISMCs.
Authors
Sohaib Khalid Hashmi, Vasia Barka, Changsong Yang, Sabine Schneider, Tatyana M. Svitkina, Robert O. Heuckeroth
Abstract
Abstract: S-Nitroso-L-cysteine (L-CSNO) behaves as a ligand. Its soluble guanylate cyclase (sGC)-independent effects are stereoselective - that is, not recapitulated by S-nitroso-D-cysteine (D-CSNO) – and are inhibited by chemical cogeners. However, candidate L-CSNO receptors have never been identified. Here, we have used two complementary affinity chromatography assays - followed by unbiased proteomic analysis - to identify voltage-gated K+ channel (Kv) proteins as binding partners for L-CSNO. Stereoselective L-CSNO-Kv interaction was confirmed structurally and functionally using surface plasmon resonance spectroscopy, hydrogen deuterium exchange and, in Kv1.1/Kv1.2/Kvβ2 overexpressing cells, patch clamp assays. Remarkably, these sGC-independent L-CSNO effects did not involve S-nitrosylation of Kv proteins. In isolated rat and mouse respiratory control (petrosyl) ganglia, L-CSNO stereoselectively inhibited Kv channel function. Genetic ablation of Kv 1.1 prevented this effect. In intact animals, L-CSNO injection at level of the carotid body (CB) dramatically and stereoselectively increased minute ventilation while having no effect on blood pressure; this effect was inhibited by the L-CSNO cogener S-methyl-L-cysteine. Kv proteins are physiologically relevant targets of endogenous L-CSNO. This may be a signaling pathway of broad relevance.
Authors
Benjamin Gaston, Laura A. Smith, Jürgen Bosch, James M. Seckler, Diana L. Kunze, Janna Kiselar, Nadzeya Marozkina, Craig Hodges, Patrick Wintrode, Kellen McGee, Tatiana Morozkina, Spencer T. Burton, Tristan Lewis, Timothy Strassmaier, Paulina Getsy, James N. Bates, Stephen J. Lewis
Abstract
Establishing the interactome of the cancer associated stress protein NUPR1 (NUclear PRotein 1), we found that it binds to several hundreds of proteins, including proteins involved in nuclear translocation, DNA repair and key factors of the SUMO pathway. We demonstrated that the NUPR1 inhibitor ZZW-115, an organic synthetic molecule, competes with importins for the binding to the NLS region of NUPR1 thereby inhibiting its nuclear translocation. We hypothesized, and then proved, that inhibition of NUPR1 by ZZW-115 sensitizes cancer cells to DNA damage induced by several genotoxic agents. Strikingly, we found that treatment with ZZW-115 reduced SUMOylation of several proteins involved in DNA damage response (DDR). We further reported that the presence of recombinant NUPR1 improved the SUMOylation in a cell-free system indicating NUPR1 directly stimulates the SUMOylation machinery. We propose that ZZW-115 sensitizes cancer cells to genotoxic agents by inhibiting the nuclear translocation of NUPR1 and thereby decreasing the SUMOylation dependent functions of key proteins involved in the DDR.
Authors
Wenjun Lan, Patricia Santofimia-Castaño, Mirna Swayden, Yi Xia, Zhengwei Zhou, Stephane Audebert, Luc Camoin, Can Huang, Ling Peng, Ana Jiménez-Alesanco, Adrián Velázquez-Campoy, Olga Abian, Gwen Lomberk, Raul Urrutia, Bruno Rizzuti, Vincent Geli, Philippe Soubeyran, Jose Luis Neira, Juan L. Iovanna
Abstract
Dysregulated sensing of self nucleic acid is a leading cause of autoimmunity in multifactorial and monogenic diseases. Mutations in Wiskott-Aldrich syndrome protein (WASp), a key regulator of cytoskeletal dynamics in immune cells, cause autoimmune manifestations and increased production of type-I interferons by innate cells. Here we show that complexes of self-DNA and autoantibodies (DNA-IC) contribute to elevated interferon levels via activation of the cGAS-STING pathway of cytosolic sensing. Mechanistically, lack of endosomal F-actin nucleation by WASp causes a delay in endolysosomal maturation and prolongs the transit time of ingested DNA-IC. Stalling in maturation-defective organelles facilitates leakage of DNA-IC into the cytosol, promoting activation of the TBK1-STING pathway. Genetic deletion of STING, STING and cGAS chemical inhibitors abolish interferon production and rescue systemic activation of interferon stimulated genes in vivo. These data unveil the contribution of cytosolic self-nucleic acid sensing in WAS and underscore the importance of WASp-mediated endosomal actin remodelling to prevent innate activation.
Authors
Giulia Maria Piperno, Asma Naseem, Giulia Silvestrelli, Roberto Amadio, Nicoletta Caronni, Karla Evelia Cervantes Luevano, Nalan Liv, Judith Klumperman, Andrea Colliva, Hashim Ali, Francesca Graziano, Philippe Benaroch, Hans Haecker, Richard N. Hanna, Federica Benvenuti
Abstract
Histone deacetylase (HDAC) enzymes regulate transcription through epigenetic modification of chromatin structure, but their specific functions in the kidney remain elusive. We discovered that the human kidney expresses class I HDACs. Kidney medullary-specific inhibition of class I HDACs in the rat during high salt feeding results in hypertension, polyuria, hypokalemia, and nitric oxide (NO) deficiency. Three new, inducible murine models were used to determine that HDAC1 and HDAC2 in the kidney epithelium are necessary for maintaining epithelial integrity and maintaining fluid-electrolyte balance during increased dietary sodium intake. Moreover, single nucleus RNA sequencing determined that epithelial HDAC1 and HDAC2 are necessary for expression of many sodium or water transporters and channels. In performing a systematic review and meta-analysis of serious adverse events associated with clinical HDAC inhibitor use, we found that HDAC inhibitors increased the odds ratio of experiencing fluid-electrolyte disorders such as hypokalemia. This study provides insight on the mechanisms of potential serious adverse events with HDAC inhibitors, which may be fatal to critically ill patients. In conclusion, kidney tubular HDACs provide a link between the environment, such as consumption of high salt diets, with regulation of homeostatic mechanisms to remain in fluid-electrolyte balance.
Authors
Kelly A. Hyndman, Joshua S. Speed, Luciano D. Mendoza, John Allan, Jackson Colson, Randee Sedaka, Chunhua Jin, Hyun Jun Jung, Samir El-Dahr, David Pollock, Jennifer Pollock.
Abstract
Over the last years, a number of drugs have been approved for the treatment of cystic fibrosis (CF). Among them, the new Trikafta, a combination of three drugs, holds great promises to radically improve the quality of life for a large part of CF patients carrying one copy of the most frequent CFTR mutation: F508del. Currently available, disease-modifying, CF drugs work by rescuing the function of mutated CFTR (Cystic Fibrosis Transmembrane Conductance Regulator) anion channel. Recent research work shows that membrane lipids, and the cell lipidome in general, play a significant role in the mechanism of CFTR defective trafficking and, on the other hand, in its rescue. In this paper, by using untargeted lipidomics on CFBE41o– cells, we identified distinctive changes in bronchial epithelial cell lipidome associated with treatment with the triple combination VX-661/VX-445/VX-770 (drug name: Trikafta) and other CF drugs. Particularly interesting is the reduction of ceramide levels, known molecular players in the induction of apoptosis, that appears to be associated with a decrease in cell susceptibility to undergo apoptosis. This evidence could account for additional beneficial role of the triple combination on CF phenotypes.
Authors
Nara Liessi, Emanuela Pesce, Clarissa Braccia, Sine Mandrup Bertozzi, Alessandro Giraudo, Tiziano Bandiera, Nicoletta Pedemonte, Andrea Armirotti
Abstract
Pancreatic ductal adenocarcinoma (PDAC) is characterized by a relative paucity of cancer cells that are surrounded by an abundance of non-tumor cells and extracellular matrix, known as stroma. The interaction between stroma and cancer cells contributes to poor outcome, but how proteins from these individual compartments drive aggressive tumor behavior is not known. Here, we report the proteomic analysis of laser-capture microdissected (LCM) PDAC samples. We isolated stroma, tumor, and bulk samples from a cohort with long- and short-term survivors. Compartment-specific proteins were measured by mass spectrometry, yielding the largest PDAC proteome landscape to date. These analyses revealed that in bulk analysis, tumor-derived proteins were typically masked and that LCM was required to reveal biology and novel prognostic markers. We validated tumor CALB2 and stromal COL11A1 expression as compartment-specific prognostic markers. We identified and functionally addressed the contributions of the tumor cell receptor EPHA2 to tumor cell viability and motility, underscoring the value of compartment-specific protein analysis in PDAC.
Authors
Tessa Y.S. Le Large, G. Mantini, Laura L. Meijer, T.V. Pham, N. Funel, Nicole C.T. van Grieken, B. Kok, Jaco C. Knol, H.W.M. van Laarhoven, S.R. Piersma, C.R. Jimenez, G. Kazemier, E. Giovannetti, M.F. Bijlsma
Abstract
Cigarette smoking (CS) and genetic susceptibility determine the risk for development, progression, and severity of chronic obstructive pulmonary diseases (COPD). We posited that an incidental balanced reciprocal chromosomal translocation was linked to a patient’s risk of severe COPD. We determined 46,XX,t(1;4)(p13.1;q34.3) caused a breakpoint in IGSF3 (immunoglobulin superfamily, member 3) gene, with markedly decreased expression. Examination of COPDGene cohort identified 14 IGSF3 SNPs of which, rs1414272 and rs12066192 were directly- and rs6703791 inversely associated with COPD severity, including COPD exacerbations. We confirmed that IGSF3 is a tetraspanin-interacting protein that colocalized with CD9 and integrin B1 in tetraspanin enriched domains. IGSF3-deficient patient-derived lymphoblastoids exhibited multiple alterations in gene expression, especially in the unfolded protein response and ceramide pathways. IGSF3-deficient lymphoblastoids had high ceramide- and sphingosine-1 phosphate-, but low glycosphingolipids- and gangliosides levels; were less apoptotic and more adherent; with marked changes in multiple TNFRSF molecules. Similarly, IGSF3 knockdown increased ceramide in lung structural cells, rendering them more adherent, with impaired wound repair and a weakened barrier function. These findings suggest that, by maintaining sphingolipid and membrane receptor homeostasis, IGSF3 is required for cell mobility-mediated lung injury repair. IGSF3 deficiency may increase susceptibility to CS-induced lung injury in COPD.
Authors
Kelly S. Schweitzer, Natini Jinawath, Raluca Yonescu, Kevin Ni, Natalia Rush, Varodom Charoensawan, Irina Bronova, Evgeny Berdyshev, Sonia M. Leach, Lucas A. Gillenwater, Russell P. Bowler, David B. Pearse, Constance A. Griffin, Irina Petrache
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