Cell biology
Abstract
α-1 antitrypsin (AAT) is a serine protease inhibitor that plays a pivotal role in maintaining lung homeostasis. The most common AAT allele associated with AAT deficiency (AATD) is PiZ. Z-AAT accumulates in cells due to misfolding, causing severe AATD. The major function of AAT is to neutralize neutrophil elastase in the lung. It is generally accepted that loss of antiprotease function is a major cause of COPD in individuals with AATD. However, it is now being recognized that the toxic gain-of-function effect of Z-AAT in macrophage likely contributes to lung disease. In the present study, we determined that TLR7 signaling is activated in Z-MDMs, and the expression level of NLRP3, one of the targets of TLR7 signaling, is significantly higher in Z- compared with M-MDMs. We also determined that the level of endosomal Alu RNA is significantly higher in Z-compared with M-MDMs. Alu RNA is a known endogenous ligand that activates TLR7 signaling. Z-AAT likely induces the expression of Alu elements in MDMs and accelerates monocyte death, leading to the higher level of endosomal Alu RNA in Z-MDMs. Taken together,this study identifies a mechanism responsible for the toxic gain of function of Z-AAT macrophages.
Authors
Jungnam Lee, Naweed Mohammad, Yuanqing Lu, Keunsoo Kang, Kyudong Han, Mark Brantly
Abstract
Women of African ancestry suffer higher rates of breast cancer mortality compared to all other groups in the United States. Though the precise reasons for these disparities remain unclear, many recent studies have implicated a role for differences in tumor biology. Using an epitope-validated antibody against the endoplasmic reticulum-associated degradation (ERAD) E3 ubiquitin ligase, gp78, we show that elevated levels of gp78 in patient breast cancer cells predict poor survival. Moreover, high levels of gp78 are associated with poor outcomes in both ER-positive and ER-negative tumors, and breast cancers expressing elevated amounts of gp78 protein are enriched in gene expression pathways that influence cell cycle, metabolism, receptor-mediated signaling, and cell stress response pathways. In multivariate analysis adjusted for subtype and grade, gp78 protein is an independent predictor of poor outcomes in women of African ancestry. Furthermore, gene expression signatures, derived from patients stratified by gp78 protein expression, are strong predictors of recurrence and pathological complete response in retrospective clinical trial data and share many common features with gene sets previously identified to be overrepresented in breast cancers based on race. These findings implicate a prominent role for gp78 in tumor progression and offer new insights into our understanding of racial differences in breast cancer outcomes.
Authors
Sandeep K. Singhal, Jung S. Byun, Tingfen Yan, Ryan Yancey, Ambar Caban, Sara Gil Hernandez, Sediqua Bufford, Stephen M. Hewitt, Joy Winfield, Jaya Sarin Pradhan, Vesco Mustkov, Jasmine A. McDonald, Eliseo J. Pérez-Stable, Anna Maria Napoles, Nasreen Vohra, Adriana De Siervi, Clayton Yates, Melissa B. Davis, Mei Yang, Yien Che Tsai, Allan M. Weissman, Kevin Gardner
Abstract
Long non-coding RNA (lncRNA) plays a crucial role in the pathogenesis of various diseases, including colorectal cancer (CRC). The gene mutations of Adenomatous polyposis coli (APC) were found in most colorectal cancer patients. They are functioned as an important inducer of tumorigenesis. Based on our microarray results, we identified a specific upregulated lncRNA in colorectal cancer (SURC). Further analysis showed that high SURC expression correlated with poorer disease-free survival and overall survival in patients with colorectal cancer. Besides, we found that mutated APC genes can promote the transcription of SURC by reducing the degradation of β-catenin protein in colorectal cancer. Functional assays revealed that knockdown of SURC impaired CRC cell proliferation, colony formation, cell cycle and tumor growth. Additionally, SURC can promote CCND2 expression by inhibiting the expression of miR-185-5p in CRC cells. In conclusion, we demonstrate that SURC is a specific upregulated lncRNA in CRC and the SURC/miR-185-5p/CCND2 axis may be targetable for CRC diagnosis and therapy.
Authors
Junshu Li, Yanhong Ji, Na Chen, Huiling Wang, Chao Fang, Xiaonan Yin, Zhiyuan Jiang, Zhexu Dong, Dan Zhu, Jiamei Fu, Wencheng Zhou, Ruiyi Jiang, Ling He, Zhang Hantao, Gang Shi, Lin Cheng, Xiaolan Su, Lei Dai, Hongxin Deng
Abstract
The survival of motor neuron (SMN) protein is a major component of the pre-mRNA splicing machinery and is required for RNA metabolism. Although SMN has been considered a fundamental gene for the central nervous system, due to its relationship with neuromuscular diseases, such as spinal muscular atrophy, recent studies have also revealed the requirement of SMN in non-neuronal cells in the peripheral regions. Here, we report that the fibro-adipogenic progenitor subpopulation expressing Dpp4 (Dpp4+ FAPs) is required for the neuromuscular system. Furthermore, we also reveal that BRCA1-associated protein-1 (Bap1) is crucial for the stabilization of SMN in FAPs by preventing its ubiquitination-dependent degradation. Inactivation of Bap1 in FAPs decreased SMN levels and accompanied degeneration of the neuromuscular junction, leading to loss of motor neurons and muscle atrophy. Overexpression of the ubiquitination-resistant SMN variant, SMNK186R, in Bap1-null FAPs completely prevented neuromuscular degeneration. In addition, transplantation of Dpp4+ FAPs, but not Dpp4– FAPs, completely rescued neuromuscular defects. Our data reveal the crucial role of Bap1-mediated SMN stabilization in Dpp4+ FAPs for the neuromuscular system and provide the possibility of cell-based therapeutics to treat neuromuscular diseases.
Authors
Ji-Hoon Kim, Jong-Seol Kang, Kyusang Yoo, Jinguk Jeong, Inkuk Park, Jong Ho Park, Joonwoo Rhee, Shin Jeon, Young-Woo Jo, Sang-Hyeon Hann, Minji Seo, Seungtae Moon, Soo-Jong Um, Rho Hyun Seong, Young-Yun Kong
Abstract
The eukaryotic CDC45/MCM2-7/GINS (CMG) helicase unwinds the DNA double helix during DNA replication. The GINS subcomplex is required for helicase activity and is, therefore, essential for DNA replication and cell viability. Here, we report the identification of 7 individuals from 5 unrelated families presenting with a Meier-Gorlin syndrome–like (MGS-like) phenotype associated with hypomorphic variants of GINS3, a gene not previously associated with this syndrome. We found that MGS-associated GINS3 variants affecting aspartic acid 24 (D24) compromised cell proliferation and caused accumulation of cells in S phase. These variants shortened the protein half-life, altered key protein interactions at the replisome, and negatively influenced DNA replication fork progression. Yeast expressing MGS-associated variants of PSF3 (the yeast GINS3 ortholog) also displayed impaired growth, S phase progression defects, and decreased Psf3 protein stability. We further showed that mouse embryos homozygous for a D24 variant presented intrauterine growth retardation and did not survive to birth, and that fibroblasts derived from these embryos displayed accelerated cellular senescence. Taken together, our findings implicate GINS3 in the pathogenesis of MGS and support the notion that hypomorphic variants identified in this gene impaired cell and organismal growth by compromising DNA replication.
Authors
Mary E. McQuaid, Kashif Ahmed, Stephanie Tran, Justine Rousseau, Ranad Shaheen, Kristin D. Kernohan, Kyoko E. Yuki, Prerna Grover, Ema S. Dreseris, Sameen Ahmed, Lucie Dupuis, Jennifer Stimec, Mary Shago, Zuhair N. Al-Hassnan, Roch Tremblay, Philipp G. Maass, Michael D. Wilson, Eyal Grunebaum, Kym M. Boycott, François-Michel Boisvert, Sateesh Maddirevula, Eissa A. Faqeih, Fahad Almanjomi, Zaheer Ullah Khan, Fowzan S. Alkuraya, Philippe M. Campeau, Peter Kannu, Eric I. Campos, Hugo Wurtele
Abstract
Vertical sleeve gastrectomy (VSG) results in an increase in the number of hormone-secreting enteroendocrine cells (EECs) in the intestinal epithelium, however the mechanism remains unclear. Notably, the beneficial effects of VSG are lost in a mouse model lacking the nuclear bile acid receptor, farnesoid X receptor (FXR). FXR is a nuclear transcription factor that has been shown to regulate intestinal stem cell (ISC) function in cancer models. Therefore, we hypothesized that the VSG-induced increase in EECs is due to changes in intestinal differentiation driven by an increase in bile acid signaling through FXR. To test this, we performed VSG in mice that express eGFP in ISC/progenitor cells and performed RNA-seq on GFP-positive cells sorted from the intestinal epithelia. We also assessed changes in EEC number (marked by GLP-1) in mouse intestinal organoids following treatment with bile acids, an FXR agonist, and a FXR antagonist. RNA-seq of ISCs revealed that bile acids receptors are expressed in ISCs and that VSG explicitly alters expression of several genes that regulate EEC differentiation. Mouse intestinal organoids treated with bile acids and two different FXR agonists increased GLP-1-positive cell numbers, and administration of an FXR antagonist blocked these effects. Taken together, these data indicate that VSG drives ISC fate towards EEC differentiation through bile acid signaling.
Authors
Ki-Suk Kim, Bailey C.E. Peck, Yu-Han Hung, Kieran Koch-Laskowski, Landon Wood, Priya H. Dedhia, Jason R. Spence, Randy J. Seeley, Praveen Sethupathy, Darleen A. Sandoval
Abstract
Aberrant epithelial differentiation and regeneration contribute to colon pathologies including inflammatory bowel disease (IBD) and colitis-associated cancer (CAC). MTG16 (CBFA2T3) is a transcriptional corepressor expressed in the colonic epithelium. MTG16 deficiency in mice exacerbates colitis and increases tumor burden in CAC, though the underlying mechanisms remain unclear. Here, we identified MTG16 as a central mediator of epithelial differentiation, promoting goblet and restraining enteroendocrine cell development in homeostasis and enabling regeneration following dextran sulfate sodium (DSS)-induced colitis. Transcriptomic analyses implicated increased E box-binding transcription factor (E protein) activity in MTG16-deficient colon crypts. Using a novel mouse model with a point mutation that attenuates MTG16:E protein interactions (Mtg16P209T), we established that MTG16 exerts control over colonic epithelial differentiation and regeneration by repressing E protein-mediated transcription. Mimicking murine colitis, MTG16 expression was increased in biopsies from patients with active IBD compared to unaffected controls. Finally, uncoupling MTG16:E protein interactions partially phenocopied the enhanced tumorigenicity of Mtg16-/- colon in the azoxymethane(AOM)/DSS-induced model of CAC, indicating that MTG16 protects from tumorigenesis through additional mechanisms. Collectively, our results demonstrate that MTG16, via its repression of E protein targets, is a key regulator of cell fate decisions during colon homeostasis, colitis, and cancer.
Authors
Rachel E. Brown, Justin Jacobse, Shruti A. Anant, Koral M. Blunt, Bob Chen, Paige N. Vega, Chase T. Jones, Jennifer M. Pilat, Frank Revetta, Aidan H. Gorby, Kristy R. Stengel, Yash A. Choksi, Kimmo Palin, M. Blanca Piazuelo, Mary K. Washington, Ken S. Lau, Jeremy A. Goettel, Scott W. Hiebert, Sarah P. Short, Christopher S. Williams
Abstract
PRDM1 encodes B lymphocyte-induced maturation protein 1 (BLIMP1), also known as a master regulator of T-cell homeostasis. We observed a negative relationship between Blimp-1 and IL-21 based on our previous data that Blimp-1 overexpression in T cells suppresses autoimmune diabetes while Blimp-1 deficient T cells contribute to colitis in NOD mice. Reanalysis of published datasets also reveals an inverse correlation between PRDM1 and IL21 in Crohn’s disease. Here, we illustrate that Blimp-1 represses IL-21 by reducing chromatin accessibility and evicting an IL-21 activator c-Maf from the Il21 promoter. Moreover, IL-21-accelerated autoimmune diabetogenesis in small ubiquitin-like modifier-defective c-Maf transgenic mice can be overridden by Blimp-1 overexpression-mediated reduction in permissive chromatin structures at Il21 promoter. An autoregulatory feedback loop to harness IL-21 expression is unveiled by the evidence that addition of IL-21 induces time-dependent Blimp-1 expression and subsequently enriches its binding to the Il21 promoter to suppress IL-21 overproduction. Furthermore, intervention of this feedback loop by IL-21 blockade, IL-21R.Fc administration or IL-21 receptor deletion, attenuates Blimp-1 deficiency-mediated colitis and reinforces the circuit between Blimp-1 and IL-21 in the regulation of autoimmunity. We highlight the translation of Blimp-1-based epigenetic and transcriptomic profiles applicable to a personalized medicine approach in autoimmune diseases.
Authors
Yu-Wen Liu, Shin-Huei Fu, Ming-Wei Chien, Chao-Yuan Hsu, Ming-Hong Lin, Jia-Ling Dong, Rita Jui-Hsien Lu, Yi-Jing Lee, Pao-Yang Chen, Chih-Hung Wang, Huey-Kang Sytwu
Abstract
COVID-19 infection causes collapse of glomerular capillaries and loss of podocytes, terminating in a severe kidney disease called COVID-19 associated nephropathy (COVAN). The underlying mechanism of COVAN is unknown. We hypothesized that cytokines induced by COVID-19 trigger expression of pathogenic APOL1 via JAK-STAT signaling, resulting in podocyte loss and COVAN phenotype. Here, based on nine biopsy-proven COVAN cases, we demonstrated for the first time that APOL1 protein is abundantly expressed in podocytes and glomerular endothelial cells (GECs) of COVAN kidneys but not in controls. Moreover, a majority (77.8%) of COVAN patients carried two APOL1 risk alleles. We showed that recombinant cytokines induced by SARS-CoV-2 act synergistically to drive APOL1 expression through the JAK-STAT pathway in primary human podocytes, GECs, and kidney micro-organoids derived from a carrier of two APOL1 risk alleles but was blocked by JAK1/2-inhibitor, baricitinib. We demonstrated for the first time that cytokine-induced JAK-STAT-APOL1 signaling reduced the viability of kidney organoid podocytes but was rescued by baricitinib. Together, our results support the conclusion that COVID-19-induced cytokines are sufficient to drive COVAN-associated podocytopathy via JAK-STAT-APOL1 signaling and that JAK-inhibitor could block this pathogenic process. These findings suggest that JAK-inhibitors may have therapeutic benefits for managing cytokine-induced APOL1-mediated podocytopathy.
Authors
Sarah E. Nystrom, Guojie Li, Somenath Datta, Karen Soldano, Daniel Silas, Astrid Weins, Gentzon Hall, David B. Thomas, Opeyemi A. Olabisi
Abstract
Systemic therapies for pancreatic ductal adenocarcinoma (PDAC) remain unsatisfactory. Clinical prognosis is particularly poor for tumor subtypes with activating aberrations in the MYC pathway creating an urgent need for novel therapeutic targets. To unbiasedly find novel MYC-associated epigenetic dependencies, we conducted a drug screen in pancreatic cancer cell lines. Here, we found protein arginine N-methyltransferase 5 (PRMT5) inhibitors to trigger a MYC-associated dependency. In human and murine PDACs, a robust connection of MYC and PRMT5 was detected. By the use of gain- and loss-of-function models, we confirm the increased efficacy of PRMT5 inhibitors in MYC deregulated PDACs. Although inhibition of PRMT5 is inducing DNA-damage and arresting PDAC cells in the G2/M-phase of the cell cycle, apoptotic cell death was executed predominantly in cells with high MYC expression. Experiments in primary patient-derived PDAC models demonstrated the existence of a highly PRMT5 inhibitor sensitive subtype. Our work suggests developing PRMT5 inhibitor-based therapies for PDAC.
Authors
Felix Orben, Katharina Lankes, Christian Schneeweis, Zonera Hassan, Hannah Jakubowsky, Lukas Krauß, Fabio Boniolo, Carolin Schneider, Arlett P.G. Schäfer, Janine Murr, Christoph Schlag, Bo Kong, Rupert Öllinger, Chengdong Wang, Georg Beyer, Ujjwal Mukund Mahajan, Yonggan Xue, Julia Mayerle, Roland M. Schmid, Bernhard Kuster, Roland Rad, Christian J. Braun, Matthias Wirth, Maximilian Reichert, Dieter Saur, Günter Schneider
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