Cell biology
Abstract
The identification of new sources of β cells is an important endeavor with therapeutic implications for diabetes. Insulin resistance, in physiological states such as pregnancy or in pathological states such as type 2 diabetes (T2D), is characterized by a compensatory increase in β cell mass. To explore the existence of a dynamic β cell reserve, we superimposed pregnancy on the liver-specific insulin receptor–KO (LIRKO) model of insulin resistance that already exhibits β cell hyperplasia and used lineage tracing to track the source of new β cells. Although both control and LIRKO mice displayed increased β cell mass in response to the relative insulin resistance of pregnancy, the further increase in mass in the latter supported a dynamic source that could be traced to pancreatic ducts. Two observations support the translational significance of these findings. First, NOD/SCID-γ LIRKO mice that became pregnant following cotransplantation of human islets and human ducts under the kidney capsule showed enhanced β cell proliferation and an increase in ductal cells positive for transcription factors expressed during β cell development. Second, we identified duct cells positive for immature β cell markers in pancreas sections from pregnant humans and in individuals with T2D. Taken together, during increased insulin demand, ductal cells contribute to the compensatory β cell pool by differentiation/neogenesis.
Authors
Ercument Dirice, Dario F. De Jesus, Sevim Kahraman, Giorgio Basile, Raymond W.S. Ng, Abdelfattah El Ouaamari, Adrian Kee Keong Teo, Shweta Bhatt, Jiang Hu, Rohit N. Kulkarni
Abstract
Fibrosis is a hallmark in the pathogenesis of various diseases, with very limited therapeutic solutions. A key event in the fibrotic process is the expression of contractile proteins, including α-smooth muscle actin (αSMA) by fibroblasts, which become myofibroblasts. Here, we report the results of a high-throughput screening of a library of approved drugs that led to the discovery of haloperidol, a common antipsychotic drug, as a potent inhibitor of myofibroblast activation. We show that haloperidol exerts its antifibrotic effect on primary murine and human fibroblasts by binding to sigma receptor 1, independent from the canonical transforming growth factor-β signaling pathway. Its mechanism of action involves the modulation of intracellular calcium, with moderate induction of endoplasmic reticulum stress response, which in turn abrogates Notch1 signaling and the consequent expression of its targets, including αSMA. Importantly, haloperidol also reduced the fibrotic burden in 3 different animal models of lung, cardiac, and tumor-associated fibrosis, thus supporting the repurposing of this drug for the treatment of fibrotic conditions.
Authors
Michael Rehman, Simone Vodret, Luca Braga, Corrado Guarnaccia, Fulvio Celsi, Giulia Rossetti, Valentina Martinelli, Tiziana Battini, Carlin Long, Kristina Vukusic, Tea Kocijan, Chiara Collesi, Nadja Ring, Natasa Skoko, Mauro Giacca, Giannino Del Sal, Marco Confalonieri, Marcello Raspa, Alessandro Marcello, Michael P. Myers, Sergio Crovella, Paolo Carloni, Serena Zacchigna
Abstract
Human placenta development and a successful pregnancy is incumbent upon precise oxygen-dependent control of trophoblast migration/invasion. Persistent low oxygen leading to failed trophoblast invasion promotes inadequate spiral artery remodeling, a characteristic of preeclampsia. Angiomotin (AMOT) is a multifaceted scaffolding protein involved in cell polarity and migration, yet its upstream regulation and significance in the human placenta remain unknown. Herein, we show that AMOT is primarily expressed in migratory extravillous trophoblast cells (EVTs) of the intermediate and distal anchoring column. Its expression increases after 10 weeks of gestation when oxygen tension rises and EVT migration/invasion peaks. Time-lapse imaging confirmed that the AMOT 80-kDa isoform promotes migration of trophoblastic JEG3 and HTR-8/SVneo cells. In preeclampsia, however, AMOT expression is decreased and its localization to migratory fetomaternal interface EVTs is disrupted. We demonstrate that Jumonji C domain–containing protein 6 (JMJD6), an oxygen sensor, positively regulates AMOT via oxygen-dependent lysyl hydroxylation. Furthermore, in vitro and ex vivo studies show that transforming growth factor-β (TGF-β) regulates AMOT expression, its interaction with polarity protein PAR6, and its subcellular redistribution from tight junctions to cytoskeleton. Our data reveal an oxygen- and TGF-β–driven migratory function for AMOT in the human placenta, and implicate its deficiency in impaired trophoblast migration that plagues preeclampsia.
Authors
Abby Farrell, Sruthi Alahari, Leonardo Ermini, Andrea Tagliaferro, Michael Litvack, Martin Post, Isabella Caniggia
Abstract
The E3 ubiquitin ligase Parkin plays an important role in regulating clearance of dysfunctional or unwanted mitochondria in tissues, including the heart. However, whether Parkin also functions to prevent cardiac aging by maintaining a healthy population of mitochondria is still unclear. Here, we have examined the role of Parkin in the context of mtDNA damage and myocardial aging using a mouse model carrying a proofreading defective mitochondrial DNA polymerase gamma (POLG). We observed both decreased Parkin protein levels and development of cardiac hypertrophy in POLG hearts with age; however, cardiac hypertrophy in POLG mice was neither rescued, nor worsened by cardiac specific overexpression or global deletion of Parkin, respectively. Unexpectedly, mitochondrial fitness did not substantially decline with age in POLG mice when compared to WT. We found that baseline mitophagy receptor-mediated mitochondrial turnover and biogenesis were enhanced in aged POLG hearts. We also observed the presence of megamitochondria in aged POLG hearts. Thus, these processes may limit the accumulation of dysfunctional mitochondria as well as the degree of cardiac functional impairment in the aging POLG heart. Overall, our results demonstrate that Parkin is dispensable for constitutive mitochondrial quality control in a mtDNA mutation model of cardiac aging.
Authors
Benjamin P. Woodall, Amabel M. Orogo, Rita H. Najor, Melissa Q. Cortez, Eileen R. Moreno, Hongxia Wang, Ajit S. Divakaruni, Anne N. Murphy, Asa B. Gustafsson
Abstract
A vast body of literature has established GRK2 as a key player in the development and progression of heart failure. Inhibition of GRK2 improves cardiac function post injury in numerous animal models. In recent years, discovery of several non-canonical GRK2 targets has expanded our view of this kinase. Here, we describe the novel and exciting finding that cardiac GRK2 activity can regulate whole body metabolism. Transgenic mice with cardiac-specific expression of a peptide inhibitor of GRK2 (TgβARKct) display an enhanced obesogenic phenotype when fed a high fat diet (HFD). In contrast, mice with cardiac-specific overexpression of GRK2 (TgGRK2) show resistance to HFD induced obesity. White adipose tissue (WAT) mass was significantly enhanced in HFD fed TgβARKct mice. Furthermore, regulators of adipose differentiation were differentially regulated in WAT from mice with gain or loss of GRK2 function. Using complex metabolomics we found that cardiac GRK2 signaling altered myocardial BCAA and endocannabinoid metabolism and modulated circulating BCAA and endocannabinoid metabolite profiles on a HFD, and one of the BCAA metabolites identified here enhances adipocyte differentiation in vitro. Taken together, these results suggest that metabolic changes in the heart due to GRK2 signaling on a HFD control whole body metabolism.
Authors
Benjamin P. Woodall, Kenneth S. Gresham, Meryl A. Woodall, Mesele-Christina Valenti, Alessandro Cannavo, Jessica Pfleger, J. Kurt Chuprun, Konstantinos Drosatos, Walter J. Koch
Abstract
Systemic lupus erythematosus (SLE) is an autoimmune disorder that predominantly affects women and is driven by autoreactive T cell–mediated inflammation. It is known that individuals with multiple X-chromosomes are at increased risk for developing SLE; however, the mechanisms underlying this genetic basis are unclear. Here, we use single cell imaging to determine the epigenetic features of the inactive X (Xi) in developing thymocytes, mature T cell subsets, and T cells from SLE patients and mice. We show that Xist RNA and heterochromatin modifications transiently reappear at the Xi and are missing in mature single positive T cells. Activation of mature T cells restores Xist RNA and heterochromatin marks simultaneously back to the Xi. Notably, X-chromosome inactivation (XCI) maintenance is altered in T cells of SLE patients and late-stage–disease NZB/W F1 female mice, and we show that X-linked genes are abnormally upregulated in SLE patient T cells. SLE T cells also have altered expression of XIST RNA interactome genes, accounting for perturbations of Xi epigenetic features. Thus, abnormal XCI maintenance is a feature of SLE disease, and we propose that Xist RNA localization at the Xi could be an important factor for maintaining dosage compensation of X-linked genes in T cells.
Authors
Camille M. Syrett, Bam Paneru, Donavon Sandoval-Heglund, Jianle Wang, Sarmistha Banerjee, Vishal Sindhava, Edward M. Behrens, Michael Atchison, Montserrat C. Anguera
Abstract
The possible association between the membrane-associated guanylate kinase with inverted domain structure-1 (MAGI1) and inflammation has been suggested, but the molecular mechanisms underlying this link, especially during atherogenesis, remain unclear. In endothelial cells (ECs) exposed to disturbed flow (d-flow), p90 ribosomal S6 kinase (p90RSK) bound to MAGI1, causing MAGI1-S741 phosphorylation and sentrin/SUMO-specific protease 2 T368 phosphorylation-mediated MAGI1-K931 deSUMOylation. MAGI1-S741 phosphorylation upregulated EC activation via activating Rap1. MAGI1-K931 deSUMOylation induced both nuclear translocation of p90RSK-MAGI1 and ATF-6-MAGI1 complexes, which accelerated EC activation and apoptosis, respectively. Microarray screening revealed key roles for MAGI1 in the endoplasmic reticulum (ER) stress response. In this context, MAGI1 associated with activating transcription factor 6 (ATF-6). MAGI1 expression was upregulated in ECs and macrophages found in atherosclerotic-prone regions of mouse aortas as well as in the colonic epithelia and ECs of patients with inflammatory bowel disease. Further, reduced MAGI1 expression in Magi1–/+ mice inhibited d-flow–induced atherogenesis. In sum, EC activation and ER stress–mediated apoptosis are regulated in concert by two different types of MAGI1 posttranslational modifications, elucidating attractive drug targets for chronic inflammatory disease, particularly atherosclerosis.
Authors
Jun-ichi Abe, Kyung Ae Ko, Sivareddy Kotla, Yin Wang, Jesus Paez-Mayorga, Ik Jae Shin, Masaki Imanishi, Hang Thi Vu, Yunting Tao, Miguel M. Leiva-Juarez, Tamlyn N. Thomas, Jan L. Medina, Jong Hak Won, Yuka Fujii, Carolyn J. Giancursio, Elena McBeath, Ji-Hyun Shin, Liliana Guzman, Rei J. Abe, Jack Taunton, Naoki Mochizuki, William Faubion, John P. Cooke, Keigi Fujiwara, Scott E. Evans, Nhat-Tu Le
Abstract
Tregs require IL-2 signaling for signal transducer and activator of transcription 5 (STAT5)-mediated induction of Foxp3. While phosphatase 2A (PP2A) is a negative regulator of IL-2 production in effector T cells and Tregs do not produce IL-2, it is not known whether PP2A controls IL-2 signaling in Tregs. To address the role of PP2A in IL-2 signaling in Tregs we studied mice engineered to lack PP2A in all Foxp3-expressing cells. We report that PP2A is required to enable Foxp3 expression and to maintain sufficient numbers of Tregs in the thymus. We show for the first time that PP2A prevents the selective loss of surface IL-2Rβ and preserves IL-2R signaling potency in Tregs. The loss of IL-2Rβ in thymus- and spleen-derived Tregs that lack PP2A is due to increased sheddase activity. Pan-sheddase or selective A disintegrin and metalloproteinase 10 (ADAM10) inhibition, like forced expression of IL-2Rβ in PP2A-deficient Tregs restored IL-2Rβ expression and signaling. Thus, PP2A restrains the sheddase activity of ADAM10 in Treg cells to prevent the cleavage of IL-2Rβ from the cell surface to enable competent IL-2R signaling which is essential for Tregs development and homeostasis.
Authors
Amir Sharabi, Hao Li, Isaac R. Kasper, Wenliang Pan, Esra Meidan, Maria G. Tsokos, Vaishali R. Moulton, George C. Tsokos
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
Abstract
Human adipose cells cannot secrete endogenous PPARγ ligands and are dependent on unknown exogenous sources. We postulated that the adipose tissue microvascular endothelial cells (aMVECs) cross-talk with the adipose cells for fatty acid (FA) transport and storage and also may secrete PPARγ ligands. We isolated aMVECs from human subcutaneous adipose tissue and showed that in these cells, but not in (pre)adipocytes from the same donors, exogenous FAs increased cellular PPARγ activation and markedly increased FA transport and the transporters FABP4 and CD36. Importantly, aMVECs only accumulated small lipid droplets and could not be differentiated to adipose cells and are not adipose precursor cells. FA exchange between aMVECs and adipose cells was bidirectional, and FA-induced PPARγ activation in aMVECs was dependent on functional adipose triglyceride lipase (ATGL) protein while deleting hormone-sensitive lipase in aMVECs had no effect. aMVECs also released lipids to the medium, which activated PPARγ in reporter cells as well as in adipose cells in coculture experiments, and this positive cross-talk was also dependent on functional ATGL in aMVECs. In sum, aMVECs are highly specialized endothelial cells, cannot be differentiated to adipose cells, are adapted to regulating lipid transport and secreting lipids that activate PPARγ, and thus, regulate adipose cell function.
Authors
Silvia Gogg, Annika Nerstedt, Jan Boren, Ulf Smith
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