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Distinct changes in endosomal composition promote NLRP3 inflammasome activation. Nat Immunol 2023; 24:30-41. [PMID: 36443515 PMCID: PMC9810532 DOI: 10.1038/s41590-022-01355-3] [Citation(s) in RCA: 29] [Impact Index Per Article: 29.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2022] [Accepted: 10/06/2022] [Indexed: 11/30/2022]
Abstract
Inflammasome complexes are pivotal in the innate immune response. The NLR family pyrin domain containing protein 3 (NLRP3) inflammasome is activated in response to a broad variety of cellular stressors. However, a primary and converging sensing mechanism by the NLRP3 receptor initiating inflammasome assembly remains ill defined. Here, we demonstrate that NLRP3 inflammasome activators primarily converge on disruption of endoplasmic reticulum-endosome membrane contact sites (EECS). This defect causes endosomal accumulation of phosphatidylinositol 4-phosphate (PI4P) and a consequent impairment of endosome-to-trans-Golgi network trafficking (ETT), necessary steps for endosomal recruitment of NLRP3 and subsequent inflammasome activation. Lowering endosomal PI4P levels prevents endosomal association of NLRP3 and inhibits inflammasome activation. Disruption of EECS or ETT is sufficient to enhance endosomal PI4P levels, to recruit NLRP3 to endosomes and to potentiate NLRP3 inflammasome activation. Mice with defects in ETT in the myeloid compartment are more susceptible to lipopolysaccharide-induced sepsis. Our study thus identifies a distinct cellular mechanism leading to endosomal NLRP3 recruitment and inflammasome activation.
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Wilhelmi I, Grunwald S, Gimber N, Popp O, Dittmar G, Arumughan A, Wanker EE, Laeger T, Schmoranzer J, Daumke O, Schürmann A. The ARFRP1-dependent Golgi scaffolding protein GOPC is required for insulin secretion from pancreatic β-cells. Mol Metab 2020; 45:101151. [PMID: 33359402 PMCID: PMC7811047 DOI: 10.1016/j.molmet.2020.101151] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/15/2020] [Revised: 12/15/2020] [Accepted: 12/15/2020] [Indexed: 12/13/2022] Open
Abstract
Objective Hormone secretion from metabolically active tissues, such as pancreatic islets, is governed by specific and highly regulated signaling pathways. Defects in insulin secretion are among the major causes of diabetes. The molecular mechanisms underlying regulated insulin secretion are, however, not yet completely understood. In this work, we studied the role of the GTPase ARFRP1 on insulin secretion from pancreatic β-cells. Methods A β-cell-specific Arfrp1 knockout mouse was phenotypically characterized. Pulldown experiments and mass spectrometry analysis were employed to screen for new ARFRP1-interacting proteins. Co-immunoprecipitation assays as well as super-resolution microscopy were applied for validation. Results The GTPase ARFRP1 interacts with the Golgi-associated PDZ and coiled-coil motif-containing protein (GOPC). Both proteins are co-localized at the trans-Golgi network and regulate the first and second phase of insulin secretion by controlling the plasma membrane localization of the SNARE protein SNAP25. Downregulation of both GOPC and ARFRP1 in Min6 cells interferes with the plasma membrane localization of SNAP25 and enhances its degradation, thereby impairing glucose-stimulated insulin release from β-cells. In turn, overexpression of SNAP25 as well as GOPC restores insulin secretion in islets from β-cell-specific Arfrp1 knockout mice. Conclusion Our results identify a hitherto unrecognized pathway required for insulin secretion at the level of trans-Golgi sorting. β-cell specific deletion of the trans-Golgi residing small GTPase ARFRP1 leads to elevated blood glucose levels in mice. GOPC is a newly identified ARFRP1 dependent scaffolding protein. ARFRP1 and GOPC are required for glucose-stimulated insulin secretion from pancreatic β-cells.
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Affiliation(s)
- Ilka Wilhelmi
- German Institute of Human Nutrition (DIfE) Potsdam-Rehbruecke, Germany; German Center for Diabetes Research (DZD) Munich Neuherberg, Germany
| | - Stephan Grunwald
- Max-Delbrück Center for Molecular Medicine in the Helmholtz Association Berlin, Germany; Institute of Chemistry and Biochemistry, Freie Universität Berlin, Germany
| | - Niclas Gimber
- Advanced Medical Bioimaging Core Facility - AMBIO, Charité-Universitätsmedizin Berlin, Germany
| | - Oliver Popp
- Max-Delbrück Center for Molecular Medicine in the Helmholtz Association Berlin, Germany
| | - Gunnar Dittmar
- Max-Delbrück Center for Molecular Medicine in the Helmholtz Association Berlin, Germany
| | - Anup Arumughan
- Neuroproteomics, Max Delbrück Center for Molecular Medicine in the Helmholtz Association (MDC) Berlin, Germany
| | - Erich E Wanker
- Neuroproteomics, Max Delbrück Center for Molecular Medicine in the Helmholtz Association (MDC) Berlin, Germany
| | - Thomas Laeger
- German Institute of Human Nutrition (DIfE) Potsdam-Rehbruecke, Germany; German Center for Diabetes Research (DZD) Munich Neuherberg, Germany
| | - Jan Schmoranzer
- Advanced Medical Bioimaging Core Facility - AMBIO, Charité-Universitätsmedizin Berlin, Germany
| | - Oliver Daumke
- Max-Delbrück Center for Molecular Medicine in the Helmholtz Association Berlin, Germany; Institute of Chemistry and Biochemistry, Freie Universität Berlin, Germany
| | - Annette Schürmann
- German Institute of Human Nutrition (DIfE) Potsdam-Rehbruecke, Germany; German Center for Diabetes Research (DZD) Munich Neuherberg, Germany; University of Potsdam, Institute of Nutritional Sciences, Nuthetal, Germany; Faculty of Health Sciences, Joint Faculty of the Brandenburg University of Technology Cottbus - Senftenberg, the Brandenburg Medical School Theodor Fontane and the University of Potsdam, Germany.
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Yang F, Li T, Peng Z, Liu Y, Guo Y. The amphipathic helices of Arfrp1 and Arl14 are sufficient to determine subcellular localizations. J Biol Chem 2020; 295:16643-16654. [PMID: 32972971 PMCID: PMC7864062 DOI: 10.1074/jbc.ra120.014999] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2020] [Revised: 08/31/2020] [Indexed: 11/06/2022] Open
Abstract
The subcellular localization of Arf family proteins is generally thought to be determined by their corresponding guanine nucleotide exchange factors. By promoting GTP binding, guanine nucleotide exchange factors induce conformational changes of Arf proteins exposing their N-terminal amphipathic helices, which then insert into the membranes to stabilize the membrane association process. Here, we found that the N-terminal amphipathic motifs of the Golgi-localized Arf family protein, Arfrp1, and the endosome- and plasma membrane-localized Arf family protein, Arl14, play critical roles in spatial determination. Exchanging the amphipathic helix motifs between these two Arf proteins causes the switch of their localizations. Moreover, the amphipathic helices of Arfrp1 and Arl14 are sufficient for cytosolic proteins to be localized into a specific cellular compartment. The spatial determination mediated by the Arfrp1 helix requires its binding partner Sys1. In addition, the residues that are required for the acetylation of the Arfrp1 helix and the myristoylation of the Arl14 helix are important for the specific subcellular localization. Interestingly, Arfrp1 and Arl14 are recruited to their specific cellular compartments independent of GTP binding. Our results demonstrate that the amphipathic motifs of Arfrp1 and Arl14 are sufficient for determining specific subcellular localizations in a GTP-independent manner, suggesting that the membrane association and activation of some Arf proteins are uncoupled.
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Affiliation(s)
- Feng Yang
- Division of Life Science, Hong Kong University of Science and Technology, Hong Kong, China
| | - Tiantian Li
- Division of Life Science, Hong Kong University of Science and Technology, Hong Kong, China
| | - Ziqing Peng
- Division of Life Science, Hong Kong University of Science and Technology, Hong Kong, China
| | - Yang Liu
- Division of Life Science, Hong Kong University of Science and Technology, Hong Kong, China
| | - Yusong Guo
- Division of Life Science, Hong Kong University of Science and Technology, Hong Kong, China; Hong Kong University of Science and Technology Shenzhen Research Institute, Shenzhen, China.
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Makowski SL, Kuna RS, Field SJ. Induction of membrane curvature by proteins involved in Golgi trafficking. Adv Biol Regul 2019; 75:100661. [PMID: 31668661 PMCID: PMC7056495 DOI: 10.1016/j.jbior.2019.100661] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2019] [Revised: 09/25/2019] [Accepted: 09/30/2019] [Indexed: 12/22/2022]
Abstract
The Golgi apparatus serves a key role in processing and sorting lipids and proteins for delivery to their final cellular destinations. Vesicle exit from the Golgi initiates with directional deformation of the lipid bilayer to produce a bulge. Several mechanisms have been described by which lipids and proteins can induce directional membrane curvature to promote vesicle budding. Here we review some of the mechanisms implicated in inducing membrane curvature at the Golgi to promote vesicular trafficking to various cellular destinations.
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Affiliation(s)
- Stefanie L Makowski
- Department of Medicine, Division of Endocrinology and Metabolism, University of California, San Diego, La Jolla, CA, 92093, USA
| | - Ramya S Kuna
- Department of Medicine, Division of Endocrinology and Metabolism, University of California, San Diego, La Jolla, CA, 92093, USA
| | - Seth J Field
- Department of Medicine, Division of Endocrinology and Metabolism, University of California, San Diego, La Jolla, CA, 92093, USA.
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Ishida M, Bonifacino JS. ARFRP1 functions upstream of ARL1 and ARL5 to coordinate recruitment of distinct tethering factors to the trans-Golgi network. J Cell Biol 2019; 218:3681-3696. [PMID: 31575603 PMCID: PMC6829661 DOI: 10.1083/jcb.201905097] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2019] [Revised: 08/09/2019] [Accepted: 08/27/2019] [Indexed: 12/22/2022] Open
Abstract
SNARE-mediated fusion of endosome-derived transport carriers with the trans-Golgi network (TGN) depends on the concerted action of two types of tethering factors: long coiled-coil tethers of the golgin family, and the heterotetrameric complex GARP. Whereas the golgins mediate long-distance capture of the carriers, GARP promotes assembly of the SNAREs. It remains to be determined, however, how the functions of these tethering factors are coordinated. Herein we report that the ARF-like (ARL) GTPase ARFRP1 functions upstream of two other ARL GTPases, ARL1 and ARL5, which in turn recruit golgins and GARP, respectively, to the TGN. We also show that this mechanism is essential for the delivery of retrograde cargos to the TGN. Our findings thus demonstrate that ARFRP1 is a master regulator of retrograde-carrier tethering to the TGN. The coordinated recruitment of distinct tethering factors by a bifurcated GTPase cascade may be paradigmatic of other vesicular fusion events within the cell.
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Affiliation(s)
- Morié Ishida
- Cell Biology and Neurobiology Branch, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD
| | - Juan S Bonifacino
- Cell Biology and Neurobiology Branch, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD
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Sztul E, Chen PW, Casanova JE, Cherfils J, Dacks JB, Lambright DG, Lee FJS, Randazzo PA, Santy LC, Schürmann A, Wilhelmi I, Yohe ME, Kahn RA. ARF GTPases and their GEFs and GAPs: concepts and challenges. Mol Biol Cell 2019; 30:1249-1271. [PMID: 31084567 PMCID: PMC6724607 DOI: 10.1091/mbc.e18-12-0820] [Citation(s) in RCA: 149] [Impact Index Per Article: 29.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2019] [Revised: 02/26/2019] [Accepted: 03/11/2019] [Indexed: 12/12/2022] Open
Abstract
Detailed structural, biochemical, cell biological, and genetic studies of any gene/protein are required to develop models of its actions in cells. Studying a protein family in the aggregate yields additional information, as one can include analyses of their coevolution, acquisition or loss of functionalities, structural pliability, and the emergence of shared or variations in molecular mechanisms. An even richer understanding of cell biology can be achieved through evaluating functionally linked protein families. In this review, we summarize current knowledge of three protein families: the ARF GTPases, the guanine nucleotide exchange factors (ARF GEFs) that activate them, and the GTPase-activating proteins (ARF GAPs) that have the ability to both propagate and terminate signaling. However, despite decades of scrutiny, our understanding of how these essential proteins function in cells remains fragmentary. We believe that the inherent complexity of ARF signaling and its regulation by GEFs and GAPs will require the concerted effort of many laboratories working together, ideally within a consortium to optimally pool information and resources. The collaborative study of these three functionally connected families (≥70 mammalian genes) will yield transformative insights into regulation of cell signaling.
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Affiliation(s)
- Elizabeth Sztul
- Department of Cell, Developmental and Integrative Biology, University of Alabama at Birmingham, Birmingham, AL 35294
| | - Pei-Wen Chen
- Department of Biology, Williams College, Williamstown, MA 01267
| | - James E. Casanova
- Department of Cell Biology, University of Virginia, Charlottesville, VA 22908
| | - Jacqueline Cherfils
- Laboratoire de Biologie et Pharmacologie Appliquée, CNRS and Ecole Normale Supérieure Paris-Saclay, 94235 Cachan, France
| | - Joel B. Dacks
- Division of Infectious Disease, Department of Medicine, University of Alberta, Edmonton, AB T6G 2H7, Canada
| | - David G. Lambright
- Program in Molecular Medicine and Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Amherst, MA 01605
| | - Fang-Jen S. Lee
- Institute of Molecular Medicine, College of Medicine, National Taiwan University, Taipei 10002, Taiwan
| | | | - Lorraine C. Santy
- Department of Biochemistry and Molecular Biology, Pennsylvania State University, University Park, PA 16802
| | - Annette Schürmann
- German Institute of Human Nutrition, 85764 Potsdam-Rehbrücke, Germany
| | - Ilka Wilhelmi
- German Institute of Human Nutrition, 85764 Potsdam-Rehbrücke, Germany
| | - Marielle E. Yohe
- Pediatric Oncology Branch, Center for Cancer Research, National Cancer Institute, Bethesda, MD 20892
| | - Richard A. Kahn
- Department of Biochemistry, Emory University School of Medicine, Atlanta, GA 30322-3050
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Werno MW, Wilhelmi I, Kuropka B, Ebert F, Freund C, Schürmann A. The GTPase ARFRP1 affects lipid droplet protein composition and triglyceride release from intracellular storage of intestinal Caco-2 cells. Biochem Biophys Res Commun 2018; 506:259-265. [PMID: 30348522 DOI: 10.1016/j.bbrc.2018.10.092] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2018] [Accepted: 10/15/2018] [Indexed: 11/17/2022]
Abstract
Intestinal release of dietary triglycerides via chylomicrons is the major contributor to elevated postprandial triglyceride levels. Dietary lipids can be transiently stored in cytosolic lipid droplets (LDs) located in intestinal enterocytes for later release. ADP ribosylation factor-related protein 1 (ARFRP1) participates in processes of LD growth in adipocytes and in lipidation of lipoproteins in liver and intestine. This study aims to explore the impact of ARFRP1 on LD organization and its interplay with chylomicron-mediated triglyceride release in intestinal-like Caco-2 cells. Suppression of Arfrp1 reduced release of intracellularly derived triglycerides (0.69-fold) and increased the abundance of transitional endoplasmic reticulum ATPase TERA/VCP, fatty acid synthase-associated factor 2 (FAF2) and perilipin 2 (Plin2) at the LD surface. Furthermore, TERA/VCP and FAF2 co-occurred more frequently with ATGL at LDs, suggesting a reduced adipocyte triglyceride lipase (ATGL)-mediated lipolysis. Accordingly, inhibition of lipolysis reduced lipid release from intracellular storage pools by the same magnitude as Arfrp1 depletion. Thus, the lack of Arfrp1 increases the abundance of lipolysis-modulating enzymes TERA/VCP, FAF2 and Plin2 at LDs, which might decrease lipolysis and reduce availability of fatty acids for triglyceride synthesis and their release via chylomicrons.
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Affiliation(s)
- Martin Witold Werno
- Department of Experimental Diabetology, German Institute of Human Nutrition Potsdam-Rehbruecke (DIfE), 14558 Nuthetal, Germany; German Center for Diabetes Research, München-Neuherberg, 85764 Neuherberg, Germany
| | - Ilka Wilhelmi
- Department of Experimental Diabetology, German Institute of Human Nutrition Potsdam-Rehbruecke (DIfE), 14558 Nuthetal, Germany; German Center for Diabetes Research, München-Neuherberg, 85764 Neuherberg, Germany
| | - Benno Kuropka
- Laboratory of Protein Biochemistry, Institute of Chemistry and Biochemistry, Freie Universität Berlin, 14195 Berlin, Germany
| | - Franziska Ebert
- Department of Food Chemistry, Institute of Nutritional Science, University of Potsdam, Arthur-Scheunert-Allee 114-116, Nuthetal 14558, Germany
| | - Christian Freund
- Laboratory of Protein Biochemistry, Institute of Chemistry and Biochemistry, Freie Universität Berlin, 14195 Berlin, Germany
| | - Annette Schürmann
- Department of Experimental Diabetology, German Institute of Human Nutrition Potsdam-Rehbruecke (DIfE), 14558 Nuthetal, Germany; German Center for Diabetes Research, München-Neuherberg, 85764 Neuherberg, Germany.
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8
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Rödiger M, Werno MW, Wilhelmi I, Baumeier C, Hesse D, Wettschureck N, Offermanns S, Song K, Krauß M, Schürmann A. Adiponectin release and insulin receptor targeting share trans-Golgi-dependent endosomal trafficking routes. Mol Metab 2018; 8:167-179. [PMID: 29203237 PMCID: PMC5985030 DOI: 10.1016/j.molmet.2017.11.011] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/14/2017] [Accepted: 11/18/2017] [Indexed: 11/25/2022] Open
Abstract
OBJECTIVE Intracellular vesicle trafficking maintains cellular structures and functions. The assembly of cargo-laden vesicles at the trans-Golgi network is initiated by the ARF family of small GTPases. Here, we demonstrate the role of the trans-Golgi localized monomeric GTPase ARFRP1 in endosomal-mediated vesicle trafficking of mature adipocytes. METHODS Control (Arfrp1flox/flox) and inducible fat-specific Arfrp1 knockout (Arfrp1iAT-/-) mice were metabolically characterized. In vitro experiments on mature 3T3-L1 cells and primary mouse adipocytes were conducted to validate the impact of ARFRP1 on localization of adiponectin and the insulin receptor. Finally, secretion and transferrin-based uptake and recycling assays were performed with HeLa and HeLa M-C1 cells. RESULTS We identified the ARFRP1-based sorting machinery to be involved in vesicle trafficking relying on the endosomal compartment for cell surface delivery. Secretion of adiponectin from fat depots was selectively reduced in Arfrp1iAT-/- mice, and Arfrp1-depleted 3T3-L1 adipocytes revealed an accumulation of adiponectin in Rab11-positive endosomes. Plasma adiponectin deficiency of Arfrp1iAT-/- mice resulted in deteriorated hepatic insulin sensitivity, increased gluconeogenesis and elevated fasting blood glucose levels. Additionally, the insulin receptor, undergoing endocytic recycling after ligand binding, was less abundant at the plasma membrane of adipocytes lacking Arfrp1. This had detrimental effects on adipose insulin signaling, followed by insufficient suppression of basal lipolytic activity and impaired adipose tissue expansion. CONCLUSIONS Our findings suggest that adiponectin secretion and insulin receptor surface targeting utilize the same post-Golgi trafficking pathways that are essential for an appropriate systemic insulin sensitivity and glucose homeostasis.
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Affiliation(s)
- Maria Rödiger
- Department of Experimental Diabetology, German Institute of Human Nutrition Potsdam-Rehbruecke (DIfE), 14558 Nuthetal, Germany; German Center for Diabetes Research, München-Neuherberg, 85764 Neuherberg, Germany.
| | - Martin W Werno
- Department of Experimental Diabetology, German Institute of Human Nutrition Potsdam-Rehbruecke (DIfE), 14558 Nuthetal, Germany; German Center for Diabetes Research, München-Neuherberg, 85764 Neuherberg, Germany.
| | - Ilka Wilhelmi
- Department of Experimental Diabetology, German Institute of Human Nutrition Potsdam-Rehbruecke (DIfE), 14558 Nuthetal, Germany; German Center for Diabetes Research, München-Neuherberg, 85764 Neuherberg, Germany.
| | - Christian Baumeier
- Department of Experimental Diabetology, German Institute of Human Nutrition Potsdam-Rehbruecke (DIfE), 14558 Nuthetal, Germany; German Center for Diabetes Research, München-Neuherberg, 85764 Neuherberg, Germany.
| | - Deike Hesse
- Department of Experimental Diabetology, German Institute of Human Nutrition Potsdam-Rehbruecke (DIfE), 14558 Nuthetal, Germany; German Center for Diabetes Research, München-Neuherberg, 85764 Neuherberg, Germany.
| | - Nina Wettschureck
- Department of Pharmacology, Max Planck Institute for Heart and Lung Research, 61231 Bad Nauheim, Germany.
| | - Stefan Offermanns
- Department of Pharmacology, Max Planck Institute for Heart and Lung Research, 61231 Bad Nauheim, Germany.
| | - Kyungyeun Song
- Department of Molecular Pharmacology and Cell Biology, Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP), 13125 Berlin, Germany.
| | - Michael Krauß
- Department of Molecular Pharmacology and Cell Biology, Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP), 13125 Berlin, Germany.
| | - Annette Schürmann
- Department of Experimental Diabetology, German Institute of Human Nutrition Potsdam-Rehbruecke (DIfE), 14558 Nuthetal, Germany; German Center for Diabetes Research, München-Neuherberg, 85764 Neuherberg, Germany.
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Lim YS, Ngo HTT, Lee J, Son K, Park EM, Hwang SB. ADP-ribosylation Factor-related Protein 1 Interacts with NS5A and Regulates Hepatitis C Virus Propagation. Sci Rep 2016; 6:31211. [PMID: 27550144 PMCID: PMC4994002 DOI: 10.1038/srep31211] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2016] [Accepted: 07/08/2016] [Indexed: 12/12/2022] Open
Abstract
The life cycle of hepatitis C virus (HCV) is tightly coupled to the lipid metabolism of host cells. In order to identify host factors involved in HCV propagation, we have previously screened a small interfering RNA (siRNA) library targeting host genes that control lipid metabolism and lipid droplet (LD) formation using cell culture-grown HCV (HCVcc)-infected cells. In this study, we selected and characterized the gene encoding ADP-ribosylation factor-related protein 1 (ARFRP1). ARFRP1 is essential for LD growth and is involved in the regulation of lipolysis. siRNA-mediated knockdown of ARFRP1 significantly inhibited HCV replication in both subgenomic replicon cells and HCVcc-infected cells. ARFRP1 interacted with NS5A and NS5A partially colocalized with LD. Silencing of ARFRP1 abrogated HCV-induced LD growth and viral protein expressions. Moreover, ARFRP1 recruited synaptosomal-associated protein 23 (SNAP23) to sites in close proximity to LDs in HCV-infected cells. Silencing of ARFRP1 ablated relocalization of SNAP23 to LD. These data indicate that HCV regulates ARFRP1 for LD growth to facilitate viral propagation and thus ARFRP1 may be a potential target for antiviral therapy.
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Affiliation(s)
- Yun-Sook Lim
- National Research Laboratory of Hepatitis C Virus and Ilsong Institute of Life Science, Hallym University, Anyang, South Korea
| | - Huong T T Ngo
- National Research Laboratory of Hepatitis C Virus and Ilsong Institute of Life Science, Hallym University, Anyang, South Korea
| | - Jihye Lee
- National Research Laboratory of Hepatitis C Virus and Ilsong Institute of Life Science, Hallym University, Anyang, South Korea
| | - Kidong Son
- National Research Laboratory of Hepatitis C Virus and Ilsong Institute of Life Science, Hallym University, Anyang, South Korea
| | - Eun-Mee Park
- National Research Laboratory of Hepatitis C Virus and Ilsong Institute of Life Science, Hallym University, Anyang, South Korea.,Korea National Institute of Health, Cheongwon-gun, South Korea
| | - Soon B Hwang
- National Research Laboratory of Hepatitis C Virus and Ilsong Institute of Life Science, Hallym University, Anyang, South Korea
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Affiliation(s)
- Yusong Guo
- Department of Molecular and Cell Biology, Howard Hughes Medical Institute, University of California, Berkeley, California 94720-3200;
| | - Daniel W. Sirkis
- Department of Molecular and Cell Biology, Howard Hughes Medical Institute, University of California, Berkeley, California 94720-3200;
| | - Randy Schekman
- Department of Molecular and Cell Biology, Howard Hughes Medical Institute, University of California, Berkeley, California 94720-3200;
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Lu L, Hong W. From endosomes to the trans-Golgi network. Semin Cell Dev Biol 2014; 31:30-9. [PMID: 24769370 DOI: 10.1016/j.semcdb.2014.04.024] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2014] [Revised: 04/16/2014] [Accepted: 04/16/2014] [Indexed: 12/11/2022]
Abstract
The retrograde trafficking from endosomes to the trans-Golgi network (TGN) is one of the major endocytic pathways to divert proteins and lipids away from lysosomal degradation. Retrograde transported cargos enter the TGN via two itineraries from either the early endosome/recycling endosome or the late endosome and involve various machinery components such as retromer, sorting nexins, clathrin, small GTPases, tethering factors and SNAREs. Recently, the pathway has been recognized for its role in signal transduction, physiology and pathogenesis of human diseases.
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Affiliation(s)
- Lei Lu
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore 637551, Singapore.
| | - Wanjin Hong
- Institute of Molecular and Cell Biology, 61 Biopolis Drive, Proteos, Singapore 138673, Singapore; School of Pharmaceutical Sciences, Xiamen University, Xiamen, People's Republic of China
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Abstract
The ARF-like (ARL) proteins, within the ARF family, are a collection of functionally diverse GTPases that share extensive (>40 %) identity with the ARFs and each other and are assumed to share basic mechanisms of regulation and a very incompletely documented degree of overlapping regulators. At least four ARLs were already present in the last eukaryotic common ancestor, along with one ARF, and these have been expanded to >20 members in mammals. We know little about the majority of these proteins so our review will focus on those about which the most is known, including ARL1, ARL2, ARL3, ARL4s, ARL6, ARL13s, and ARFRP1. From this fragmentary information we extract some generalizations and conclusions regarding the sources and extent of specificity and functions of the ARLs.
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Affiliation(s)
- Alfred Wittinghofer
- Max-Planck-Institute of Molecular Physiology, Dortmund, Nordrhein-Westfalen Germany
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13
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Hesse D, Radloff K, Jaschke A, Lagerpusch M, Chung B, Tailleux A, Staels B, Schürmann A. Hepatic trans-Golgi action coordinated by the GTPase ARFRP1 is crucial for lipoprotein lipidation and assembly. J Lipid Res 2013; 55:41-52. [PMID: 24186947 DOI: 10.1194/jlr.m040089] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The liver is a major organ in whole body lipid metabolism and malfunctioning can lead to various diseases including dyslipidemia, fatty liver disease, and type 2 diabetes. Triglycerides and cholesteryl esters are packed in the liver as very low density lipoproteins (VLDLs). Generation of these lipoproteins is initiated in the endoplasmic reticulum and further maturation likely occurs in the Golgi. ADP-ribosylation factor-related protein 1 (ARFRP1) is a small trans-Golgi-associated guanosine triphosphatase (GTPase) that regulates protein sorting and is required for chylomicron lipidation and assembly in the intestine. Here we show that the hepatocyte-specific deletion of Arfrp1 (Arfrp1(liv-/-)) results in impaired VLDL lipidation leading to reduced plasma triglyceride levels in the fasted state as well as after inhibition of lipoprotein lipase activity by Triton WR-1339. In addition, the concentration of ApoC3 that comprises 40% of protein mass of secreted VLDLs is markedly reduced in the plasma of Arfrp1(liv-/-) mice but accumulates in the liver accompanied by elevated triglycerides. Fractionation of Arfrp1(liv-/-) liver homogenates reveals more ApoB48 and a lower concentration of triglycerides in the Golgi compartments than in the corresponding fractions from control livers. In conclusion, ARFRP1 and the Golgi apparatus play an important role in lipoprotein maturation in the liver by influencing lipidation and assembly of proteins to the lipid particles.
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Affiliation(s)
- Deike Hesse
- Department of Experimental Diabetology, German Institute of Human Nutrition Potsdam-Rehbruecke, D-14558 Nuthetal, Germany
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14
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Citalán-Madrid AF, García-Ponce A, Vargas-Robles H, Betanzos A, Schnoor M. Small GTPases of the Ras superfamily regulate intestinal epithelial homeostasis and barrier function via common and unique mechanisms. Tissue Barriers 2013; 1:e26938. [PMID: 24868497 PMCID: PMC3942330 DOI: 10.4161/tisb.26938] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2013] [Revised: 10/21/2013] [Accepted: 10/24/2013] [Indexed: 12/11/2022] Open
Abstract
The intestinal epithelium forms a stable barrier protecting underlying tissues from pathogens in the gut lumen. This is achieved by specialized integral membrane structures such as tight and adherens junctions that connect neighboring cells and provide stabilizing links to the cytoskeleton. Junctions are constantly remodeled to respond to extracellular stimuli. Assembly and disassembly of junctions is regulated by interplay of actin remodeling, endocytotic recycling of junctional proteins, and various signaling pathways. Accumulating evidence implicate small G proteins of the Ras superfamily as important signaling molecules for the regulation of epithelial junctions. They function as molecular switches circling between an inactive GDP-bound and an active GTP-bound state. Once activated, they bind different effector molecules to control cellular processes required for correct junction assembly, maintenance and remodelling. Here, we review recent advances in understanding how GTPases of the Rho, Ras, Rab and Arf families contribute to intestinal epithelial homeostasis.
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Affiliation(s)
- Alí Francisco Citalán-Madrid
- Department of Molecular Biomedicine; Center for Research and Advanced Studies of the National Polytechnic Institute (Cinvestav del IPN); Mexico City, Mexico
| | - Alexander García-Ponce
- Department of Molecular Biomedicine; Center for Research and Advanced Studies of the National Polytechnic Institute (Cinvestav del IPN); Mexico City, Mexico
| | - Hilda Vargas-Robles
- Department of Molecular Biomedicine; Center for Research and Advanced Studies of the National Polytechnic Institute (Cinvestav del IPN); Mexico City, Mexico
| | - Abigail Betanzos
- Department of Infectomics and Molecular Pathogenesis; Center for Research and Advanced Studies of the National Polytechnic Institute (Cinvestav del IPN); Mexico City, Mexico
| | - Michael Schnoor
- Department of Molecular Biomedicine; Center for Research and Advanced Studies of the National Polytechnic Institute (Cinvestav del IPN); Mexico City, Mexico
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15
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Ivanov AI, Naydenov NG. Dynamics and regulation of epithelial adherens junctions: recent discoveries and controversies. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2013; 303:27-99. [PMID: 23445808 DOI: 10.1016/b978-0-12-407697-6.00002-7] [Citation(s) in RCA: 76] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Adherens junctions (AJs) are evolutionarily conserved plasma-membrane structures that mediate cell-cell adhesions in multicellular organisms. They are organized by several types of adhesive integral membrane proteins, most notably cadherins and nectins that are clustered and stabilized by a number of cytoplasmic scaffolds. AJs are key regulators of tissue architecture and dynamics via control of cell proliferation, polarity, shape, motility, and survival. They are absolutely critical for normal tissue morphogenesis and their disruption results in pathological abnormalities in different tissues. Although the field of adherens-junction research dramatically progressed in recent years, a number of important questions remain controversial and poorly understood. This review outlines basic principles that regulate organization of AJs in mammalian epithelia and discusses recent advances and standing controversies in the field. A special attention is paid to the regulation of AJs by vesicle trafficking and the intracellular cytoskeleton as well as roles and mechanisms of adherens-junction disruption during tumor progression and tissue inflammation.
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Affiliation(s)
- Andrei I Ivanov
- Department of Human and Molecular Genetics, Virginia Institute of Molecular Medicine, Virginia Commonwealth University School of Medicine, Richmond, VA 23298, USA.
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16
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Abstract
In mammalian cells, the Golgi complex has an elaborate structure consisting of stacked, flattened cisternal membranes collected into a ribbon in the center of the cell. Amazingly, the flattened cisternae can rapidly dilate to accommodate large cargo as it traffics through the organelle. The mechanism by which this occurs is unknown. Exocytosis of large cargo is essential for many physiological processes, including collagen and lipoprotein secretion, and defects in the process lead to disease. In addition, enveloped viruses that bud into the endoplasmic reticulum or Golgi complex must also be transported through Golgi cisternae for secretion from the infected cell. This review summarizes our understanding of intra-Golgi transport of large cargo, and outlines current questions open for experimentation.
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Affiliation(s)
- Carolyn E Machamer
- Department of Cell Biology, Johns Hopkins University School of Medicine, 725 N. Wolfe St., Baltimore, MD 20205, USA.
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Guo Y, Zanetti G, Schekman R. A novel GTP-binding protein-adaptor protein complex responsible for export of Vangl2 from the trans Golgi network. eLife 2013; 2:e00160. [PMID: 23326640 PMCID: PMC3539332 DOI: 10.7554/elife.00160] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2012] [Accepted: 10/18/2012] [Indexed: 01/03/2023] Open
Abstract
Planar cell polarity (PCP) requires the asymmetric sorting of distinct signaling
receptors to distal and proximal surfaces of polarized epithelial cells. We have
examined the transport of one PCP signaling protein, Vangl2, from the
trans Golgi network (TGN) in mammalian cells. Using siRNA
knockdown experiments, we find that the GTP-binding protein, Arfrp1, and the clathrin
adaptor complex 1 (AP-1) are required for Vangl2 transport from the TGN. In contrast,
TGN export of Frizzled 6, which localizes to the opposing epithelial surface from
Vangl2, does not depend on Arfrp1 or AP-1. Mutagenesis studies identified a YYXXF
sorting signal in the C-terminal cytosolic domain of Vangl2 that is required for
Vangl2 traffic and interaction with the μ subunit of AP-1. We propose that
Arfrp1 exposes a binding site on AP-1 that recognizes the Vangl2 sorting motif for
capture into a transport vesicle destined for the proximal surface of a polarized
epithelial cell. DOI:http://dx.doi.org/10.7554/eLife.00160.001 Most cells in multicellular organisms possess a property known as polarity that is
reflected, in part, in the organization of the cell surface into distinct domains.
One well-known axis in epithelial cells, such as those in the skin, divides the cell
into an apical domain, which faces out, and a basal domain, which faces the
underlying tissue. These cells rely on the distribution of structural components
inside the cell, or within the cell membrane, to tell the difference between these
two directions. Epithelial cells also possess a second type of polarity, planar cell
polarity, that ensures that cells adjacent to each other in the plane parallel to the
skin tissue are oriented correctly with respect to each other during development.
This ensures, in turn, that hairs, scales, feathers and so on are all aligned. All eukaryotic cells sort and process proteins within an organelle called the Golgi
apparatus, and proteins that are required at a specific destination within the cell,
such as the cell surface membrane, carry specific molecular sorting signals that act
as address labels to convey the protein into and within the secretory pathway. As one
of these proteins moves through the Golgi apparatus, its sorting signals are
recognized by coat proteins, such as clathrin, that subsequently form a vesicle
around it. The assembly of this vesicle is initiated by an enzyme from the Arf
family, but the enzyme must first undergo a conformational change (by exchanging a
molecule of GDP for one of GTP) before formation can begin. The resulting vesicle can
then be sent on its way to the address indicated by its Golgi-to-cell-surface sorting
signal. These sorting signals also help to establish planar cell polarity in cells by
ensuring that proteins called signaling receptors are distributed asymmetrically
within the cell membrane. Guo et al. have now examined the mechanism behind the asymmetric sorting of two
proteins that are involved in planar cell polarity: Vangl2 and Frizzled 6. In an
effort to understand why these proteins are localized to opposite surfaces of
epithelial cells, Guo et al. used genetic techniques to reduce the expression of
Golgi-localized Arf proteins in epithelial cell cultures. They found that knockdown
of a protein called Arfrp1 caused Vangl2 to accumulate in the last station of the
Golgi complex instead of being transported to the cell surface membrane. Then, using
a technique called affinity chromatography, they demonstrated that a coat protein
called the clathrin adaptor complex (AP-1) had to be present for the formation of
vesicles around Vangl2. Moreover, disrupting AP-1 and Arfrp1 did not prevent Frizzled
6 being transported to the cell surface membrane. This suggests that cells use
several distinct adaptor proteins and coat complexes to ensure that proteins from the
Golgi apparatus go to specific locations on the cell surface and, thus, help to
establish planar cell polarity. DOI:http://dx.doi.org/10.7554/eLife.00160.002
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Affiliation(s)
- Yusong Guo
- Department of Molecular and Cell Biology , Howard Hughes Medical Institute, University of California-Berkeley , Berkeley , United States
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18
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GTPase ARFRP1 is essential for normal hepatic glycogen storage and insulin-like growth factor 1 secretion. Mol Cell Biol 2012; 32:4363-74. [PMID: 22927645 DOI: 10.1128/mcb.00522-12] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
The GTPase ADP-ribosylation factor-related protein 1 (ARFRP1) is located at the trans-Golgi compartment and regulates the recruitment of Arf-like 1 (ARL1) and its effector golgin-245 to this compartment. Here, we show that liver-specific knockout of Arfrp1 in the mouse (Arfrp1(liv-/-)) resulted in early growth retardation, which was associated with reduced hepatic insulin-like growth factor 1 (IGF1) secretion. Accordingly, suppression of Arfrp1 in primary hepatocytes resulted in a significant reduction of IGF1 release. However, the hepatic secretion of IGF-binding protein 2 (IGFBP2) was not affected in the absence of ARFRP1. In addition, Arfrp1(liv-/-) mice exhibited decreased glucose transport into the liver, leading to a 50% reduction of glycogen stores as well as a marked retardation of glycogen storage after fasting and refeeding. These abnormalities in glucose metabolism were attributable to reduced protein levels and intracellular retention of the glucose transporter GLUT2 in Arfrp1(liv-/-) livers. As a consequence of impaired glucose uptake into the liver, the expression levels of carbohydrate response element binding protein (ChREBP), a transcription factor regulated by glucose concentration, and its target genes (glucokinase and pyruvate kinase) were markedly reduced. Our data indicate that ARFRP1 in the liver is involved in the regulation of IGF1 secretion and GLUT2 sorting and is thereby essential for normal growth and glycogen storage.
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Chen KY, Tsai PC, Liu YW, Lee FJS. Competition between the golgin Imh1p and the GAP Gcs1p stabilizes activated Arl1p at the late-Golgi. J Cell Sci 2012; 125:4586-96. [PMID: 22767516 DOI: 10.1242/jcs.107797] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Golgins play diverse roles in regulating the structure and function of the Golgi. The yeast golgin Imh1p is targeted to the trans-Golgi network (TGN) through interaction of its GRIP domain with GTP-bound Arl1p. Recycling of Arl1p and Imh1p to the cytosol requires the hydrolysis of GTP bound to Arl1p; however, the point at which GTP hydrolysis occurs remains unknown. Here, we report that self-interaction of Imh1p plays a role in modulating spatial inactivation of Arl1p. Deletion of IMH1 in yeast decreases the amount of the GTP-bound Arl1p and results in less Arl1p residing on the TGN. Biochemically, purified Imh1p competes with Gcs1p, an Arl1p GTPase-activating protein (GAP), for binding to Arl1p, thus interfering with the GAP activity of Gcs1p toward Arl1p. Furthermore, we demonstrate that the self-interaction of Imh1p attenuates the Gcs1p-dependent GTP hydrolysis of Arl1p. Thus, we propose that the golgin Imh1p serves as a feedback regulator to modulate the GTP hydrolysis of Arl1p.
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Affiliation(s)
- Kuan-Yu Chen
- Institute of Molecular Medicine, College of Medicine, National Taiwan University and Department of Medical Research, National Taiwan University Hospital, Taipei 100, Taiwan
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20
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Jaschke A, Chung B, Hesse D, Kluge R, Zahn C, Moser M, Petzke KJ, Brigelius-Flohé R, Puchkov D, Koepsell H, Heeren J, Joost HG, Schürmann A. The GTPase ARFRP1 controls the lipidation of chylomicrons in the Golgi of the intestinal epithelium. Hum Mol Genet 2012; 21:3128-42. [PMID: 22505585 PMCID: PMC3384381 DOI: 10.1093/hmg/dds140] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The uptake and processing of dietary lipids by the small intestine is a multistep process that involves several steps including vesicular and protein transport. The GTPase ADP-ribosylation factor-related protein 1 (ARFRP1) controls the ARF-like 1 (ARL1)-mediated Golgi recruitment of GRIP domain proteins which in turn bind several Rab-GTPases. Here, we describe the essential role of ARFRP1 and its interaction with Rab2 in the assembly and lipidation of chylomicrons in the intestinal epithelium. Mice lacking Arfrp1 specifically in the intestine (Arfrp1vil−/−) exhibit an early post-natal growth retardation with reduced plasma triacylglycerol and free fatty acid concentrations. Arfrp1vil−/− enterocytes as well as Arfrp1 mRNA depleted Caco-2 cells absorbed fatty acids normally but secreted chylomicrons with a markedly reduced triacylglycerol content. In addition, the release of apolipoprotein A-I (ApoA-I) was dramatically decreased, and ApoA-I accumulated in the Arfrp1vil−/− epithelium, where it predominantly co-localized with Rab2. The release of chylomicrons from Caco-2 was markedly reduced after the suppression of Rab2, ARL1 and Golgin-245. Thus, the GTPase ARFRP1 and its downstream proteins are required for the lipidation of chylomicrons and the assembly of ApoA-I to these particles in the Golgi of intestinal epithelial cells.
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Affiliation(s)
- Alexander Jaschke
- Department of Experimental Diabetology, German Institute of Human Nutrition Potsdam-Rehbruecke, D-14558 Nuthetal, Germany
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21
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Gouzi M, Kim YH, Katsumoto K, Johansson K, Grapin-Botton A. Neurogenin3 initiates stepwise delamination of differentiating endocrine cells during pancreas development. Dev Dyn 2011; 240:589-604. [PMID: 21287656 DOI: 10.1002/dvdy.22544] [Citation(s) in RCA: 111] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/08/2010] [Indexed: 12/23/2022] Open
Abstract
During development, pancreatic endocrine cells are specified within the pancreatic epithelium. They subsequently delaminate out of the epithelium and cluster in the mesenchyme to form the islets of Langerhans. Neurogenin3 (Ngn3) is a transcription factor required for the differentiation of all endocrine cells and we investigated its role in their delamination. We observed in the mouse pancreas that most Ngn3-positive cells have lost contact with the lumen of the epithelium, showing that the delamination from the progenitor layer is initiated in endocrine progenitors. Subsequently, in both mouse and chick newly born endocrine cells at the periphery of the epithelium strongly decrease E-cadherin, break-down the basal lamina and cluster into islets of Langerhans. Repression of E-cadherin is sufficient to promote delamination from the epithelium. We further demonstrate that Ngn3 indirectly controls Snail2 protein expression post-transcriptionally to repress E-cadherin. In the chick embryo, Ngn3 independently controls epithelium delamination and differentiation programs.
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22
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Chen KY, Tsai PC, Hsu JW, Hsu HC, Fang CY, Chang LC, Tsai YT, Yu CJ, Lee FJS. Syt1p promotes activation of Arl1p at the late Golgi to recruit Imh1p. J Cell Sci 2010; 123:3478-89. [PMID: 20841378 DOI: 10.1242/jcs.074237] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
In yeast, Arl3p recruits Arl1p GTPase to regulate Golgi function and structure. However, the molecular mechanism involved in regulating activation of Arl1p at the Golgi is unknown. Here, we show that Syt1p promoted activation of Arl1p and recruitment of a golgin protein, Imh1p, to the Golgi. Deletion of SYT1 resulted in the majority of Arl1p being distributed diffusely throughout the cytosol. Overexpression of Syt1p increased Arl1p-GTP production in vivo and the Syt1-Sec7 domain promoted nucleotide exchange on Arl1p in vitro. Syt1p function required the N-terminal region, Sec7 and PH domains. Arl1p, but not Arl3p, interacted with Syt1p. Localization of Syt1p to the Golgi did not require Arl3p. Unlike arl1Δ or arl3Δ mutants, syt1Δ did not show defects in Gas1p transport, cell wall integrity or vacuolar structure. These findings reveal that activation of Arl1p is regulated in part by Syt1p, and imply that Arl1p activation, by using more than one GEF, exerts distinct biological activities at the Golgi compartment.
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Affiliation(s)
- Kuan-Yu Chen
- Institute of Molecular Medicine, College of Medicine, National Taiwan University, and Department of Medical Research, National Taiwan University Hospital, Taipei 100, Taiwan
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23
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Altered GLUT4 trafficking in adipocytes in the absence of the GTPase Arfrp1. Biochem Biophys Res Commun 2010; 394:896-903. [PMID: 20230794 DOI: 10.1016/j.bbrc.2010.03.059] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2010] [Accepted: 03/10/2010] [Indexed: 12/16/2022]
Abstract
The GTPase ADP-ribosylation factor related protein 1 (ARFRP1) controls the recruitment of proteins such as golgin-245 to the trans-Golgi. ARFRP1 is highly expressed in adipose tissues in which the insulin-sensitive glucose transporter GLUT4 is processed through the Golgi to a specialized endosomal compartment, the insulin-responsive storage compartment from which it is translocated to the plasma membrane in response to a stimulation of cells by insulin. In order to examine the role of ARFRP1 for GLUT4 targeting, subcellular distribution of GLUT4 was investigated in adipose tissue specific Arfrp1 knockout (Arfrp1(ad)(-/-)) mice. Immunohistochemical and ultrastructural studies of brown adipocytes demonstrated an abnormal trans-Golgi in Arfrp1(ad)(-/-) adipocytes. In addition, in Arfrp1(ad)(-/-) adipocytes GLUT4 protein accumulated at the plasma membrane rather than being sequestered in an intracellular compartment. A similar missorting of GLUT4 was produced by siRNA-mediated knockdown of Arfrp1 in 3T3-L1 adipocytes which was associated with significantly elevated uptake of deoxyglucose under basal conditions. Thus, Arfrp1 appears to be involved in sorting of GLUT4.
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24
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The ARF-like GTPase ARFRP1 is essential for lipid droplet growth and is involved in the regulation of lipolysis. Mol Cell Biol 2009; 30:1231-42. [PMID: 20038528 DOI: 10.1128/mcb.01269-09] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
ADP-ribosylation factor (ARF)-related protein 1 (ARFRP1) is a GTPase regulating protein trafficking between intracellular organelles. Here we show that mice lacking Arfrp1 in adipocytes (Arfrp1(ad-/-)) are lipodystrophic due to a defective lipid droplet formation in adipose cells. Ratios of mono-, di-, and triacylglycerol, as well as the fatty acid composition of triglycerides, were unaltered. Lipid droplets of brown adipocytes of Arfrp1(ad-/-) mice were considerably smaller and exhibited ultrastructural alterations, such as a disturbed interaction of small lipid-loaded particles with the larger droplets, suggesting that ARFRP1 mediates the transfer of newly formed small lipid particles to the large storage droplets. SNAP23 (synaptosomal-associated protein of 23 kDa) associated with small lipid droplets of control adipocytes but was located predominantly in the cytosol of Arfrp1(ad-/-) adipocytes, suggesting that lipid droplet growth is defective in Arfrp1(ad-/-) mice. In addition, levels of phosphorylated hormone-sensitive lipase (HSL) were elevated, and association of adipocyte triglyceride lipase (ATGL) with lipid droplets was enhanced in brown adipose tissue from Arfrp1(ad-/-) mice. Accordingly, basal lipolysis was increased after knockdown of Arfrp1 in 3T3-L1 adipocytes. The data indicate that disruption of ARFRP1 prevents the normal enlargement of lipid droplets and produces an activation of lipolysis.
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25
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Scherneck S, Nestler M, Vogel H, Blüher M, Block MD, Diaz MB, Herzig S, Schulz N, Teichert M, Tischer S, Al-Hasani H, Kluge R, Schürmann A, Joost HG. Positional cloning of zinc finger domain transcription factor Zfp69, a candidate gene for obesity-associated diabetes contributed by mouse locus Nidd/SJL. PLoS Genet 2009; 5:e1000541. [PMID: 19578398 PMCID: PMC2696593 DOI: 10.1371/journal.pgen.1000541] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2009] [Accepted: 06/01/2009] [Indexed: 01/24/2023] Open
Abstract
Polygenic type 2 diabetes in mouse models is associated with obesity and results from a combination of adipogenic and diabetogenic alleles. Here we report the identification of a candidate gene for the diabetogenic effect of a QTL (Nidd/SJL, Nidd1) contributed by the SJL, NON, and NZB strains in outcross populations with New Zealand Obese (NZO) mice. A critical interval of distal chromosome 4 (2.1 Mbp) conferring the diabetic phenotype was identified by interval-specific congenic introgression of SJL into diabetes-resistant C57BL/6J, and subsequent reporter cross with NZO. Analysis of the 10 genes in the critical interval by sequencing, qRT–PCR, and RACE–PCR revealed a striking allelic variance of Zfp69 encoding zinc finger domain transcription factor 69. In NZO and C57BL/6J, a retrotransposon (IAPLTR1a) in intron 3 disrupted the gene by formation of a truncated mRNA that lacked the coding sequence for the KRAB (Krüppel-associated box) and Znf-C2H2 domains of Zfp69, whereas the diabetogenic SJL, NON, and NZB alleles generated a normal mRNA. When combined with the B6.V-Lepob background, the diabetogenic Zfp69SJL allele produced hyperglycaemia, reduced gonadal fat, and increased plasma and liver triglycerides. mRNA levels of the human orthologue of Zfp69, ZNF642, were significantly increased in adipose tissue from patients with type 2 diabetes. We conclude that Zfp69 is the most likely candidate for the diabetogenic effect of Nidd/SJL, and that retrotransposon IAPLTR1a contributes substantially to the genetic heterogeneity of mouse strains. Expression of the transcription factor in adipose tissue may play a role in the pathogenesis of type 2 diabetes. Type 2 diabetes in humans as well as in obese mice is caused by a combination of adipogenic and diabetogenic gene variants. We have identified a gene that appears to be involved in the pathogenesis of hyperglycaemia in obese mice: in some mouse strains, the gene Zfp69 is disrupted by a retroviral transposon (IAPLTR1a), which generates a truncated mRNA. Disruption of the gene was associated with a reduced susceptibility for diabetes, whereas the normal allele enhanced hyperglycaemia in obese mice. Zfp69 encodes a transcription factor which appears to interfere with lipid storage in adipose tissue, and thereby enhances lipid deposition in liver. In humans with type 2 diabetes, mRNA levels of the human orthologue of Zfp69 (ZNF642) were increased in adipose tissue. Thus, the transcription factor ZFP69/ZNF642 may be involved in the pathogenesis of obesity-associated diabetes.
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Affiliation(s)
- Stephan Scherneck
- Department of Pharmacology, German Institute of Human Nutrition Potsdam-Rehbruecke, Nuthetal, Germany
| | - Matthias Nestler
- Department of Pharmacology, German Institute of Human Nutrition Potsdam-Rehbruecke, Nuthetal, Germany
| | - Heike Vogel
- Department of Pharmacology, German Institute of Human Nutrition Potsdam-Rehbruecke, Nuthetal, Germany
| | - Matthias Blüher
- Department of Medicine, University of Leipzig, Leipzig, Germany
| | - Marcel-Dominique Block
- Department of Pharmacology, German Institute of Human Nutrition Potsdam-Rehbruecke, Nuthetal, Germany
| | - Mauricio Berriel Diaz
- Emmy Noether and Marie Curie Research Group Molecular Metabolic Control, DKFZ-ZMBH Alliance, German Cancer Research Center, Heidelberg, Germany
| | - Stephan Herzig
- Emmy Noether and Marie Curie Research Group Molecular Metabolic Control, DKFZ-ZMBH Alliance, German Cancer Research Center, Heidelberg, Germany
| | - Nadja Schulz
- Department of Pharmacology, German Institute of Human Nutrition Potsdam-Rehbruecke, Nuthetal, Germany
| | - Marko Teichert
- Department of Pharmacology, German Institute of Human Nutrition Potsdam-Rehbruecke, Nuthetal, Germany
| | - Sina Tischer
- Department of Pharmacology, German Institute of Human Nutrition Potsdam-Rehbruecke, Nuthetal, Germany
| | - Hadi Al-Hasani
- Department of Pharmacology, German Institute of Human Nutrition Potsdam-Rehbruecke, Nuthetal, Germany
| | - Reinhart Kluge
- Department of Pharmacology, German Institute of Human Nutrition Potsdam-Rehbruecke, Nuthetal, Germany
| | - Annette Schürmann
- Department of Pharmacology, German Institute of Human Nutrition Potsdam-Rehbruecke, Nuthetal, Germany
| | - Hans-Georg Joost
- Department of Pharmacology, German Institute of Human Nutrition Potsdam-Rehbruecke, Nuthetal, Germany
- * E-mail:
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Acloque H, Adams MS, Fishwick K, Bronner-Fraser M, Nieto MA. Epithelial-mesenchymal transitions: the importance of changing cell state in development and disease. J Clin Invest 2009; 119:1438-49. [PMID: 19487820 DOI: 10.1172/jci38019] [Citation(s) in RCA: 1035] [Impact Index Per Article: 69.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
The events that convert adherent epithelial cells into individual migratory cells that can invade the extracellular matrix are known collectively as epithelial-mesenchymal transition (EMT). Throughout evolution, the capacity of cells to switch between these two cellular states has been fundamental in the generation of complex body patterns. Here, we review the EMT events that build the embryo and further discuss two prototypical processes governed by EMT in amniotes: gastrulation and neural crest formation. Cells undergo EMT to migrate and colonize distant territories. Not surprisingly, this is also the mechanism used by cancer cells to disperse throughout the body.
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Affiliation(s)
- Hervé Acloque
- Instituto de Neurociencias (CSIC-UMH), San Juan de Alicante, Spain
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Acloque H, Adams MS, Fishwick K, Bronner-Fraser M, Nieto MA. Epithelial-mesenchymal transitions: the importance of changing cell state in development and disease. J Clin Invest 2009. [PMID: 19487820 DOI: 10.1172/jci38019.] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
The events that convert adherent epithelial cells into individual migratory cells that can invade the extracellular matrix are known collectively as epithelial-mesenchymal transition (EMT). Throughout evolution, the capacity of cells to switch between these two cellular states has been fundamental in the generation of complex body patterns. Here, we review the EMT events that build the embryo and further discuss two prototypical processes governed by EMT in amniotes: gastrulation and neural crest formation. Cells undergo EMT to migrate and colonize distant territories. Not surprisingly, this is also the mechanism used by cancer cells to disperse throughout the body.
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Affiliation(s)
- Hervé Acloque
- Instituto de Neurociencias (CSIC-UMH), San Juan de Alicante, Spain
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Nishimoto-Morita K, Shin HW, Mitsuhashi H, Kitamura M, Zhang Q, Johannes L, Nakayama K. Differential effects of depletion of ARL1 and ARFRP1 on membrane trafficking between the trans-Golgi network and endosomes. J Biol Chem 2009; 284:10583-92. [PMID: 19224922 DOI: 10.1074/jbc.m900847200] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
ARFRP1 and ARL1, which are both ARF-like small GTPases, are mammalian orthologs of yeast Arl3p and Arl1p, respectively. In yeast, Arl3p targeted to trans-Golgi network (TGN) membranes activates Arl1p, and the activated Arl1p in turn recruits a GRIP domain-containing protein; this complex regulates retrograde transport to the TGN and anterograde transport from the TGN. In the present study, using RNA interference-mediated knockdown of ARFRP1 and ARL1, we have examined whether the orthologs of Arl3p-Arl1p-GRIP story serve similar functions in mammalian cells. However, we have unexpectedly found differential roles of ARL1 and ARFRP1. Specifically, ARL1 and ARFRP1 regulate retrograde transport of Shiga toxin to the TGN and anterograde transport of VSVG from the TGN, respectively. Furthermore, we have obtained evidence suggesting that a SNARE complex containing Vti1a, syntaxin 6, and syntaxin 16 is involved in Shiga toxin transport downstream of ARL1.
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Affiliation(s)
- Kirika Nishimoto-Morita
- Graduate School of Pharmaceutical Sciences, Kyoto University, Sakyo-ku, Kyoto 606-8501, Japan
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