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Sar1 Affects the Localization of Perilipin 2 to Lipid Droplets. Int J Mol Sci 2022; 23:ijms23126366. [PMID: 35742827 PMCID: PMC9223735 DOI: 10.3390/ijms23126366] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2022] [Revised: 06/03/2022] [Accepted: 06/03/2022] [Indexed: 02/05/2023] Open
Abstract
Lipid droplets (LDs) are intracellular organelles that are ubiquitous in many types of cells. The LD core consists of triacylglycerols (TGs) surrounded by a phospholipid monolayer and surface proteins such as perilipin 2 (PLIN2). Although TGs accumulate in the phospholipid bilayer of the endoplasmic reticulum (ER) and subsequently nascent LDs buds from ER, the mechanism by which LD proteins are transported to LD particles is not fully understood. Sar1 is a GTPase known as a regulator of coat protein complex Ⅱ (COPⅡ) vesicle budding, and its role in LD formation was investigated in this study. HuH7 human hepatoma cells were infected with adenoviral particles containing genes coding GFP fused with wild-type Sar1 (Sar1 WT) or a GTPase mutant form (Sar1 H79G). When HuH7 cells were treated with oleic acid, Sar1 WT formed a ring-like structure around the LDs. The transient expression of Sar1 did not significantly alter the levels of TG and PLIN2 in the cells. However, the localization of PLIN2 to the LDs decreased in the cells expressing Sar1 H79G. Furthermore, the effects of Sar1 on PLIN2 localization to the LDs were verified by the suppression of endogenous Sar1 using the short hairpin RNA technique. In conclusion, it was found that Sar1 has some roles in the intracellular distribution of PLIN2 to LDs in liver cells.
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Nakagawa H, Komori M, Nishimura K. Carbon tetrachloride suppresses ER-Golgi transport by inhibiting COPII vesicle formation on the ER membrane in the RLC-16 hepatocyte cell line. Cell Biol Int 2021; 45:633-641. [PMID: 33247607 DOI: 10.1002/cbin.11510] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2020] [Revised: 10/20/2020] [Accepted: 11/21/2020] [Indexed: 01/14/2023]
Abstract
Carbon tetrachloride (CCl4 ) causes hepatotoxicity in mammals, with its hepatocytic metabolism producing radicals that attack the intracellular membrane system and destabilize intracellular vesicle transport. Inhibition of intracellular transport causes lipid droplet retention and abnormal protein distribution. The intracellular transport of synthesized lipids and proteins from the endoplasmic reticulum (ER) to the Golgi apparatus is performed by coat complex II (COPII) vesicle transport, but how CCl4 inhibits COPII vesicle transport has not been elucidated. COPII vesicle formation on the ER membrane is initiated by the recruitment of Sar1 protein from the cytoplasm to the ER membrane, followed by that of the COPII coat constituent proteins (Sec23, Sec24, Sec13, and Sec31). In this study, we evaluated the effect of CCl4 on COPII vesicle formation using the RLC-16 rat hepatocyte cell line. Our results showed that CCl4 suppressed ER-Golgi transport in RLC-16 cells. Using a reconstituted system of rat liver tissue-derived cytoplasm and RLC-16 cell-derived ER membranes, CCl4 treatment inhibited the recruitment of Sar1 and Sec13 from the cytosolic fraction to ER membranes. CCl4 -induced changes in the ER membrane accordingly inhibited the accumulation of COPII vesicle-coated constituent proteins on the ER membrane, as well as the formation of COPII vesicles, which suppressed lipid and protein transport between the ER and Golgi apparatus. Our data suggest that CCl4 inhibits ER-Golgi intracellular transport by inhibiting COPII vesicle formation on the ER membrane in hepatocytes.
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Affiliation(s)
- Hiroshi Nakagawa
- Laboratory of Toxicology, Graduate School of Veterinary Sciences, Osaka Prefecture University, Izumisano, Osaka, Japan
| | - Masayuki Komori
- Laboratory of Cellular and Molecular Biology, Graduate School of Veterinary Sciences, Osaka Prefecture University, Izumisano, Osaka, Japan
| | - Kazuhiko Nishimura
- Laboratory of Toxicology, Graduate School of Veterinary Sciences, Osaka Prefecture University, Izumisano, Osaka, Japan
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Yonemura Y, Li X, Müller K, Krämer A, Atigbire P, Mentrup T, Feuerhake T, Kroll T, Shomron O, Nohl R, Arndt HD, Hoischen C, Hemmerich P, Hirschberg K, Kaether C. Inhibition of cargo export at ER exit sites and the trans-Golgi network by the secretion inhibitor FLI-06. J Cell Sci 2016; 129:3868-3877. [PMID: 27587840 DOI: 10.1242/jcs.186163] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2016] [Accepted: 08/25/2016] [Indexed: 12/21/2022] Open
Abstract
Export out of the endoplasmic reticulum (ER) involves the Sar1 and COPII machinery acting at ER exit sites (ERES). Whether and how cargo proteins are recruited upstream of Sar1 and COPII is unclear. Two models are conceivable, a recruitment model where cargo is actively transported through a transport factor and handed over to the Sar1 and COPII machinery in ERES, and a capture model, where cargo freely diffuses into ERES where it is captured by the Sar1 and COPII machinery. Using the novel secretion inhibitor FLI-06, we show that recruitment of the cargo VSVG to ERES is an active process upstream of Sar1 and COPII. Applying FLI-06 before concentration of VSVG in ERES completely abolishes its recruitment. In contrast, applying FLI-06 after VSVG concentration in ERES does not lead to dispersal of the concentrated VSVG, arguing that it inhibits recruitment to ERES as opposed to capture in ERES. FLI-06 also inhibits export out of the trans-Golgi network (TGN), suggesting that similar mechanisms might orchestrate cargo selection and concentration at the ER and TGN. FLI-06 does not inhibit autophagosome biogenesis and the ER-peroxisomal transport route, suggesting that these rely on different mechanisms.
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Affiliation(s)
- Yoji Yonemura
- Leibniz Institut für Alternsforschung-Fritz Lipmann Institut, Jena 07745, Germany
| | - Xiaolin Li
- Leibniz Institut für Alternsforschung-Fritz Lipmann Institut, Jena 07745, Germany
| | - Katja Müller
- Leibniz Institut für Alternsforschung-Fritz Lipmann Institut, Jena 07745, Germany
| | - Andreas Krämer
- Leibniz Institut für Alternsforschung-Fritz Lipmann Institut, Jena 07745, Germany
| | - Paul Atigbire
- Leibniz Institut für Alternsforschung-Fritz Lipmann Institut, Jena 07745, Germany
| | - Torben Mentrup
- Leibniz Institut für Alternsforschung-Fritz Lipmann Institut, Jena 07745, Germany
| | - Talitha Feuerhake
- Leibniz Institut für Alternsforschung-Fritz Lipmann Institut, Jena 07745, Germany
| | - Torsten Kroll
- Leibniz Institut für Alternsforschung-Fritz Lipmann Institut, Jena 07745, Germany
| | - Olga Shomron
- Pathology Department, Sackler School of Medicine, Tel-Aviv University, Tel-Aviv 69978, Israel
| | - Richard Nohl
- Lehrstuhl für organische Chemie I, Friedrich-Schiller Universität, Jena 07743, Germany
| | - Hans-Dieter Arndt
- Lehrstuhl für organische Chemie I, Friedrich-Schiller Universität, Jena 07743, Germany
| | - Christian Hoischen
- Leibniz Institut für Alternsforschung-Fritz Lipmann Institut, Jena 07745, Germany
| | - Peter Hemmerich
- Leibniz Institut für Alternsforschung-Fritz Lipmann Institut, Jena 07745, Germany
| | - Koret Hirschberg
- Pathology Department, Sackler School of Medicine, Tel-Aviv University, Tel-Aviv 69978, Israel
| | - Christoph Kaether
- Leibniz Institut für Alternsforschung-Fritz Lipmann Institut, Jena 07745, Germany
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Petrosyan A, Cheng PW, Clemens DL, Casey CA. Downregulation of the small GTPase SAR1A: a key event underlying alcohol-induced Golgi fragmentation in hepatocytes. Sci Rep 2015; 5:17127. [PMID: 26607390 PMCID: PMC4660820 DOI: 10.1038/srep17127] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2015] [Accepted: 10/26/2015] [Indexed: 12/14/2022] Open
Abstract
The hepatic asialoglycoprotein receptor (ASGP-R) is posttranslationally modified in the Golgi en route to the plasma membrane, where it mediates clearance of desialylated serum glycoproteins. It is known that content of plasma membrane-associated ASGP-R is decreased after ethanol exposure, although the mechanisms remain elusive. Previously, we found that formation of compact Golgi requires dimerization of the largest Golgi matrix protein giantin. We hypothesize that ethanol-impaired giantin function may be related to altered trafficking of ASGP-R. Here we report that in HepG2 cells expressing alcohol dehydrogenase and hepatocytes of ethanol-fed rats, ethanol metabolism results in Golgi disorganization. This process is initiated by dysfunction of SAR1A GTPase followed by altered COPII vesicle formation and impaired Golgi delivery of the protein disulfide isomerase A3 (PDIA3), an enzyme that catalyzes giantin dimerization. Additionally, we show that SAR1A gene silencing in hepatocytes mimics the effect of ethanol: dedimerization of giantin, arresting PDIA3 in the endoplasmic reticulum (ER) and large-scale alterations in Golgi architecture. Ethanol-induced Golgi fission has no effect on ER-to-Golgi transportation of ASGP-R, however, it results in its deposition in cis-medial-, but not trans-Golgi. Thus, alcohol-induced deficiency in COPII vesicle formation predetermines Golgi fragmentation which, in turn, compromises the Golgi-to-plasma membrane transportation of ASGP-R.
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Affiliation(s)
- Armen Petrosyan
- Department of Biochemistry and Molecular Biology, College of Medicine, Omaha, NE, USA
| | - Pi-Wan Cheng
- Department of Biochemistry and Molecular Biology, College of Medicine, Omaha, NE, USA
- Nebraska Western Iowa Health Care System, VA Service, Department of Research Service, Omaha, NE, USA
| | - Dahn L. Clemens
- Department of Internal Medicine, University of Nebraska Medical Center, Omaha, NE, USA
- Nebraska Western Iowa Health Care System, VA Service, Department of Research Service, Omaha, NE, USA
| | - Carol A. Casey
- Department of Internal Medicine, University of Nebraska Medical Center, Omaha, NE, USA
- Nebraska Western Iowa Health Care System, VA Service, Department of Research Service, Omaha, NE, USA
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