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Campbell LE, Anderson AM, Chen Y, Johnson SM, McMahon CE, Liu J. Identification of motifs and mechanisms for lipid droplet targeting of the lipolytic inhibitors G0S2 and HIG2. J Cell Sci 2022; 135:285951. [PMID: 36420951 PMCID: PMC10112975 DOI: 10.1242/jcs.260236] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2022] [Accepted: 11/15/2022] [Indexed: 11/27/2022] Open
Abstract
G0S2 and HIG2 are two selective inhibitors of ATGL (also known as PNPLA2), the key enzyme for intracellular lipolysis. Whereas G0S2 regulates triglyceride (TG) mobilization in adipocytes and hepatocytes, HIG2 functions to enhance intracellular TG accumulation under hypoxic conditions. A homologous hydrophobic domain (HD) is shared by G0S2 and HIG2 (also known as HILPDA) for binding to ATGL. However, the determinants of their lipid droplet (LD) localization are unknown. Here, we study how G0S2 and HIG2 are targeted to LDs, and identify both ATGL-independent and -dependent mechanisms. Structural prediction and studies in cells reveal that ATGL-independent localization of G0S2 to both the endoplasmic reticulum (ER) and LDs is mediated by a hairpin structure consisting of two hydrophobic sequences. Positively charged residues in the hinge region play a crucial role in sorting G0S2, which initially localizes to ER, to LDs. Interestingly, the role of these positive charges becomes dispensable when ATGL is co-expressed. In comparison, HIG2, which lacks a similar hairpin structure, is dependent on ATGL for its full LD targeting. Thus, our studies identify specific structural features and mechanisms for mediating accumulation of these two ATGL inhibitors on LDs.
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Affiliation(s)
- Latoya E Campbell
- Department of Biochemistry and Molecular Biology, Mayo Clinic College of Medicine & Science, Rochester, MN 55905, USA.,College of Health Solutions, Arizona State University, Tempe, AZ 85281, USA
| | - Aaron M Anderson
- Department of Biochemistry and Molecular Biology, Mayo Clinic College of Medicine & Science, Rochester, MN 55905, USA.,Department of Developmental Biology, Washington University School of Medicine in St. Louis, St. Louis, MO 63110, USA
| | - Yongbin Chen
- Department of Biochemistry and Molecular Biology, Mayo Clinic College of Medicine & Science, Rochester, MN 55905, USA
| | - Scott M Johnson
- Department of Biochemistry and Molecular Biology, Mayo Clinic College of Medicine & Science, Rochester, MN 55905, USA.,Mayo Clinic Graduate School of Biomedical Sciences, Rochester, MN 55905, USA
| | - Cailin E McMahon
- Department of Biochemistry and Molecular Biology, Mayo Clinic College of Medicine & Science, Rochester, MN 55905, USA
| | - Jun Liu
- Department of Biochemistry and Molecular Biology, Mayo Clinic College of Medicine & Science, Rochester, MN 55905, USA.,Division of Endocrinology, Diabetes, Metabolism and Nutrition, Mayo Clinic in Rochester, Rochester, MN 55905, USA
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Transcriptome Analysis of Protection by Dendrobium Nobile Alkaloids (DNLA) against Chronic Alcoholic Liver Injury in Mice. Biomedicines 2022; 10:biomedicines10112800. [PMID: 36359319 PMCID: PMC9687597 DOI: 10.3390/biomedicines10112800] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2022] [Revised: 10/28/2022] [Accepted: 11/01/2022] [Indexed: 11/06/2022] Open
Abstract
Objective: To investigate the protective effects of Dendrobium nobile Lindl. alkaloids (DNLA) against chronic alcoholic liver injury. C57BL/6J mice were fed with the Lieber−DeCarli alcohol diet to induce chronic alcoholic liver injury. DNLA (20 mg/kg/day) was gavaged along with the alcohol diet for 28 days. Liver injury was evaluated by serum enzymes. Triglyceride levels, histopathology, and transcriptome changes were examined by RNA-Seq and qPCR. DNLA decreased serum triglyceride levels in mice receiving alcohol. Hepatocyte degeneration and steatosis were ameliorated by DNLA, as evidenced by H&E and Oil-red O staining. DNLA brought the alcohol-induced aberrant gene expression pattern towards normal. Alcohol induced 787 differentially expressed genes (padj < 0.01). DNLA induced 280 differentially expressed genes to a much less extent. Ingenuity pathway analysis showed that DNLA ameliorated alcohol-induced oxidative stress and xenobiotic metabolism disruption. qPCR verified that DNLA alleviated over-activation of Cyp2a4, Cyp2b10, and Abcc4; attenuated oxidative stress (Hmox1, Gstm3, Nupr1), reduced the expression of Nrf2 genes (Nqo1, Gclc, Vldlr); and rescued some metabolic genes (Insig1, Xbp1, Socs3, Slc10a2). In conclusion, DNLA was effective against alcohol-induced fatty liver disease, and the protection may be attributed to alleviated oxidative stress and restored metabolism homeostasis, probably through modulating nuclear receptor CAR-, PXR-, and Nrf2-mediated gene expression pathways.
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The vesicular transporter STX11 governs ATGL-mediated hepatic lipolysis and lipophagy. iScience 2022; 25:104085. [PMID: 35372814 PMCID: PMC8971941 DOI: 10.1016/j.isci.2022.104085] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2021] [Revised: 01/23/2022] [Accepted: 03/14/2022] [Indexed: 01/22/2023] Open
Abstract
Hepatic lipid accumulation is closely associated with nonalcoholic fatty liver disease (NAFLD). Adipose-triglyceride-lipase (ATGL) regulates triglyceride hydrolysis and maintains energy homeostasis in hepatocytes. Identifying key factors in the regulation of ATGL will help tackle hepatic lipid accumulation and related metabolic diseases. Herein, we demonstrate that syntaxin11 (STX11), a member of the SNARE family, generally expressed in immune cells, mediates lipid metabolism by binding to ATGL and inhibiting lipid droplet degradation and lipid autophagy in hepatocytes. Our data show that the C-terminal of STX11 and the patatin domain-containing segment of ATGL have direct physical interactions. Thus, STX11 overexpression prevents spatial translocation of ATGL onto LDs by recruitment of ATGL to the ER. Conversely, STX11 deficiency in hepatocytes promotes lipid hydrolysis, and the ATGL-SIRT1 signaling pathway enhances lipophagy. Overall, this study uncovered that the regulation of lipolysis and lipophagy is achieved by STX11 through the attenuation of ATGL action in hepatocytes. STX11 inhibits lipid droplet degradation via ATGL in hepatocytes Interaction of ATGL and STX11 affects trafficking of ATGL STX11 suppresses lipophagy in association with ATGL and SIRT1
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Bai X, Liao Y, Sun F, Xiao X, Fu S. Diurnal regulation of oxidative phosphorylation restricts hepatocyte proliferation and inflammation. Cell Rep 2021; 36:109659. [PMID: 34496251 DOI: 10.1016/j.celrep.2021.109659] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2020] [Revised: 05/14/2021] [Accepted: 08/13/2021] [Indexed: 12/13/2022] Open
Abstract
The principles guiding the diurnal organization of biological pathways remain to be fully elucidated. Here, we perturb the hepatic transcriptome through nutrient regulators (high-fat diet and mTOR signaling components) to identify enduring properties of pathway organization. Temporal separation and counter-regulation between pathways of energy metabolism and inflammation/proliferation emerge as persistent transcriptome features across animal models, and network analysis identifies the G0s2 and Rgs16 genes as potential mediators at the metabolism-inflammation interface. Mechanistically, G0s2 and Rgs16 are sequentially induced during the light phase, promoting amino acid oxidation and suppressing overall mitochondrial respiration. In their absence, sphingolipids and diacylglycerides accumulate, accompanied by hepatic inflammation and hepatocyte proliferation. Notably, the expression of G0s2 and Rgs16 is further induced in obese mouse livers, and silencing of their expression accentuates hepatic fibrosis. Therefore, diurnal regulation of energy metabolism alleviates inflammatory and proliferative stresses under physiological and pathological conditions.
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Affiliation(s)
- Xiaojie Bai
- School of Life Sciences, Tsinghua University, Beijing, China 100084
| | - Yilie Liao
- School of Life Sciences, Tsinghua University, Beijing, China 100084
| | - Fangfang Sun
- School of Life Sciences, Tsinghua University, Beijing, China 100084
| | - Xia Xiao
- School of Life Sciences, Tsinghua University, Beijing, China 100084
| | - Suneng Fu
- School of Life Sciences, Tsinghua University, Beijing, China 100084; Department of Basic Research, Guangzhou Laboratory, Guangdong, China 510005.
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Mashek DG. Hepatic lipid droplets: A balancing act between energy storage and metabolic dysfunction in NAFLD. Mol Metab 2020; 50:101115. [PMID: 33186758 PMCID: PMC8324678 DOI: 10.1016/j.molmet.2020.101115] [Citation(s) in RCA: 115] [Impact Index Per Article: 28.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/26/2020] [Revised: 10/21/2020] [Accepted: 11/06/2020] [Indexed: 02/06/2023] Open
Abstract
BACKGROUND Non-alcoholic fatty liver disease (NAFLD) is defined by the abundance of lipid droplets (LDs) in hepatocytes. While historically considered simply depots for energy storage, LDs are increasingly recognized to impact a wide range of biological processes that influence cellular metabolism, signaling, and function. While progress has been made toward understanding the factors leading to LD accumulation (i.e. steatosis) and its progression to advanced stages of NAFLD and/or systemic metabolic dysfunction, much remains to be resolved. SCOPE OF REVIEW This review covers many facets of LD biology. We provide a brief overview of the major pathways of lipid accretion and degradation that contribute to steatosis and how they are altered in NAFLD. The major focus is on the relationship between LDs and cell function and the detailed mechanisms that couple or uncouple steatosis from the severity and progression of NAFLD and systemic comorbidities. The importance of specific lipids and proteins within or on LDs as key components that determine whether LD accumulation is linked to cellular and metabolic dysfunction is presented. We discuss emerging areas of LD biology and future research directions that are needed to advance our understanding of the role of LDs in NAFLD etiology. MAJOR CONCLUSIONS Impairments in LD breakdown appear to contribute to disease progression, but inefficient incorporation of fatty acids (FAs) into LD-containing triacylglycerol (TAG) and the consequential changes in FA partitioning also affect NAFLD etiology. Increased LD abundance in hepatocytes does not necessarily equate to cellular dysfunction. While LD accumulation is the prerequisite step for most NAFLD cases, the protein and lipid composition of LDs are critical factors in determining the progression from simple steatosis. Further defining the detailed molecular mechanisms linking LDs to metabolic dysfunction is important for designing effective therapeutic approaches targeting NAFLD and its comorbidities.
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Affiliation(s)
- Douglas G Mashek
- Department of Biochemistry, Molecular Biology, and Biophysics, Department of Medicine, Division of Diabetes, Endocrinology, and Metabolism, University of Minnesota, Suite 6-155, 321 Church St. SE, Minneapolis, MN, 55455, USA.
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Sousa-Victor P, Neves J, Cedron-Craft W, Ventura PB, Liao CY, Riley RR, Soifer I, van Bruggen N, Kolumam GA, Villeda SA, Lamba DA, Jasper H. MANF regulates metabolic and immune homeostasis in ageing and protects against liver damage. Nat Metab 2019; 1:276-290. [PMID: 31489403 PMCID: PMC6727652 DOI: 10.1038/s42255-018-0023-6] [Citation(s) in RCA: 83] [Impact Index Per Article: 16.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Aging is accompanied by altered intercellular communication, deregulated metabolic function, and inflammation. Interventions that restore a youthful state delay or reverse these processes, prompting the search for systemic regulators of metabolic and immune homeostasis. Here we identify MANF, a secreted stress-response protein with immune modulatory properties, as an evolutionarily conserved regulator of systemic and in particular liver metabolic homeostasis. We show that MANF levels decline with age in flies, mice and humans, and MANF overexpression extends lifespan in flies. MANF deficient flies exhibit enhanced inflammation and shorter lifespans, and MANF heterozygous mice exhibit inflammatory phenotypes in various tissues, as well as progressive liver damage, fibrosis, and steatosis. We show that immune cell-derived MANF protects against liver inflammation and fibrosis, while hepatocyte-derived MANF prevents hepatosteatosis. Liver rejuvenation by heterochronic parabiosis in mice further depends on MANF, while MANF supplementation ameliorates several hallmarks of liver aging, prevents hepatosteatosis induced by diet, and improves age-related metabolic dysfunction. Our findings identify MANF as a systemic regulator of homeostasis in young animals, suggesting a therapeutic application for MANF in age-related metabolic diseases.
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Affiliation(s)
- Pedro Sousa-Victor
- Paul F. Glenn Center for Biology of Aging Research, Buck Institute for Research on Aging, Novato, CA, USA
| | - Joana Neves
- Paul F. Glenn Center for Biology of Aging Research, Buck Institute for Research on Aging, Novato, CA, USA
| | - Wendy Cedron-Craft
- Paul F. Glenn Center for Biology of Aging Research, Buck Institute for Research on Aging, Novato, CA, USA
| | - P Britten Ventura
- Department of Anatomy, University of California, San Francisco, San Francisco, CA, USA
- The Eli and Edythe Broad Center of Regeneration Medicine and Stem Cell Research, University of California, San Francisco, San Francisco, CA, USA
| | - Chen-Yu Liao
- Paul F. Glenn Center for Biology of Aging Research, Buck Institute for Research on Aging, Novato, CA, USA
| | - Rebeccah R Riley
- Paul F. Glenn Center for Biology of Aging Research, Buck Institute for Research on Aging, Novato, CA, USA
| | - Ilya Soifer
- Calico Life Sciences LLC, South San Francisco, CA, USA
| | | | | | - Saul A Villeda
- Department of Anatomy, University of California, San Francisco, San Francisco, CA, USA
- The Eli and Edythe Broad Center of Regeneration Medicine and Stem Cell Research, University of California, San Francisco, San Francisco, CA, USA
| | - Deepak A Lamba
- Paul F. Glenn Center for Biology of Aging Research, Buck Institute for Research on Aging, Novato, CA, USA
- The Eli and Edythe Broad Center of Regeneration Medicine and Stem Cell Research, University of California, San Francisco, San Francisco, CA, USA
- Department of Ophthalmology, University of California, San Francisco, San Francisco, CA, USA
| | - Heinrich Jasper
- Paul F. Glenn Center for Biology of Aging Research, Buck Institute for Research on Aging, Novato, CA, USA.
- Immunology Discovery, Genentech, South San Francisco, CA, USA.
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Zhang X, Heckmann BL, Campbell LE, Liu J. G0S2: A small giant controller of lipolysis and adipose-liver fatty acid flux. Biochim Biophys Acta Mol Cell Biol Lipids 2017. [PMID: 28645852 DOI: 10.1016/j.bbalip.2017.06.007] [Citation(s) in RCA: 57] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
The discovery of adipose triglyceride lipase (ATGL) and its coactivator comparative gene identification-58 (CGI-58) provided a major paradigm shift in the understanding of intracellular lipolysis in both adipocytes and nonadipocyte cells. The subsequent discovery of G0/G1 switch gene 2 (G0S2) as a potent endogenous inhibitor of ATGL revealed a unique mechanism governing lipolysis and fatty acid (FA) availability. G0S2 is highly conserved in vertebrates, and exhibits cyclical expression pattern between adipose tissue and liver that is critical to lipid flux and energy homeostasis in these two tissues. Biochemical and cell biological studies have demonstrated that a direct interaction with ATGL mediates G0S2's inhibitory effects on lipolysis and lipid droplet degradation. In this review we examine evidence obtained from recent in vitro and in vivo studies that lends support to the proof-of-principle concept that G0S2 functions as a master regulator of tissue-specific balance of TG storage vs. mobilization, partitioning of metabolic fuels between adipose and liver, and the whole-body adaptive energy response. This article is part of a Special Issue entitled: Recent Advances in Lipid Droplet Biology edited by Rosalind Coleman and Matthijs Hesselink.
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Affiliation(s)
- Xiaodong Zhang
- Department of Biochemistry & Molecular Biology, Mayo Clinic College of Medicine, Scottsdale, AZ, United States; HEAL(th) Program, Mayo Clinic, Scottsdale, AZ, United States
| | - Bradlee L Heckmann
- Department of Immunology, St. Jude Children's Research Hospital, Memphis, TN, United States
| | - Latoya E Campbell
- School of Life Sciences, Arizona State University, Tempe, AZ, United States
| | - Jun Liu
- Department of Biochemistry & Molecular Biology, Mayo Clinic College of Medicine, Scottsdale, AZ, United States; HEAL(th) Program, Mayo Clinic, Scottsdale, AZ, United States; Division of Endocrinology, Mayo Clinic, Scottsdale, AZ, United States.
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