TY - JOUR
T1 - PNPLA3, CGI-58, and Inhibition of Hepatic Triglyceride Hydrolysis in Mice
AU - Wang, Yang
AU - Kory, Nora
AU - BasuRay, Soumik
AU - Cohen, Jonathan C.
AU - Hobbs, Helen H.
N1 - Funding Information:
We thank Dr. Liqing Yu (University of Maryland, Baltimore, MD) for providing the Ls-Cgi58 KO mice. We thank Drs. Robert Farese and Tobias Walther (Harvard University, Boston, MA) for providing the ssBFP-KDEL vector and Dr. Orion D. Weiner (University of California at San Francisco, San Francisco, CA) for the pMXs-CMV-mC vector. We thank Dorothy Mundy and Katherine Luby-Phelps in the University of Texas Southwestern Imaging Core for their assistance. Soumik BasuRay provided helpful conversations. We thank Christina Zhao, Liangcai Nie, and Fang Xu for excellent technical assistance.
Funding Information:
Received December 30, 2018; accepted February 16, 2019. Additional Supporting Information may be found at onlinelibrary.wiley.com/doi/10.1002/hep.30583/suppinfo. Supported by the National Institutes of Health (RO1DK090056 and PO1 HL20948) and the Howard Hughes Medical Institute. © 2019 The Authors. H epatology published by Wiley Periodicals, Inc. on behalf of American Association for the Study of Liver Diseases.
Publisher Copyright:
© 2019 The Authors. Hepatology published by Wiley Periodicals, Inc. on behalf of American Association for the Study of Liver Diseases.
PY - 2019/6
Y1 - 2019/6
N2 - A variant (148M) in patatin-like phospholipase domain-containing protein 3 (PNPLA3) is a major risk factor for fatty liver disease. Despite its clinical importance, the pathogenic mechanism linking the variant to liver disease remains poorly defined. Previously, we showed that PNPLA3(148M) accumulates to high levels on hepatic lipid droplets (LDs). Here we examined the effect of that accumulation on triglyceride (TG) hydrolysis by adipose triglyceride lipase (ATGL), the major lipase in the liver. As expected, overexpression of ATGL in cultured hepatoma (HuH-7) cells depleted the cells of LDs, but unexpectedly, co-expression of PNPLA3(wild type [WT] or 148M) with ATGL inhibited that depletion. The inhibitory effect of PNPLA3 was not caused by the displacement of ATGL from LDs. We tested the hypothesis that PNPLA3 interferes with ATGL activity by interacting with its cofactor, comparative gene identification-58 (CGI-58). Evidence supporting such an interaction came from two findings. First, co-expression of PNPLA3 and CGI-58 resulted in LD depletion in cultured cells, but expression of PNPLA3 alone did not. Second, PNPLA3 failed to localize to hepatic LDs in liver-specific Cgi-58 knockout (KO) mice. Moreover, overexpression of PNPLA3(148M) increased hepatic TG levels in WT, but not in Cgi-58 KO mice. Thus, the pro-steatotic effects of PNPLA3 required the presence of CGI-58. Co-immunoprecipitation and pulldown experiments in livers of mice and in vitro using purified proteins provided evidence that PNPLA3 and CGI-58 can interact directly. Conclusion: Taken together, these findings are consistent with a model in which PNPLA3(148M) promotes steatosis by CGI-58-dependent inhibition of ATGL on LDs.
AB - A variant (148M) in patatin-like phospholipase domain-containing protein 3 (PNPLA3) is a major risk factor for fatty liver disease. Despite its clinical importance, the pathogenic mechanism linking the variant to liver disease remains poorly defined. Previously, we showed that PNPLA3(148M) accumulates to high levels on hepatic lipid droplets (LDs). Here we examined the effect of that accumulation on triglyceride (TG) hydrolysis by adipose triglyceride lipase (ATGL), the major lipase in the liver. As expected, overexpression of ATGL in cultured hepatoma (HuH-7) cells depleted the cells of LDs, but unexpectedly, co-expression of PNPLA3(wild type [WT] or 148M) with ATGL inhibited that depletion. The inhibitory effect of PNPLA3 was not caused by the displacement of ATGL from LDs. We tested the hypothesis that PNPLA3 interferes with ATGL activity by interacting with its cofactor, comparative gene identification-58 (CGI-58). Evidence supporting such an interaction came from two findings. First, co-expression of PNPLA3 and CGI-58 resulted in LD depletion in cultured cells, but expression of PNPLA3 alone did not. Second, PNPLA3 failed to localize to hepatic LDs in liver-specific Cgi-58 knockout (KO) mice. Moreover, overexpression of PNPLA3(148M) increased hepatic TG levels in WT, but not in Cgi-58 KO mice. Thus, the pro-steatotic effects of PNPLA3 required the presence of CGI-58. Co-immunoprecipitation and pulldown experiments in livers of mice and in vitro using purified proteins provided evidence that PNPLA3 and CGI-58 can interact directly. Conclusion: Taken together, these findings are consistent with a model in which PNPLA3(148M) promotes steatosis by CGI-58-dependent inhibition of ATGL on LDs.
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U2 - 10.1002/hep.30583
DO - 10.1002/hep.30583
M3 - Article
C2 - 30802989
AN - SCOPUS:85064049744
VL - 69
SP - 2427
EP - 2441
JO - Hepatology
JF - Hepatology
SN - 0270-9139
IS - 6
ER -