Adipose triglyceride lipase (ATGL) is the rate-limiting enzyme for triacylglycerol (TAG) hydrolysis in adipocytes. The precise mechanisms whereby ATGL is regulated remain uncertain. Here, we demonstrate that a protein encoded by G0/G1 switch gene 2 (G0S2) is a selective regulator of ATGL. G0S2 is highly expressed in adipose tissue and differentiated adipocytes. When overexpressed in HeLa cells, G0S2 localizes to lipid droplets and prevents their degradation mediated by ATGL. Moreover, G0S2 specifically interacts with ATGL through the hydrophobic domain of G0S2 and the patatin-like domain of ATGL. More importantly, interaction with G0S2 inhibits ATGL TAG hydrolase activity. Knockdown of endogenous G0S2 accelerates basal and stimulated lipolysis in adipocytes, whereas overexpression of G0S2 diminishes the rate of lipolysis in both adipocytes and adipose tissue explants. Thus, G0S2 functions to attenuate ATGL action both in vitro and in vivo and by this mechanism regulates TAG hydrolysis.
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We thank Drs. Carole Sztalryd, Matthew J. Brady, Xiaowei Chen, Alan Cheng, and William V. Everson for reviewing the manuscript and helpful discussions. We also thank Dr. Say Viengchareun for excellent technical advice. The work was supported by a NIH grant DK 078742 and a Center of Biomedical Research Excellence pilot grant from the University of Kentucky (5P20 RR0202171) to J.L. and NIH grants RR015592 and DK077632 to E.J.S.