TY - JOUR
T1 - Identification of a novel phosphorylation site in adipose triglyceride lipase as a regulator of lipid droplet localization
AU - Xie, Xitao
AU - Langlais, Paul
AU - Zhang, Xiaodong
AU - Heckmann, Bradlee L.
AU - Saarinen, Alicia M.
AU - Mandarino, Lawrence J.
AU - Liu, Jun
PY - 2014/6/15
Y1 - 2014/6/15
N2 - Adipose triglyceride lipase (ATGL), the rate-limiting enzyme for triacylglycerol (TG) hydrolysis, has long been known to be a phosphoprotein. However, the potential phosphorylation events that are involved in the regulation of ATGL function remain incompletely defined. Here, using a combinatorial proteomics approach, we obtained evidence that at least eight different sites of ATGL can be phosphorylated in adipocytes. Among them, Thr372 resides within the hydrophobic region known to mediate lipid droplet (LD) targeting. Although it had no impact on the TG hydrolase activity, substitution of phosphorylation-mimic Asp for Thr372 eliminated LD localization and LD-degrading capacity of ATGL expressed in HeLa cells. In contrast, mutation of Thr372 to Ala gave a protein that bound LDs and functioned the same as the wild-type protein. In nonstimulated adipocytes, the Asp mutation led to decreased LD association and basal lipolytic activity of ATGL, whereas the Ala mutation produced opposite effects. Moreover, the LD translocation of ATGL upon β-adrenergic stimulation was also compromised by the Asp mutation. In accord with these findings, the Ala mutation promoted and the Asp mutation attenuated the capacity of ATGL to mediate lipolysis in adipocytes under both basal and stimulated conditions. Collectively, these studies identified Thr372 as a novel phosphorylation site that may play a critical role in determining subcellular distribution as well as lipolytic action of ATGL.
AB - Adipose triglyceride lipase (ATGL), the rate-limiting enzyme for triacylglycerol (TG) hydrolysis, has long been known to be a phosphoprotein. However, the potential phosphorylation events that are involved in the regulation of ATGL function remain incompletely defined. Here, using a combinatorial proteomics approach, we obtained evidence that at least eight different sites of ATGL can be phosphorylated in adipocytes. Among them, Thr372 resides within the hydrophobic region known to mediate lipid droplet (LD) targeting. Although it had no impact on the TG hydrolase activity, substitution of phosphorylation-mimic Asp for Thr372 eliminated LD localization and LD-degrading capacity of ATGL expressed in HeLa cells. In contrast, mutation of Thr372 to Ala gave a protein that bound LDs and functioned the same as the wild-type protein. In nonstimulated adipocytes, the Asp mutation led to decreased LD association and basal lipolytic activity of ATGL, whereas the Ala mutation produced opposite effects. Moreover, the LD translocation of ATGL upon β-adrenergic stimulation was also compromised by the Asp mutation. In accord with these findings, the Ala mutation promoted and the Asp mutation attenuated the capacity of ATGL to mediate lipolysis in adipocytes under both basal and stimulated conditions. Collectively, these studies identified Thr372 as a novel phosphorylation site that may play a critical role in determining subcellular distribution as well as lipolytic action of ATGL.
KW - Adipose triglyceride lipase
KW - Lipid droplet
KW - Lipid metabolism
KW - Lipolysis
KW - Phosphorylation
KW - Triglyceride
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U2 - 10.1152/ajpendo.00663.2013
DO - 10.1152/ajpendo.00663.2013
M3 - Article
C2 - 24801391
AN - SCOPUS:84902665686
SN - 0193-1849
VL - 306
SP - E1449-E1459
JO - American Journal of Physiology - Endocrinology and Metabolism
JF - American Journal of Physiology - Endocrinology and Metabolism
IS - 12
ER -