title: Identification of a novel phosphorylation site in adipose triglyceride lipase as a regulator of lipid droplet localization.
abstract: 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.
authors.affiliation: Department of Biochemistry and Molecular Biology, Mayo Clinic, Scottsdale, Arizona; HEALth Program, Mayo Clinic, Scottsdale, Arizona;
authors.forename: Xitao
authors.initials: X
authors.lastname: Xie
authors.affiliation: HEALth Program, Mayo Clinic, Scottsdale, Arizona;
authors.forename: Paul
authors.initials: P
authors.lastname: Langlais
authors.affiliation: Department of Biochemistry and Molecular Biology, Mayo Clinic, Scottsdale, Arizona; HEALth Program, Mayo Clinic, Scottsdale, Arizona;
authors.forename: Xiaodong
authors.initials: X
authors.lastname: Zhang
authors.affiliation: Department of Biochemistry and Molecular Biology, Mayo Clinic, Scottsdale, Arizona; HEALth Program, Mayo Clinic, Scottsdale, Arizona; Mayo Graduate School, Rochester, Minnesota; and.
authors.forename: Bradlee L
authors.initials: BL
authors.lastname: Heckmann
authors.affiliation: Department of Biochemistry and Molecular Biology, Mayo Clinic, Scottsdale, Arizona; HEALth Program, Mayo Clinic, Scottsdale, Arizona;
authors.forename: Alicia M
authors.initials: AM
authors.lastname: Saarinen
authors.affiliation: HEALth Program, Mayo Clinic, Scottsdale, Arizona; Division of Endocrinology, Mayo Clinic, Scottsdale, Arizona; Center for Metabolic and Vascular Biology, Arizona State University, Tempe, Arizona.
authors.forename: Lawrence J
authors.initials: LJ
authors.lastname: Mandarino
authors.affiliation: Department of Biochemistry and Molecular Biology, Mayo Clinic, Scottsdale, Arizona; HEALth Program, Mayo Clinic, Scottsdale, Arizona; Division of Endocrinology, Mayo Clinic, Scottsdale, Arizona; liu.jun@mayo.edu.
authors.forename: Jun
authors.initials: J
authors.lastname: Liu
mesh_terms: D041721:3T3-L1 Cells; D052438:Adipocytes, White / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D000318:Adrenergic beta-Agonists / Q000494:pharmacology; D019943:Amino Acid Substitution; D000818:Animals; D003594:Cytoplasmic Granules / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism*; D006367:HeLa Cells; D022781:Hepatocytes / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D006801:Humans; D057927:Hydrophobic and Hydrophilic Interactions; D008049:Lipase / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D008066:Lipolysis / Q000187:drug effects; D051379:Mice; D050505:Mutant Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D011499:Protein Processing, Post-Translational / Q000187:drug effects; D021381:Protein Transport / Q000187:drug effects; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000378:metabolism; D013912:Threonine / Q000378:metabolism*; D014280:Triglycerides / Q000378:metabolism*; D000217:Acyltransferases
chemical_list: D000318:Adrenergic beta-Agonists; D008049:Lipase; D050505:Mutant Proteins; D011993:Recombinant Fusion Proteins; D013912:Threonine; D014280:Triglycerides; C494445:PNPLA2 protein, mouse; D000217:Acyltransferases
keywords: adipose triglyceride lipase; lipid droplet; lipid metabolism; lipolysis; phosphorylation; triglyceride