title: Protein Phosphatase 1-α Regulates AS160 Ser588 and Thr642 Dephosphorylation in Skeletal Muscle.
abstract: Akt substrate of 160 kDa (AS160) phosphorylation on Thr(642) and Ser(588) by Akt is essential for insulin's full effect on glucose transport. However, protein phosphorylation is determined by the balance of actions by kinases and phosphatases, and the specific phosphatase(s) controlling AS160 dephosphorylation is (are) unknown. Accordingly, we assessed roles of highly expressed skeletal muscle serine/threonine phosphatases (PP1, PP2A, PP2B, and PP2C) on AS160 dephosphorylation. Preliminary screening of candidate phosphatases used an AS160 dephosphorylation assay. Lysates from insulin-stimulated skeletal muscle were treated with pharmacological phosphatase inhibitors and assessed for AS160 Ser(588) and Thr(642) dephosphorylation. AS160 dephosphorylation on both phosphorylation sites was unaltered by PP2B or PP2C inhibitors. Okadaic acid (low dose inhibits PP2A; high dose inhibits PP1) delayed AS160 Ser(588) (both doses) and Thr(642) (high dose only) dephosphorylation concomitant with greater Akt phosphorylation (both doses). AS160 was coimmunoprecipitated with PP1-α but not with PP1-β, PP1-γ1, or PP2A. Recombinant inhibitor-2 protein (a selective PP1 inhibitor) delayed AS160 dephosphorylation on both phosphorylation sites without altering Akt phosphorylation. Furthermore, knockdown of PP1-α but not PP1-β or PP1-γ1 by small interfering RNA caused greater AS160 Ser(588) and Thr(642) phosphorylation concomitant with unaltered Akt phosphorylation. Together, these results identified PP1-α as a regulator of AS160 Thr(642) and Ser(588) dephosphorylation in skeletal muscle.
authors.affiliation: Muscle Biology Laboratory, School of Kinesiology, University of Michigan, Ann Arbor, MI.
authors.forename: Pragya
authors.initials: P
authors.lastname: Sharma
authors.affiliation: Muscle Biology Laboratory, School of Kinesiology, University of Michigan, Ann Arbor, MI.
authors.forename: Edward B
authors.initials: EB
authors.lastname: Arias
authors.affiliation: Muscle Biology Laboratory, School of Kinesiology, University of Michigan, Ann Arbor, MI Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, MI Institute of Gerontology, University of Michigan, Ann Arbor, MI gcartee@umich.edu.
authors.forename: Gregory D
authors.initials: GD
authors.lastname: Cartee
mesh_terms: D000818:Animals; D053119:Benzophenanthridines / Q000494:pharmacology; D002460:Cell Line; D020690:GTPase-Activating Proteins / Q000235:genetics / Q000378:metabolism*; D015151:Immunoblotting; D047468:Immunoprecipitation; D007546:Isoquinolines / Q000494:pharmacology; D008297:Male; D018482:Muscle, Skeletal / Q000187:drug effects / Q000378:metabolism*; D019319:Okadaic Acid / Q000494:pharmacology; D010749:Phosphoprotein Phosphatases / Q000235:genetics / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D054645:Protein Phosphatase 1 / Q000235:genetics / Q000378:metabolism*; D054648:Protein Phosphatase 2 / Q000235:genetics / Q000378:metabolism; D034741:RNA, Small Interfering / Q000235:genetics; D051381:Rats; D017208:Rats, Wistar; D011924:Rats, Zucker; D012694:Serine / Q000235:genetics / Q000378:metabolism; D016559:Tacrolimus / Q000494:pharmacology
chemical_list: D053119:Benzophenanthridines; D020690:GTPase-Activating Proteins; D007546:Isoquinolines; D034741:RNA, Small Interfering; C533101:TBC1D4 protein, rat; D019319:Okadaic Acid; D012694:Serine; C005705:sanguinarine; D010749:Phosphoprotein Phosphatases; D054645:Protein Phosphatase 1; D054648:Protein Phosphatase 2; D016559:Tacrolimus