title: Serine phosphorylation sites on IRS2 activated by angiotensin II and protein kinase C to induce selective insulin resistance in endothelial cells.
abstract: Protein kinase C (PKC) activation, induced by hyperglycemia and angiotensin II (AngII), inhibited insulin-induced phosphorylation of Akt/endothelial nitric oxide (eNOS) by decreasing tyrosine phosphorylation of IRS2 (p-Tyr-IRS2) in endothelial cells. PKC activation by phorbol ester (phorbol myristate acetate [PMA]) reduced insulin-induced p-Tyr-IRS2 by 46% ± 13% and, similarly, phosphorylation of Akt/eNOS. Site-specific mutational analysis showed that PMA increased serine phosphorylation at three sites on IRS2 (positions 303, 343, and 675), which affected insulin-induced tyrosine phosphorylation of IRS2 at positions 653, 671, and 911 (p-Tyr-IRS2) and p-Akt/eNOS. Specific PKCβ2 activation decreased p-Tyr-IRS2 and increased the phosphorylation of two serines (Ser303 and Ser675) on IRS2 that were confirmed in cells overexpressing single point mutants of IRS2 (S303A or S675A) containing a PKCβ2-dominant negative or selective PKCβ inhibitor. AngII induced phosphorylation only on Ser303 of IRS2 and inhibited insulin-induced p-Tyr911 of IRS2 and p-Akt/eNOS, which were blocked by an antagonist of AngII receptor I, losartan, or overexpression of single mutant S303A of IRS2. Increases in p-Ser303 and p-Ser675 and decreases in p-Tyr911 of IRS2 were observed in vessels of insulin-resistant Zucker fatty rats versus lean rats. Thus, AngII or PKCβ activation can phosphorylate Ser303 and Ser675 in IRS2 to inhibit insulin-induced p-Tyr911 and its anti-atherogenic actions (p-Akt/eNOS) in endothelial cells.
authors.affiliation: Section of Vascular Cell Biology, Joslin Diabetes Center, Harvard Medical School, Boston, Massachusetts, USA.
authors.forename: Kyoungmin
authors.initials: K
authors.lastname: Park
authors.forename: Qian
authors.initials: Q
authors.lastname: Li
authors.forename: Christian
authors.initials: C
authors.lastname: Rask-Madsen
authors.forename: Akira
authors.initials: A
authors.lastname: Mima
authors.forename: Koji
authors.initials: K
authors.lastname: Mizutani
authors.forename: Jonathon
authors.initials: J
authors.lastname: Winnay
authors.forename: Yasutaka
authors.initials: Y
authors.lastname: Maeda
authors.forename: Katharine
authors.initials: K
authors.lastname: D'Aquino
authors.forename: Morris F
authors.initials: MF
authors.lastname: White
authors.forename: Edward P
authors.initials: EP
authors.lastname: Feener
authors.forename: George L
authors.initials: GL
authors.lastname: King
mesh_terms: D000804:Angiotensin II / Q000378:metabolism*; D000818:Animals; D002417:Cattle; D002460:Cell Line; D042783:Endothelial Cells / Q000378:metabolism*; D004789:Enzyme Activation; D007328:Insulin / Q000378:metabolism; D055504:Insulin Receptor Substrate Proteins / Q000737:chemistry / Q000378:metabolism*; D007333:Insulin Resistance; D008297:Male; D051379:Mice; D008822:Mice, Transgenic; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D010766:Phosphorylation; D011493:Protein Kinase C / Q000235:genetics / Q000378:metabolism*; D064546:Protein Kinase C beta; D051381:Rats; D011924:Rats, Zucker; D012694:Serine / Q000737:chemistry / Q000378:metabolism; D013755:Tetradecanoylphorbol Acetate / Q000378:metabolism; D013912:Threonine / Q000737:chemistry / Q000378:metabolism; D014443:Tyrosine / Q000737:chemistry / Q000378:metabolism
chemical_list: D007328:Insulin; D055504:Insulin Receptor Substrate Proteins; C526298:Irs2 protein, mouse; C526299:Irs2 protein, rat; D000804:Angiotensin II; D013912:Threonine; D014443:Tyrosine; D012694:Serine; D019869:Phosphatidylinositol 3-Kinases; D011493:Protein Kinase C; D064546:Protein Kinase C beta; D013755:Tetradecanoylphorbol Acetate