Insulin and insulin antagonists evoke phosphorylation of P20 at serine 157and serine 16 respectively in rat skeletal muscle

We show here that insulin and insulin antagonists differentially modify pho sphorylation of three phospho-isoforms of P20 (termed S1, S2 and S3) in rat skeletal muscle. Precise phosphorylation sites of S1 and S2,were mapped to serine 157 and serine 16 respectively. Insulin evoked phosphorylation of P 20 at serine 157 through the phosphatidylinositol (PI) 3-kinase pathway. Ep inephrine and calcitonin gene-related peptide decreased phosphorylation at serine 157 and increased phosphorylation at serine 16 and other unidentifie d sites. These results demonstrate that the PI-3-kinase pathway of anabolic insulin and the cAMP pathway of catabolic hormones converge on P20 and sug gest a potential role of this protein in regulating energy metabolism of sk eletal muscle. (C) 1999 Federation of European Biochemical Societies.