Inactivation of glycogen synthase kinase-3 beta by phosphorylation: new kinase connections in insulin and growth-factor signalling.
The beta-isoform of glycogen synthase kinase-3 (GSK3 beta) isolated from rabbit skeletal muscle was inactivated 90-95% following incubation with MgATP and either MAP kinase-activated protein kinase-1 (MAPKAP kinase-1, also termed RSK-2) or p70 S6 kinase (p70S6K), and re-activated with protein phosphatase 2A. MAPKAP kinase-1 and p70S6K phosphorylated the same tryptic peptide on GSK3 beta, and the site of phosphorylation was identified as the serine located nine residues from the N-terminus of the protein. The inhibitory effect of Ser-9 phosphorylation on GSK3 beta activity was observed with three substrates, (inhibitor-2, c-jun and a synthetic peptide), and also with glycogen synthase provided that 0.15 M KCl was added to the assays. The results suggest that Ser-9 phosphorylation underlies the reported inhibition of GSK3 beta by insulin and that GSK3 may represent a point of convergence of two major growth-factor-stimulated protein kinase cascades.
Sutherland
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C
Department of Biochemistry, University of Dundee, Scotland, U.K.
Leighton
I A
IA
Cohen
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D000255:Adenosine Triphosphate / Q000494:pharmacology; D000595:Amino Acid Sequence; D000818:Animals; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000037:antagonists & inhibitors / Q000302:isolation & purification / Q000378:metabolism*; D002852:Chromatography, Ion Exchange; D004789:Enzyme Activation; D038341:Glycogen Synthase Kinases; D007328:Insulin / Q000494:pharmacology*; D007700:Kinetics; D008969:Molecular Sequence Data; D008970:Molecular Weight; D009132:Muscles / Q000201:enzymology; D010446:Peptide Fragments / Q000302:isolation & purification; D010455:Peptides / Q000138:chemical synthesis; D010748:Phosphopeptides / Q000302:isolation & purification; D010749:Phosphoprotein Phosphatases / Q000378:metabolism*; D010766:Phosphorylation; D054648:Protein Phosphatase 2; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D011817:Rabbits; D038744:Ribosomal Protein S6 Kinases, 90-kDa; D015398:Signal Transduction
D007328:Insulin; D010446:Peptide Fragments; D010455:Peptides; D010748:Phosphopeptides; D000255:Adenosine Triphosphate; D038341:Glycogen Synthase Kinases; D017346:Protein Serine-Threonine Kinases; D038744:Ribosomal Protein S6 Kinases, 90-kDa; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D010749:Phosphoprotein Phosphatases; D054648:Protein Phosphatase 2