Abstract
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.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Adenosine Triphosphate / pharmacology
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Amino Acid Sequence
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Animals
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Calcium-Calmodulin-Dependent Protein Kinases / antagonists & inhibitors
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Calcium-Calmodulin-Dependent Protein Kinases / isolation & purification
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Calcium-Calmodulin-Dependent Protein Kinases / metabolism*
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Chromatography, Ion Exchange
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Enzyme Activation
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Glycogen Synthase Kinases
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Insulin / pharmacology*
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Kinetics
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Molecular Sequence Data
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Molecular Weight
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Muscles / enzymology
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Peptide Fragments / isolation & purification
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Peptides / chemical synthesis
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Phosphopeptides / isolation & purification
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Phosphoprotein Phosphatases / metabolism*
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Phosphorylation
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Protein Phosphatase 2
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Protein Serine-Threonine Kinases / metabolism
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Rabbits
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Ribosomal Protein S6 Kinases, 90-kDa
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Signal Transduction*
Substances
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Insulin
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Peptide Fragments
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Peptides
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Phosphopeptides
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Adenosine Triphosphate
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Glycogen Synthase Kinases
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Protein Serine-Threonine Kinases
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Ribosomal Protein S6 Kinases, 90-kDa
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Calcium-Calmodulin-Dependent Protein Kinases
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Phosphoprotein Phosphatases
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Protein Phosphatase 2