Abstract
PHAS-I is a heat-stable protein (relative molecular mass approximately 12,400) found in many tissues. It is rapidly phosphorylated in rat adipocytes incubated with insulin or growth factors. Nonphosphorylated PHAS-I bound to initiation factor 4E (eIF-4E) and inhibited protein synthesis. Serine-64 in PHAS-I was rapidly phosphorylated by mitogen-activated (MAP) kinase, the major insulin-stimulated PHAS-I kinase in adipocyte extracts. Results obtained with antibodies, immobilized PHAS-I, and a messenger RNA cap affinity resin indicated that PHAS-I did not bind eIF-4E when serine-64 was phosphorylated. Thus, PHAS-I may be a key mediator of the stimulation of protein synthesis by the diverse group of agents and stimuli that activate MAP kinase.
Publication types
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Research Support, Non-U.S. Gov't
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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3T3 Cells
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Adaptor Proteins, Signal Transducing
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Adipocytes / metabolism
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Animals
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Carrier Proteins*
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Cell Cycle Proteins
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Eukaryotic Initiation Factors
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Insulin / pharmacology*
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Intracellular Signaling Peptides and Proteins
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Mice
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Mitogen-Activated Protein Kinase 1
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Peptide Initiation Factors / isolation & purification
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Peptide Initiation Factors / metabolism*
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Phosphoproteins / metabolism*
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Phosphorylation
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Protein Biosynthesis*
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Protein Serine-Threonine Kinases / metabolism*
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Protein-Tyrosine Kinases / metabolism*
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Rats
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Recombinant Proteins / metabolism
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Serine / metabolism
Substances
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Adaptor Proteins, Signal Transducing
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Carrier Proteins
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Cell Cycle Proteins
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Eif4ebp1 protein, mouse
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Eif4ebp1 protein, rat
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Eukaryotic Initiation Factors
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Insulin
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Intracellular Signaling Peptides and Proteins
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Peptide Initiation Factors
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Phosphoproteins
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Recombinant Proteins
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eIF-4
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Serine
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Protein-Tyrosine Kinases
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Protein Serine-Threonine Kinases
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Mitogen-Activated Protein Kinase 1