Characterization of a natural inhibitor of the insulin receptor tyrosine kinase: cDNA cloning, purification, and anti-mitogenic activity.
Amino acid sequence of the precursor of the phosphorylated N-glycoprotein (pp63) secreted by rat hepatocytes was deduced from the cDNA sequence. This polypeptide (Mr = 40,586) was rich in both cysteine and proline and contained three potential N-glycosylation sites. A single pp63 mRNA species (approximately 2000 bp), found in normal hepatocytes but not in FaO hepatoma cells, appeared to result from transcription of a single gene. pp63 purified by affinity chromatography inhibited insulin receptor tyrosine kinase and receptor autophosphorylation. Only the phosphorylated form of the protein was active. In additon, pp63 antagonized the growth-promoting action of insulin in FaO cells but did not affect hormone-mediated increase in amino acid transport capacity or tyrosine aminotransferase induction in these cells.
Centre CNRS-INSERM de pharmacologie endocrinologie, Montpellier, France.
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D000209:Acute-Phase Proteins; D000595:Amino Acid Sequence; D000596:Amino Acids / Q000378:metabolism; D000818:Animals; D001483:Base Sequence; D002455:Cell Division / Q000187:drug effects; D003001:Cloning, Molecular; D004247:DNA / Q000235:genetics; D006023:Glycoproteins / Q000235:genetics / Q000302:isolation & purification; D007329:Insulin Antagonists / Q000235:genetics / Q000302:isolation & purification / Q000494:pharmacology; D008114:Liver Neoplasms, Experimental; D008969:Molecular Sequence Data; D010750:Phosphoproteins / Q000235:genetics* / Q000302:isolation & purification / Q000494:pharmacology; D010766:Phosphorylation; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors*; D051381:Rats; D011972:Receptor, Insulin / Q000037:antagonists & inhibitors*
D000209:Acute-Phase Proteins; D000596:Amino Acids; D006023:Glycoproteins; D007329:Insulin Antagonists; D010750:Phosphoproteins; C047026:acute-phase phosphoprotein pp63; D004247:DNA; D011505:Protein-Tyrosine Kinases; D011972:Receptor, Insulin