Insulin-stimulated tyrosine phosphorylation of the insulin receptor in detergent extracts of human placental membranes. Comparison to epidermal growth factor-stimulated phosphorylation.
Addition of insulin to Triton-solubilized extracts of human placental membranes selectively stimulates the incorporation of 32P from [gamma-32P]ATP into an endogenous 95,000-dalton protein, which is identified as a component of the insulin receptor by immunoprecipitation. The insulin-stimulated increment in 32P is recovered largely in [32P]tyrosine after acid hydrolysis. E Epidermal growth factor (EGF) stimulates the phosphorylation of a 150,000-dalton protein in these detergent extracts. This reaction differs in several respects from the insulin-stimulated phosphorylation of the 95,000-dalton protein. Insulin-stimulated phosphorylation exhibits an absolute requirement for Mn2+ as the sole divalent cation, whereas EGF-stimulated phosphorylation is supported by Mg2+ and Co2+ as well as Mn2+. In the presence of Mn2+, insulin-stimulated phosphorylation is not detected at less than 50 microM ATP, whereas EGF-stimulated phosphorylation is well expressed at 5 microM ATP. Thus, in detergent-solubilized membrane extracts, insulin stimulates the phosphorylation of its own receptor on tyrosine residues. This reaction has enzymatic properties distinct from those of the EGF-stimulated phosphorylation in these same extracts. The role of this insulin-stimulated phosphorylation reaction in the initiation of insulin's many biologic actions merits further study.
D000255:Adenosine Triphosphate / Q000378:metabolism; D002413:Cations, Divalent; D002462:Cell Membrane / Q000378:metabolism; D004815:Epidermal Growth Factor / Q000494:pharmacology*; D005260:Female; D006801:Humans; D007328:Insulin / Q000494:pharmacology*; D007700:Kinetics; D010766:Phosphorylation; D010920:Placenta / Q000378:metabolism*; D011247:Pregnancy; D011972:Receptor, Insulin / Q000378:metabolism*; D014443:Tyrosine
D002413:Cations, Divalent; D007328:Insulin; D014443:Tyrosine; D004815:Epidermal Growth Factor; D000255:Adenosine Triphosphate; D011972:Receptor, Insulin