Insulin-stimulated phosphorylation of the insulin receptor precursor.
The alpha and beta subunits of the insulin receptor, Mr = 135K and 95K, appear to be synthesized via a single polypeptide precursor of Mr = 190K. We have investigated whether insulin stimulates the phosphorylation of this proreceptor, as is the case with mature receptor. Rat liver endoplasmic reticulum membranes were solubilized in Triton X-100 and chromatographed sequentially on wheat-germ agglutinin-agarose and lentil lectin-agarose columns. Phosphorylation of the lentil eluate with [gamma 32P]ATP revealed an insulin-stimulated phosphoprotein of Mr = 192K, which was recognized by antireceptor antibody, compatible with the receptor precursor. This suggests that further processing of the Mr = 190K insulin receptor precursor is not necessary for insulin binding, kinase activation, and receptor phosphorylation.
D000818:Animals; D004721:Endoplasmic Reticulum / Q000378:metabolism; D007328:Insulin / Q000494:pharmacology*; D008099:Liver / Q000378:metabolism; D046911:Macromolecular Substances; D010766:Phosphorylation; D011498:Protein Precursors / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D011972:Receptor, Insulin / Q000096:biosynthesis*
D007328:Insulin; D046911:Macromolecular Substances; D011498:Protein Precursors; D011972:Receptor, Insulin