Insulin receptors on RINm5F cell membranes (an insulin-producing rat pancreatic cell line) were studied. To study the insulin receptor alpha-subunit, 125I-labelled photoreactive insulin was covalently bound to the membranes in the absence or presence of unlabelled insulin. Sodium dodecyl sulphate/polyacrylamide-gel electrophoresis under reducing conditions showed specific labelling of an Mr 130 000 protein. The receptor beta-subunit was studied by using a cell-free phosphorylation assay. Analysis under reducing conditions showed a phosphoprotein of Mr 95 000 whose level of phosphorylation was selectively increased by insulin, and which was specifically immunoprecipitated by antibodies to the insulin receptor. Further, covalent hormone-receptor complexes purified with anti-insulin antibodies were able to undergo autophosphorylation, indicating the existence of operational receptor subunit arrangements. RINm5F cell insulin receptors (and, by analogy, possibly those of native B-cells) thus display structural and functional integrity comparable with those of conventional insulin target cells.
Identification of functional insulin receptors on membranes from an insulin-producing cell line (RINm5F)
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H Gazzano, P Halban, M Prentki, R Ballotti, D Brandenburg, M Fehlmann, E Van Obberghen; Identification of functional insulin receptors on membranes from an insulin-producing cell line (RINm5F). Biochem J 15 March 1985; 226 (3): 867–872. doi: https://doi.org/10.1042/bj2260867
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