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Tyrosine phosphorylation of the insulin receptor is not required for receptor internalization: studies in
J M Backer1, C R Kahn, M F White
1Joslin Diabetes Center, Department of Medicine, Brigham and Women's Hospital, Boston, MA 02215.
Abstract:
The relation between insulin-stimulated autophosphorylation of the insulin receptor and internalization of the receptor was studied in Fao rat hepatoma cells. Treatment of Fao cells with 2,4-dinitrophenol for 45 min depleted cellular ATP by 80% and equally inhibited insulin-stimulated receptor autophosphorylation, as determined by immunoprecipitation of surface-iodinated or [32P]phosphate-labeled cells with anti-phosphotyrosine antibody. In contrast, internalization of the insulin receptor and internalization and degradation of 125I-labeled insulin by 2,4-dinitrophenol-treated cells were normal. These data show that autophosphorylation of the insulin receptor is not required for the receptor-mediated internalization of insulin in Fao cells and suggest that insulin receptor recycling is independent of autophosphorylation.