Role of Hsp70 synthesis in the fate of the insulin-receptor complex after heat shock in cultured fetal hepatocytes
Abstract
The influence of a mild heat shock on the fate of the insulin-receptor complex was studied in cultured fetal rat hepatocytes whose insulin glycogenic response is sensitive to heat [Zachayus and Plas (1995): J Cell Physiol 162:330-340]. After exposure from 15 min to 2 hr at 42.5 degrees C, the amount of (125)1-insulin associated with cells at 37 degrees C was progressively decreased (by 35% after 1 hr), while the release of (125)1-insulin degradation products into the medium was also inhibited (by 75%), more than expected from the decrease in insulin binding. Heat shock did not affect the insulin-induced internalization of cell surface insulin receptors but progressively suppressed the recycling at 37 degrees C of receptors previously internalized at 42.5 degrees C in the presence of insulin. When compared to the inhibitory effects of chloroquine on insulin degradation and insulin receptor recycling, which were immediate (within 15 min), those of heat shock developed within 1 hr of heating. The protein level of insulin receptors was not modified after heat shock and during recovery at 37 degrees C, while that of Hsp72/73 exhibited a transitory accumulation inversely correlated with variations in insulin binding, as assayed by We...Continue Reading
References
Interaction of Hsp 70 with newly synthesized proteins: implications for protein folding and assembly
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