Cycloheximide causes accumulation of insulin receptors at the cell surface of cultured fibroblasts.

Abstract

Incubation of confluent cultures of mouse fibroblasts with cycloheximide caused a time-dependent increase in the binding of 125I-insulin. The increase was concentration-dependent between 0.05 and 3.5 microM cycloheximide and showed a high correlation (r = 0.97) between the increase in 125I-insulin binding and the inhibition of protein synthesis. In the presence of 3.5 microM cycloheximide, insulin binding increased to 236% of control and incorporation of [3H]valine into proteins fell to 10-20% of control. Scatchard analysis of the binding data indicated that cycloheximide-treated cultures had a total of 6.6 X 10(4) binding sites/cell compared to 3.9 X 10(4) sites/cell in untreated cultures. No significant changes in affinity were observed. Other protein synthesis inhibitors also caused an increase in 125I-insulin binding. With 25 mM ethionine and 2 mM sodium fluoride, binding was 155 and 245% of control and incorporation of [3H]leucine into proteins was decreased to 41 and 47% of control, respectively. These results suggest that the accumulation of insulin receptors at the cell surface following treatment with cycloheximide results from inhibition of synthesis of proteins involved in insulin receptor turnover.