Dexamethasone can modulate glucose‐regulated and heat shock protein synthesis

Abstract

Abstract When L929 cells are cultured in the abssence of glucose the rate of synthesis of two polypeptides (95,000 and 82,000 M r ) is increased while that of an 85,000 M r polypeptide is correspondingly decreased. It has been shown recently that the 85,000 M r polypeptide is identical with the heat shock protein that is associated with the Rous sarcoma virus transforming gene product (pp60 src ). The present study shows that dexamethasone completely inhibits the alterations in the pattern of protein synthesis that would normally ensue following glucose deprivation. In fact, synthesis of the 85,000 M r polypeptide and another polypeptide (69,000 M,) that is not glucose regulated are dramatically increased. In contrast, when L929 cells are maintained in ample glucose the effects of dexamethasone are much less dramatic with only one major SDS polyacrylamide gel band (90,000 M r ) being affected. This effect is specific for glucocorticoids. One‐dimensional peptide mapping did not demonstrate any obvious structural relatedness among the 95,000, 90,000, 85,000, and 82,000 M r polypeptides. Therefore, the observed changes appear to result from alterations in the rate of protein synthesis rather than from changes in precursor‐product relationships. It is suggested on the basis of this data that glucocorticoids may play a role in modulating the response of cultured cells to glucose deprivation by eliciting a heat shock‐like response.