Change in activity of an adenosine triphosphate-stimulated glucocorticoid receptor translocation promoter in the cytosol and nucleus of rat liver under various physiological conditions.

Rat liver contains an ATP-stimulated translocation promoter (ASTP), which is not a receptor and which enhances nuclear binding of activated receptor-glucocorticoid complex in the presence of ATP. Studies were made on changes in ASTP activity under various conditions to elucidate its physiological role in the action of glucocorticoid hormone. ASTP activity in the cytosol fraction increased markedly after adrenalectomy. Conversely, 30 min after a single injection of dexamethasone it decreased and then gradually increased. The increase in ASTP activity after adrenalectomy was inhibited by actinomycin D or cycloheximide. With decrease in ASTP activity in the cytosol fraction after the administration of glucocorticoids, activity appeared in the nuclear fraction 30 min after injection and then decreased. Thus, after the dexamethasone injection, the changes in ASTP activity in the cytosol and nuclei were similar to but not coincident with those in the glucocorticoid receptor. These results suggest, but do not prove, that ASTP is translocated or binds to nuclei with activated receptor-glucocorticoid complexes. From these results, we consider that ASTP may be an integral part of the regulatory mechanism for the action of steroid hormones and may influence specific gene expression by increasing nuclear binding of the activated complex.