REGULATION OF EXPRESSION OF THE STEROIDOGENIC ACUTE REGULATORY (STAR)PROTEIN BY ACTH IN BOVINE ADRENAL FASCICULATA CELLS

Immunocytochemical studies and immunoblotting analysis demonstrated th at there exists the StAR protein in bovine adrenal fasciculata cells, and ACTH activated expression of the StAR protein. Then roles of intra cellular signal transduction systems in the regulation of expression o f the StAR protein were studied. The addition of Bt(2)cAMP and forskol in, or phorbol ester plus calcium ionophore 23187 activated expression of the StAR protein as well as cortisol production, suggesting that c yclic AMP- or protein kinase C-dependent process plays a crucial role in the regulation of expression of the StAR protein. Activating effect s of ACTH which activates cyclic AMP formation on the StAR protein and cortisol production were inhibited by pretreatment with calphostin C which is a protein kinase C inhibitor, suggesting that ACTH enhances e xpression of the StAR protein possibly via both of two signal transduc tion systems such as cyclic AMP- and protein kinase C-dependent proces ses. (C) 1996 Academic Press. Inc.