Angiotensin II and cyclic adenosine 3 ',5 '-monophosphate induce human steroidogenic acute regulatory protein transcription through a common steroidogenic factor-1 element

Steroidogenic acute regulatory protein (StAR) synthesis and steroidogenesis are stimulated by activation of divergent signaling pathways in the adrena l cortex. The two major physiological regulators of aldosterone synthesis i n the adrenal zona glomerulosa are angiotensin II (AII) and extracellular K +, which both mediate an increase in intracellular calcium levels, although by distinct mechanisms. Previously, we demonstrated that increased mineral ocorticoid synthesis by N-6,2'-O-dibutyryl cAMP (Bt(2)cAMP), AII, and K+ tr eatment is paralleled by an increase in StAR protein in the H295R human adr enocortical cell line. We now show that StAR steady state messenger RNA lev els are increased by Bt(2)cAMP and All, but not by K+ or 12-O-tetradecanoyl phorbol-13-acetate, treatment of H295R cells. Northern analysis detected tw o major transcripts of 1.7 and 2.7 kb present in H295R cells, with the most prominent effect of agonist treatment on induction of the 1.7-kb messenger RNA. Similarly, StAR promoter activity in transient transfections of H295R cells with a luciferase reporter gene driven by 1.3 kb of the human promot er was increased only by Bt(2)cAMP and AII treatment. 5'-Deletion analysis of the StAR promoter indicates that both the cAMP- and AII responsive eleme nts are within 150 bases of the transcriptional start site. Mutation of a s teroidogenic factor-1/AdBP4 element localized at -95 abolishes both Bt(2)cA MP- and AII-induced luciferase activity in these transient transfection ass ays. Thus, transcriptional activation of the StAR gene by a steroidogenic f actor-1-dependent mechanism may represent a common pathway for ACTH (protei n kinase A) and AII action in stimulating steroid production in the adrenal fasciculata and glomerulosa.