Angiotensin II promotes the phosphorylation of cyclic AMP-responsive element binding protein (CREB) at Ser133 through an ERK1/2-dependent mechanism

In cells from the adrenal medulla, angiotensin II (All) regulates both the activity and mRNA levels of catecholamine biosynthetic enzymes whose expression is thought to be under the control of cAMP-responsive element (CRE) binding protein (CREB). In this study, we evaluated the effect of All stimulation on CREB phosphorylation at Ser133 (pCREB) in bovine adrenal chromaffin cells (BACC). We found that All produces a rapid and All type-1 receptor (AT1)-dependent increase in pCREB levels, which is blocked by the MEK1/2 inhibitor U0126 but not by H-89, SB203580 or KN-93, suggesting that it is mediated by the extracellular-regulated protein kinases 1 and 2 (ERK1/2) and not by cAMP-dependent protein kinase (PKA), p38 mitogen-activated protein kinase (p38MAPK) or Ca2+/calmodulin-dependent protein kinases (CaMKs) dependent pathways. Gel-shift experiments showed that the increase in pCREB levels is accompanied by an ERK1/2-dependent upregulation of CRE-binding activity, We also found that All promotes a rapid and reversible increase in the activity of the non-receptor tyrosine kinase Src and that the inhibition of this enzyme completely blocks the All-induced phosphorylation of ERK1/2, the CREB kinase p90RSK and CREB. Our data support the hypothesis that in BACC, All upregulates CREB functionality through a mechanism that requires Src-mediated activation of ERK1/2 and p90RSK.