P-327: Intracellular and extracellular angiotensin II stimulate the at1 receptor through both common and unique signaling pathways

Intracellular and extracellular interactions of angiotensin II (AII) with the AT1 receptor have functionally unique consequences. COS-7 cells were transfected, independently and concurrently, with plasmids encoding fluorescent fusion proteins of angiotensin II (pECFP/AII, encodes a cyan fluorescent fusion protein), AT1a receptor (pAT1R/EYFP, encodes a yellow fluorescent fusion protein), an endosome-specific targeting sequence, a marker of the endoplasmic reticulum, a golgi marker and/or a nuclear marker. The angiotensin II fluorescent fusion protein possesses no secretory signal peptide and deconvolution microscopy shows that is maintained within these cells with a predominant localization to the nucleus. AT1R/EYFP is absent from the nucleus when expressed independently or in untreated cells. AT1R/EYFP accumulates in the nucleus following exogenous AII treatment or when co-expressed with ECFP/AII. In a recent study, we determined that exogenous AII treatment of AT1R/EYFP-expressing COS-7 cells activates CREB and stimulates cell growth. Intracellular co-expression of ECFP/AII and AT1R/EYFP similarly activates CREB and stimulates growth (in press). We now show that AII treatment of AT1R/EYFP-expressing COS-7 cells also activates p38 MAPK. Furthermore, the p38 MAPK inhibitor, SB203580, partially inhibits exogenous AII-conferred CREB activation confirming that p38 MAPK mediates CREB phosphorylation. In contrast, however, intracellular co-expression of ECFP/AII and AT1R/EYFP, which we have shown to activate CREB, does not activate p38 MAPK; CREB is likely activated through an alternative kinase pathway in this system. Intracellular and extracellular stimulation of the AT1 receptor mediate functional consequences by altering signal transduction; these processes share some common and some unique pathways. Am J Hypertens (2004) 17, 154A–154A; doi: 10.1016/j.amjhyper.2004.03.402