Angiotensin subtype-2 receptor (AT(2)) negatively regulates subtype-1 receptor (AT(1)) in signal transduction pathways in cultured porcine adrenal medullary chromaffin cells

Background Two distinct types of angiotensin II (AngII) receptors, AT(1) an d AT(2), have been cloned. We have shown previously that stimulation of AT( 2) reduces intracellular cyclic guanosine monophosphate (cGMP) levels in cu ltured porcine chromaffin cells in which AT(2) is the predominantly express ed receptor. However, it has not been determined whether AT(1) or AT(2) aff ects signal transduction pathways involving mitogen-activated protein kinas es; (MAPKs) and signal transducers and activators of transcription (STATs) in chromaffin cells. Also, it is unclear whether cGMP/protein kinase G (PKG ) is involved in the regulation of MAPKs and STATs in these cells. Design Chromaffin cells were derived from porcine adrenal medulla. The effe cts of AngII alone (representing physiological conditions), AngII plus CV-1 1974 (an AT(1) antagonist, which simulates specific AT(2) stimulation), An gII plus PD 123319 (an AT(2) antagonist which simulates specific AT, stimul ation), and 8-Br-cGMP (a membrane-permeable cGMP analogue) alone on MAPKs ( ERKs, JNK, p-38 MAPK) and STATs (STATs 1, 3 and 5) activity were measured. Methods Phosphorylated MAPKs (extracellular signal-related kinases (ERKs), c-jun N-terminal kinase (JNK) and p38 MAPK) and STATs (STATs 1, 3 and 5) we re measured by immunoprecipitation-Western blot analysis (IP-Western blot). Results AT(1) stimulation markedly increased expression of ERKs, JNK, p38 M APK via Ca2+-dependent protein kinase C (PKC) isoforms (cPKC), as well as S TATs 1, 3 and 5 in cultured porcine chromaffin cells. In contrast, AT(2) st imulation markedly decreased the expression of these signaling molecules. A lso, 8-Br-cGMP alone induced increases in ERKs, JNK, p38 MAPK, and STATs 1, 3 and 5. Because AT(2) inhibits cGMP production, we speculate that AT(2) m ay act to suppress cGMP production, which in turn reduces the activity of b oth MAPKs and STATs in chromaffin cells. Conclusion AT(2) negatively regulates AT(1) in signal transduction pathways in chromaffin cells. (C) 2001 Lippincott Williams & Wilkins.