Role of PKCζ-NADPH oxidase signaling axis in PKCα-mediated Giα2 phosphorylation for inhibition of adenylate cyclase activity by angiotensin II in pulmonary artery smooth muscle cells

We sought to determine the mechanism by which angiotensin II (AngII) inhibits isoproterenol induced increase in adenylate cyclase (AC) activity and cyclic adenosine monophosphate (cAMP) production in bovine pulmonary artery smooth muscle cells (BPASMCs). Treatment with AngII stimulates protein kinase C-zeta (PKC-zeta), nicotinamide adenine dinucleotide phosphate (NADPH) oxidase, and PKC-alpha activities, and also inhibits isoproterenol induced increase in AC activity and cAMP production in the cells. Pertussis toxin pretreatment eliminates AngII caused inhibition of isoproterenol induced increase in AC activity without a discernible change in PKC-zeta, NADPH oxidase, and PKC-alpha activities. Treatment of the cells with AngII increases alpha 2 isoform of Gi (Gi alpha 2) phosphorylation; while pretreatment with chemical and genetic inhibitors of PKC-zeta and NADPH oxidase attenuate AngII induced increase in PKC-alpha activity and Gi alpha 2 phosphorylation, and also reverse AngII caused inhibition of isoproterenol induced increase in AC activity. Pretreatment of the cells with chemical and genetic inhibitors of PKC-alpha attenuate AngII induced increase in Gi alpha 2 phosphorylation and inhibits isoproterenol induced increase in AC activity without a discernible change in PKC-zeta and NADPH oxidase activities. Overall, PKC zeta-NADPH oxidase-PKC alpha signaling axis plays a crucial role in Gi alpha 2 phosphorylation resulting in AngII-mediated inhibition of isoproterenol induced increase in AC activity in BPASMCs.