Angiotensin II modulates ANP-R2/ANP-C receptor-mediated inhibition of adenylyl cyclase in vascular smooth muscle cells: role of protein kinase C.
In the present studies, we have investigated the modulation of atrial natriuretic peptide (ANP) receptor of R2 subtype (ANP-R2/ANP-C) coupled to adenylyl cyclase/cAMP signal transduction system by angiotensin II (angII). C-ANF4-23 [des(Gln18, Ser19, Gln20, Leu21, Gly22)ANF4-23-NH2] and AngII inhibited adenylyl cyclase activity in a concentration-dependent manner in vascular smooth muscle cells (VSmc A-10). The maximal inhibitions observed were about 40 and 30%, respectively, with an apparent Ki of about 1 and 10 nm. Pretreatment of the cells with AngII resulted in the attenuation of both C-ANF4-23 and AngII-mediated inhibitions of adenylyl cyclase, without altering [125I]-ANF binding. The levels of Gialpha-2 and Gialpha-3 proteins as determined by immunoblotting were also augmented by AngII treatment. In addition, AngII treatment stimulated the phosphorylation of Gialpha2 but not of Gialpha3 or ANP-C receptor, as revealed by immunoprecipitation of the proteins using specific antibodies after prelabelling the cells with [32P]orthophosphate. Staurosporine and chelerythrine, protein kinase C (PKC) inhibitors at 1 and 100 nm, respectively, prevented the AngII-mediated desensitization of C-ANF 4-23-sensitive adenylyl cyclase. In addition, the AngII-mediated phosphorylation of Gialpha2 protein was also inhibited partially by about 35% by staurosporine treatment. These results suggest that the attenuation of C-ANF4-23-mediated inhibition of adenylyl cyclase activity by AngII may not be attributed to the downregulation of receptors or to the decreased levels of G-proteins, and may involve PKC-dependent mechanisms.
Palaparti
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Groupe de recherche sur le système nerveux autonome, and Department of Physiology, University of Montreal, Montreal, Quebec, H3C 3J7, Canada.
Anand-Srivastava
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D000067956:Adenylyl Cyclase Inhibitors; D000470:Alkaloids; D000804:Angiotensin II / Q000378:metabolism / Q000494:pharmacology*; D000818:Animals; D053119:Benzophenanthridines; D002478:Cells, Cultured; D015536:Down-Regulation / Q000187:drug effects; D051960:GTP-Binding Protein alpha Subunit, Gi2; D019206:GTP-Binding Protein alpha Subunits, Gi-Go / Q000187:drug effects / Q000378:metabolism; D019204:GTP-Binding Proteins / Q000187:drug effects / Q000378:metabolism; D006162:Guanylate Cyclase / Q000378:metabolism*; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D010617:Phenanthridines / Q000494:pharmacology; D010766:Phosphorylation / Q000187:drug effects; D011493:Protein Kinase C / Q000378:metabolism*; D011518:Proto-Oncogene Proteins / Q000187:drug effects / Q000378:metabolism; D051381:Rats; D017461:Receptors, Atrial Natriuretic Factor / Q000187:drug effects / Q000378:metabolism*; D019311:Staurosporine / Q000494:pharmacology
D000067956:Adenylyl Cyclase Inhibitors; D000470:Alkaloids; D053119:Benzophenanthridines; D010617:Phenanthridines; D011518:Proto-Oncogene Proteins; D000804:Angiotensin II; C016299:chelerythrine; D011493:Protein Kinase C; D019204:GTP-Binding Proteins; D051960:GTP-Binding Protein alpha Subunit, Gi2; D019206:GTP-Binding Protein alpha Subunits, Gi-Go; C498017:Gnai2 protein, rat; D006162:Guanylate Cyclase; D017461:Receptors, Atrial Natriuretic Factor; C073616:atrial natriuretic factor receptor C; D019311:Staurosporine