Modulation of ANP-C receptor signaling by endothelin-1 in A-10 smooth muscle cells.
We have previously shown that pretreatment of A-10 smooth muscle cells (SMC) with angiotensin II (Ang II) attenuated atrial natriuretic peptide (ANP) receptor-C (ANP-C)-mediated inhibition of adenylyl cyclase without altering (125)I-ANP binding. In the present studies, we have investigated the modulation of ANP-C receptor signaling by endothelin-1 (ET-1). Pretreatment of A-10 SMC with ET-1 for 24 h attenuated the expression of ANP-C receptor by about 60% as determined by immunoblotting which was reflected in attenuation of ANP-C-receptor-mediated inhibition of adenylyl cyclase. C-ANP(4-23) [des(Gln(18),Ser(19),Gln(20),Leu(21),Gly(22))ANP(4-23)-NH(2)], a ring-deleted peptide of ANP that interacts specifically with ANP-C receptor, inhibited adenylyl cyclase activity in a concentration-dependent manner with an apparent K(i) of about 1 nM in control cells. The maximal inhibition observed was about 30% which was almost completely attenuated in ET-1-treated cells. In addition, Ang II- and oxotremorine-mediated inhibitions of adenylyl cyclase were also attenuated by ET-1 treatment; however, the expression of Gialpha-2 and Gialpha-3 proteins and not of Gsalpha and Gbeta proteins was augmented by such treatment. The increased expression of Gialpha-2 and Gialpha-3 proteins by ET-1 treatment was inhibited by actinomycin D treatment (RNA synthesis inhibitor). On the other hand, the Gsalpha-mediated effects of some agonists on adenylyl cyclase activity were significantly decreased by ET-1 treatment. These results suggest that ET-1-induced downregulation of ANP-C receptor and not the overexpression of Gi proteins may be responsible for the attenuation of C-ANP(4-23)-mediated inhibition of adenylyl cyclase activity. From these studies it may be suggested that the downregulation of ANP-C receptors by increased levels of endothelin in vivo may be one of the possible mechanisms for the pathophysiology of hypertension.
Boumati
Malika
M
Department of Physiology and Groupe de Recherche sur le Système Nerveux Autonome, Faculty of Medicine, University of Montreal, C.P. 6128, Succursale Centre-Ville, Montreal, Quebec, Canada H3C 3J7.
Li
Yuan
Y
Anand-Srivastava
Madhu B
MB
D000067956:Adenylyl Cyclase Inhibitors; D000262:Adenylyl Cyclases / Q000378:metabolism; D000804:Angiotensin II / Q000494:pharmacology; D000818:Animals; D009320:Atrial Natriuretic Factor / Q000494:pharmacology; D002460:Cell Line; D005576:Colforsin / Q000494:pharmacology; D015536:Down-Regulation; D019332:Endothelin-1 / Q000494:pharmacology*; D019206:GTP-Binding Protein alpha Subunits, Gi-Go / Q000378:metabolism; D019205:GTP-Binding Protein alpha Subunits, Gs / Q000378:metabolism; D019204:GTP-Binding Proteins / Q000378:metabolism; D006162:Guanylate Cyclase / Q000187:drug effects* / Q000378:metabolism*; D007700:Kinetics; D009131:Muscle, Smooth, Vascular / Q000187:drug effects* / Q000378:metabolism*; D010095:Oxotremorine / Q000494:pharmacology; D010446:Peptide Fragments / Q000494:pharmacology; D051381:Rats; D017461:Receptors, Atrial Natriuretic Factor / Q000187:drug effects* / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects; D012969:Sodium Fluoride / Q000494:pharmacology
D000067956:Adenylyl Cyclase Inhibitors; D019332:Endothelin-1; D010446:Peptide Fragments; D000804:Angiotensin II; C065367:atrial natriuretic factor (4-23)NH2, de-Gln(18)-de-Ser(19)-de-Gly(20,22)-de-Leu(21)-; D005576:Colforsin; D010095:Oxotremorine; D009320:Atrial Natriuretic Factor; D012969:Sodium Fluoride; D019204:GTP-Binding Proteins; D019206:GTP-Binding Protein alpha Subunits, Gi-Go; D019205:GTP-Binding Protein alpha Subunits, Gs; D000262:Adenylyl Cyclases; D006162:Guanylate Cyclase; D017461:Receptors, Atrial Natriuretic Factor; C073616:atrial natriuretic factor receptor C