Characterization of ANF-R2 receptor-mediated inhibition of adenylate cyclase |
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Authors: | Madhu B. Anand-Srivastava |
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Affiliation: | (1) Département de physiologic, Faculté de Médecine, Université de Montréal, Succursale A, C.P. 6128, H3C3J7 Montreal, Québec, Canada;(2) Département de physiologic, Faculté de Médecine, Université de Montréal, Succursale A, C.P. 6128, H3C3J7 Montréal, Québec, Canada |
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Abstract: | We have characterized the ANF-R2 receptor-mediated inhibition of adenylate cyclase with respect to its modulation by several regulators. ANF (99–126) inhibits adenylate cyclase activity only in the presence of guanine nucleotides. The maximal inhibition ( 45%) was observed in the presence of 10-30 M GTPS, and at higher concentrations, the inhibitory effect of ANF was completely abolished. ANF-mediated inhibition was not dependent on the presence of monovalent cations, however Na+ enhanced the degree of inhibition by about 60%, whereas K+ and Li+ suppressed the extent of inhibition by about 50%. On the other hand, divalent cation, such as Mn2+ decreased the degree of inhibition in a concentration dependent manner, with an apparent Ki of about 0.7 mM, and at 2 mM; the inhibition was completely abolished. In addition, proteolytic digestion of the membranes with trypsin (40 ng/ml) resulted in the attenuation of ANF-mediated inhibition of adenylate cyclase. Other membrane disrupting agents such as neuraminidase and phospholipase A2 treatments also inhibited completely, the ANF-mediated inhibition of enzyme activity. N-Ethylmaleimide (NEM), phorbol ester and Ca2+-phospholipid dependent protein kinase (C-kinase) which have been shown to interact with inhibitory guanine nucleotide regulating protein (Gi) also resulted in the attenuation of ANF-mediated inhibition of adenylate cyclase activity. These results indicate that in addition to the Gi, the phospholipids and glycoproteins may also play an important role in the expression of ANF-R2 receptor-mediated inhibition of adenylate cyclase.Abbreviations ANF Atrial Natriuretic Factor - GTPS Guanosine 5-0-(Thiotriphosphate) - Gi inhibitory guanine nucleotide regulatory protein - NEM N-Ethylmaleimide - PMA Phorbol, 12-Myristate, 13-Acetate, C-kinase, Ca 2+, phospholipid-dependent protein kinase - PHL-A2 Phospholipase A, |
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Keywords: | ANF-R2 receptor adenylate cyclase Gi-protein Phorbol ester C-kinase |
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