title: Modulation of guanylate cyclase-coupled atrial natriuretic factor receptor activity by mastoparan and ANF in murine Leydig tumor cells: role of G-proteins.
abstract: Mastoparan potently stimulated catalytic activity of guanylate cyclase-coupled atrial natriuretic factor receptor (GC-A/ANF-R), both in the plasma membranes and intact Leydig tumor (MA-10) cells. In plasma membrane preparations, a maximum of 5-fold GC catalytic activity was stimulated by 100 microM mastoparan and the half maximum stimulation (EC50) was achieved at 40 microM concentration. Mastoparan potentiated GC activity by more than 40%, above the level, stimulated by ANF. Mas 7, an active analog of mastoparan, stimulated the GC activity in a similar manner to mastoparan whereas Mas 17, an inactive analog, did not enhance GC activity. In membranes prepared from mastoparan-treated intact MA-10 cells, GC catalytic activity was enhanced by more than 4-fold as compared with untreated control cells. Pretreatment of membranes with either anti-Gs alpha or anti-Gi alpha antibodies had no effect on mastoparan-stimulated GC activity, however, anti-Go alpha antibodies inhibited the stimulatory effect of mastoparan by almost 50%. Agents known to modulate the effect of mastoparan such as EGTA (Ca2+ chelator), W7 (calmodulin inhibitor) and staurosporine (protein kinase C inhibitor) had no effect on the mastoparan-stimulated GC activity. Mastoparan enhanced the ANF-stimulated GC activity in detergent solubilized membrane preparations without a significant change in ANF-binding capacity. The data establish a role for mastoparan in the ANF-dependent stimulation of GC-A/ANF-R catalytic activity, both in the plasma membrane preparations and intact Leydig tumor (MA-10) cells. Furthermore, these findings provide new evidence that mastoparan (isolated from wasp venom) potently stimulates guanylate cyclase activity of GC-A/ANF-R by activating G-proteins.
authors.affiliation: Department of Biochemistry and Molecular Biology, Medical College of Georgia, School of Medicine, Augusta 30912-2100.
authors.forename: M L
authors.initials: ML
authors.lastname: Khurana
authors.forename: K N
authors.initials: KN
authors.lastname: Pandey
mesh_terms: D000818:Animals; D009320:Atrial Natriuretic Factor / Q000494:pharmacology*; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D019204:GTP-Binding Proteins / Q000502:physiology*; D006162:Guanylate Cyclase / Q000378:metabolism*; D036341:Intercellular Signaling Peptides and Proteins; D007984:Leydig Cell Tumor / Q000378:metabolism*; D051379:Mice; D010455:Peptides; D017461:Receptors, Atrial Natriuretic Factor / Q000187:drug effects* / Q000378:metabolism; D014862:Wasp Venoms / Q000494:pharmacology*
chemical_list: D036341:Intercellular Signaling Peptides and Proteins; D010455:Peptides; D014862:Wasp Venoms; C037500:mastoparan; D009320:Atrial Natriuretic Factor; D019204:GTP-Binding Proteins; D006162:Guanylate Cyclase; D017461:Receptors, Atrial Natriuretic Factor