Effects of 9-beta-D-arabinofuranosyl-guanine-5'-triphosphate on adenylate cyclase: comparison with GTP and GPP(NH)P.

The present communication describes the actions of 9-beta-D-arabino-furanosylguanine-5'-triphosphate (AraGTP) on hamster white and brown adipocyte and chick cardiac adenylate cyclase. AraGTP supports isoproterenol stimulation of adenylate cyclase in a GTP-like manner. Preincubation of membranes with AraGTP (with or without isoproterenol) does not irreversibly activate the adenylate cyclase as Gpp(NH)p does. In chick cardiac and hamster white adipocyte membranes both AraGTP and GTP alone inhibit adenylate cyclase. AraGTP mimics GTP and Gpp(NH)p in their abilities to lower agonist affinity for the inhibitory muscarinic receptor in cardiac membranes. These observations suggest AraGTP can interact with guanine nucleotide dependent regulatory proteins. In contrast to GTP though, AraGTP does not support hormonal attenuation of adenylate cyclase in any of these tissues.