THE CHARACTERIZATION OF A NOVEL HUMAN ADENYLYL-CYCLASE WHICH IS PRESENT IN BRAIN AND OTHER TISSUES

We characterized a human cDNA clone which encodes a novel adenylyl cyc lase. Data from Southern and Northern blot analysis, and analysis of s equence similarity with a recently cloned mouse adenylyl cyclase (10), indicated that the human adenylyl cyclase was a species variant of ty pe VII adenylyl cyclase. The sequence of the novel human adenylyl cycl ase indicated it was a member of the type II adenylyl cyclase family, and we compared the regulatory characteristics of the novel human enzy me with those of type II adenylyl cyclase. The human type VII and rat type II adenylyl cyclases, expressed in human embryonic kidney 293 cel ls, were activated by prostaglandin E(1) (PGE(1)), but only type VII w as activated by isoproterenol. The stimulation of type VII adenylyl cy clase by PGE(1) and isoproterenol was attenuated by pretreatment of th e cells with staurosporine. Phorbol 12,13-dibutyrate synergistically e nhanced the stimulation of both type VII and type II enzyme activity b y PGE, and by the constitutively active G(s) mutant G(s) (Q227L). The human type VII adenylyl cyclase activity was unresponsive to capacitat ively induced changes in intracellular Ca2+. The functional characteri stics of human type VII adenylyl cyclase resemble those of the rat typ e II enzyme, but the enzymes may respond differently to in vivo phosph orylation conditions. While the mRNA for adenylyl cyclase type II was found in several brain areas, the message for type VII adenylyl cyclas e was localized primarily to the cerebellar granule cell layer.