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 cyclase. Data from Southern and Northern blot analysis, and analysis of sequence similarity with a recently cloned mouse adenylyl cyclase (10), indicated that the human adenylyl cyclase was a species variant of type VII adenylyl cyclase. The sequence of the novel human adenylyl cyclase indicated it was a member of the type II adenylyl cyclase family, and we compared the regulatory characteristics of the novel human enzyme with those of type II adenylyl cyclase. The human type VII and rat type II adenylyl cyclases, expressed in human embryonic kidney 293 cells, were activated by prostaglandin E1 (PGE1), but only type VII was activated by isoproterenol. The stimulation of type VII adenylyl cyclase by PGE1 and isoproterenol was attenuated by pretreatment of the cells with staurosporine. Phorbol 12,13-dibutyrate synergistically enhanced the stimulation of both type VII and type II enzyme activity by PGE1 and by the constitutively active Gs mutant Gs (Q227L). The human type VII adenylyl cyclase activity was unresponsive to capacitatively induced changes in intracellular Ca2+. The functional characteristics of human type VII adenylyl cyclase resemble those of the rat type II enzyme, but the enzymes may respond differently to in vivo phosphorylation conditions. While the mRNA for adenylyl cyclase type II was found in several brain areas, the message for type VII adenylyl cyclase was localized primarily to the cerebellar granule cell layer.