MOLECULAR AND FUNCTIONAL DIVERSITY OF MAMMALIAN G(S)-STIMULATED ADENYLYL CYCLASES

Receptor-regulated adenylyl cyclase in mammalian systems is among the best-studied of the cell surface signaling pathways that utilize G-proteins as transducers. In addition to the multiplicity of receptors and G(s) proteins that function in this pathway, recent studies have shown that substantial molecular diversity exists in the effector as well. Full-length cDNAs encoding six different G-protein-regulated adenylyl cyclases have been isolated, and partial sequences identifying two more are known. These eight mammalian adenylyl cyclases can be grouped into five distinct families. The different types share some common properties such as stimulation by G(s) and the diterpene forskolin. They show very distinct patterns of regulation by the betagamma-subunits of G-proteins and protein kinases such as protein kinase C. The different types also appear to be localized in a tissue-specific manner. This diversity of regulatory features indicates that the effector can play an important role in determining the routing of signals to the cAMP pathway. The tissue and cell type-specific localization of the individual forms suggests that effectors such as adenylyl cyclase could be potential targets for a new generation of cell and tissue-specific drugs.