Novel regulation of adenylyl cyclases by direct protein-protein interactions: insights from snapin and ric8a.

Adenosine 3',5'-cyclic mononucleotide (cAMP) is one of the most important second messengers which govern cellular signal transductions. Adenylyl cyclases (ACs), which are cAMP-synthesizing enzymes, are responsible for cAMP production during extracellular stimulation or intracellular metabolic alteration. In mammals, 9 transmembrane ACs and 1 soluble AC have been identified and characterized. In the past 2 decades, the biochemical properties of these ACs have been extensively studied. Genetic knockout and transgenic overexpression mouse models of at least 6 ACs have been produced, revealing their specific in vivo functions. An awareness of the importance of microdomains and cellular compartmentation for selective AC regulation has also been fostered. Most intriguingly, a handful of novel AC-binding proteins have recently been reported. Selective binding of ACs to their binding partners allows the precise compartmentalization of ACs and permits unique regulation. Based on recent studies on AC-interacting proteins (particularly Snapin and Ric8a), this review focuses on the importance and possible involvement of AC-interacting proteins in (1) the association of the cAMP signaling pathway with various cellular machineries and (2) the coordination of tightly regulated cAMP signaling by other signaling molecules. Copyright 2009 S. Karger AG, Basel.