G-BETA-GAMMA-MEDIATED SIGNALING IN THE HEART - IMPLICATIONS OF BETA-SUBUNIT AND GAMMA-SUBUNIT HETEROGENEITY

A family of G proteins, composed of alpha, beta, and gamma subunits, p lays a central role in coupling receptors to a variety of enzymes and ion channels. In the cardiovascular system, G proteins are involved in coupling receptors for epinephrine, norepinephrine, acetylcholine, ad enosine, angiotensin II, and endothelin to regulation of adenylyl cycl ases, phospholipases, and ion channels. For many years, the classic vi ew has been that G protein alpha subunits provide the requisite specif icity for receptor and effector interactions. Recent advances, however , have revealed that the beta and gamma subunits also play prominent r oles in transducing information from receptors to the appropriate effe ctors. With the identification of multiple subtypes of beta and gamma subunits in the heart, questions are raised regarding their respective roles in signal transduction processes regulating cardiac function.