Gβγ-Mediated signaling in the heart: Implications of β and γ subunit heterogeneity

A family of G proteins, composed of α, β, and γ subunits, plays 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, adenosine, angiotensin II, and endothelin to regulation of adenylyl cyclases, phospholipases, and ion channels. For many years, the classic view has been that G protein α subunits provide the requisite specificity for receptor and effector interactions. Recent advances, however, have revealed that the β and γ subunits also play prominent roles in transducing information from receptors to the appropriate effectors. With the identification of multiple subtypes of β and γ subunits in the heart, questions are raised regarding their respective roles in signal transduction processes regulating cardiac function.