Signal-transduction pathways that regulate smooth muscle function. II. Receptor-ion channel coupling mechanisms in gastrointestinal smooth muscle.

Regulation of membrane ion channels by second messengers is an important mechanism by which gastrointestinal smooth muscle excitability is controlled. Receptor-mediated phosphorylation of Ca(2+) channels has been known for some time; however, recent findings indicate that these channels may also modulate intracellular signaling. The plasmalemma ion channels may also function as a point of convergence between different receptor types. In this review, the molecular mechanisms that link channel function and signal transduction are discussed. Emerging evidence also indicates altered second-messenger modulation of the Ca(2+) channel in the pathophysiology of smooth muscle dysmotility.