Sodium-calcium exchange: A molecular perspective

Plasma membrane Na+-Ca2+ exchange is an essential component of Ca2+ signali ng pathways in several tissues. Activity is especially high in the heart wh ere the exchanger is an important regulator of contractility. An expanding exchanger superfamily includes three mammalian Na+-Ca2+ exchanger genes and a number of alternative splicing products. New information indicates that the exchanger protein has nine transmembrane segments. The exchanger, which transports Naf and Ca2+, is also regulated by these substrates. Some molec ular information is available on regulation by Na+ and Ca2+ and by PIP2 and phosphorylation. Altered expression of the exchanger in pathophysiological states may contribute to various cardiac phenotypes. Use of transgenic app roaches is beginning to improve our knowledge of exchanger function.