Phospholipase D: molecular and cell biology of a novel gene family

Interaction of extracellular-signal molecules with cell-surface receptors o ften activates a phospholipase D (PLD)-mediated hydrolysis of phosphatidylc holine and other phospholipids, generating phosphatidic acid. The activatio n of PLD is believed to play an important role in the regulation of cell fu nction and cell fate. Multiple PLD activities were characterized in eukaryo tic cells, and, more recently, several PLD genes have been cloned. A PLD ge ne superfamily, defined by a number of structural domains and sequence moti fs, also includes phosphatidyltransferases and certain phosphodiesterases. Among the eukaryotic PLD genes are those from mammals, nematodes, fungi and plants. The present review focuses on the structure, localization, regulat ion and possible functions of cloned mammalian and yeast PLDs, In addition, an overview of plant PLD genes, and of several distinct PLD activities tha t have not yet been cloned, is provided. Emerging evidence from recent work employing new molecular tools indicates that different PLD isoforms are lo calized in distinct cellular organelles, where they are likely to serve div erse functions iq signal transduction, membrane vesicle trafficking and cyt oskeletal dynamics.