The TRP ion channel family

Mammalian homologues of the Drosophila transient receptor potential (TRP) c hannel gene encode a family of at least 20 ion channel proteins. They are w idely distributed in mammalian tissues, but their specific physiological fu nctions are largely unknown. A common theme that links the TRP channels is their activation or modulation by phosphatidylinositol signal transduction pathways. The channel subunits have six transmembrane domains that most pro bably assemble into tetramers to form non-selective cationic channels, whic h allow for the influx of calcium ions into cells. Three subgroups comprise the TRP channel family; the best understood of these mediates responses to painful stimuli. Other proposed functions include repletion of intracellul ar calcium stores, receptor-mediated excitation and modulation of the cell cycle.