Emerging roles of TRPM channels

The molecular characterization of the genes encoding the transient receptor potential (TRP) cation channels found in Drosophila photoreceptors gave rise to a systematic cloning strategy for mammalian isoforms. Using expressed sequence tag (EST) and genomic database searches, at least 20 new mammalian TRP-related genes have been cloned and the resulting channels extensively characterized. Here, we will focus on TRP channels from the TRPM subfamily. Although generally classified as non-selective cation channels, individual members of this family feature considerable functional diversity in terms of selectivity, specific expression pattern, as well as diverse gating and regulatory mechanisms. The functional characteristics of these channels have profound impact on the regulation of ion homeostasis that go beyond simple Ca2+ signalling. They activate and function in the context of a variety of physiological and pathological conditions, which make them exciting targets for drug discovery.