Functional characterization and physiological relevance of the TRPC3/6/7 subfamily of cation channels

The mammalian transient receptor potential (TRP) superfamily of cation channels can be divided into six major families. Among them, the "classical" or "cannonical" TRPC family is most closely related to Drosophila TRP, the founding member of the superfamily. All seven channels of this family designated TRPC1-7 share the common property of activation through phospholipase C (PLC)-coupled receptors, but their gating by receptor- or store-operated mechanisms is still controversial. The TRPC3, 6, and 7 channels are 75% identical and are also gated by direct exposure to diacylglycerols (DAG). TRPC3, 6, and 7 interact physically and, upon coexpression, coassemble to form functional tetrameric channels. This review will focus on the TRPC3/6/7 subfamily and describe their functional properties and regulation as homomers obtained from overexpression studies in cell lines. It will also summarize their heteromultimerization potential in vitro and in vivo and will present preliminary data concerning their physiological functions analyzed in isolated tissues with downregulated channel activity and gene-deficient mouse models.