The TRPC Ion Channels: Association with Orai1 and STIM1 Proteins and Participation in Capacitative and Non-capacitative Calcium Entry
Gines M. Salido, Isaac Jardín, and Juan A. Rosado
Transient receptor potential (TRP) proteins are involved in a large number of non-selective cation channels that are permeable to both monovalent and divalent cations. Two general classes of receptor-mediated Ca2+ entry has been proposed: one of then is conduced by receptor-operated Ca2+ channels (ROC), the second is mediated by channels activated by the emptying of intracellular Ca2+ stores (store-operated channels or SOC). TRP channels have been presented as subunits of both ROC and SOC, although the precise mechanism that regulates the participation of TRP proteins in these Ca2+ entry mechanisms remains unclear. Recently, TRPC proteins have been shown to associate with Orai1 and STIM1 in a dynamic ternary complex regulated by the occupation of membrane receptors in several cell models, which might play an important role in the function of TRPC proteins. The present review summarizes the current knowledge concerning the association of TRP proteins with Orai and STIM proteins and how this affects the participation of TRP proteins in store-operated or receptor-operated Ca2+ entry.