Biochemical and functional properties of the store-operated Ca2+ channels

Store-operated calcium entry (SOCE) is a major mechanism for Ca2+ entry in excitable and non-excitable cells. The best-characterised store-operated current is ICRAC, but other currents activated by Ca2+ store depletion have also been reported. The recent identification of the proteins stromal interaction molecule 1 (STIM1) and Orai1 has shed new light on the nature and regulation of SOC channels. STIM1 has been presented as the endoplasmic reticulum (ER) Ca2+ sensor that communicates the content of the Ca2+ stores to the store-operated channels, a mechanism that involves redistribution of STIM1 to peripheral ER sites and co-clustering with the Ca2+ channel subunit, Orai1. Interestingly, TRPC1, which has long been proposed as a SOC channel candidate, associates with Orai1 and STIM1 in a ternary complex that appears to increase the variability of SOC currents available to modulate cell function.