STIM-TRP pathways the STIM1/Orai/TRPC channels multiple Ca²⁺ influx complexes

Receptor-evoked Ca²⁺ influx is a central component of the Ca²⁺ signal. A ubiquitous form of Ca²⁺ influx is activated by depletion of endoplasmic Ca²⁺ stores, the SOC channels. The two established Ca²⁺ influx channels that are activated by depletion of the endoplasmic reticulum Ca²⁺ store are the TRPC channels and the newly discovered Orai channels. The two channels can function independently and are gated by different STIM1 domains. Yet, the two channels also affect the function of each other by competition for STIM1 and by yet unresolved mechanism in which their function is required for their mutual activity. This chapter will discuss the evidence for the regulation of the Orai and TRPC channels by STIM1 and the interrelations between the two activities. The function and properties of the Orai channels and their regulation by STIM1 is extensively covered in other chapters and will only be briefly discussed here as they relate to the function of TRPC channels.