Pore-forming subunit of inward rectifying Ca(2+) release- activated Ca(2+) (CRAC) channels. Assembles with ORAI1 and ORAI3 to form hexameric CRAC channels that mediate Ca(2+) influx upon depletion of endoplasmic reticulum Ca(2+) store and channel activation by Ca(2+) sensor STIM1, a process known as store-operated Ca(2+) entry (SOCE). Various pore subunit combinations may account for distinct CRAC channel spatiotemporal and cell-type specific dynamics. ORAI1 mainly contributes to the generation of Ca(2+) plateaus involved in sustained Ca(2+) entry and is dispensable for cytosolic Ca(2+) oscillations, whereas ORAI2 and ORAI3 generate oscillatory patterns. CRAC channels assemble in Ca(2+) signaling microdomains where Ca(2+) influx is coupled to calmodulin and calcineurin signaling and activation of NFAT transcription factors recruited to ORAI1 via AKAP5. CRAC channels are the main pathway for Ca(2+) influx in T cells and promote the immune response to pathogens by activating NFAT-dependent cytokine and chemokine transcription. {ECO:0000269|PubMed:16807233, ECO:0000269|PubMed:17442569, ECO:0000269|PubMed:17452328, ECO:0000269|PubMed:19182790, ECO:0000269|PubMed:19706554, ECO:0000269|PubMed:32415068, ECO:0000269|PubMed:33941685}. This is the function of ENSG00000160991 (ORAI2, ORAI calcium release-activated calcium modulator 2).