Orai1: Proteins and Enzymes

Orai1 is a membrane calcium channel subunit that is activated by the calcium sensor STIM1 when calcium stores are depleted. Orai1 is a pore subunit of Ca(2+) release-activated Ca(2+) CRAC channels, and STIM1 acts as an endoplasmic reticulum (ER) Ca(2+) sensor that detects store depletion. This type of channel is the primary way for calcium influx into T-cells. Defects in Orai1 are a cause of immune dysfunction with T-cell inactivation due to calcium entry defect type 1.