Calcium release-activated calcium channel protein (commonly, Orai1; see below for other isoforms) (Orai (also Orai1, Orai2, Orai3 for specific isoforms))

Calcium release-activated calcium channel proteins (Orai family: Orai1, Orai2, Orai3) are the principal components of store-operated calcium entry in mammalian cells[2][3][7]. These channels are activated when intracellular Ca^2+ stores (endoplasmic reticulum) are depleted, sensed by the STIM proteins, which migrate to the plasma membrane and physically interact with Orai to trigger channel opening[1][3][4][7]. Structurally, Orai channels are hexameric complexes formed by six Orai subunits, each containing four transmembrane helices that surround a central ion pore[1][3][5][7]. This highly specialized pore allows selective Ca^2+ influx into cells, thereby initiating diverse downstream signaling events critical for gene expression, cell proliferation, differentiation, migration, and immune response[2][4][7][8]. Orai channels are implicated in a wide range of diseases, notably several immune disorders (like severe combined immunodeficiency and autoimmune diseases), muscular diseases, heart and vascular disorders, and numerous cancers[2][4][8]. Pharmacological blockade of Orai1 is under active investigation for treating conditions such as acute pancreatitis, autoimmune disorders, and inflammatory diseases, with multiple small-molecule inhibitors (e.g., CM4620) currently in clinical trials[6][8]. In summary, Orai channels are essential store-operated calcium channels and represent validated therapeutic targets for several pathological conditions, with ongoing drug development focused on selective channel inhibition or modulation.

Other names

OraiOrai1Orai2Orai3CRAC channelCalcium release-activated calcium channelStore-operated calcium channel

Direct pore blockade (Orai1/CRAC channel inhibitors) Inhibition of STIM-Orai interaction Blockade of calcium influx and downstream signaling