ORAI1 Gene

ORAI1 (ORAI Calcium Release-Activated Calcium Modulator 1) is a protein-coding gene located on chromosome 12q24.3. Molecular activities associated with this gene include protein binding and store-operated calcium channel activities. Associated signaling pathways include platelet homeostasis and TCR signaling in naive CD4+ T cells.

Mutations in ORAI2 are a cause of:

• Immunodeficiency 9 (Immune Dysfunction with T-Cell Inactivation Due to Calcium Entry Defect 1)
• and for
• Myopathy, tubular aggregate, 2 (TAM2) (congenital myopathy resulting in muscle weakness, and features of ectodermal dysplasia, including soft enamel).

The protein encoded by this gene is a calcium channel subunit (CRAC channels) that is activated by the calcium sensor STIM1 when calcium stores are depleted. CRAC channels are the major pathway for calcium influx into T cells. They promote the immune response to pathogens by activating the transcription factor NFAT.

CRAC channels play an important role in Ca(2+) influx at the basolateral membrane of mammary epithelial cells, independent of the Ca(2+) content of the endoplasmic reticulum or Golgi stores. They may mediate transepithelial transport of large amounts of Ca(2+) for milk secretion.

1. Feske S et al. (2007) The duration of nuclear residence of NFAT determines the pattern of cytokine expression in human SCID T cells. J. Immun. 165: 297-305.
2. Feske S et al. (2006) A mutation in Orai1 causes immune deficiency by abrogating CRAC channel function. Nature 441: 179-185.
3. Le Deist F et al (1995) A primary T-cell immunodeficiency associated with defective transmembrane calcium influx. Blood 85: 1053-1062.
4. McCarl C-A et al.(2009) ORAI1 deficiency and lack of store-operated Ca(2+) entry cause immunodeficiency, myopathy, and ectodermal dysplasia. J Allergy Clin Immun 124: 1311-1318.
5. Partiseti M et al (1994) The calcium current activated by T cell receptor and store depletion in human lymphocytes is absent in a primary immunodeficiency. J Biol Chem 269: 32327-32335.
6. Schlesier M et al (1993) Primary severe immunodeficiency due to impaired signal transduction in T cells. Immunodeficiency 4: 133-136.