- Synthetic peptide mapping to an extracellular sequence of human Orai1 (Accession Q96D31).
- HEK-293 cells transfected with human Orai1 (1:200-1:1000).
- Western blot analysis using Mouse Anti-Human Orai1 (extracellular) Antibody (#ALM-025), (1:200):1. HEK-293 cells transfected with human Orai1.
2. HEK-293 cells transfected with control vector.
- Intact living human Jurkat T cells (5-10 µg antibody/0.5-1 x 106 cells).
- HEK-293 cells transfected with human Orai1.
Cytosolic calcium (Ca2+) has long been known to act as a key second messenger in many intracellular pathways including synaptic transmission, muscle contraction, hormonal secretion, cell growth and proliferation.1,2 The mechanism controlling intracellular Ca2+ level influx either by the calcium-release-activated Ca2+ channels (CRAC), or from intracellular stores, has become of great interest.
Recently, several key players of the store operated complex have been identified3. Orai1 (also known as CRACM1) acts as the store operated Ca2+ channel (SOC) and STIM1, which acts as the endoplasmic reticulum Ca2+ sensor3,4. The formation of functional channels requires the presence of both Orai1 and STIM1 proteins working as a complex and involves the co-clustering of Orai1 on the plasma membrane with STIM1 on the endoplasmic reticulum4-6. TRPC1, a member of the transient receptor potential family was also suggested to act as a player in the SOC complex7. In T-cells, Ca2+ entry following activation by antigen-receptor engagement occurs solely through CRAC channels where Orai1 constitutes the pore forming subunit3,8.
Orai1 is a plasma membrane protein with four potential transmembrane domains and intracellular N- and C-terminus. In addition, two mammalian homologs to Orai1 have been identified; Orai2 and Orai33,9. All three, Orai1 Orai2 and Orai3, are capable of forming store operated channels with different magnitudes9.