Cytosolic calcium (Ca⁺²) 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 Ca⁺² level influx either by the calcium-release-activated Ca⁺² channels (CRAC), or from intracellular stores, has become of great interest.

Recently, several key players of the store operated complex have been identified.³  Orai1 (also known as CRACM1) acts as the store operated calcium channel (SOC) and STIM1, which acts as the endoplasmic reticulum Ca⁺² sensor.^3,4 The formation of functional channels by Orai1 requires the presence of both Orai1 and STIM1 proteins working as a complex that involves the co-clustering of Orai1 on the plasma membrane with STIM1 on the endoplasmic reticulum.^4-6 TRPC1, a member of the transient receptor potential family was also suggested to act as a player in the SOC complex.⁷ In T-cells, Ca⁺² entry following activation by antigen-receptor engagement occurs solely through CRAC channels where Orai1 constitutes the pore forming subunit.^3,8

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 Orai3.^3,9 All three, Orai1 Orai2 and Orai3, are capable of forming store operated channels with different magnitudes.⁹

Alomone Labs is pleased to offer a new antibody raised against an extracellular epitope of the human Orai1 channel, Anti-Orai1(extracellular) antibody.