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 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 acts as an endoplasmic reticulum (ER) Ca⁺² sensor.^3,4 The formation of functional channels requires the presence of both Orai1 and STIM1 proteins working as a complex that involves co-clustering of Orai1 on the plasma membrane with STIM1 on the ER.^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-termini. In addition, two mammalian homologs of Orai1 have been identified: Orai2 and Orai3.^3,9 All three (Orai1, Orai2, and Orai3) have been shown to be capable of forming store-operated channels.^9,10

Alomone Labs is pleased to offer a new version of the Anti-Human Orai1 (extracellular) antibody (#ACC-060) directly conjugated to FITC. The Anti-Human Orai1 (extracellular)-FITC antibody (#ACC-060-F) can be used for immunofluorescent applications such as direct flow cytometry and  recognizes Orai1 from human samples.