Primary structure, chromosomal localization and expression in immune cells of the murine ORAI and STIM genes.

Recently ORAI and STIM proteins were identified as components of the CRAC channel and the endoplasmic reticulum Ca(2+) sensor, respectively. The ORAI proteins share a predicted structure that includes four transmembrane domains with intracellular N- and C-termini. They share structural similarity with proteins of the tetraspanin superfamily which includes the gamma subunits of voltage-activated Ca(2+) channels (CaVgamma), the transmembrane AMPA regulatory proteins (TARPs), the claudins and the tumor-associated membrane proteins (TMPs). The mouse genome contains four genes which encode the ORAI1, ORAI2 and ORAI3 proteins and two genes which encode the type I single-pass transmembrane STIM1 and STIM2 proteins. ORAI2 transcripts are present in primary cortical neurons and ORAI1, 2, 3 and STIM1, 2 expression is readily detectable in CD3+/CD4+-, CD3+/CD8+-, and CD19+-lymphocytes as well as in mast cells from mouse.