Transcripts expression In immune cells, transcripts taken from isolated primary CD3+/CD4+ cells (Th-lymphocytes), CD3+/CD8+ cells (Tc-lymphocytes), CD19+ cells (B-lymphocytes) and BMMC showed that ORAI3 expression is readily detectable in Th-, Tc-, and B- lymphocytes and BMMC (Gross et al., 2007). mRNA expression in normal tissues has been assessed by different techniques (microarrays, RNAseq, SAGE). Microarrays analyses show that ORAI3 is overexpressed in prostate, lung, monocytes and whole blood (http://biogps.org/#goto=genereport&id=93129, with overexpression defined as 3 times the mean expression observed in the 83 tissues or cells tested in this study). ORAI3 mRNA expression is least important in pancreas, brain (especially the occipital lobe) and T cells (CD4+ as well as CD8+).
Post-translational modifications of the protein
Glycosylation: Unlike ORAI1, ORAI3 does not have a glycosylation site on the asparagine residue (N223) situated between the transmembrane domains TM3 et TM4 (Frischauf et al., 2008; Prakriya et al., 2006). ORAI1 has a putative N-glycosylation motif (NVS) in its extracellular loop between predicted transmembrane segments 3 and 4. This motif is absent in ORAI2 and 3 (Gwack et al., 2007). ORAI3 migration properties do not change by tunicamycin treatment. Indeed, HEK293 cells stably transfected with FLAG-tagged ORAI and treated with 2μg/ml tunicamycin, showed that ORAI3 migrated at positions close to their predicted molecular masse (32.5 kDa). Phosphorylation: Since ORAI3 is a tetraspanning plasma membrane protein, it contains three intracellular regions that can potentially be phosphorylated by intracellular protein kinases: the N-terminus, an intracellular loop between transmembrane domains 2 and 3, and the C-terminus, each intracellular region potentially contains one or more phosphorylation sites. Ser-27 and Ser-30 have been identified as the main phosphorylation sites in ORAI1 within its N-terminus. They are conserved throughout evolution in all mammalian ORAI1 proteins. Mutations at these phosphorylation sites increase store-operated Ca2+ entry (SOCE) and CRAC current suggesting that ORAI1 phosphorylation at these residues by protein kinase C (PKC) suppresses SOCE and CRAC channel activation. However, Ser-27 and Ser-30 are not present in ORAI2 and ORAI3. A phosphorylation of ORAI3 peptide has been revealed by a phosphoproteome analysis of human liver cells (Sui et al., 2008). This phosphorylation site is located in the C-terminus of ORAI3 on a tyrosine residue (Y278). Experimental ORAI3 phosphorylation has also been demonstrated in HEK293 cells (Kawasaki et al., 2010). To examine in vivo PKC-mediated phosphorylation, HEK293 cells expressing FLAG-tagged ORAI were incubated with 32P monosodium phosphate, and then stimulated with thapsigargin in the presence of extracellular Ca2+. Thapsigargin mobilizes Ca2+ from the ER and the extracellular space and activates Ca2+/DAG-dependent PKC isoforms. ORAI1 phosphorylation is enhanced in response to thapsigargin. The levels of ORAI3 phosphorylation have been less than half of that observed for ORAI1 (Kawasaki et al., 2010). Other phosphorylation sites on ORAI3 were predicted by NetPhos2.0: 13 serine sites (S20, S45, S50, S57, S64, S65, S68, S86, S191, S203, S213, S214 and S20), 3 threonine sites (T26, T183 and T190) and 2 tyrosine sites (Y146 and Y278).
NCBI: 93129 MIM: 610930 HGNC: 28185 Ensembl: ENSG00000175938
dbSNP: 93129 ClinVar: 93129 TCGA: ENSG00000175938 COSMIC: ORAI3
Jessy Hasna ; Nazim Benzerdjeb ; Malika Faouzi ; Anne-Sophie Ay ; Philippe Kischel ; Frédéric Hague ; Henri Sevestre ; Ahmed Ahidouch ; Halima Ouadid-Ahidouch
ORAI3 (ORAI calcium release-activated calcium modulator 3)
Atlas Genet Cytogenet Oncol Haematol. 2014-06-01
Online version: http://atlasgeneticsoncology.org/gene/51589/orai3