title: ORAI1 deficiency impairs activated T cell death and enhances T cell survival.
abstract: ORAI1 is a pore subunit of Ca(2+) release-activated Ca(2+) channels that mediate TCR stimulation-induced Ca(2+) entry. A point mutation in ORAI1 (ORAI1(R91W)) causes SCID in human patients that is recapitulated in Orai1(-/-) mice, emphasizing its important role in the immune cells. In this study, we have characterized a novel function of ORAI1 in T cell death. CD4(+) T cells from Orai1(-/-) mice showed robust proliferation with repetitive stimulations and strong resistance to stimulation-induced cell death due to reduced mitochondrial Ca(2+) uptake and altered gene expression of proapoptotic and antiapoptotic molecules (e.g., Fas ligand, Noxa, and Mcl-1). Nuclear accumulation of NFAT was severely reduced in ORAI1-deficient T cells, and expression of ORAI1 and a constitutively active mutant of NFAT recovered cell death. These results indicate NFAT-mediated cell death pathway as one of the major downstream targets of ORAI1-induced Ca(2+) entry. By expressing various mutants of ORAI1 in wild-type and Orai1(-/-) T cells to generate different levels of intracellular Ca(2+), we have shown that activation-induced cell death is directly proportional to the intracellular Ca(2+) concentration levels. Consistent with the in vitro results, Orai1(-/-) mice showed strong resistance to T cell depletion induced by injection of anti-CD3 Ab. Furthermore, ORAI1-deficient T cells showed enhanced survival after adoptive transfer into immunocompromised hosts. Thus, our results demonstrate a crucial role of the ORAI1-NFAT pathway in T cell death and highlight the important role of ORAI1 as a major route of Ca(2+) entry during activated T cell death.
authors.affiliation: Department of Physiology, David Geffen School of Medicine at University of California, Los Angeles, Los Angeles, CA 90095, USA.
authors.forename: Kyun-Do
authors.initials: KD
authors.lastname: Kim
authors.forename: Sonal
authors.initials: S
authors.lastname: Srikanth
authors.forename: Ma-Khin Win
authors.initials: MK
authors.lastname: Yee
authors.forename: Dennis C
authors.initials: DC
authors.lastname: Mock
authors.forename: Gregory W
authors.initials: GW
authors.lastname: Lawson
authors.forename: Yousang
authors.initials: Y
authors.lastname: Gwack
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000276:immunology*; D015496:CD4-Positive T-Lymphocytes / Q000166:cytology / Q000276:immunology* / Q000378:metabolism; D015220:Calcium Channels / Q000276:immunology* / Q000378:metabolism; D020013:Calcium Signaling / Q000276:immunology*; D002469:Cell Separation; D002470:Cell Survival; D005434:Flow Cytometry; D006801:Humans; D015151:Immunoblotting; D051379:Mice; D018345:Mice, Knockout; D008928:Mitochondria / Q000378:metabolism; D050778:NFATC Transcription Factors / Q000276:immunology / Q000378:metabolism; D000071740:ORAI1 Protein; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014161:Transduction, Genetic
chemical_list: D015220:Calcium Channels; D050778:NFATC Transcription Factors; D000071740:ORAI1 Protein; C520430:Orai1 protein, mouse