Differential redox regulation of ORAI ion channels: a mechanism to tune cellular calcium signaling.
Reactive oxygen species (ROS) are involved in many physiological and pathophysiological cellular processes. We used lymphocytes, which are exposed to highly oxidizing environments during inflammation, to study the influence of ROS on cellular function. Calcium ion (Ca(2+)) influx through Ca(2+) release-activated Ca(2+) (CRAC) channels composed of proteins of the ORAI family is essential for the activation, proliferation, and differentiation of T lymphocytes, but whether and how ROS affect ORAI channel function have been unclear. Here, we combined Ca(2+) imaging, patch-clamp recordings, and measurements of cell proliferation and cytokine secretion to determine the effects of hydrogen peroxide (H(2)O(2)) on ORAI channel activity and human T helper lymphocyte (T(H) cell) function. ORAI1, but not ORAI3, channels were inhibited by oxidation by H(2)O(2). The differential redox sensitivity of ORAI1 and ORAI3 channels depended mainly on an extracellularly located reactive cysteine, which is absent in ORAI3. T(H) cells became progressively less redox-sensitive after differentiation into effector cells, a shift that would allow them to proliferate, differentiate, and secrete cytokines in oxidizing environments. The decreased redox sensitivity of effector T(H) cells correlated with increased expression of Orai3 and increased abundance of several cytosolic antioxidants. Knockdown of ORAI3 with small-interfering RNA rendered effector T(H) cells more redox-sensitive. The differential expression of Orai isoforms between naïve and effector T(H) cells may tune cellular responses under oxidative stress.
Bogeski
Ivan
I
Department of Biophysics, Saarland University, 66421 Homburg, Germany. ivan.bogeski@uks.eu
Kummerow
Carsten
C
Al-Ansary
Dalia
D
Schwarz
Eva C
EC
Koehler
Richard
R
Kozai
Daisuke
D
Takahashi
Nobuaki
N
Peinelt
Christine
C
Griesemer
Desiree
D
Bozem
Monika
M
Mori
Yasuo
Y
Hoth
Markus
M
Niemeyer
Barbara A
BA
D015220:Calcium Channels / Q000378:metabolism; D020013:Calcium Signaling; D002454:Cell Differentiation; D049109:Cell Proliferation; D002470:Cell Survival; D006801:Humans; D006861:Hydrogen Peroxide / Q000737:chemistry / Q000378:metabolism; D007376:Interleukin-2 / Q000378:metabolism; D019169:Jurkat Cells; D000071740:ORAI1 Protein; D010084:Oxidation-Reduction; D018408:Patch-Clamp Techniques; D020033:Protein Isoforms; D034741:RNA, Small Interfering / Q000378:metabolism; D017382:Reactive Oxygen Species; D013601:T-Lymphocytes / Q000378:metabolism
D015220:Calcium Channels; D007376:Interleukin-2; D000071740:ORAI1 Protein; C510746:ORAI1 protein, human; D020033:Protein Isoforms; D034741:RNA, Small Interfering; D017382:Reactive Oxygen Species; D006861:Hydrogen Peroxide