Article

The Proapoptotic Factors Bax and Bak Regulate T Cell Proliferation through Control of Endoplasmic Reticulum Ca2+ Homeostasis

Department of Cancer Biology, Abramson Family Cancer Research Institute, University of Pennsylvania, Philadelphia, PA 19104, USA.
Immunity (Impact Factor: 19.75). 09/2007; 27(2):268-80. DOI: 10.1016/j.immuni.2007.05.023
Source: PubMed

ABSTRACT The Bcl-2-associated X protein (Bax) and Bcl-2-antagonist/killer (Bak) are essential regulators of lymphocyte apoptosis, but whether they play a role in viable T cell function remains unclear. Here, we report that T cells lacking both Bax and Bak display defects in antigen-specific proliferation because of Ca(2+)-signaling defects. Bax(-/-), Bak(-/-) T cells displayed defective T cell receptor (TCR)- and inositol-1,4,5-trisphosphate (IP(3))-dependent Ca(2+) mobilization because of altered endoplasmic reticulum (ER) Ca(2+) regulation that was reversed by Bax's reintroduction. The ability of TCR-dependent Ca(2+) signals to stimulate mitochondrial NADH production in excess of that utilized for ATP synthesis was dependent on Bax and Bak. Blunting of Ca(2+)-induced mitochondrial NADH elevation in the absence of Bax and Bak resulted in decreased reactive-oxygen-species production, which was required for T cell proliferation. Together, the data establish that Bax and Bak play an essential role in the control of T cell proliferation by modulating ER Ca(2+) release.

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