Regulation of T cell function by the ubiquitin-specific protease USP9X via modulating the Carma1-Bcl10-Malt1 complex.

Division of Cell Biology, La Jolla Institute for Allergy and Immunology, La Jolla, CA 92037.
The ubiquitin conjugation system plays an important role in immune regulation; however, the ubiquitin-specific proteases (USPs) that carry out deubiquitination of cellular substrates are poorly understood. Here we show that in vivo knockdown of the deubiquitinating enzyme USP9X attenuates T-cell proliferation. In addition, naive CD4(+) T cells from USP9X knockdown chimeric mice display decreased cytokine production and T helper cell differentiation in vitro, which we confirmed in vivo by performing adoptive transfer of transgenic T cells and subsequent immunization. USP9X silencing in both a human T-cell line and mouse primary T cells reduced T-cell receptor (TCR) signaling-induced NF-κB activation. Mechanistically, USP9X interacts with Bcl10 of the Carma1-Bcl10-Malt1 (CBM) complex and removes the TCR-induced ubiquitin chain from Bcl10, which facilitates the association of Carma1 with Bcl0-Malt1. These results demonstrate that USP9X is a crucial positive regulator of the TCR signaling pathway and is required for T-cell function through the modulation of CBM complex formation.
Proc. Natl. Acad. Sci. U.S.A. Jun. 04, 2013; 110(23);9433-8 [PUBMED:23690623]
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