The ubiquitin-specific protease USP8 is critical for the development and homeostasis of T cells

Abstract

The modification of proteins by ubiquitin has a major role in cells of the immune system and is counteracted by various deubiquitinating enzymes (DUBs) with poorly defined functions. Here we identified the ubiquitin-specific protease USP8 as a regulatory component of the T cell antigen receptor (TCR) signalosome that interacted with the adaptor Gads and the regulatory molecule 14-3-3 . Caspasedependent processing of USP8 occurred after stimulation of the TCR. T cell-specific deletion of USP8 in mice revealed that USP8 was essential for thymocyte maturation and upregulation of the gene encoding the cytokine receptor IL-7R mediated by the transcription factor Foxo1. Mice with T cell-specific USP8 deficiency developed colitis that was promoted by disturbed T cell homeostasis, a predominance of CD8(+) T cells in the intestine and impaired regulatory T cell function. Collectively, our data reveal an unexpected role for USP8 as an immunomodulatory DUB in T cells. Ubiquitin-modification is counteracted by deubiquitinating enzymes (DUBs). Here we identify 32 USP8 as a novel component of the TCR signalosome that interacts with the adapter 33 molecule GADS and 14-3-3β. Upon TCR-stimulation USP8 is processed in a caspase-34 dependent manner. T-cell-specific deletion in mice (USP8 f/f CD4-Cre) revealed that USP8 is 35 essential for thymocyte transition to the CD4 + and CD8 + single positive stages and critical for 36 TCR and Foxo1-mediated IL7Rα upregulation. In vivo reconstitution showed that enzymatic 37 activity and SH3-binding are essential for USP8 function in T-cells. USP8 f/f CD4-Cre mice 38 DOI

Regulatory interplay between deubiquitinating enzymes and cytokines

“…Dufner et al found that USP8 was essential in T cell maturation and homeostasis, although it was not required for negative selection [81]. Inhibiting USP8 leads to decrease in IL-7ra mRNA as well as Ccr7 [81].…”

Mechanisms of regulation and diversification of deubiquitylating enzyme function

“…Disease mutants result in tUSP8 that now promotes EGFR recycling to the plasma membrane, instead of downregulating the receptor. Interestingly, USP8 is also cleaved in a caspase-dependent manner in T cells following TCR activation (Dufner et al, 2015).…”

USP8 – Another DUB in the T cell club

“…2 We now identified ubiquitinspecific protease 8 (USP8) as a novel component of the T cell receptor (TCR) signalosome that interacts with the adapter molecule Gads and the regulatory protein 14-3-3b. 3 Gads is highly abundant in T cells and modulates signal diversification. 4 As typical for 14-3-3 proteins, the interaction with 14-3-3b was dependent on a serine phosphorylation motif within the 14-3-3 binding motif (14-3-3BM) of USP8 (Fig.…”

“…6 Similar to the USP8 variants found in CD patients, we identified rapid processing of USP8 in murine T cells upon activation of the TCR. 3 This processing was caspase-dependent and resulted in the generation of mouse USP8 fragments that were homologous to the fragments of the human USP8 variants found in corticotropinomas. These findings confirmed that murine and human USP8 are both proteolytically cleaved.…”

“…[5][6][7] Remarkably, in contrast to MEFs and hepatocytes, lack of USP8 had no influence on the stability of components of the endosomal sorting machinery in T cells. 3,5 The adaptor molecule STAM2 for example, which interacts with USP8 via SH3 binding ( Fig. 1) was not destabilized in T cells.…”