Functional role of the ubiquitin specific protease 8 (USP8/UBPy) in T cells
Immunology
Final Report Abstract
In the previous funding period we identified USP8 as a novel component of the TCR signalosome that interacts with the adapter molecule GADS and 14-3-3β. As typical for 14-3-3 proteins, the interaction with 14-3-3β is dependent on a serine phosphorylation motif within the 14-3-3 BM of USP8. Intriguingly, we were also able to show that USP8 is processed in a caspase-dependent manner upon TCR-stimulation. T-cell-specific deletion in mice (USP8f/fCD4-Cre) revealed that USP8 is essential for thymocyte transition to the CD4+ and CD8+ single positive (SP) stages and efficient positive selection. USP8 is not required for CD3/CD28-induced signal transduction or negative selection, but critical for TCR upregulation and Foxo1-mediated IL7Rα and C-C chemokine receptor type 7 (CCR7) expression. We were finally able to publish these results in Nature Immunology. Based on these results, we proposed to further investigate the role of the underlying mechanisms in the current grant. Here we contributed to a seminal study published 2017 in Nature Immunology which identified CHMP5 as a major USP8 target required for positive selection of thymocytes via the control of BCL2 stability. We extended and redirected our focus on the function of USP8 in B cells, as inhibition of the proteasome, which degrades ubiquitin-modified proteins, is a well- established therapy for B cell malignancies and Ubiquitin-specific protease 8 (USP8) was identified as a potential target in a multiple myeloma vulnerability screen. Here we characterized the in vivo function of USP8 in B cells and analyzed its impact on the global and ubiquitin-modified proteome. Early stage Usp8 inactivation blocked B-lymphocyte development in mice. Usp8 deletion from the pre-B cell stage on caused a partial block with a shift towards immature and innate-like B cells with elevated immune-response and impaired Roquin expression. Mechanistically, we show that USP8 is essential to prevent proteotoxic stress. Cells expressing catalytically inactive USP8 accumulate mixed ubiquitin/NEDD8 chains as a hallmark of proteotoxic stress, which we identified as favored USP8 substrates. Importantly, USP8 inhibition resensitized bortezomib resistant multiple myeloma cells to treatment uncovering its therapeutic potential.
Publications
- The ubiquitin-specific protease USP8 is critical for the development and homeostasis of T cells. Nat Immunol. 2015 Sep;16(9):950-60
Dufner A, Kisser A, Niendorf S, Basters A, Reissig S, Schönle A, Aichem A, Kurz T, Schlosser A, Yablonski D, Groettrup M, Buch T, Waisman A, Schamel WW, Prinz M, Knobeloch KP
(See online at https://doi.org/10.1038/ni.3230) - USP8--Another DUB in the T cell club. Cell Cycle. 2015;14(24):3775-6
Dufner A, Knobeloch KP
(See online at https://doi.org/10.1080/15384101.2015.1105698) - Post-translational control of T cell development by the ESCRT protein CHMP5. Nat Immunol. 2017 Jul;18(7):780-790
Adoro S, Park KH, Bettigole SE, Lis R, Shin HR, Seo H, Kim JH, Knobeloch KP, Shim JH, Glimcher LH
(See online at https://doi.org/10.1038/ni.3764) - DC Respond to Cognate T Cell Interaction in the Antigen-Challenged Lymph Node. Front Immunol. 2019 Apr 25;10:86
Curato C, Bernshtein B, Zupancič E, Dufner A, Jaitin D, Giladi A, David E, Chappell-Maor L, Leshkowitz D, Knobeloch KP, Amit I, Florindo HF, Jung S
(See online at https://doi.org/10.3389/fimmu.2019.00863) - Ubiquitin-specific protease 8 (USP8/UBPy): a prototypic multidomain deubiquitinating enzyme with pleiotropic functions. Biochem Soc Trans. 2019 Dec 20;47(6):1867-1879
Dufner A, Knobeloch KP
(See online at https://doi.org/10.1042/bst20190527)
