Raptor plays a critical role in mTORC1 signaling. High expression of Raptor is associated with resistance of cancer cells to PI3K/mTOR inhibitors. Here, we found that OTUB1-stabilized Raptor in a non-canonical manner. Using biochemical assays, we found that the tyrosine 26 residue (Y26) of OTUB1 played a critical role in the interaction between OTUB1 and Raptor. Furthermore, non-receptor tyrosine kinases (Src and SRMS kinases) induced phosphorylation of OTUB1 at Y26, which stabilized Raptor. Interestingly, phosphorylation of OTUB1 at Y26 did not affect the stability of other OTUB1-targeted substrates. However, dephosphorylation of OTUB1 destabilized Raptor and sensitized cancer cells to anti-cancer drugs via mitochondrial reactive oxygen species-mediated mitochondrial dysfunction. Furthermore, we detected high levels of phospho-OTUB1 and Raptor in samples of patients with renal clear carcinoma. Our results suggested that regulation of OTUB1 phosphorylation may be an effective and selective therapeutic target for treating cancers via down-regulation of Raptor.
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The biospecimens and data used for the present study were provided by the Biobank of Keimyung University Dongsan Hospital Biobank, a member of the Korea Biobank Network.
This work was supported by an NRF grant funded by the Korea Government (MSIP) [NRF-2021R1A4A1029238, NRF-2019R1A2C2005921 and NRF-2020R1C1C1009889]. This work was supported by a grant from the KRIBB Research Initiative Program.
The authors declare no competing interests.
The present study was approved by the Ethics Committee of Keimyung Medical University.
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Seo, S.U., Woo, S.M., Kim, M.W. et al. Phosphorylation of OTUB1 at Tyr 26 stabilizes the mTORC1 component, Raptor. Cell Death Differ 30, 82–93 (2023). https://doi.org/10.1038/s41418-022-01047-3