FLICE-like inhibitory protein (FLIP) is a critical regulator of death receptor-mediated apoptosis. Here, we found ubiquitin-specific peptidase 8 (USP8) to be a novel deubiquitylase of the long isoform of FLIP (FLIP L). USP8 directly deubiquitylates and stabilizes FLIP L, but not the short isoform. USP8 depletion induces FLIP L destabilization, promoting anti-Fas-, tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)-and tumor necrosis factor alpha-induced extrinsic apoptosis by facilitating death-inducing signaling complex or TNFR1 complex II formation, which results in the activation of caspase-8 and caspase-3. USP8 mRNA levels are elevated in melanoma and cervical cancers, and the protein levels of USP8 and FLIP L are positively correlated in these cancer cell lines. Xenograft analyses using ME-180 cervical cancer cells showed that USP8 depletion attenuated tumor growth upon TRAIL injection. Taken together, our data indicate that USP8 functions as a novel deubiquitylase of FLIP L and inhibits extrinsic apoptosis by stabilizing FLIP L.
Bibliographical noteFunding Information:
This work was supported by a grant from the National Research Foundation of Korea (NRF), funded by the Ministry of Science, ICT and Future Planning (NRF-2015R1A3A2066581) (to J Song) and by the Ministry of Education (2012R1A6A3A04040105) (to E-WL).
All Science Journal Classification (ASJC) codes
- Molecular Biology
- Cancer Research