Ubiquitin-Specific Protease 14 Negatively Regulates Toll-Like Receptor 4-Mediated Signaling and Autophagy Induction by Inhibiting Ubiquitination of TAK1-Binding Protein 2 and Beclin 1

Yoon Min; Sena Lee; Mi-Jeong Kim; Eunyoung Chun; Ki-Young Lee

doi:10.3389/fimmu.2017.01827

Ubiquitin-Specific Protease 14 Negatively Regulates Toll-Like Receptor 4-Mediated Signaling and Autophagy Induction by Inhibiting Ubiquitination of TAK1-Binding Protein 2 and Beclin 1

Front Immunol. 2017 Dec 15:8:1827. doi: 10.3389/fimmu.2017.01827. eCollection 2017.

Authors

Yoon Min¹, Sena Lee¹, Mi-Jeong Kim¹, Eunyoung Chun^{2

3}, Ki-Young Lee^{1

4

5}

Affiliations

¹ Department of Molecular Cell Biology, Samsung Biomedical Research Institute, Sungkyunkwan University School of Medicine, Suwon, South Korea.
² Department of Immunology and Infectious Diseases, Harvard School of Public Health, Boston, MA, United States.
³ The Department of Medicine, Harvard Medical School, Boston, MA, United States.
⁴ Samsung Medical Center, Seoul, South Korea.
⁵ Department of Health Sciences and Technology, Samsung Advanced Institute for Health Sciences & Technology, Samsung Medical Center, Sungkyunkwan University, Seoul, South Korea.

Abstract

Ubiquitin-specific protease 14 (USP14), one of three proteasome-associated deubiquitinating enzymes, has multifunctional roles in cellular context. Here, we report a novel molecular mechanism and function of USP14 in regulating autophagy induction and nuclear factor-kappa B (NF-κB) activation induced by toll-like receptor (TLR) 4 (TLR4). USP14 interacted with tumor necrosis factor (TNF) receptor-associated factor 6 (TRAF6) and interrupted the association of Beclin 1 with TRAF6, leading to inhibition of TRAF6-mediated ubiquitination of Beclin 1. Reduced expression of USP14 in USP14-knockdown (USP14^KD) THP-1 cells enhanced autophagy induction upon TLR4 stimulation as shown by the increased conversion of cytosolic LC3-I to membrane-bound LC3-II. Moreover, USP14^KD human breast carcinoma MDA-MB-231 cells and USP14^KD human hepatic adenocarcinoma SK-HEP-1 cells showed increased cell migration and invasion, indicating that USP14 is negatively implicated in the cancer progression by the inhibition of autophagy induction. Furthermore, we found that USP14 interacted with TAK1-binding protein (TAB) 2 protein and induced deubiquitination of TAB 2, a key factor in the activation of NF-κB. Functionally, overexpression of USP14 suppressed TLR4-induced activation of NF-κB. In contrast, USP14^KD THP-1 cells showed enhanced activation of NF-κB, NF-κB-dependent gene expression, and production of pro-inflammatory cytokines such as IL-6, IL-1β, and tumor necrosis factor-α. Taken together, our data demonstrate that USP14 can negatively regulate autophagy induction by inhibiting Beclin 1 ubiquitination, interrupting association between TRAF6 and Beclin 1, and affecting TLR4-induced activation of NF-κB through deubiquitination of TAB 2 protein.

Keywords: Beclin 1; TAK1-binding protein 2; autophagy; toll-like receptor 4; tumor necrosis factor receptor-associated factor 6; ubiquitination.