The Deubiquitinating Enzyme USP20 Regulates the TNFα-Induced NF-κB Signaling Pathway through Stabilization of p62.

Jihoon Ha,Jin Seok Park,Seok Hee Park,Jinjoo Lee,Dongyeob Seo,Jaewon Lee,Minbeom Kim

doi:10.3390/ijms21093116

Jihoon Ha, Jin Seok Park + Show 5 more

Open Access

https://doi.org/10.3390/ijms21093116

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Abstract

p62/sequestosome-1 is a scaffolding protein involved in diverse cellular processes such as autophagy, oxidative stress, cell survival and death. It has been identified to interact with atypical protein kinase Cs (aPKCs), linking these kinases to NF-κB activation by tumor necrosis factor α (TNFα). The diverse functions of p62 are regulated through post-translational modifications of several domains within p62. Among the enzymes that mediate these post-translational modifications, little is known about the deubiquitinating enzymes (DUBs) that remove ubiquitin chains from p62, compared to the E3 ligases involved in p62 ubiquitination. In this study, we first demonstrate a role of ubiquitin-specific protease USP20 in regulating p62 stability in TNFα-mediated NF-κB activation. USP20 specifically binds to p62 and acts as a positive regulator for NF-κB activation by TNFα through deubiquitinating lysine 48 (K48)-linked polyubiquitination, eventually contributing to cell survival. Furthermore, depletion of USP20 disrupts formation of the atypical PKCζ-RIPK1-p62 complex required for TNFα-mediated NF-κB activation and significantly increases the apoptosis induced by TNFα plus cycloheximide or TNFα plus TAK1 inhibitor. These findings strongly suggest that the USP20-p62 axis plays an essential role in NF-κB-mediated cell survival induced by the TNFα-atypical PKCζ signaling pathway.

Highlights

Ever since p62— known as sequestosome-1 (SQSTM1)—was identified as a scaffold protein for atypical protein kinase C [1,2], it has been recognized as a signaling hub for diverse cellular signaling pathways involved in autophagy, oxidative stress, cell survival and cell death [3,4]
P62 is primarily degraded through selective autophagy [5,6], it can be degraded by the proteasome or endosomal-related autophagy [7,8,9], and p62 levels are commonly measured to monitor autophagic flux [10,11]. p62 is involved in other cellular processes such as the nuclear factor-κB (NF-κB) signaling pathway through atypical protein kinase Cs (aPKCs) [1,2], receptor interacting protein kinase-1 (RIPK1) [12] and tumor necrosis factor receptor-associated factor 6 (TRAF6) [13], adipogenesis through interaction with extracellular signal-regulated kinase 1 (ERK1) [14], the antioxidant response through interaction with Keap1 [15], apoptosis through caspase-8 [16] and nutrient sensing through interactions with Raptor in the mammalian target of rapamycin pathway [17]
Ever since ubiquitin-specific protease 20 (USP20) was identified as a substrate of the cullin-RING ligase family member CRLVHL [33,34], accumulating evidence has revealed that USP20 is involved in diverse cellular signaling pathways such as hypoxia, the DNA damage response, TLR4-mediated innate immune response, the mitogen-signaling pathway and autophagy [13,28,35,36,37,38]

Summary

Introduction

Ever since p62— known as sequestosome-1 (SQSTM1)—was identified as a scaffold protein for atypical protein kinase C (aPKC) [1,2], it has been recognized as a signaling hub for diverse cellular signaling pathways involved in autophagy, oxidative stress, cell survival and cell death [3,4]. These diverse functions seem to be due to scaffolding activities mediated by multiple domains within p62, which interact with various binding partners [4]. USP15 reverses the polyubiquitination of p62 by RNF26 in the endocytic pathway [26] whereas USP8 removes lysine 11-linked ubiquitin chains from p62 to suppress autophagic activity [27]

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