MKP-1 modulates ubiquitination/phosphorylation of TLR signaling.

Jaya Talreja,Christian Bauerfeld,Xiantao Wang,Lobelia Samavati,Yusen Liu,Markus Hafner

doi:10.26508/lsa.202101137

Abstract

Ubiquitination and phosphorylation are reversible posttranslational protein modifications regulating physiological and pathological processes. MAPK phosphatase (MKP)-1 regulates innate and adaptive immunity. The multifaceted roles of MKP-1 were attributed to dephosphorylation of p38 and JNK MAPKs. We show that the lack of MKP-1 modulates the landscape of ubiquitin ligases and deubiquitinase enzymes (DUBs). MKP-1-/- showed an aberrant regulation of several DUBs and increased expression of proteins and genes involved in IL-1/TLR signaling upstream of MAPK, including IL-1R1, IRAK1, TRAF6, phosphorylated TAK1, and an increased K63 polyubiquitination on TRAF6. Increased K63 polyubiquitination on TRAF6 was associated with an enhanced phosphorylated form of A20. Among abundant DUBs, ubiquitin-specific protease-13 (USP13), which cleaves polyubiquitin-chains on client proteins, was substantially enhanced in murine MKP-1-deficient BMDMs. An inhibitor of USP13 decreased the K63 polyubiquitination on TRAF6, TAK1 phosphorylation, IL-1β, and TNF-α induction in response to LPS in BMDMs. Our data show for the first time that MKP-1 modulates the ligase activity of TRAF6 through modulation of specific DUBs.

Highlights

MAPK phosphatase (MKP)-1 dephosphorylates TXY motifs on MAPKs, thereby negatively regulating MAPKs that are involved in the synthesis of pro-inflammatory cytokines (Liu et al, 2007; Wang et al, 2007; Wang et al, 2008)
Because of increased expression of IL-1R1 and IRAK1, altered TNF receptor–associated factor 6 (TRAF6) ubiquitination and signaling complex formation in MKP-1– deficient BMDMs, we examined if MKP-1 deficiency is associated with an aberrant ubiquitin conjugation enzyme 13 (Ubc13) expression
We examined the effects of MKP-1 deficiency on the critical signaling molecules in the proximity of TLR signaling and upstream of the MAP kinases, especially on TRAF6/A20 and TAK1

Summary

Introduction

MAPK phosphatase (MKP)-1 dephosphorylates TXY motifs on MAPKs, thereby negatively regulating MAPKs that are involved in the synthesis of pro-inflammatory cytokines (Liu et al, 2007; Wang et al, 2007; Wang et al, 2008). MKP-1 regulates the activities of numerous transcription factors of inflammatory genes (Liu et al, 2008; Talwar, Bauerfeld et al, 2017a; Bauerfeld et al, 2020). We have shown that MKP-1–deficient BMDMs exhibit marked up-regulation of key mitochondrial proteins involved in oxidative phosphorylation (Bauerfeld et al, 2012; Bauerfeld et al, 2020). The multitude effects of MKP-1 on the innate immunity, adaptive immunity, cellular metabolism, and in cancer biology raise an interesting question of whether all these effects are dependent on MAPKs deactivation

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