Abstract
Ubiquitination and phosphorylation are reversible post-translational 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 mitogen activated kinases (MAPKs). We show that the lack of MKP-1 modulates the landscape of ubiquitin ligases and deubiquitinase enzymes (DUBs). MKP-1 deficient mice 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.
Abbreviations
- MAPKs
- mitogen activated kinases
- MKP
- MAPK phosphatase
- TLR
- Toll-like receptors
- IL-1R
- interleukin-1 receptor
- TRAF6
- Tumor necrosis factor receptor activated factor 6
- TAK1
- Transforming growth factor b-activated kinase 1
- IRAKs
- interleukin 1 receptor–associated kinases
- PAMPs
- pathogen-associated molecular patterns
- TCR
- T cell receptor
- E1
- ubiquitin-activating enzyme
- E2
- ubiquitin conjugating enzyme
- E3
- ubiquitin ligase enzyme
- Ub
- polyubiquitination
- DUBs
- deubiquitinase enzymes
- USPs
- ubiquitin-specific proteases
- Ubc13
- Ubiquitin conjugation enzyme 13
- UCHs
- ubiquitin carboxy-terminal hydrolases
- TNFAIP3
- tumor necrosis factor alpha-induced protein 3
- OTUs
- ovarian-tumor proteases
- JAMM
- Machado–Joseph disease protein domain-associated metallopeptidases
- BMDMs
- bone marrow derived murine macrophages
- ELISA
- enzyme-linked immunosorbent assay
- LPS
- lipopolysaccharide
- IL-1β
- interleukin-1beta
- TNF
- tumor necrosis factor
- PVDF
- polyvinylidene difluoride
- β-ME
- beta mercaptoethanol