TRAF6-mediated degradation of DOK3 is required for production of IL-6 and TNFα in TLR9 signaling

Mol Immunol. 2015 Dec;68(2 Pt C):699-705. doi: 10.1016/j.molimm.2015.10.021. Epub 2015 Nov 6.

Abstract

Our previous study showed that the downstream of kinase 3 (DOK3) is degraded during macrophage stimulation with CpG. However, the underlying mechanism and role in Toll-like receptor 9 (TLR9) signaling remains elusive. In this study, we demonstrate that CpG treatment leads to ubiquitin-mediated degradation of DOK3 via interaction with an E3 ligase TNFR-associated factor 6 (TRAF6). We also identified the 27th amino acid (lysine) of DOK3 is responsible for Ly48 polyubiquitination of DOK3. Furthermore, reintroduction of DOK3 (K27R) into DOK3-deficient macrophages abolishes DOK3 degradation induced by CpG and suppresses the production of IL-6 and TNFα. More importantly, our study uncovers a novel role of an E3 ligase TRAF6, namely, TRAF6 is also able to catalyse Lys 48 polyubiquitylation of target protein except for Lys 63 polyubiquitylation.

Keywords: DOK3; TLR9; TRAF6.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adaptor Proteins, Signal Transducing / immunology
  • Adaptor Proteins, Signal Transducing / metabolism*
  • Animals
  • Cells, Cultured
  • Immunoblotting
  • Immunoprecipitation
  • Interleukin-6 / biosynthesis*
  • Macrophages / immunology
  • Macrophages / metabolism
  • Mice
  • RNA, Small Interfering
  • Real-Time Polymerase Chain Reaction
  • TNF Receptor-Associated Factor 6 / immunology
  • TNF Receptor-Associated Factor 6 / metabolism*
  • Toll-Like Receptor 9 / immunology
  • Toll-Like Receptor 9 / metabolism*
  • Transfection
  • Tumor Necrosis Factor-alpha / biosynthesis*

Substances

  • Adaptor Proteins, Signal Transducing
  • Dok3 protein, mouse
  • Interleukin-6
  • RNA, Small Interfering
  • TNF Receptor-Associated Factor 6
  • Tlr9 protein, mouse
  • Toll-Like Receptor 9
  • Tumor Necrosis Factor-alpha
  • interleukin-6, mouse