RSK2 is required for TRAF6 phosphorylation-mediated colon inflammation

Oncogene. 2018 Jun;37(26):3501-3513. doi: 10.1038/s41388-018-0167-6. Epub 2018 Mar 22.

Abstract

Inflammation is a complex biological host reaction to tissue damage, infection and trauma. Extensive study of the inflammatory response has led to the identification of several protein kinases that are essential for signaling and could be potential therapeutic targets. The RSK family of kinases has multiple cellular functions. In our study, we found that RSK2 is a mediator for inflammation signaling and interacts with TRAF6. In vitro kinase assay results indicated that RSK2 strongly phosphorylates TRAF6 at serines 46, 47 and 48. Ectopic overexpression of TRAF6 or knocking down RSK2 expression confirmed that RSK2 is a positive regulator of TRAF6 K63 ubiquitination. TRAF6 is also required for RSK2 ubiquitination. TRAF6 bridges the TNF receptor superfamily and intracellular signaling for the induction of proinflammatory cytokines. We developed a colon inflammation model using RSK2 wild type (WT) and knockout (KO) mice. As expected, F4/80 and CD3 infiltration were significantly upregulated in WT mice compared to RSK2 KO mice. Furthermore, inflammation signaling, including Ikkα/β, p38 and JNKs, was dramatically upregulated in WT mice. Colon tissue immunoprecipitation results further confirmed that TRAF6 K63 ubiquitination was lower in RSK2 KO mice. Overall, these results indicate that phosphorylation of TRAF6 (S46, 47, 48) by RSK2 is required for TRAF6 K63 ubiquitination and inflammation signaling.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Antigens, Differentiation / metabolism
  • CD3 Complex / metabolism
  • Cell Line, Tumor
  • Colitis / pathology*
  • Colon / immunology
  • Colon / pathology*
  • Female
  • HEK293 Cells
  • Humans
  • Inflammation / pathology
  • Intracellular Signaling Peptides and Proteins
  • JNK Mitogen-Activated Protein Kinases / metabolism
  • MAP Kinase Signaling System
  • Male
  • Mice
  • Mice, Inbred BALB C
  • Mice, Knockout
  • NF-KappaB Inhibitor alpha / metabolism
  • Phosphorylation
  • RAW 264.7 Cells
  • Ribosomal Protein S6 Kinases, 90-kDa / genetics*
  • TNF Receptor-Associated Factor 6 / metabolism*
  • Ubiquitination / genetics
  • p38 Mitogen-Activated Protein Kinases / metabolism

Substances

  • Antigens, Differentiation
  • CD3 Complex
  • Intracellular Signaling Peptides and Proteins
  • TNF Receptor-Associated Factor 6
  • Tifab protein, human
  • monocyte-macrophage differentiation antigen
  • NF-KappaB Inhibitor alpha
  • Ribosomal Protein S6 Kinases, 90-kDa
  • ribosomal protein S6 kinase, 90kDa, polypeptide 3
  • JNK Mitogen-Activated Protein Kinases
  • p38 Mitogen-Activated Protein Kinases