The GTPase-activating protein GIT2 protects against colitis by negatively regulating Toll-like receptor signaling

Proc Natl Acad Sci U S A. 2014 Jun 17;111(24):8883-8. doi: 10.1073/pnas.1309218111. Epub 2014 May 30.

Abstract

G protein-coupled receptor kinase-interactor 2 (GIT2) regulates thymocyte positive selection, neutrophil-direction sensing, and cell motility during immune responses by regulating the activity of the small GTPases ADP ribosylation factors (Arfs) and Ras-related C3 botulinum toxin substrate 1 (Rac1). Here, we show that Git2-deficient mice were more susceptible to dextran sodium sulfate (DSS)-induced colitis, Escherichia coli, or endotoxin-shock challenge, and a dramatic increase in proinflammatory cytokines was observed in Git2 knockout mice and macrophages. GIT2 is a previously unidentified negative regulator of Toll-like receptor (TLR)-induced NF-κB signaling. The ubiquitination of TNF receptor associated factor 6 (TRAF6) is critical for the activation of NF-κB. GIT2 terminates TLR-induced NF-κB and MAPK signaling by recruiting the deubiquitinating enzyme Cylindromatosis to inhibit the ubiquitination of TRAF6. Finally, we show that the susceptibility of Git2-deficient mice to DSS-induced colitis depends on TLR signaling. Thus, we show that GIT2 is an essential terminator of TLR signaling and that loss of GIT2 leads to uncontrolled inflammation and severe organ damage.

Keywords: CYLD; GIT; IBD; TRAF6.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adenosine Diphosphate / chemistry
  • Animals
  • Cell Cycle Proteins / genetics
  • Cell Cycle Proteins / metabolism*
  • Colitis / metabolism*
  • Colitis / prevention & control*
  • Cysteine Endopeptidases / metabolism
  • Deubiquitinating Enzyme CYLD
  • Endotoxins / chemistry
  • Enzyme-Linked Immunosorbent Assay
  • Escherichia coli / metabolism
  • GTP Phosphohydrolases / metabolism*
  • GTPase-Activating Proteins
  • HEK293 Cells
  • Humans
  • Inflammation
  • Intercellular Signaling Peptides and Proteins
  • Mice
  • Mice, Knockout
  • Myeloid Differentiation Factor 88 / genetics
  • NF-kappa B / metabolism
  • Neutrophils / cytology
  • Phosphoproteins / genetics
  • Phosphoproteins / metabolism*
  • Sepsis / metabolism
  • Signal Transduction
  • TNF Receptor-Associated Factor 6 / metabolism
  • Thymocytes / metabolism
  • Toll-Like Receptors / metabolism*

Substances

  • Cell Cycle Proteins
  • Endotoxins
  • GTPase-Activating Proteins
  • Git2 protein, mouse
  • Intercellular Signaling Peptides and Proteins
  • Myd88 protein, mouse
  • Myeloid Differentiation Factor 88
  • NF-kappa B
  • Phosphoproteins
  • TNF Receptor-Associated Factor 6
  • Toll-Like Receptors
  • Adenosine Diphosphate
  • CYLD protein, mouse
  • Deubiquitinating Enzyme CYLD
  • Cysteine Endopeptidases
  • GTP Phosphohydrolases