Bid Promotes K63-Linked Polyubiquitination of Tumor Necrosis Factor Receptor Associated Factor 6 (TRAF6) and Sensitizes to Mutant SOD1-Induced Proinflammatory Signaling in Microglia

eNeuro. 2016 May 12;3(2):ENEURO.0099-15.2016. doi: 10.1523/ENEURO.0099-15.2016. eCollection Mar-Apr 2016.

Abstract

Mutations in the superoxide dismutase 1 (SOD1) gene contribute to motoneuron degeneration and are evident in 20% of familial amyotrophic lateral sclerosis cases. Mutant SOD1 induces microglial activation through a stimulation of Toll-like receptors 2 and 4 (TLR2 and TLR4). In the present study, we identified the proapoptotic Bcl-2 family protein Bid as a positive regulator of mutant SOD1-induced TLR-nuclear factor-κB (NF-κB) signaling in microglia. bid-deficient primary mouse microglia showed reduced NF-κB signaling in response to TLR4 activation or exposure to conditioned medium derived from SOD1 (G93A) expressing NSC-34 cells. Attenuation of NF-κB signaling in bid-deficient microglia was associated with lower levels of phosphorylated IKKα/β and p65, with a delayed degradation of IκBα and enhanced degradation of Peli1. Upstream of IKK, we found that Bid interacted with, and promoted, the K63-linked polyubiquitination of the E3 ubiquitin ligase tumor necrosis factor receptor associated factor 6 (TRAF6) in microglia. Our study suggests a key role for Bid in the regulation of TLR4-NF-κB proinflammatory signaling during mutant SOD1-induced disease pathology. Bid promotes TLR4-NF-κB signaling by interacting with TRAF6 and promoting TRAF6 K63-linked polyubiquitination in microglia.

Keywords: NF-κB; SOD1G93A protein; TLR; Toll-like receptor 4; microglia.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • BH3 Interacting Domain Death Agonist Protein / deficiency*
  • BH3 Interacting Domain Death Agonist Protein / genetics
  • Cells, Cultured
  • Coculture Techniques
  • Culture Media, Conditioned / pharmacology
  • Female
  • Gene Expression Regulation / genetics
  • Humans
  • I-kappa B Kinase / metabolism
  • Lipopolysaccharides / pharmacology
  • Male
  • Mice
  • Mice, Inbred C57BL
  • Mice, Transgenic
  • Microglia / physiology*
  • Mutation / genetics*
  • Phosphatidylcholines / pharmacology
  • Signal Transduction / drug effects
  • Signal Transduction / physiology*
  • Superoxide Dismutase / genetics*
  • Superoxide Dismutase / metabolism
  • TNF Receptor-Associated Factor 6 / genetics
  • TNF Receptor-Associated Factor 6 / metabolism*
  • Toll-Like Receptor 4 / genetics
  • Toll-Like Receptor 4 / metabolism
  • Ubiquitination / drug effects
  • Ubiquitination / genetics

Substances

  • BH3 Interacting Domain Death Agonist Protein
  • Bid protein, mouse
  • Culture Media, Conditioned
  • Lipopolysaccharides
  • Phosphatidylcholines
  • TNF Receptor-Associated Factor 6
  • Tlr4 protein, mouse
  • Toll-Like Receptor 4
  • oxidized-L-alpha-1-palmitoyl-2-arachidonoyl-sn-glycero-3-phosphorylcholine
  • SOD1 G93A protein
  • Superoxide Dismutase
  • I-kappa B Kinase