ER-localized Hrd1 ubiquitinates and inactivates Usp15 to promote TLR4-induced inflammation during bacterial infection

Nat Microbiol. 2019 Dec;4(12):2331-2346. doi: 10.1038/s41564-019-0542-2.

Abstract

The special organelle-located MAVS, STING and TLR3 are important for clearing viral infections. Although TLR4 triggers NF-κB activation to produce pro-inflammatory cytokines for bacterial clearance, effectors with special organelle localization have not been identified. Here, we screened more than 280 E3 ubiquitin ligases and discovered that the endoplasmic reticulum-located Hrd1 regulates TLR4-induced inflammation during bacterial infection. Hrd1 interacts directly with the deubiquitinating enzyme Usp15. Unlike the classical function of Hrd1 in endoplasmic reticulum-associated degradation, Usp15 is not degraded but loses its deubiquitinating activity for IκBα deubiquitination, resulting in excessive NF-κB activation. Importantly, Hrd1 deficiency in macrophages protects mice against lipopolysaccharide-induced septic shock, and knockdown of Usp15 in Hrd1-knockout macrophages restores the reduced IL-6 production. This study proposes that there is crosstalk between Hrd1 and TLR4, thereby linking the endoplasmic reticulum-plasma membrane function during bacterial infection.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Bacterial Infections / immunology*
  • Endoplasmic Reticulum / metabolism*
  • Endoplasmic Reticulum / pathology
  • Endoplasmic Reticulum-Associated Degradation
  • Gene Knockdown Techniques
  • HEK293 Cells
  • Humans
  • Inflammation / metabolism*
  • Lipopolysaccharides / adverse effects
  • Macrophages / metabolism
  • Mice
  • Mice, Knockout
  • Proteolysis
  • Salmonella typhimurium
  • Shock, Septic / chemically induced
  • Toll-Like Receptor 4 / metabolism*
  • Ubiquitin-Protein Ligases / genetics
  • Ubiquitin-Protein Ligases / metabolism*
  • Ubiquitin-Specific Proteases / genetics
  • Ubiquitin-Specific Proteases / metabolism*
  • Ubiquitination*

Substances

  • Lipopolysaccharides
  • Tlr4 protein, mouse
  • Toll-Like Receptor 4
  • Syvn1 protein, mouse
  • Ubiquitin-Protein Ligases
  • Ubiquitin-Specific Proteases
  • Usp15 protein, mouse