Reversible ubiquitination shapes NLRC5 function and modulates NF-κB activation switch

J Cell Biol. 2015 Dec 7;211(5):1025-40. doi: 10.1083/jcb.201505091. Epub 2015 Nov 30.

Abstract

NLRC5 is an important regulator in innate immune responses. However, the ability of NLRC5 to inhibit NF-κB activation is controversial in different cell types. How dynamic modification of NLRC5 shapes NF-κB signaling remains unknown. We demonstrated that NLRC5 undergoes robust ubiquitination by TRAF2/6 after lipopolysaccharide treatment, which leads to dissociation of the NLRC5-IκB kinase complex. Experimental and mathematical analyses revealed that the K63-linked ubiquitination of NLRC5 at lysine 1,178 generates a coherent feedforward loop to further sensitize NF-κB activation. Meanwhile, we found USP14 specifically removes the polyubiquitin chains from NLRC5 to enhance NLRC5-mediated inhibition of NF-κB signaling. Furthermore, we found that different cell types may exhibit different sensitivities to NF-κB activation in response to NLRC5 ablation, possibly as a result of the various intrinsic levels of deubiquitinases and NLRC5. This might partially reconcile controversial studies and explain why NLRC5 exhibits diverse inhibitory efficiencies. Collectively, our results provide the regulatory mechanisms of reversible NLRC5 ubiquitination and its role in the dynamic control of innate immunity.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Computer Simulation
  • Fibroblasts / metabolism
  • HEK293 Cells
  • HeLa Cells
  • Humans
  • Immunity, Innate
  • Intracellular Signaling Peptides and Proteins / chemistry*
  • Kinetics
  • Lipopolysaccharides / chemistry
  • Lysine / chemistry
  • Mice
  • Models, Theoretical
  • NF-kappa B p50 Subunit / metabolism*
  • RNA Interference
  • Signal Transduction
  • TNF Receptor-Associated Factor 2 / metabolism
  • TNF Receptor-Associated Factor 6 / metabolism
  • Ubiquitin / chemistry*
  • Ubiquitin Thiolesterase / genetics
  • Ubiquitin Thiolesterase / metabolism
  • Ubiquitination

Substances

  • Intracellular Signaling Peptides and Proteins
  • Lipopolysaccharides
  • NF-kappa B p50 Subunit
  • NFKB1 protein, human
  • NLRC5 protein, human
  • NLRC5 protein, mouse
  • TNF Receptor-Associated Factor 2
  • TNF Receptor-Associated Factor 6
  • USP14 protein, human
  • Ubiquitin
  • Usp14 protein, mouse
  • Nfkb1 protein, mouse
  • Ubiquitin Thiolesterase
  • Lysine