OTULIN restricts Met1-linked ubiquitination to control innate immune signaling

Mol Cell. 2013 Jun 27;50(6):818-830. doi: 10.1016/j.molcel.2013.06.004.

Abstract

Conjugation of Met1-linked polyubiquitin (Met1-Ub) by the linear ubiquitin chain assembly complex (LUBAC) is an important regulatory modification in innate immune signaling. So far, only few Met1-Ub substrates have been described, and the regulatory mechanisms have remained elusive. We recently identified that the ovarian tumor (OTU) family deubiquitinase OTULIN specifically disassembles Met1-Ub. Here, we report that OTULIN is critical for limiting Met1-Ub accumulation after nucleotide-oligomerization domain-containing protein 2 (NOD2) stimulation, and that OTULIN depletion augments signaling downstream of NOD2. Affinity purification of Met1-Ub followed by quantitative proteomics uncovered RIPK2 as the predominant NOD2-regulated substrate. Accordingly, Met1-Ub on RIPK2 was largely inhibited by overexpressing OTULIN and was increased by OTULIN depletion. Intriguingly, OTULIN-depleted cells spontaneously accumulated Met1-Ub on LUBAC components, and NOD2 or TNFR1 stimulation led to extensive Met1-Ub accumulation on receptor complex components. We propose that OTULIN restricts Met1-Ub formation after immune receptor stimulation to prevent unwarranted proinflammatory signaling.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Endopeptidases / physiology*
  • Gene Expression
  • Gene Knockdown Techniques
  • HEK293 Cells
  • Humans
  • Immunity, Innate*
  • Inflammation Mediators / metabolism
  • Methionine / metabolism*
  • NF-kappa B / metabolism
  • Nod2 Signaling Adaptor Protein / metabolism
  • Protein Interaction Mapping
  • Receptor-Interacting Protein Serine-Threonine Kinase 2 / metabolism
  • Signal Transduction*
  • Ubiquitination*
  • X-Linked Inhibitor of Apoptosis Protein / metabolism

Substances

  • Inflammation Mediators
  • NF-kappa B
  • NOD2 protein, human
  • Nod2 Signaling Adaptor Protein
  • X-Linked Inhibitor of Apoptosis Protein
  • XIAP protein, human
  • Methionine
  • RIPK2 protein, human
  • Receptor-Interacting Protein Serine-Threonine Kinase 2
  • Endopeptidases
  • gumby protein, human