Disease-causing mutations in the XIAP BIR2 domain impair NOD2-dependent immune signalling

EMBO Mol Med. 2013 Aug;5(8):1278-95. doi: 10.1002/emmm.201303090. Epub 2013 Jul 1.

Abstract

X-linked Inhibitor of Apoptosis (XIAP) is an essential ubiquitin ligase for pro-inflammatory signalling downstream of the nucleotide-binding oligomerization domain containing (NOD)-1 and -2 pattern recognition receptors. Mutations in XIAP cause X-linked lymphoproliferative syndrome type-2 (XLP2), an immunodeficiency associated with a potentially fatal deregulation of the immune system, whose aetiology is not well understood. Here, we identify the XIAP baculovirus IAP repeat (BIR)2 domain as a hotspot for missense mutations in XLP2. We demonstrate that XLP2-BIR2 mutations severely impair NOD1/2-dependent immune signalling in primary cells from XLP2 patients and in reconstituted XIAP-deficient cell lines. XLP2-BIR2 mutations abolish the XIAP-RIPK2 interaction resulting in impaired ubiquitylation of RIPK2 and recruitment of linear ubiquitin chain assembly complex (LUBAC) to the NOD2-complex. We show that the RIPK2 binding site in XIAP overlaps with the BIR2 IBM-binding pocket and find that a bivalent Smac mimetic compound (SMC) potently antagonises XIAP function downstream of NOD2 to limit signalling. These findings suggest that impaired immune signalling in response to NOD1/2 stimulation is a general defect in XLP2 and demonstrate that the XIAP BIR2-RIPK2 interaction may be targeted pharmacologically to modulate inflammatory signalling.

Keywords: BIR2; NOD2; Smac mimetic compounds; XIAP; XLP2.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Apoptosis
  • Binding Sites
  • Cell Line, Tumor
  • HEK293 Cells
  • Humans
  • Inflammation / immunology*
  • Mutation, Missense*
  • Nod2 Signaling Adaptor Protein / metabolism*
  • Protein Binding
  • Protein Structure, Tertiary
  • Receptor-Interacting Protein Serine-Threonine Kinase 2
  • Signal Transduction*
  • Ubiquitin / metabolism
  • Ubiquitination
  • X-Linked Inhibitor of Apoptosis Protein / genetics*
  • X-Linked Inhibitor of Apoptosis Protein / physiology

Substances

  • NOD2 protein, human
  • Nod2 Signaling Adaptor Protein
  • Ubiquitin
  • X-Linked Inhibitor of Apoptosis Protein
  • XIAP protein, human
  • Receptor-Interacting Protein Serine-Threonine Kinase 2