A CARD9 Founder Mutation Disrupts NF-κB Signaling by Inhibiting BCL10 and MALT1 Recruitment and Signalosome Formation

Front Immunol. 2018 Oct 31:9:2366. doi: 10.3389/fimmu.2018.02366. eCollection 2018.


Background: Inherited CARD9 deficiency constitutes a primary immunodeficiency predisposing uniquely to chronic and invasive fungal infections. Certain mutations are shown to negatively impact CARD9 protein expression and/or NF-κB activation, but the underlying biochemical mechanism remains to be fully understood. Objectives: To investigate a possible founder origin of a known CARD9 R70W mutation in five families of Turkish origin. To explore the biochemical mechanism of immunodeficiency by R70W CARD9. Methods: We performed haplotype analysis using microsatellite markers and SNPs. We designed a model system exploiting a gain-of-function (GOF) CARD9 L213LI mutant that triggers constitutive NF-κB activation, analogous to an oncogenic CARD11 mutant, to study NF-κB signaling and signalosome formation. We performed reporter assays, immunoprecipitation and confocal imaging on HEK cells overexpressing different CARD9 variants. Results: We identified a common haplotype, thus providing evidence for a common Turkish founder. CARD9 R70W failed to activate NF-κB and abrogated NF-κB activation by WT CARD9 and by GOF CARD9. Notably, R70W CARD9 also exerted negative effects on NF-κB activation by CARD10, CARD11, and CARD14. Consistent with the NF-κB results, the R70W mutation prevented GOF CARD9 to pull down the signalosome partner proteins BCL10 and MALT1. This reflected into drastic reduction of BCL10 filamentous assemblies in a cellular context. Indeed, structural analysis revealed that position R70 in CARD9 maps at the putative interface between successive CARD domains in CARD9 filaments. Conclusions: The R70W mutation in CARD9 prevents NF-κB activation by inhibiting productive interactions with downstream BCL10 and MALT1, necessary for assembly of the filamentous CARD9-BCL10-MALT1 signalosome.

Keywords: BCL10; CARD9 deficiency; CBM complex; MALT1; NF-κB; filament; founder mutation; signalosome.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • B-Cell CLL-Lymphoma 10 Protein / metabolism*
  • CARD Signaling Adaptor Proteins / chemistry
  • CARD Signaling Adaptor Proteins / genetics*
  • Cell Line
  • Disease Susceptibility
  • Female
  • Founder Effect*
  • Gain of Function Mutation
  • Humans
  • Male
  • Models, Molecular
  • Mucosa-Associated Lymphoid Tissue Lymphoma Translocation 1 Protein / metabolism*
  • Mutation*
  • NF-kappa B / metabolism*
  • Pedigree
  • Protein Binding
  • Protein Conformation
  • Signal Transduction*
  • Structure-Activity Relationship
  • T-Lymphocyte Subsets / immunology
  • T-Lymphocyte Subsets / metabolism


  • B-Cell CLL-Lymphoma 10 Protein
  • BCL10 protein, human
  • CARD Signaling Adaptor Proteins
  • CARD9 protein, human
  • NF-kappa B
  • MALT1 protein, human
  • Mucosa-Associated Lymphoid Tissue Lymphoma Translocation 1 Protein