AUTHOR=De Bruyne Marieke , Hoste Levi , Bogaert Delfien J. , Van den Bossche Lien , Tavernier Simon J. , Parthoens Eef , Migaud Mélanie , Konopnicki Deborah , Yombi Jean Cyr , Lambrecht Bart N. , van Daele Sabine , Alves de Medeiros Ana Karina , Brochez Lieve , Beyaert Rudi , De Baere Elfride , Puel Anne , Casanova Jean-Laurent , Goffard Jean-Christophe , Savvides Savvas N. , Haerynck Filomeen , Staal Jens , Dullaers Melissa
TITLE=A CARD9 Founder Mutation Disrupts NF-κB Signaling by Inhibiting BCL10 and MALT1 Recruitment and Signalosome Formation
JOURNAL=Frontiers in Immunology
VOLUME=9
YEAR=2018
URL=https://www.frontiersin.org/journals/immunology/articles/10.3389/fimmu.2018.02366
DOI=10.3389/fimmu.2018.02366
ISSN=1664-3224
ABSTRACT=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.