Disease-associated dominant negative CARD11 mutations perturb the CARD11 Opening step during T cell receptor-induced activation of NF-κB and JNK2

Abstract

Abstract CARD11 is an oligomeric, multidomain scaffold that mediates lymphocyte activation. Upon antigen receptor engagement, CARD11 becomes active and signals through NF-κB, JNK, and mTOR to elicit the adaptive immune response. The CARD11 signaling cycle consists of at least four stages beginning with the Opening step, followed by Cofactor Recruitment, Enzyme Activation, and Complex Disassembly. Primary Immunodeficiency Diseases (PIDDs) have been attributed to both autosomal dominant and recessive CARD11 variants. Combined Immunodeficiency with atopy is caused by the inheritance of a single dominant negative CARD11 allele, but the mechanistic basis for the dominant negative effects is not well understood. In this study, we investigated the mechanistic basis for dominant negative CARD11 mutations in T cells by assessing the activity of loss-of-function variants in the presence and absence of co-expressed wild-type CARD11. In the absence of wild-type CARD11, the variants perturbed the Opening step and downstream signaling steps, including recruitment of Bcl10, HOIP, and MALT1 to CARD11, Bcl10 polyubiquitinylation, MALT1 protease activity, NF-κB and JNK2 activation, and IL-2 production. When the variants were co-expressed with wild-type CARD11, a range of dominant negative effects on NF-κB activation was observed, which correlated with the ability of the CARD11 oligomer to open, recruit cofactors, and mediate IL-2 production. We conclude that dominant negative mutations interfere with the CARD11 Opening step and provide insights into the manifestation of PIDDs caused by the inheritance of dominant and recessive CARD11 alleles.