Identification of the SLAM Adapter Molecule EAT-2 as a Lupus-Susceptibility Gene That Acts through Impaired Negative Regulation of Dendritic Cell Signaling

Abstract

We showed previously that C57BL/6 congenic mice with an introgressed homozygous 70 cM (125.6 Mb) to 100 cM (179.8 Mb) interval on c1 from the lupus-prone New Zealand Black (NZB) mouse develop high titers of antinuclear Abs and severe glomerulonephritis. Using subcongenic mice, we found that a genetic locus in the 88–96 cM region was associated with altered dendritic cell (DC) function and synergized with T cell functional defects to promote expansion of pathogenic proinflammatory T cell subsets. In this article, we show that the promoter region of the NZB gene encoding the SLAM signaling pathway adapter molecule EWS-activated transcript 2 (EAT-2) is polymorphic, which results in an ∼70% reduction in EAT-2 in DC. Silencing of the EAT-2 gene in DC that lacked this polymorphism led to increased production of IL-12 and enhanced differentiation of T cells to a Th1 phenotype in T cell–DC cocultures, reproducing the phenotype observed for DC from congenic mice with the NZB c1 70–100 cM interval. SLAM signaling was shown to inhibit production of IL-12 by CD40L-activated DCs. Consistent with a role for EAT-2 in this inhibition, knockdown of EAT-2 resulted in increased production of IL-12 by CD40-stimulated DC. Assessment of downstream signaling following CD40 cross-linking in the presence or absence of SLAM cross-linking revealed that SLAM coengagement blocked activation of p38 MAPK and JNK signaling pathways in DC, which was reversed in DC with the NZB EAT-2 allele. We conclude that EAT-2 negatively regulates cytokine production in DC downstream of SLAM engagement and that a genetic polymorphism that disturbs this process promotes the development of lupus.

Multiple tolerance defects contribute to the breach of B cell tolerance in New Zealand Black chromosome 1 congenic mice

“…Studies in lupus-prone mice have revealed numerous B and T cell tolerance defects that contribute to autoantibody production [13,23,29,43]; however, the manner in which these tolerance defects reinforce one another, and the critical point at which the balance tips to autoimmunity, remains unclear. In this study, we show that mice with the 96–100 cM interval from NZB chromosome 1 breach anergy to the neo-self antigen HEL, with significantly higher levels of anti-HEL Abs and antibody-producing cells compared with their non-autoimmune B6 counterparts.…”

Dendritic Cells in Systemic Lupus Erythematosus: From Pathogenic Players to Therapeutic Tools

“…Besides the opportunity to assess the relative and temporal contribution of different DC populations to the development of specific disease manifestations, mouse models also allow for the identification of specific processes in DCs which affect disease development. Targeted deletion of regulatory molecules associated with SLE susceptibility in humans, including Shp1, A20, Blimp-1, Lyn, or Eat-2, specifically in CD11c + cells resulted in increased DC activity and development of inflammatory and autoimmune phenotypes characterized by the production of autoreactive antibodies and several manifestations of SLE, including severe glomerulonephritis [ 128 – 132 ].…”

B cell contribution of the CD4+T cell inflammatory phenotypes in systemic lupus erythematosus

“…T:B interactions regulated by SAP and Ly108 ( Slamf6 ) as well as CD84 ( Slamf5 ) are necessary for GC formation [62]. Mutations in SLAM family genes [63] as well as in EAT-2 [64] have been associated with lupus susceptibility in mice. The SLAM family genes are arranged in a cluster in tight linkage disequilibrium, and it has been difficult to delineate the contribution of each gene to the autoimmune process [65].…”