b1 integrin signaling governs necroptosis via the chromatin remodeling factor CHD4
Fibrosis, characterized by sustained activation of myofibroblasts and excessive extracellular matrix (ECM) deposition, is known to be associated with chronic inflammation. RIPK3, a key kinase mediating TNF-driven necroptosis signaling, is upregulated in fibrosis and contributes to the TNF-mediated inflammation. In biliary duct ligation-induced liver fibrosis, we found that myofibroblasts are the major cell type expressing RIPK3. Genetic ablation of b1 integrins, the major profibrotic ECM receptors in fibroblasts, not only abolished ECM fibrillogenesis but also blunted RIPK3 expression via an epigenetic mechanism mediated by the chromatin remodeling factor CHD4. While the function of CHD4 has been conventionally linked to NuRD and ChAHP complexes, we found that CHD4 potently repressed a set of genes, including Ripk3, with high locus specificity but independent of either the NuRD or ChAHP complex. Thus, our data uncover that b1 integrin intrinsically links fibrotic signaling to RIPK3-driven inflammation via a novel mode of action of CHD4. Overall design: Chromatin accessibility analysis by ATAC-seq of Control, Chd4KO and Gatad2a/b DKO