Raver1 links Ripk1 RNA splicing to caspase-8-mediated pyroptotic cell death, inflammation, and pathogen resistance
Multiple cell death and inflammatory signaling pathways converge on two critical factors: receptor interacting serine/threonine kinase 1 (RIPK1) and caspase-8. Careful regulation of these molecules is critical to control apoptosis, pyroptosis and inflammation. Here we discovered a pivotal role of Raver1 as an essential regulator of Ripk1 pre-mRNA splicing, expression, and functionality, and the subsequent caspase-8-dependent inflammatory cell death. Macrophages from Raver1-deficient mice exhibit altered splicing of Ripk1, accompanied by diminished cell death and reduced activation of caspase-8, Gasdermin D and E, caspase-1, as well as decreased interleukin-18 (IL-18) and IL-1ß production. These effects were triggered by Yersinia bacteria, or by restraining TAK1 or IKKß in the presence of LPS, TNF family members, or IFN?. Consequently, animals lacking Raver1 showed heightened susceptibility to Yersinia infection. Raver1 and RIPK1 also controlled the expression and function of the C-type lectin receptor Mincle. Our study underscores the critical regulatory role of Raver1 in modulating innate immune responses and highlights its significance in directing in vivo and in vitro inflammatory processes. Overall design: To investigate the function of Raver1 in the regulation of cell death and inflammation, we established RNA-seq samples from WT and Raver1-/-  bone marrow-derived macrophages (BMDMs), each from 3 different mice as biological triplicates. Cells were either untreated (NT), TNF or TNF+TAK1-i treated for 1 hour. We then performed differential gene expression profiling and splicing analysis on RNAseq data comparing WT to Raver1-/- cells.