A genome-wide screen identifies a critical role for mitochondrial NDP kinases in inflammasome activation

While there has been a remarkable progress in understanding the mechanisms of cytosolic LPS sensing by caspase11, the cellular processes regulating non-canonical inflammasome activation are less clearly understood. To address this, we conducted a genome-scale siRNA screen for macrophage responses to cytosolic LPS by IL-1α HTRF assay. We identified numerous expected genes among the top screen hits, including Myd88, Irak4, Irak2, Casp4, Gsdmd and Il1a, and also discovered numerous novel regulators. Significant mitochondrial-associated gene enrichment supported an important role for the mitochondria and cellular metabolism in inflammasome activation. Specifically, we investigated the role of Nme4 in inflammasome activation and find Nme4^-/- macrophages have a strongly diminished IL-1α response to cytosolic-LPS, show defective ROS- and cardiolipin-dependent mitochondrial licensing, and have markedly dysregulated inflammasome priming and triggering. Metabolic analysis suggests Nme4 is critical to priming-induced glycolytic commitment, however we observe normal NF-κB and MAPK activation in primed Nme4^-/-, suggesting the mitochondrial and metabolic contribution to inflammasome priming occurs independently of these signaling responses. We also find that Nme4 deficient mice show substantial resistance to LPS-induced endotoxic shock. Our data delineate the mitochondrial and metabolic processes critical to inflammasome activation.

This work was supported by the Intramural Research Program of NIAID, NIH.