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

Authors

• O Rabinovich Ernst
• J Sun
• B Lin
• B Banoth
• C Rice
• S Katz
• SJ Vayttaden
• M Dorrington
• J Liang
• N Slepushkina
• E Buehler
• Z Wang
• D McVicar
• J Khillan
• C Bryant
• F Sutterwala
• S Martin
• M Lal-Nag
• I Fraser

Abstract

While there has been remarkable progress in understanding the mechanisms of inflammasome activation post-inflammasome assembly, the cellular processes that precede inflammasome activation are less clearly understood. To address this, we have conducted a genome-scale siRNA screen for the non-canonical inflammasome response to cytosolic LPS. We identified numerous expected genes among the top hits, including Myd88, Irak4, Irak2, Casp4, and Gsdmd. We noted a significant enrichment of mitochondrial-associated genes, supporting an important role for the mitochondria and cellular metabolism in inflammasome activation. Among these genes we identified three nucleotide diphosphate kinases, and we further investigated the role of the Nme4 gene. We find that Nme4-/- macrophages are dramaticly defected in IL-1 response to cytosolic LPS. They exhibit constitutively elevated cardiolipin levels in their mitochondrial outer membrane and show defective cardiolipin switching in response to mitochondrial stress signals. Interestingly, we find that in the absence of Nme4 the priming step of inflammasome activation is markedly defected. Metabolic analysis suggests that Nme4 is critical to the glycolytic commitment induced during inflammasome priming, while NF-kB and MAPK activation isn’t affected in primed Nme4-/- cells, 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. In ongoing studies, dynamic live cell imaging reporters for mitochondrial function and inflammasome triggering are used to further delineate the mitochondrial and metabolic processes that support inflammasome activation. This work was supported by the Intramural Research Program of NIAID.

Scientific Focus Area: Immunology

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