ER-to-lysosome Ca 2+ refilling followed by K + efflux-coupled store-operated Ca 2+ entry in inflammasome activation and metabolic inflammation.

We studied lysosomal Ca 2+ in inflammasome. Lipopolysaccharide (LPS) + palmitic acid (PA) decreased lysosomal Ca 2+ ([Ca 2+ ] Lys ) and increased [Ca 2+ ] i through mitochondrial ROS, which was suppressed in Trpm2 -KO macrophages. Inflammasome activation and metabolic inflammation in adipose tissue of high-fat diet (HFD)-fed mice were ameliorated by Trpm2 KO. ER→lysosome Ca 2+ refilling occurred after lysosomal Ca 2+ release whose blockade attenuated LPS + PA-induced inflammasome. Subsequently, store-operated Ca 2+ entry (SOCE) was activated whose inhibition suppressed inflammasome. SOCE was coupled with K + efflux whose inhibition reduced ER Ca 2+ content ([Ca 2+ ] ER ) and impaired [Ca 2+ ] Lys recovery. LPS + PA activated KCa3.1 channel, a Ca 2+ -activated K + channel. Inhibitors of KCa3.1 channel or Kcnn4 KO reduced [Ca 2+ ] ER , attenuated increase of [Ca 2+ ] i or inflammasome activation by LPS + PA, and ameliorated HFD-induced inflammasome or metabolic inflammation. Lysosomal Ca 2+ release induced delayed JNK and ASC phosphorylation through CAMKII-ASK1. These results suggest a novel role of lysosomal Ca 2+ release sustained by ER → lysosome Ca 2+ refilling and K + efflux through KCa3.1 channel in inflammasome activation and metabolic inflammation.