ER-to-lysosome Ca²⁺ refilling followed by K⁺ efflux-coupled store-operated Ca²⁺ entry in inflammasome activation and metabolic inflammation.

Abstract

We studied lysosomal Ca²⁺ in inflammasome. Lipopolysaccharide (LPS) + palmitic acid (PA) decreased lysosomal Ca²⁺ ([Ca²⁺]_Lys) and increased [Ca²⁺]_i through mitochondrial ROS, which was suppressed in <i>Trpm2</i>-KO macrophages. Inflammasome activation and metabolic inflammation in adipose tissue of high-fat diet (HFD)-fed mice were ameliorated by <i>Trpm2</i> KO. ER→lysosome Ca²⁺ refilling occurred after lysosomal Ca²⁺ release whose blockade attenuated LPS + PA-induced inflammasome. Subsequently, store-operated Ca²⁺entry (SOCE) was activated whose inhibition suppressed inflammasome. SOCE was coupled with K⁺ efflux whose inhibition reduced ER Ca²⁺ content ([Ca²⁺]_ER) and impaired [Ca²⁺]_Lys recovery. LPS + PA activated KCa3.1 channel, a Ca²⁺-activated K⁺ channel. Inhibitors of KCa3.1 channel or <i>Kcnn4</i> KO reduced [Ca²⁺]_ER, attenuated increase of [Ca²⁺]_i or inflammasome activation by LPS + PA, and ameliorated HFD-induced inflammasome or metabolic inflammation. Lysosomal Ca²⁺ release induced delayed JNK and ASC phosphorylation through CAMKII-ASK1. These results suggest a novel role of lysosomal Ca²⁺ release sustained by ER<b>→</b>lysosome Ca²⁺ refilling and K⁺ efflux through KCa3.1 channel in inflammasome activation and metabolic inflammation.