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 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 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 Kcnn4 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→lysosome Ca²⁺ refilling and K⁺ efflux through KCa3.1 channel in inflammasome activation and metabolic inflammation.

Keywords: diabetes; immunology; inflammation; lipid; lysosome; mouse.