Orai1 is an Entotic Ca 2+ Channel for Non-Apoptotic Cell Death, Entosis in Cancer Development.

Entosis is a non-apoptotic cell death process that forms characteristic cell-in-cell structures in cancers, killing invading cells. Intracellular Ca 2+ dynamics are essential for cellular processes, including actomyosin contractility, migration, and autophagy. However, the significance of Ca 2+ and Ca 2+ channels participating in entosis is unclear. Here, it is shown that intracellular Ca 2+ signaling regulates entosis via SEPTIN-Orai1-Ca 2+ /CaM-MLCK-actomyosin axis. Intracellular Ca 2+ oscillations in entotic cells show spatiotemporal variations during engulfment, mediated by Orai1 Ca 2+ channels in plasma membranes. SEPTIN controlled polarized distribution of Orai1 for local MLCK activation, resulting in MLC phosphorylation and actomyosin contraction, leads to internalization of invasive cells. Ca 2+ chelators and SEPTIN, Orai1, and MLCK inhibitors suppress entosis. This study identifies potential targets for treating entosis-associated tumors, showing that Orai1 is an entotic Ca 2+ channel that provides essential Ca 2+ signaling and sheds light on the molecular mechanism underlying entosis that involves SEPTIN filaments, Orai1, and MLCK.