A distinctive PI(4,5)P 2 compartment forms during entosis and related engulfment processes

Entosis is a form of cell cannibalism prevalent in human tumours. During entosis, one live and viable epithelial cell is completely internalised by another, then housed inside a large, single-membrane, endolysosomal vacuole in the host cytosol. The composition and maturation of this specialised, macroendocytic compartment has not been fully defined, but ultimately, the inner cell is killed and digested by host lysosomes. Here, we investigate the molecular characteristics and maturation profile of the entotic vacuole. Like phagosomes and macropinosomes, this vacuole undergoes a series of phospholipid modifications, but its maturation profile bears distinctive dynamics. While PI(4,5)P 2 is lost rapidly during phagosome maturation, entosis yields an unusual, intracellular PI(4,5)P 2 -positive compartment, that can persist for hours, suggesting vacuole maturation is uncoupled from membrane scission. Loss of PI(4,5)P 2 is eventually triggered, a requisite step for lysosomal killing of the internalised cell. More broadly, PI(4,5)P 2 -positive vacuoles also form during T-cell engulfment by thymic nurse cells, dependent on ROCK activity, suggesting this distinctive compartment represents a shared feature of entosis-like cell engulfments.