The ATPase Activity of the Phosphatidylethanolamine Flippase TAT-5 Inhibits Extracellular Vesicle Budding from the Plasma Membrane.

Cells release extracellular vesicles (EVs) from their surface, but the mechanisms that govern EV release by plasma membrane budding are poorly understood. The lipid flippase TAT-5 inhibits EV release from the plasma membrane in C. elegans , but how the level of flippase activity regulates EV release was unknown. We generated point mutations in the DGET motif of TAT-5 predicted to lead to a partial or complete loss of ATPase activity. We discovered that tat-5(E246Q) mutants were sterile, while tat-5(D244T) mutants produced embryos that arrested during development. Using degron-based reporters, we found that EV release was increased in tat-5(D244T) mutant embryos and that phagocytosis was also disrupted. These data suggest that a low level of flippase activity can promote fertility, while a higher level of flippase activity is required to inhibit EV release, allow phagocytosis, and carry out embryonic development.