Transport through recycling endosomes requires EHD1 recruitment by a phosphatidylserine translocase

Abstract

P ₄-ATPases translocate aminophospholipids, such as phosphatidylserine (PS), to the cytosolic leaflet of membranes. PS is highly enriched in recycling endosomes (REs) and is essential for endosomal membrane traffic. Here, we show that PS flipping by an RE-localized P ₄-ATPase is required for the recruitment of the membrane fission protein EHD1. Depletion of ATP8A1 impaired the asymmetric transbilayer distribution of PS in REs, dissociated EHD1 from REs, and generated aberrant endosomal tubules that appear resistant to fission. EHD1 did not show membrane localization in cells defective in PS synthesis. ATP8A2, a tissue-specific ATP8A1 paralogue, is associated with a neurodegenerative disease (CAMRQ). ATP8A2, but not the disease-causative ATP8A2 mutant, rescued the endosomal defects in ATP8A1-depleted cells. Primary neurons from Atp8a2 ^−/− mice showed a reduced level of transferrin receptors at the cell surface compared to Atp8a2 ^+/+ mice. These findings demonstrate the role of P ₄-ATPase in membrane fission and give insight into the molecular basis of CAMRQ.