P4-ATPase endosomal recycling relies on multiple retromer-dependent localization signals

Type IV P-type ATPases (P4-ATPases) are lipid flippases that generate an asymmetric membrane organization essential for cell viability. The five budding yeast P4-ATPases traffic between the Golgi complex, plasma membrane, and endosomes but how they are recycled from the endolysosomal system to the Golgi complex is poorly understood. In this study, we find that P4-ATPase endosomal recycling is primarily driven by the retromer complex and the F-box protein Rcy1. Defects in P4-ATPase recycling result in their mislocalization to the vacuole and a substantial loss of membrane asymmetry. The P4-ATPases contain multiple predicted retromer sorting signals, and the characterization of these signals in Dnf1 and Dnf2 led to the identification of a novel retromer-dependent signal, IPM[ST] that acts redundantly with predicted motifs. Together, these results emphasize the importance of endosomal recycling for the functional localization of P4-ATPases and membrane organization. SIGNIFICANCE STATEMENT center dot P4-ATPase intracellular trafficking is critical for establishing cell membrane asymmetry; however, their recycling from the endolysosomal system to the Golgi is complex and poorly understood. center dot Using Saccharomyces cerevisiae, the authors found that the retromer complex is the primary driver of P4-ATPase recycling out of the endolysosomal system and further characterized a novel retromer-dependent sorting signal, IPM[TS]. In addition, P4-ATPase mislocalization in retromer mutants causes significant changes in membrane organization. center dot As both P4-ATPase and retromer deficiency are linked to human neurological disease, their role in membrane organization may be a key factor in neurodegeneration.