Drs2p-related P-type ATPases Dnf1p and Dnf2p Are Required for Phospholipid Translocation across the Yeast Plasma Membrane and Serve a Role in Endocytosis

  • Pomorski T
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Abstract

Plasma membranes in eukaryotic cells display asymmetric lipid distributions with aminophospholipids concentrated in the inner and sphingolipids in the outer leaflet. This asymmetry is maintained by {ATP-driven} lipid transporters whose identities are unknown. The yeast plasma membrane contains two P-type {ATPases,} Dnf1p and Dnf2p, with structural similarity to {ATPase} {II,} a candidate aminophospholipid translocase from bovine chromaffin granules. Loss of Dnf1p and Dnf2p virtually abolished {ATP-dependent} transport of {NBD-labeled} phosphatidylethanolamine, phosphatidylserine, and phosphatidylcholine from the outer to the inner plasma membrane leaflet, leaving transport of sphingolipid analogs unaffected. Labeling with trinitrobenzene sulfonic acid revealed that the amount of phosphatidylethanolamine exposed on the surface of {Deltadnf1Deltadnf2} cells increased twofold relative to wild-type cells. Phosphatidylethanolamine exposure by {Deltadnf1Deltadnf2} cells further increased upon removal of Drs2p, an {ATPase} {II} homolog in the yeast Golgi. These changes in lipid topology were accompanied by a cold-sensitive defect in the uptake of markers for bulk-phase and receptor-mediated endocytosis. Our findings demonstrate a requirement for Dnf1p and Dnf2p in lipid translocation across the yeast plasma membrane. Moreover, it appears that Dnf1p, Dnf2p and Drs2p each help regulate the transbilayer lipid arrangement in the plasma membrane, and that this regulation is critical for budding endocytic vesicles.

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Authors

  • T. Pomorski

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