title: Phosphatidylserine translocation at the yeast trans-Golgi network regulates protein sorting into exocytic vesicles.
abstract: Sorting of plasma membrane proteins into exocytic vesicles at the yeast trans-Golgi network (TGN) is believed to be mediated by their coalescence with specific lipids, but how these membrane-remodeling events are regulated is poorly understood. Here we show that the ATP-dependent phospholipid flippase Drs2 is required for efficient segregation of cargo into exocytic vesicles. The plasma membrane proteins Pma1 and Can1 are missorted from the TGN to the vacuole in drs2∆ cells. We also used a combination of flippase mutants that either gain or lose the ability to flip phosphatidylserine (PS) to determine that PS flip by Drs2 is its critical function in this sorting event. The primary role of PS flip at the TGN appears to be to control the oxysterol-binding protein homologue Kes1/Osh4 and regulate ergosterol subcellular distribution. Deletion of KES1 suppresses plasma membrane-missorting defects and the accumulation of intracellular ergosterol in drs2 mutants. We propose that PS flip is part of a homeostatic mechanism that controls sterol loading and lateral segregation of protein and lipid domains at the TGN.
authors.affiliation: Department of Biological Sciences, Vanderbilt University, Nashville, TN 37235.
authors.forename: Hannah M
authors.initials: HM
authors.lastname: Hankins
authors.affiliation: Department of Biochemistry, Weill Cornell Medical College, New York, NY 10065.
authors.forename: Yves Y
authors.initials: YY
authors.lastname: Sere
authors.affiliation: Department of Biological Sciences, Vanderbilt University, Nashville, TN 37235.
authors.forename: Nicholas S
authors.initials: NS
authors.lastname: Diab
authors.affiliation: Department of Biochemistry, Weill Cornell Medical College, New York, NY 10065.
authors.forename: Anant K
authors.initials: AK
authors.lastname: Menon
authors.affiliation: Department of Biological Sciences, Vanderbilt University, Nashville, TN 37235 tr.graham@vanderbilt.edu.
authors.forename: Todd R
authors.initials: TR
authors.lastname: Graham
mesh_terms: D000251:Adenosine Triphosphatases / Q000235:genetics; D026923:Amino Acid Transport Systems, Basic / Q000378:metabolism; D000252:Calcium-Transporting ATPases / Q000235:genetics* / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism; D005089:Exocytosis / Q000235:genetics; D008565:Membrane Proteins / Q000235:genetics* / Q000378:metabolism; D009154:Mutation; D010718:Phosphatidylserines / Q000378:metabolism; D021381:Protein Transport / Q000235:genetics; D006180:Proton-Translocating ATPases / Q000378:metabolism; D011987:Receptors, Steroid / Q000235:genetics* / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics* / Q000378:metabolism; D022161:Transport Vesicles / Q000235:genetics* / Q000378:metabolism; D021601:trans-Golgi Network / Q000235:genetics*; D000098825:Oxysterol Binding Proteins
chemical_list: D000251:Adenosine Triphosphatases; D026923:Amino Acid Transport Systems, Basic; D000252:Calcium-Transporting ATPases; D008565:Membrane Proteins; D010718:Phosphatidylserines; D006180:Proton-Translocating ATPases; D011987:Receptors, Steroid; D029701:Saccharomyces cerevisiae Proteins; C502212:CAN1 protein, S cerevisiae; C104014:DRS2 protein, S cerevisiae; C087901:KES1 protein, S cerevisiae; D000098825:Oxysterol Binding Proteins; C092477:PMA1 protein, S cerevisiae