title: Vacuolar import of phosphatidylcholine requires the ATP-binding cassette transporter Ybt1.
abstract: ATP-binding cassette (ABC) transporters are well known for their roles as multidrug resistance determinants but also play important roles in regulation of lipid levels. In the yeast Saccharomyces cerevisiae, the plasma membrane ABC transporter proteins Pdr5 and Yor1 are required for normal rates of transport of phosphatidyethanolamine to the surface of the cell. Loss of these ABC transporters causes a defect in phospholipid asymmetry across the plasma membrane and has been linked with slowed rates of trafficking of other membrane proteins. Four ABC transporter proteins are found on the limiting membrane of the yeast vacuole and loss of one of these vacuolar ABC transporters, Ybt1, caused a major defect in the normal delivery of the phosphatidylcholine (PC) analog NBD-PC (7-nitro-2,1,3-benzoxadiazol-PC) to the lumen of the vacuole. NBD-PC accumulates on cytosolic membranes in an ybt1Δ strain. We demonstrated that Ybt1 is required to import NBD-PC into vacuoles in the presence of ATP in vitro. Loss of Ybt1 prevented vacuolar remodeling of PC analogs. Turnover of Ybt1 was reduced under conditions in which function of this vacuolar remodeling pathway was required. Our data describe a novel vacuolar route for lipid remodeling and reutilization in addition to previously described enzymatic avenues in the cytoplasm.
authors.affiliation: Department of Molecular Physiology and Biophysics, Carver College of Medicine, 6-530 Bowen Science Building, University of Iowa, Iowa City, IA 52246, USA.
authors.forename: Kailash
authors.initials: K
authors.lastname: Gulshan
authors.forename: W Scott
authors.initials: WS
authors.lastname: Moye-Rowley
mesh_terms: D018528:ATP-Binding Cassette Transporters / Q000235:genetics / Q000378:metabolism*; D000255:Adenosine Triphosphate / Q000378:metabolism; D001692:Biological Transport / Q000502:physiology; D002462:Cell Membrane / Q000378:metabolism; D010713:Phosphatidylcholines / Q000737:chemistry / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000166:cytology / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*; D014617:Vacuoles / Q000378:metabolism*
chemical_list: D018528:ATP-Binding Cassette Transporters; D010713:Phosphatidylcholines; D011993:Recombinant Fusion Proteins; D029701:Saccharomyces cerevisiae Proteins; C106609:YBT1 protein, S cerevisiae; D000255:Adenosine Triphosphate