title: Cfs1p, a Novel Membrane Protein in the PQ-Loop Family, Is Involved in Phospholipid Flippase Functions in Yeast.
abstract: Type 4 P-type ATPases (P4-ATPases) function as phospholipid flippases, which translocate phospholipids from the exoplasmic leaflet to the cytoplasmic leaflet of the lipid bilayer, to generate and maintain asymmetric distribution of phospholipids at the plasma membrane and endosomal/Golgi membranes. The budding yeast Saccharomyces cerevisiae has four heteromeric flippases (Drs2p, Dnf1p, Dnf2p, and Dnf3p), associated with the Cdc50p family noncatalytic subunit, and one monomeric flippase, Neo1p They have been suggested to function in vesicle formation in membrane trafficking pathways, but details of their mechanisms remain to be clarified. Here, to search for novel factors that functionally interact with flippases, we screened transposon insertional mutants for strains that suppressed the cold-sensitive growth defect in the cdc50Δ mutant. We identified a mutation of YMR010W encoding a novel conserved membrane protein that belongs to the PQ-loop family including the cystine transporter cystinosin and the SWEET sugar transporters. We named this gene CFS1 (cdc fifty suppressor 1). GFP-tagged Cfs1p was partially colocalized with Drs2p and Neo1p to endosomal/late Golgi membranes. Interestingly, the cfs1Δ mutation suppressed growth defects in all flippase mutants. Accordingly, defects in membrane trafficking in the flippase mutants were also suppressed. These results suggest that Cfs1p and flippases function antagonistically in membrane trafficking pathways. A growth assay to assess sensitivity to duramycin, a phosphatidylethanolamine (PE)-binding peptide, suggested that the cfs1Δ mutation changed PE asymmetry in the plasma membrane. Cfs1p may thus be a novel regulator of phospholipid asymmetry.
authors.affiliation: Graduate School of Life Science, Division of Molecular Interaction, Institute for Genetic Medicine, Hokkaido University, Sapporo 060-0815, Japan.
authors.forename: Takaharu
authors.initials: T
authors.lastname: Yamamoto
authors.affiliation: Graduate School of Life Science, Division of Molecular Interaction, Institute for Genetic Medicine, Hokkaido University, Sapporo 060-0815, Japan.
authors.forename: Konomi
authors.initials: K
authors.lastname: Fujimura-Kamada
authors.affiliation: Graduate School of Medicine, Division of Molecular Interaction, Institute for Genetic Medicine, Hokkaido University, Sapporo 060-0815, Japan.
authors.forename: Eno
authors.initials: E
authors.lastname: Shioji
authors.affiliation: Graduate School of Medicine, Division of Molecular Interaction, Institute for Genetic Medicine, Hokkaido University, Sapporo 060-0815, Japan.
authors.forename: Risa
authors.initials: R
authors.lastname: Suzuki
authors.affiliation: Graduate School of Life Science, Division of Molecular Interaction, Institute for Genetic Medicine, Hokkaido University, Sapporo 060-0815, Japan k-tanaka@igm.hokudai.ac.jp.
authors.forename: Kazuma
authors.identifier: 0000-0003-1936-2856
authors.initials: K
authors.lastname: Tanaka
mesh_terms: D000251:Adenosine Triphosphatases / Q000235:genetics*; D001430:Bacteriocins / Q000494:pharmacology; D011992:Endosomes / Q000235:genetics* / Q000378:metabolism; D006056:Golgi Apparatus / Q000235:genetics / Q000378:metabolism; D008565:Membrane Proteins / Q000235:genetics*; D026901:Membrane Transport Proteins / Q000235:genetics*; D009154:Mutation; D010455:Peptides / Q000494:pharmacology; D010743:Phospholipids / Q000235:genetics / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics*
chemical_list: D001430:Bacteriocins; C000625017:Cfs1 protein, S cerevisiae; D008565:Membrane Proteins; D026901:Membrane Transport Proteins; D010455:Peptides; D010743:Phospholipids; D029701:Saccharomyces cerevisiae Proteins; C040522:duramycin; D000251:Adenosine Triphosphatases
keywords: P4-ATPase; floppase; membrane transport; phospholipid asymmetry; scramblase