title: Lipid droplet proteins, Lds1p, Lds2p, and Rrt8p, are implicated in membrane protein transport associated with ergosterol.
abstract: Lipid droplets (LDs) are ubiquitous organelles, enclosed in a monolayer of phospholipid, which store excess fatty acids as neutral lipids such as triacylglycerol and sterol esters. Previous studies have revealed that LDs contain many proteins with various functions required for lipid metabolism and vesicular trafficking. Among them, Lds (Lipid Droplet in Sporulation) proteins, Lds1p and Lds2p, are reportedly induced and localized to LDs during yeast sporulation, but their cellular function has not been clarified. Here we show that the Lds proteins, Lds1p, Lds2p and Rrt8p, are expressed and localized at LDs in vegetative cells, being required for proper localization of plasma membrane proteins. We found that deletion of Lds genes led to mis-sorting of Wsc1p, a cell wall stress sensor, from the plasma membrane to the vacuole. We also demonstrated that lack of these proteins partially suppressed the growth defect and mis-sorting of the high-affinity tryptophan transporter Tat2p, induced by impairment of ergosterol biosynthesis. Furthermore, we identified Sec39p/Dsl3p, a component of the DSL1 tethering complex that mediates the interaction with COPI vesicles, as a binding partner for Lds2p. These results suggest a possible role of Lds proteins in maintenance of membrane lipid homeostasis and accompanying membrane protein transport.
authors.affiliation: Department of Biological Science and Technology, Tokyo University of Science, 6-3-1 Niijyuku, Katsushika-ku, Tokyo 125-8585, Japan.
authors.forename: Kazuma
authors.initials: K
authors.lastname: Ueno
authors.affiliation: Department of Biological Science and Technology, Tokyo University of Science, 6-3-1 Niijyuku, Katsushika-ku, Tokyo 125-8585, Japan.
authors.forename: Makoto
authors.initials: M
authors.lastname: Nagano
authors.affiliation: Department of Biological Science and Technology, Tokyo University of Science, 6-3-1 Niijyuku, Katsushika-ku, Tokyo 125-8585, Japan.
authors.forename: Shigeki
authors.initials: S
authors.lastname: Shimizu
authors.affiliation: School of Health Sciences, Tokyo University of Technology, 5-23-22 Nishikamata, Ohta-ku, Tokyo 144-8535, Japan. Electronic address: toshimajk@stf.teu.ac.jp.
authors.forename: Junko Y
authors.initials: JY
authors.lastname: Toshima
authors.affiliation: Department of Biological Science and Technology, Tokyo University of Science, 6-3-1 Niijyuku, Katsushika-ku, Tokyo 125-8585, Japan. Electronic address: jtosiscb@rs.noda.tus.ac.jp.
authors.forename: Jiro
authors.initials: J
authors.lastname: Toshima
mesh_terms: D004705:Endocytosis; D004875:Ergosterol / Q000235:genetics / Q000378:metabolism*; D017353:Gene Deletion; D015966:Gene Expression Regulation, Fungal; D066292:Lipid Droplets / Q000378:metabolism* / Q000648:ultrastructure; D008780:Methyltransferases / Q000235:genetics / Q000378:metabolism; D021381:Protein Transport; D012441:Saccharomyces cerevisiae / Q000166:cytology / Q000235:genetics / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000032:analysis / Q000235:genetics / Q000378:metabolism*
chemical_list: C000618863:Lds1 protein, S cerevisiae; C000618864:Lds2 protein, S cerevisiae; C000618865:Rrt8 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D008780:Methyltransferases; C022670:delta 24-sterol methyltransferase; D004875:Ergosterol
keywords: Endocytosis; Ergosterol; Lipid droplets; Tat2p; Wsc1p