title: Functions of Ceramide Synthase Paralogs YPR114w and YJR116w of Saccharomyces cerevisiae.
abstract: Ceramide is synthesized in yeast by two redundant acyl-CoA dependent synthases, Lag1 and Lac1. In lag1∆ lac1∆ cells, free fatty acids and sphingoid bases are elevated, and ceramides are produced through the redundant alkaline ceramidases Ypc1 and Ydc1, working backwards. Even with all four of these genes deleted, cells are surviving and continue to contain small amounts of complex sphingolipids. Here we show that these residual sphingolipids are not synthesized by YPR114w or YJR116w, proteins of unknown function showing a high degree of homology to Lag1 and Lac1. Indeed, the hextuple lag1∆ lac1∆ ypc1∆ ydc1∆ ypr114w∆ yjr116w∆ mutant still contains ceramides and complex sphingolipids. Yjr116w∆ exhibit an oxygen-dependent hypersensitivity to Cu2+ due to an increased mitochondrial production of reactive oxygen species (ROS) and a mitochondrially orchestrated programmed cell death in presence of copper, but also a general copper hypersensitivity that cannot be counteracted by the antioxidant N-acetyl-cysteine (NAC). Myriocin efficiently represses the synthesis of sphingoid bases of ypr114w∆, but not its growth. Both yjr116w∆ and ypr114w∆ have fragmented vacuoles and produce less ROS than wild type, before and after diauxic shift. Ypr114w∆/ypr114w∆ have an increased chronological life span. Thus, Yjr116w and Ypr114w are related, but not functionally redundant.
authors.affiliation: Division of Biochemistry, Department of Biology, University of Fribourg, Chemin du Musée 10, Fribourg, CH-1700, Switzerland.
authors.forename: Shamroop K
authors.initials: SK
authors.lastname: Mallela
authors.affiliation: Department of Biochemistry and Molecular Biology, University of Southern Denmark, Campusvej 55, DK-5230, Odense M, Denmark.
authors.forename: Reinaldo
authors.initials: R
authors.lastname: Almeida
authors.affiliation: Department of Biochemistry and Molecular Biology, University of Southern Denmark, Campusvej 55, DK-5230, Odense M, Denmark.
authors.forename: Christer S
authors.initials: CS
authors.lastname: Ejsing
authors.affiliation: Division of Biochemistry, Department of Biology, University of Fribourg, Chemin du Musée 10, Fribourg, CH-1700, Switzerland.
authors.forename: Andreas
authors.initials: A
authors.lastname: Conzelmann
mesh_terms: D000111:Acetylcysteine / Q000494:pharmacology; D055574:Alkaline Ceramidase / Q000235:genetics / Q000378:metabolism; D000581:Amidohydrolases / Q000235:genetics / Q000378:metabolism; D000935:Antifungal Agents / Q000494:pharmacology; D000975:Antioxidants / Q000494:pharmacology; D002413:Cations, Divalent; D002518:Ceramides / Q000096:biosynthesis*; D003300:Copper / Q000633:toxicity; D005229:Fatty Acids, Monounsaturated / Q000494:pharmacology; D017353:Gene Deletion; D015966:Gene Expression Regulation, Fungal; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism; D008928:Mitochondria / Q000378:metabolism; D010088:Oxidoreductases / Q000235:genetics / Q000378:metabolism; D010100:Oxygen / Q000494:pharmacology; D010802:Phylogeny; D017382:Reactive Oxygen Species / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000145:classification / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics* / Q000378:metabolism; D014617:Vacuoles / Q000378:metabolism
chemical_list: D000935:Antifungal Agents; D000975:Antioxidants; D002413:Cations, Divalent; D002518:Ceramides; D005229:Fatty Acids, Monounsaturated; C087436:LAG1 protein, S cerevisiae; D008565:Membrane Proteins; D017382:Reactive Oxygen Species; D029701:Saccharomyces cerevisiae Proteins; D003300:Copper; D010088:Oxidoreductases; C513563:LAC1 protein, S cerevisiae; D000581:Amidohydrolases; C000588734:alkaline dihydroceramidase, S cerevisiae; D055574:Alkaline Ceramidase; C582674:YPC1 protein, S cerevisiae; D010100:Oxygen; D000111:Acetylcysteine; C001996:thermozymocidin