title: Characterization of yeast mutants lacking alkaline ceramidases YPC1 and YDC1.
abstract: Humans and yeast possess alkaline ceramidases located in the early secretory pathway. Single deletions of the highly homologous yeast alkaline ceramidases YPC1 and YDC1 have very little genetic interactions or phenotypes. Here, we performed chemical-genetic screens to find deletions/conditions that would alter the growth of ypc1∆ydc1∆ double mutants. These screens were essentially negative, demonstrating that ceramidase activity is not required for cell growth even under genetic stresses. A previously reported protein targeting defect of ypc1∆ could not be reproduced and reported abnormalities in sphingolipid biosynthesis detected by metabolic labeling do not alter the mass spectrometric lipid profile of ypc1∆ydc1∆ cells. Ceramides of ypc1∆ydc1∆ remained normal even in presence of aureobasidin A, an inhibitor of inositolphosphorylceramide synthase. Moreover, in caloric restriction conditions Ypc1p reduces chronological life span. A novel finding is that, when working backwards as a ceramide synthase in vivo, Ypc1p prefers C24 and C26 fatty acids as substrates, whereas it prefers C16:0, when solubilized in detergent and working in vitro. Therefore, its physiological activity may not only concern the minor ceramides containing C14 and C16. Intriguingly, so far the sole discernable benefit of conserving YPC1 for yeast resides with its ability to convey relative resistance toward H2O2.
authors.affiliation: Department of Biology, University of Fribourg, Fribourg, Switzerland.
authors.forename: Natalia S
authors.initials: NS
authors.lastname: Voynova
authors.forename: Shamroop K
authors.initials: SK
authors.lastname: Mallela
authors.forename: Hector M
authors.initials: HM
authors.lastname: Vazquez
authors.forename: Vanessa
authors.initials: V
authors.lastname: Cerantola
authors.forename: Mélanie
authors.initials: M
authors.lastname: Sonderegger
authors.forename: Jens
authors.initials: J
authors.lastname: Knudsen
authors.forename: Christer S
authors.initials: CS
authors.lastname: Ejsing
authors.forename: Andreas
authors.initials: A
authors.lastname: Conzelmann
mesh_terms: D055574:Alkaline Ceramidase / Q000235:genetics / Q000378:metabolism*; D000581:Amidohydrolases / Q000235:genetics / Q000378:metabolism*; D002518:Ceramides / Q000378:metabolism; D055786:Gene Knockout Techniques; D012441:Saccharomyces cerevisiae / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D002518:Ceramides; D029701:Saccharomyces cerevisiae Proteins; D000581:Amidohydrolases; C000588734:alkaline dihydroceramidase, S cerevisiae; D055574:Alkaline Ceramidase; C582674:YPC1 protein, S cerevisiae
keywords: aureobasidin A; chronological life span; secretion; sphingolipid; synthetic genetic array; vesicular traffic