title: Identification of C18:1-phytoceramide as the candidate lipid mediator for hydroxyurea resistance in yeast.
abstract: Recent studies showed that deletion of ISC1, the yeast homologue of the mammalian neutral sphingomyelinase, resulted in an increased sensitivity to hydroxyurea (HU). This raised an intriguing question as to whether sphingolipids are involved in pathways initiated by HU. In this study, we show that HU treatment led to a significant increase in Isc1 activity. Analysis of sphingolipid deletion mutants and pharmacological analysis pointed to a role for ceramide in mediating HU resistance. Lipid analysis revealed that HU induced increases in phytoceramides in WT cells but not in isc1Δ cells. To probe functions of specific ceramides, we developed an approach to supplement the medium with fatty acids. Oleate (C18:1) was the only fatty acid protecting isc1Δ cells from HU toxicity in a ceramide-dependent manner. Because phytoceramide activates protein phosphatases in yeast, we evaluated the role of CDC55, the regulatory subunit of ceramide-activated protein phosphatase PP2A. Overexpression of CDC55 overcame the sensitivity to HU in isc1Δ cells. However, addition of oleate did not protect the isc1Δ,cdc55Δ double mutant from HU toxicity. These results demonstrate that HU launches a lipid pathway mediated by a specific sphingolipid, C18:1-phytoceramide, produced by Isc1, which provides protection from HU by modulating Swe1 levels through the PP2A subunit Cdc55.
authors.affiliation: Stony Brook Cancer Center and the Department of Medicine, Stony Brook University, Stony Brook, New York 11794-8155, USA.
authors.forename: Nabil
authors.initials: N
authors.lastname: Matmati
authors.forename: Alessandra
authors.initials: A
authors.lastname: Metelli
authors.forename: Kaushlendra
authors.initials: K
authors.lastname: Tripathi
authors.forename: Shuqi
authors.initials: S
authors.lastname: Yan
authors.forename: Bidyut K
authors.initials: BK
authors.lastname: Mohanty
authors.forename: Yusuf A
authors.initials: YA
authors.lastname: Hannun
mesh_terms: D018797:Cell Cycle Proteins / Q000378:metabolism; D002518:Ceramides / Q000502:physiology*; D025141:Drug Resistance, Fungal; D004795:Enzyme Stability; D055786:Gene Knockout Techniques; D006918:Hydroxyurea / Q000494:pharmacology*; D050356:Lipid Metabolism; D009829:Oleic Acids / Q000502:physiology*; D054648:Protein Phosphatase 2 / Q000378:metabolism; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D012264:Ribonucleotide Reductases / Q000037:antagonists & inhibitors; D012441:Saccharomyces cerevisiae / Q000187:drug effects / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism; D010738:Type C Phospholipases / Q000235:genetics / Q000378:metabolism
chemical_list: C071246:CDC55 protein, S cerevisiae; D018797:Cell Cycle Proteins; D002518:Ceramides; D009829:Oleic Acids; D029701:Saccharomyces cerevisiae Proteins; D012264:Ribonucleotide Reductases; C099685:SWE1 protein, S cerevisiae; D011505:Protein-Tyrosine Kinases; D054648:Protein Phosphatase 2; C419391:ISC1 protein, S cerevisiae; D010738:Type C Phospholipases; D006918:Hydroxyurea
keywords: Cell Cycle; Hydroxyurea; Phosphatase; Sphingolipid; Stress Response; Yeast