Reference: Kitagaki H, et al. (2007) Isc1 regulates sphingolipid metabolism in yeast mitochondria. Biochim Biophys Acta 1768(11):2849-61

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Abstract


The Saccharomyces cerevisiae inositol sphingolipid phospholipase C (Isc1p), a homolog of mammalian neutral sphingomyelinases, hydrolyzes complex sphingolipids to produce ceramide in vitro. Epitope-tagged Isc1p associates with the mitochondria in the post-diauxic phase of yeast growth. In this report, the mitochondrial localization of Isc1p and its role in regulating sphingolipid metabolism were investigated. First, endogenous Isc1p activity was enriched in highly purified mitochondria, and western blots using highly purified mitochondrial membrane fractions demonstrated that epitope-tagged Isc1p localized to the outer mitochondrial membrane as an integral membrane protein. Next, LC/MS was employed to determine the sphingolipid composition of highly purified mitochondria which were found to be significantly enriched in alpha-hydroxylated phytoceramides (21.7 fold) relative to the whole cell. Mitochondria, on the other hand, were significantly depleted in sphingoid bases. Compared to the parental strain, mitochondria from isc1Delta in the post-diauxic phase showed drastic reduction in the levels of alpha-hydroxylated phytoceramide (93.1% loss compared to WT mitochondria with only 2.58 fold enrichment in mitochondria compared to whole cell). Functionally, isc1Delta showed a higher rate of respiratory-deficient cells after incubation at high temperature and was more sensitive to hydrogen peroxide and ethidium bromide, indicating that isc1Delta exhibits defects related to mitochondrial function. These results suggest that Isc1p generates ceramide in mitochondria, and the generated ceramide contributes to the normal function of mitochondria. This study provides a first insight into the specific composition of ceramides in mitochondria.

Reference Type
Journal Article | Research Support, N.I.H., Extramural | Research Support, U.S. Gov't, Non-P.H.S.
Authors
Kitagaki H, Cowart LA, Matmati N, Vaena de Avalos S, Novgorodov SA, Zeidan YH, Bielawski J, Obeid LM, Hannun YA
Primary Lit For
ISC1

Gene Ontology Annotations 2 entries for 1 gene


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Gene/ComplexQualifierGene Ontology TermAnnotation ExtensionEvidenceSourceAssigned On
ISC1located inmitochondrial outer membraneIDASGD2022-08-26
ISC1involved inceramide biosynthetic processIMPSGD2013-08-07
Showing 1 to 2 of 2 entries

Phenotype Annotations 4 entries for 1 gene


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GenePhenotypeExperiment TypeMutant InformationStrain BackgroundChemicalDetails
ISC1petite
classical geneticsnull
Allele: isc1-Δ
OtherMedia: YPGE (yeast peptone glycerol ethanol media)
ISC1petite
classical geneticsnull
Allele: isc1-Δ
OtherTemperature: elevated temperature, 39 °C
ISC1resistance to chemicals: decreased
classical geneticsnull
Allele: isc1-Δ
Other1 mM hydrogen peroxide
ISC1resistance to chemicals: decreased
classical geneticsnull
Allele: isc1-Δ
Other50 uM ethidium bromide
Showing 1 to 4 of 4 entries