Knowledge of the mechanisms for regulating lifespan is advancing rapidly, but lifespan is a complex phenotype and new features are likely to be identified. Here we reveal a novel approach for regulating lifespan. Using a genetic or a pharmacological strategy to lower the rate of sphingolipid synthesis, we show that Saccharomyces cerevisiae cells live longer. The longer lifespan is due in part to a reduction in Sch9 protein kinase activity and a consequent reduction in chromosomal mutations and rearrangements and increased stress resistance. Longer lifespan also arises in ways that are independent of Sch9 or caloric restriction, and we speculate on ways that sphingolipids might mediate these aspects of increased lifespan. Sch9 and its mammalian homolog S6 kinase work downstream of the target of rapamycin, TOR1, protein kinase, and play evolutionarily conserved roles in regulating lifespan. Our data establish Sch9 as a focal point for regulating lifespan by integrating nutrient signals from TOR1 with growth and stress signals from sphingolipids. Sphingolipids are found in all eukaryotes and our results suggest that pharmacological down-regulation of one or more sphingolipids may provide a means to reduce age-related diseases and increase lifespan in other eukaryotes.

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Published in PLOS Genetics, v. 8, issue. 2, e1002493.

© 2012 Huang et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

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Supporting information, including supporting figures, table, and references. Figure S1: Outline of sphingolipid metabolism in Saccharomyces cerevisiae. Metabolic intermediates and complex sphingolipids are shown in bold font, genes are shown in italics and enzyme names are in regular lettering. Structures of compounds have been presented previously [74], [75]. Figure S2: Myriocin treatment decreases cell size. DBY746 cells were grown with and without myriocin (Myr) as in a CLS assay using SDC medium (pH 4.5, 3X iron). After 72 hrs of incubation, cells were stained directly with Calcofluor white M2R (25 µ/ml) and photographed at room temperature by using a Nikon Eclipse E600 fluorescence microscope equipped with a Plan Apo 100× 1.40 oil immersion objective, a SPOT RT 9.0 Monochrome-6 camera and SPOT basic software. For measurements, we excluded extremely large or small cells and cell diameter was calculated by measuring and averaging the long and short axes (perpendicular to each other) of each cell as described previously [30]. The median diameter for one hundred cells is indicated by a horizontal bar in the scatter plot. Figure S3: CLS of WT (DBY746) cells grown in SDC medium (pH 4.5, 3X iron) with CR (0.5% glucose) or without CR (NR, 2% glucose) +/− myriocin (Myr) treatment. Data represent the mean ± SEM of survival (* p<0.05, ** p<0.01, No Myr vs 450 or 600 ng/ml Myr, CR cultures). Figure S4: Sphingolipids activate the Pkh1/2 protein kinases. (A) Growth sensitivity was measured by diluting cells from CLS day 1 (10-fold serial dilution from left to right), spotting onto YPD plates containing the indicated concentration of myriocin, and incubating 3 days at 30 °C. Strains are: WT (R1158, LCB1), tetO7-LCB1 (RCD956), tetO7-LCB1/pkh1Δ (RCD1048), and tetO7-LCB1/pkh2Δ (RCD1051). (B) Same strains as used in A, but spotted onto YPD plates containing Dox. Table S1: Strains used in this study.