Down-Regulating Sphingolipid Synthesis Increases Yeast Lifespan
of sphingolipid biosynthesis in yeast .
GBA Gene - GeneCards | GLCM Protein | GLCM Antibody
Sphingolipids and their metabolites are known to modulate various cellular events including proliferation, differentiation, and apoptosis. Serine palmitoyltransferase (SPT) is the enzyme that catalyzes the first step of the biosynthesis of all sphingolipids. Here, we report that a newly identified antibiotic, sulfamisterin, derived from the fungus sp., is a specific inhibitor of SPT. The chemical structure of sulfamisterin resembles both that of sphingosine as well as a potent inhibitor of SPT, ISP-1 (myriocin). Sulfamisterin inhibited SPT activity with IC50 = 3 nM in a cell-free lysate prepared from Chinese hamster ovary (CHO) fibroblasts. Sulfamisterin markedly inhibited the biosynthesis of sphingolipids in living CHO cells and in yeast as monitored by radioactive precursors. Unlike the cell-free experiments, 10 μM sulfamisterin was required for complete inhibition of sphingolipid biosynthesis in intact cells. We also synthesized a series of structural analogues of sulfamisterin and examined their activities both in cell-free and in living cell systems.
Sphingolipids (SLs) are essential components of cell membranes and are broad-range bioactive signaling molecules. SL levels must be tightly regulated as imbalances affect cellular function and contribute to pathologies ranging from neurodegenerative and metabolic disorders to cancer and aging. Deciphering how SL homeostasis is maintained and uncovering new regulators is required for understanding lipid biology and for identifying new targets for therapeutic interventions. Here we combine omics technologies to identify the changes of the transcriptome, proteome, and phosphoproteome in the yeast upon SL depletion induced by myriocin. Surprisingly, while SL depletion triggers important changes in the expression of regulatory proteins involved in SL homeostasis, the most dramatic regulation occurs at the level of the phosphoproteome, suggesting that maintaining SL homeostasis demands rapid responses. To discover which of the phosphoproteomic changes are required for the cell’s first-line response to SL depletion, we overlaid our omics results with systematic growth screens for genes required during growth in myriocin. By following the rate of SL biosynthesis in those candidates that are both affecting growth and are phosphorylated in response to the drug, we uncovered Atg9, Stp4, and Gvp36 as putative new regulators of SL homeostasis.
STS Gene - GeneCards | STS Protein | STS Antibody
Figure S-1. Transcriptomic workflow. Figure S-2. Effect of sphingolipid synthesis inhibition on yeast growing in various concentrations of myriocin. Figure S-3. Qualitative evaluation of cell viability in response to low-dose of myriocin. Figure S-4. Protein expression heatmap of proteins involved in (de)phosphorylation processes. Figure S-5. Individual dynamic profile of Sec16 phosphorylation. ()
Sphingolipids are essential components of eukaryotic cell membranes, particularly the plasma membrane, and are involved in a diverse array of signal transduction pathways. Mammals produce sphingomyelin (SM) as the primary complex sphingolipid via the well characterised SM synthase. In contrast yeast, plants and some protozoa utilise an evolutionarily related inositol phosphorylceramide (IPC) synthase to synthesise IPC. This activity has no mammalian equivalent and IPC synthase has been proposed as a target for anti-fungals and anti-protozoals. However, detailed knowledge of the sphingolipid biosynthetic pathway of the apicomplexan protozoan parasites was lacking. In this study bioinformatic analyses indicated a single copy orthologue of the putative SM synthase from the apicomplexan Plasmodium falciparum (the causative agent of malaria) was a bona fide sphingolipid synthase in the related model parasite, Toxoplasma gondii (TgSLS). Subsequently, TgSLS was indicated, by complementation of a mutant cell line, to be a functional orthologue of the yeast IPC synthase (AUR1p), demonstrating resistance to the well characterised AUR1p inhibitor aureobasidin A. In vitro, recombinant TgSLS exhibited IPC synthase activity and, for the first time, the presence of IPC was demonstrated in T. gondii lipid extracts by mass spectrometry. Furthermore, host sphingolipid biosynthesis was indicated to influence, but be non-essential for, T. gondii proliferation, suggesting that whilst scavenging does take place de novo sphingolipid synthesis may be important for parasitism.
main heading methoxsalen refers to 8-methoxypsoralen
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KEGG PATHWAY Database (KEGG)
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