Rom2-dependent Phosphorylation of Elo2 Controls the Abundance of Very Long-chain Fatty Acids

Olson, Daniel K.; Fröhlich, Florian; Christiano, Romain; Hannibal-Bach, Hans Kristian; Ejsing, Christer S.; Walther, Tobias C.

doi:10.1074/jbc.m114.629279

Cited by 28 publications

(25 citation statements)

References 57 publications

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“…A set of genes involved in fatty acid biosynthesis, elongation, unsaturation, and metabolism were downregulated. Many of these genes were reported to be involved in the length and number of double bonds in fatty acids and in the response to various forms of stress (33,34), which may influence the species of phospholipid produced (35). Meanwhile, key genes involved in phospholipid and sphingolipid metabolism were also downregulated, thus contributing to a decreased phospholipid and sphingolipid biosynthesis in the med15BΔ strain.…”

Section: Discussionmentioning

confidence: 95%

Med15B Regulates Acid Stress Response and Tolerance in Candida glabrata by Altering Membrane Lipid Composition

Liu

et al. 2017

Appl Environ Microbiol

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Candida glabrata is a promising producer of organic acids. To elucidate the physiological function of the Mediator tail subunit Med15B in the response to low-pH stress, we constructed a deletion strain, C. glabrata med15BΔ, and an overexpression strain, C. glabrata HTUΔ/CgMED15B. Deletion of MED15B caused biomass production, glucose consumption rate, and cell viability to decrease by 28.3%, 31.7%, and 26.5%, respectively, compared with those of the parent (HTUΔ) strain at pH 2.0. Expression of lipid metabolism-related genes was significantly downregulated in the med15BΔ strain, whereas key genes of ergosterol biosynthesis showed abnormal upregulation. This caused the proportion of C 18:1 fatty acids, the ratio of unsaturated to saturated fatty acids (UFA/SFA), and the total phospholipid content to decrease by 11.6%, 27.4%, and 37.6%, respectively. Cells failed to synthesize fecosterol and ergosterol, leading to the accumulation and a 60.3-fold increase in the concentration of zymosterol. Additionally, cells showed reductions of 69.2%, 11.6%, and 21.8% in membrane integrity, fluidity, and H ϩ -ATPase activity, respectively. In contrast, overexpression of Med15B increased the C 18:1 levels, total phospholipids, ergosterol content, and UFA/SFA by 18.6%, 143.5%, 94.5%, and 18.7%, respectively. Membrane integrity, fluidity, and H ϩ -ATPase activity also increased by 30.2%, 6.9%, and 51.8%, respectively. Furthermore, in the absence of pH buffering, dry weight of cells and pyruvate concentrations were 29.3% and 61.2% higher, respectively, than those of the parent strain. These results indicated that in C. glabrata, Med15B regulates tolerance toward low pH via transcriptional regulation of acid stress response genes and alteration in lipid composition. IMPORTANCE This study explored the role of the Mediator tail subunit Med15B in the metabolism of Candida glabrata under acidic conditions. Overexpression of MED15B enhanced yeast tolerance to low pH and improved biomass production, cell viability, and pyruvate yield. Membrane lipid composition data indicated that Med15B might play a critical role in membrane integrity, fluidity, and H ϩ -ATPase activity homeostasis at low pH. Thus, controlling membrane composition may serve to increase C. glabrata productivity at low pH.KEYWORDS Candida glabrata, Mediator subunit Med15B, low-pH stress, transcriptomics, membrane lipid T he Mediator coactivator complex is required for transcription initiation in eukaryotes (1, 2). It is recruited by transcription activators and conveys regulatory information from gene-specific regulators to promoters (3, 4). Mediator can influence almost all stages of transcription and coordinated processes such as chromatin remodeling, transcription elongation, and posttranslational modifications (5, 6). Mediator is a multisubunit assembly comprising four modules: head, middle, tail, and cyclin-dependent kinase 8 (CDK8) (7). The head and middle modules are highly

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Section: Discussionmentioning

confidence: 95%

Med15B Regulates Acid Stress Response and Tolerance in Candida glabrata by Altering Membrane Lipid Composition

Liu

et al. 2017

Appl Environ Microbiol

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“…The yeast Saccharomyces cerevisiae is a powerful system to decipher sphingolipid regulation. For instance, inhibition of sphingolipid synthesis by myriocin, inhibiting serine–palmitoyl–transferase, the enzymatic protein complex catalyzing the first and committed step of de novo sphingolipid synthesis, has been useful to reveal the response to restore sphingolipid homeostasis [–6].…”

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confidence: 99%

Proteomic and phosphoproteomic analyses of yeast reveal the global cellular response to sphingolipid depletion

et al. 2016

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Sphingolipids are essential components of eukaryotic cells with important functions in membrane biology and cellular signaling. Their levels are tightly controlled and coordinated with the abundance of other membrane lipids. How sphingolipid homeostasis is achieved is not yet well understood. Studies performed primarily in yeast showed that the phosphorylation states of several enzymes and regulators of sphingolipid synthesis are important, although a global understanding for such regulation is lacking. Here, we used high-resolution mass-spectrometry-based proteomics and phosphoproteomics to analyze the cellular response to sphingolipid synthesis inhibition. Our dataset reveals that changes in protein phosphorylation, rather than protein abundance, dominate the response to blocking sphingolipid synthesis. We identified Ypk signaling as a pathway that is activated under these conditions, and we identified potential Ypk1 target proteins. Our data provide a rich resource for on-going mechanistic studies of key elements of the cellular response to the depletion of sphingolipid levels and the maintenance of sphingolipid homeostasis.

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“…It subsequently became clear that Rom2 acts by regulating phosphorylation of the Elo2 elongase. Elo2 phosphorylation is decreased when sphingolipid levels fall, which increases VLCFA synthesis (73). How Rho1 signaling is initiated is unknown, but it involves two potential transmembrane sensor proteins, Wsc1 and Wsc2 (73)…”

Section: How Are Sphingolipids Sensed At the Plasma Membrane?mentioning

confidence: 99%

“…To provide these, Rom2-dependent signaling from the plasma membrane regulates the activity of Elo2 (73), the fatty acid elongase controlling VLCFA levels in yeast (82). In this case, depletion of sphingolipids leads to down-regulation of Rom2-signaling and de-phosphorylation of Elo2, which in turn increases VLCFA synthesis.…”

Section: How Do Cells Adjust Sphingolipid Synthesis?mentioning

confidence: 99%

“…How the signal is transduced from Rom2 to Elo2 is not well understood, but appears to involve only the initial kinases of the cell wall integrity pathway. It is not clear which kinases transduce the signal from this pathway to phosphorylate Elo2, but the GSK3 kinase Mck1 is required (73,83). Since mutants in downstream components of the pathway are nonetheless sensitive to sphingolipid synthesis inhibition, the pathway might have targets other than Elo2 that are important for sphingolipid homeostasis (73).…”

Section: How Do Cells Adjust Sphingolipid Synthesis?mentioning

confidence: 99%

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Taming the sphinx: Mechanisms of cellular sphingolipid homeostasis

Olson

Fröhlich

Farese

et al. 2016

Biochimica et Biophysica Acta (BBA) - Molecular and Cell Biolog

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Sphingolipids are important structural membrane components of eukaryotic cells, and potent signaling molecules. As such, their levels must be maintained to optimize cellular functions in different cellular membranes. Here, we review the current knowledge of homeostatic sphingolipid regulation. We describe recent studies in Saccharomyces cerevisiae that have provided insights into how cells sense changes in sphingolipid levels in the plasma membrane and acutely regulate sphingolipid biosynthesis by altering signaling pathways. We also discuss how cellular trafficking has emerged as an important determinant of sphingolipid homeostasis. Finally, we highlight areas where work is still needed to elucidate the mechanisms of sphingolipid regulation and the physiological functions of such regulatory networks, especially in mammalian cells.

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Rom2-dependent Phosphorylation of Elo2 Controls the Abundance of Very Long-chain Fatty Acids

Cited by 28 publications

References 57 publications

Med15B Regulates Acid Stress Response and Tolerance in Candida glabrata by Altering Membrane Lipid Composition

Med15B Regulates Acid Stress Response and Tolerance in Candida glabrata by Altering Membrane Lipid Composition

Proteomic and phosphoproteomic analyses of yeast reveal the global cellular response to sphingolipid depletion

Taming the sphinx: Mechanisms of cellular sphingolipid homeostasis

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