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Srf1 is a novel regulator of phospholipase D activity and is essential to buffer the toxic effects of C16:0 platelet activating factor.

Kennedy MA, Kabbani N, Lambert JP, Swayne LA, Ahmed F, Figeys D, Bennett SA, Bryan J, Baetz K - PLoS Genet. (2011)

Bottom Line: As C16:0 PAF is a naturally occurring lipid involved in cellular signaling, it is likely that mechanisms exist to protect cells against its toxic effects.Deletion of YDL133w, a previously uncharacterized gene which we have renamed SRF1 (Spo14 Regulatory Factor 1), resulted in the greatest differential sensitivity to C16:0 PAF over C16:0 lyso-PAF.Though C16:0 PAF treatment does not impact hydrolysis of phosphatidylcholine in yeast, C16:0 PAF does promote delocalization of GFP-Spo14 and phosphatidic acid from the cell periphery.

View Article: PubMed Central - PubMed

Affiliation: Ottawa Institute of Systems Biology, Department of Biochemistry, Microbiology, and Immunology, University of Ottawa, Ottawa, Canada.

ABSTRACT
During Alzheimer's Disease, sustained exposure to amyloid-β₄₂ oligomers perturbs metabolism of ether-linked glycerophospholipids defined by a saturated 16 carbon chain at the sn-1 position. The intraneuronal accumulation of 1-O-hexadecyl-2-acetyl-sn-glycerophosphocholine (C16:0 PAF), but not its immediate precursor 1-O-hexadecyl-sn-glycerophosphocholine (C16:0 lyso-PAF), participates in signaling tau hyperphosphorylation and compromises neuronal viability. As C16:0 PAF is a naturally occurring lipid involved in cellular signaling, it is likely that mechanisms exist to protect cells against its toxic effects. Here, we utilized a chemical genomic approach to identify key processes specific for regulating the sensitivity of Saccharomyces cerevisiae to alkyacylglycerophosphocholines elevated in Alzheimer's Disease. We identified ten deletion mutants that were hypersensitive to C16:0 PAF and five deletion mutants that were hypersensitive to C16:0 lyso-PAF. Deletion of YDL133w, a previously uncharacterized gene which we have renamed SRF1 (Spo14 Regulatory Factor 1), resulted in the greatest differential sensitivity to C16:0 PAF over C16:0 lyso-PAF. We demonstrate that Srf1 physically interacts with Spo14, yeast phospholipase D (PLD), and is essential for PLD catalytic activity in mitotic cells. Though C16:0 PAF treatment does not impact hydrolysis of phosphatidylcholine in yeast, C16:0 PAF does promote delocalization of GFP-Spo14 and phosphatidic acid from the cell periphery. Furthermore, we demonstrate that, similar to yeast cells, PLD activity is required to protect mammalian neural cells from C16:0 PAF. Together, these findings implicate PLD as a potential neuroprotective target capable of ameliorating disruptions in lipid metabolism in response to accumulating oligomeric amyloid-β₄₂.

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Related in: MedlinePlus

The differential sensitivity of yeast to C16:0 PAF and C16:0 lyso-PAF.Growth of wild type (YPH499) strain (OD600) as a function of time in hours. Wild type yeast cells were grown in YPD liquid culture with or without C16:0 PAF or C16:0 lyso-PAF as indicated. Growth curves were performed in triplicate and the error bars represent 1 standard deviation.
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pgen-1001299-g001: The differential sensitivity of yeast to C16:0 PAF and C16:0 lyso-PAF.Growth of wild type (YPH499) strain (OD600) as a function of time in hours. Wild type yeast cells were grown in YPD liquid culture with or without C16:0 PAF or C16:0 lyso-PAF as indicated. Growth curves were performed in triplicate and the error bars represent 1 standard deviation.

Mentions: Previous studies have determined that, similar to neuronal cells [1], S. cerevisiae are sensitive to C16:0 PAF [17]. To determine whether C16:0 PAF and C16:0 lyso-PAF differentially impact the growth of S. cerevisiae and to identify an appropriate working concentration range for these lipids in subsequent studies we performed liquid growth curve analysis using wild type haploid yeast cultured with increasing concentrations of C16:0 PAF, C16:0 lyso-PAF or ethanol (carrier control). As expected, C16:0 PAF inhibited wild type haploid yeast growth in liquid culture in a concentration-dependent manner whereas C16:0 lyso-PAF was found to be comparatively less toxic at similar concentrations (Figure 1). Although both lipids impact viability at higher concentrations, the distinct effects of these two lipids at lower concentrations have not previously been appreciated and parallels their toxicity to neuronal cells [1], [19].


Srf1 is a novel regulator of phospholipase D activity and is essential to buffer the toxic effects of C16:0 platelet activating factor.

Kennedy MA, Kabbani N, Lambert JP, Swayne LA, Ahmed F, Figeys D, Bennett SA, Bryan J, Baetz K - PLoS Genet. (2011)

The differential sensitivity of yeast to C16:0 PAF and C16:0 lyso-PAF.Growth of wild type (YPH499) strain (OD600) as a function of time in hours. Wild type yeast cells were grown in YPD liquid culture with or without C16:0 PAF or C16:0 lyso-PAF as indicated. Growth curves were performed in triplicate and the error bars represent 1 standard deviation.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3037409&req=5

pgen-1001299-g001: The differential sensitivity of yeast to C16:0 PAF and C16:0 lyso-PAF.Growth of wild type (YPH499) strain (OD600) as a function of time in hours. Wild type yeast cells were grown in YPD liquid culture with or without C16:0 PAF or C16:0 lyso-PAF as indicated. Growth curves were performed in triplicate and the error bars represent 1 standard deviation.
Mentions: Previous studies have determined that, similar to neuronal cells [1], S. cerevisiae are sensitive to C16:0 PAF [17]. To determine whether C16:0 PAF and C16:0 lyso-PAF differentially impact the growth of S. cerevisiae and to identify an appropriate working concentration range for these lipids in subsequent studies we performed liquid growth curve analysis using wild type haploid yeast cultured with increasing concentrations of C16:0 PAF, C16:0 lyso-PAF or ethanol (carrier control). As expected, C16:0 PAF inhibited wild type haploid yeast growth in liquid culture in a concentration-dependent manner whereas C16:0 lyso-PAF was found to be comparatively less toxic at similar concentrations (Figure 1). Although both lipids impact viability at higher concentrations, the distinct effects of these two lipids at lower concentrations have not previously been appreciated and parallels their toxicity to neuronal cells [1], [19].

Bottom Line: As C16:0 PAF is a naturally occurring lipid involved in cellular signaling, it is likely that mechanisms exist to protect cells against its toxic effects.Deletion of YDL133w, a previously uncharacterized gene which we have renamed SRF1 (Spo14 Regulatory Factor 1), resulted in the greatest differential sensitivity to C16:0 PAF over C16:0 lyso-PAF.Though C16:0 PAF treatment does not impact hydrolysis of phosphatidylcholine in yeast, C16:0 PAF does promote delocalization of GFP-Spo14 and phosphatidic acid from the cell periphery.

View Article: PubMed Central - PubMed

Affiliation: Ottawa Institute of Systems Biology, Department of Biochemistry, Microbiology, and Immunology, University of Ottawa, Ottawa, Canada.

ABSTRACT
During Alzheimer's Disease, sustained exposure to amyloid-β₄₂ oligomers perturbs metabolism of ether-linked glycerophospholipids defined by a saturated 16 carbon chain at the sn-1 position. The intraneuronal accumulation of 1-O-hexadecyl-2-acetyl-sn-glycerophosphocholine (C16:0 PAF), but not its immediate precursor 1-O-hexadecyl-sn-glycerophosphocholine (C16:0 lyso-PAF), participates in signaling tau hyperphosphorylation and compromises neuronal viability. As C16:0 PAF is a naturally occurring lipid involved in cellular signaling, it is likely that mechanisms exist to protect cells against its toxic effects. Here, we utilized a chemical genomic approach to identify key processes specific for regulating the sensitivity of Saccharomyces cerevisiae to alkyacylglycerophosphocholines elevated in Alzheimer's Disease. We identified ten deletion mutants that were hypersensitive to C16:0 PAF and five deletion mutants that were hypersensitive to C16:0 lyso-PAF. Deletion of YDL133w, a previously uncharacterized gene which we have renamed SRF1 (Spo14 Regulatory Factor 1), resulted in the greatest differential sensitivity to C16:0 PAF over C16:0 lyso-PAF. We demonstrate that Srf1 physically interacts with Spo14, yeast phospholipase D (PLD), and is essential for PLD catalytic activity in mitotic cells. Though C16:0 PAF treatment does not impact hydrolysis of phosphatidylcholine in yeast, C16:0 PAF does promote delocalization of GFP-Spo14 and phosphatidic acid from the cell periphery. Furthermore, we demonstrate that, similar to yeast cells, PLD activity is required to protect mammalian neural cells from C16:0 PAF. Together, these findings implicate PLD as a potential neuroprotective target capable of ameliorating disruptions in lipid metabolism in response to accumulating oligomeric amyloid-β₄₂.

Show MeSH
Related in: MedlinePlus