Limits...
A Yeast Mutant Deleted of GPH1 Bears Defects in Lipid Metabolism.

Gsell M, Fankl A, Klug L, Mascher G, Schmidt C, Hrastnik C, Zellnig G, Daum G - PLoS ONE (2015)

Bottom Line: Here we show that deletion of this gene also causes decreased levels of phosphatidylcholine (PC), triacylglycerols and steryl esters.Depletion of the two non-polar lipids in a Δgph1 strain leads to lack of lipid droplets, and decrease of the PC level results in instability of the plasma membrane.Altogether, Gph1p besides its function as a glycogen mobilizing enzyme appears to play a regulatory role in yeast lipid metabolism.

View Article: PubMed Central - PubMed

Affiliation: Institute of Biochemistry, Graz University of Technology, NaWi Graz, Petersgasse 12/2, 8010, Graz, Austria.

ABSTRACT
In a previous study we demonstrated up-regulation of the yeast GPH1 gene under conditions of phosphatidylethanolamine (PE) depletion caused by deletion of the mitochondrial (M) phosphatidylserine decarboxylase 1 (PSD1) (Gsell et al., 2013, PLoS One. 8(10):e77380. doi: 10.1371/journal.pone.0077380). Gph1p has originally been identified as a glycogen phosphorylase catalyzing degradation of glycogen to glucose in the stationary growth phase of the yeast. Here we show that deletion of this gene also causes decreased levels of phosphatidylcholine (PC), triacylglycerols and steryl esters. Depletion of the two non-polar lipids in a Δgph1 strain leads to lack of lipid droplets, and decrease of the PC level results in instability of the plasma membrane. In vivo labeling experiments revealed that formation of PC via both pathways of biosynthesis, the cytidine diphosphate (CDP)-choline and the methylation route, is negatively affected by a Δgph1 mutation, although expression of genes involved is not down regulated. Altogether, Gph1p besides its function as a glycogen mobilizing enzyme appears to play a regulatory role in yeast lipid metabolism.

No MeSH data available.


Related in: MedlinePlus

Synthesis of phosphatidylcholine is down regulated in the Δgph1 deletion mutant in vivo.Black bar, wild type BY4741; grey bar, Δgph1 deletion mutant; (A) The so-called Kennedy pathway (CDP-choline pathways) was analyzed by incorporation of [methyl-14C]choline chloride into PC. (B) To analyze the methylation pathway of PC, the incorporation of L-[3H]serine into PS, PE and PC was measured. Wild type BY4741 was set at 100%.
© Copyright Policy
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4556709&req=5

pone.0136957.g003: Synthesis of phosphatidylcholine is down regulated in the Δgph1 deletion mutant in vivo.Black bar, wild type BY4741; grey bar, Δgph1 deletion mutant; (A) The so-called Kennedy pathway (CDP-choline pathways) was analyzed by incorporation of [methyl-14C]choline chloride into PC. (B) To analyze the methylation pathway of PC, the incorporation of L-[3H]serine into PS, PE and PC was measured. Wild type BY4741 was set at 100%.

Mentions: As described above, the PC level in the Δgph1 deletion mutant was markedly decreased compared to wild type. As there are two pathways of PC synthesis in Saccharomyces cerevisiae we wished to estimate which one was affected by the Δgph1 deletion. PC can be synthesized (i) via the CDP-choline branch of the Kennedy pathway which utilizes choline as a substrate [10]; or (ii) through a three step methylation of PE catalyzed by Cho2p and Opi3p [42–44]. To analyze the CDP-choline pathway we labeled cells with [methyl-14C]choline chloride and measured incorporation of the label into PC. As shown in Fig 3A, the synthesis of PC in vivo via this pathway was reduced to 60% of wild type. Interestingly, however, also the methylation pathway was affected by the Δgph1 deletion (Fig 3B). In this assay, cells were labeled with L-[3H]serine, and sequential incorporation of the label into PS, PE (catalyzed by Psd1p or Psd2p), and PC (catalyzed by Cho2p and Opi3p) was measured. Whereas the first two steps in the biosynthetic route of aminoglycerophospholipids were reduced by 20%, the methylation of PE to PC in Δgph1 was approximately only 50% of wild type. In summary, formation of PC through both pathways was strongly decreased in the mutant.


A Yeast Mutant Deleted of GPH1 Bears Defects in Lipid Metabolism.

Gsell M, Fankl A, Klug L, Mascher G, Schmidt C, Hrastnik C, Zellnig G, Daum G - PLoS ONE (2015)

Synthesis of phosphatidylcholine is down regulated in the Δgph1 deletion mutant in vivo.Black bar, wild type BY4741; grey bar, Δgph1 deletion mutant; (A) The so-called Kennedy pathway (CDP-choline pathways) was analyzed by incorporation of [methyl-14C]choline chloride into PC. (B) To analyze the methylation pathway of PC, the incorporation of L-[3H]serine into PS, PE and PC was measured. Wild type BY4741 was set at 100%.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4556709&req=5

pone.0136957.g003: Synthesis of phosphatidylcholine is down regulated in the Δgph1 deletion mutant in vivo.Black bar, wild type BY4741; grey bar, Δgph1 deletion mutant; (A) The so-called Kennedy pathway (CDP-choline pathways) was analyzed by incorporation of [methyl-14C]choline chloride into PC. (B) To analyze the methylation pathway of PC, the incorporation of L-[3H]serine into PS, PE and PC was measured. Wild type BY4741 was set at 100%.
Mentions: As described above, the PC level in the Δgph1 deletion mutant was markedly decreased compared to wild type. As there are two pathways of PC synthesis in Saccharomyces cerevisiae we wished to estimate which one was affected by the Δgph1 deletion. PC can be synthesized (i) via the CDP-choline branch of the Kennedy pathway which utilizes choline as a substrate [10]; or (ii) through a three step methylation of PE catalyzed by Cho2p and Opi3p [42–44]. To analyze the CDP-choline pathway we labeled cells with [methyl-14C]choline chloride and measured incorporation of the label into PC. As shown in Fig 3A, the synthesis of PC in vivo via this pathway was reduced to 60% of wild type. Interestingly, however, also the methylation pathway was affected by the Δgph1 deletion (Fig 3B). In this assay, cells were labeled with L-[3H]serine, and sequential incorporation of the label into PS, PE (catalyzed by Psd1p or Psd2p), and PC (catalyzed by Cho2p and Opi3p) was measured. Whereas the first two steps in the biosynthetic route of aminoglycerophospholipids were reduced by 20%, the methylation of PE to PC in Δgph1 was approximately only 50% of wild type. In summary, formation of PC through both pathways was strongly decreased in the mutant.

Bottom Line: Here we show that deletion of this gene also causes decreased levels of phosphatidylcholine (PC), triacylglycerols and steryl esters.Depletion of the two non-polar lipids in a Δgph1 strain leads to lack of lipid droplets, and decrease of the PC level results in instability of the plasma membrane.Altogether, Gph1p besides its function as a glycogen mobilizing enzyme appears to play a regulatory role in yeast lipid metabolism.

View Article: PubMed Central - PubMed

Affiliation: Institute of Biochemistry, Graz University of Technology, NaWi Graz, Petersgasse 12/2, 8010, Graz, Austria.

ABSTRACT
In a previous study we demonstrated up-regulation of the yeast GPH1 gene under conditions of phosphatidylethanolamine (PE) depletion caused by deletion of the mitochondrial (M) phosphatidylserine decarboxylase 1 (PSD1) (Gsell et al., 2013, PLoS One. 8(10):e77380. doi: 10.1371/journal.pone.0077380). Gph1p has originally been identified as a glycogen phosphorylase catalyzing degradation of glycogen to glucose in the stationary growth phase of the yeast. Here we show that deletion of this gene also causes decreased levels of phosphatidylcholine (PC), triacylglycerols and steryl esters. Depletion of the two non-polar lipids in a Δgph1 strain leads to lack of lipid droplets, and decrease of the PC level results in instability of the plasma membrane. In vivo labeling experiments revealed that formation of PC via both pathways of biosynthesis, the cytidine diphosphate (CDP)-choline and the methylation route, is negatively affected by a Δgph1 mutation, although expression of genes involved is not down regulated. Altogether, Gph1p besides its function as a glycogen mobilizing enzyme appears to play a regulatory role in yeast lipid metabolism.

No MeSH data available.


Related in: MedlinePlus