Gsell Martina, Fankl Ariane, Klug Lisa, Mascher Gerald, Schmidt Claudia, Hrastnik Claudia, Zellnig Günther, Daum Günther
Institute of Biochemistry, Graz University of Technology, NaWi Graz, Petersgasse 12/2, 8010, Graz, Austria.
Institute of Plant Sciences, Karl Franzens University Graz, NaWi Graz, Austria.
PLoS One. 2015 Sep 1;10(9):e0136957. doi: 10.1371/journal.pone.0136957. eCollection 2015.
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.
在先前的一项研究中，我们证明了在由线粒体（M）磷脂丝氨酸脱羧酶1（PSD1）缺失导致的磷脂酰乙醇胺（PE）耗竭条件下，酵母GPH1基因上调（Gsell等人，2013年，《公共科学图书馆·综合》。8(10):e77380。doi: 10.1371/journal.pone.0077380）。Gph1p最初被鉴定为一种糖原磷酸化酶，在酵母的稳定生长期催化糖原降解为葡萄糖。在此我们表明，该基因的缺失还会导致磷脂酰胆碱（PC）、三酰甘油和甾醇酯水平降低。Δgph1菌株中两种非极性脂质的耗竭导致脂滴缺乏，PC水平的降低导致质膜不稳定。体内标记实验表明，尽管相关基因的表达未下调，但通过生物合成的两条途径，即胞苷二磷酸（CDP）-胆碱途径和甲基化途径形成PC均受到Δgph1突变的负面影响。总之，Gph1p除了作为一种糖原动员酶的功能外，似乎在酵母脂质代谢中发挥调节作用。
