Evidence for an intrinsic toxicity of phosphatidylcholine to Sec14p-dependent protein transport from the yeast Golgi complex.
Yeast phosphatidylinositol-transfer protein (Sec14p) is essential for Golgi secretory function and cell viability. This requirement of Sec14p is relieved by genetic inactivation of the cytidine diphosphate-choline pathway for phosphatidycholine (PtdCho) biosynthesis. Standard phenotypic analyses indicate that inactivation of the phosphatidylethanolamine (PtdEtn) pathway for PtdCho biosynthesis, however, does not rescue the growth and secretory defects associated with Sec14p deficiency. We now report inhibition of choline uptake from the media reveals an efficient "bypass Sec14p" phenotype associated with PtdEtn-methylation pathway defects. We further show that the bypass Sec14p phenotype associated with PtdEtn-methylation pathway defects resembles other bypass Sec14p mutations in its dependence on phospholipase D activity. Finally, we find that increased dosage of enzymes that catalyze phospholipase D-independent turnover of PtdCho, via mechanisms that do not result in a direct production of phosphatidic acid or diacylglycerol, effect a partial rescue of sec14-1(ts)-associated growth defects. Taken together, these data support the idea that PtdCho is intrinsically toxic to yeast Golgi secretory function.
Xie
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Department of Cell Biology, University of Alabama at Birmingham, 35294-0005, USA.
Fang
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Bankaitis
V A
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D019870:1-Phosphatidylinositol 4-Kinase / Q000096:biosynthesis / Q000235:genetics; D001692:Biological Transport; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D002794:Choline / Q000378:metabolism; D003470:Culture Media; D005656:Fungal Proteins / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D015870:Gene Expression; D006056:Golgi Apparatus / Q000378:metabolism*; D008245:Lysophospholipase; D008565:Membrane Proteins; D026901:Membrane Transport Proteins; D008745:Methylation; D010713:Phosphatidylcholines / Q000378:metabolism*; D010714:Phosphatidylethanolamines / Q000378:metabolism; D049294:Phospholipid Transfer Proteins; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins
D002352:Carrier Proteins; D003470:Culture Media; D005656:Fungal Proteins; D008565:Membrane Proteins; D026901:Membrane Transport Proteins; D010713:Phosphatidylcholines; D010714:Phosphatidylethanolamines; D049294:Phospholipid Transfer Proteins; C483438:SEC14 protein, S cerevisiae; C118289:SEC24 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; C065637:choline transporter; D019870:1-Phosphatidylinositol 4-Kinase; C441760:PIK1 protein, S cerevisiae; D008245:Lysophospholipase; C490270:PLB1 protein, S cerevisiae; D002794:Choline