Role of the Yeast Phosphatidylinositol/Phosphatidylcholine Transfer Protein (Sec14p) in Phosphatidylcholine Turnover and INO1 Regulation (original) (raw)

1997, Journal of Biological Chemistry

In yeast, mutations in the CDP-choline pathway for phosphatidylcholine biosynthesis permit the cell to grow even when the SEC14 gene is completely deleted (Cleves, A., McGee, T., Whitters, E., Champion, K., Aitken, J., Dowhan, W., Goebl, M., and Bankaitis, V. (1991) Cell 64, 789 -800). We report that strains carrying mutations in the CDP-choline pathway, such as cki1, exhibit a choline excretion phenotype due to production of choline during normal turnover of phosphatidylcholine. Cells carrying cki1 in combination with sec14 ts , a temperature-sensitive allele in the gene encoding the phosphatidylinositol/phosphatidylcholine transporter, have a dramatically increased choline excretion phenotype when grown at the sec14 ts -restrictive temperature. We show that the increased choline excretion in sec14 ts cki1 cells is due to increased turnover of phosphatidylcholine via a mechanism consistent with phospholipase D-mediated turnover. We propose that the elevated rate of phosphatidylcholine turnover in sec14 ts cki1 cells provides the metabolic condition that permits the secretory pathway to function when Sec14p is inactivated.