ENHANCEMENT BY CYTIDINE OF MEMBRANE PHOSPHOLIPID-SYNTHESIS

被引:18
作者
COVIELLA, ILG [1 ]
WURTMAN, RJ [1 ]
机构
[1] MIT, DEPT BRAIN & COGNIT SCI, CAMBRIDGE, MA 02139 USA
关键词
ACETYLCHOLINE; CHOLINE; CYTIDINE; PC12-CELLS; PHOSPHATIDYLCHOLINE; PHOSPHOLIPIDS;
D O I
10.1111/j.1471-4159.1992.tb08909.x
中图分类号
Q5 [生物化学]; Q7 [分子生物学];
学科分类号
071010 ; 081704 ;
摘要
Cytidine, as cytidine 5'-diphosphate choline, is a major precursor in the synthesis of phosphatidylcholine in cell membranes. In the present study, we examined the relationships between extracellular levels of cytidine, the conversion of [C-14]choline to [C-14]phosphatidylcholine, and the net syntheses of phosphatidylcholine and phosphatidylethanolamine by PC12 cells. The rate at which cytidine (as [H-3]cytidine) was incorporated into the PC12 cells followed normal Michaelis-Menten kinetics (k(m) = 5-mu-M; V(max) = 12 x 10(-3) mmol/mg of protein/min) when the cytidine concentrations in the medium were below 50-mu-M; at higher concentrations, intracellular [H-3]cytidine nucleotide levels increased linearly. Once inside the cell, cytidine was converted mainly into cytidine triphosphate. In pulse-chase experiments, addition of cytidine to the medium caused a time- and dose-dependent increase (by up to 30%) in the incorporation of [C-14]choline into membrane [C-14]-Phosphatidylcholine. When the PC12 cells were supplemented with both cytidine and choline for 14 h, small but significant elevations (p < 0.05) were observed in their absolute contents of membrane phosphatidylcholine, phosphatidylethanolamine, and phosphatidylserine, all increasing by 10-15% relative to their levels in cells incubated with choline alone. Exogenous cytidine, acting via cytidine triphosphate. can thus affect the synthesis and levels of cell membrane phospholipids.
引用
收藏
页码:338 / 343
页数:6
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