The effect of amino acids on choline uptake and phosphatidylcholine biosynthesis in mammalian hearts

Lipids ◽  
1992 ◽  
Vol 27 (6) ◽  
pp. 466-469 ◽  
Author(s):  
Monroe Chan ◽  
O Karmin ◽  
Adrian S. Man ◽  
Patrick C. Choy
Keyword(s):  
Amino Acids ◽  
Choline Uptake ◽  
Phosphatidylcholine Biosynthesis

Effects of amino acids and ethanolamine on choline uptake and phosphatidylcholine biosynthesis in baby hamster kidney-21 cells

1992 ◽  
Vol 70 (12) ◽  
pp. 1319-1324 ◽  
Author(s):  
Xiliang Zha ◽  
Francis T. Jay ◽  
Patrick C. Choy
Keyword(s):  
Amino Acids ◽  
Culture Media ◽  
Specific Radioactivity ◽  
Kinetic Studies ◽  
Choline Uptake ◽  
Dependent Manner ◽  
Baby Hamster Kidney ◽  
Concentration Dependent Manner ◽  
Cell Culture Media ◽  
Phosphatidylcholine Biosynthesis

The effects of amino acids and ethanolamine on choline uptake and phosphatidylcholine biosynthesis in baby hamster kidney (BHK-21) cells were investigated. The cells were incubated with labelled choline in the presence of an amino acid or ethanolamine. The uptake of labelled choline was noncompetitively inhibited by amino acids. Glycine, L-alanine, L-serine, L-leucine, L-aspartate, and L-arginine were effective inhibitors and a maximum of 22% inhibition of choline uptake was obtained with 5 mM glycine. Analyses of the labellings in the choline-containing metabolites revealed that the conversion of choline to CDP-choline and subsequently phosphatidylcholine was not affected by the presence of amino acids. The uptake of choline was also inhibited by ethanolamine in a concentration-dependent manner. Kinetic studies on the uptake of choline indicated that the inhibition by ethanolamine was competitive in nature. Although ethanolamine is a potent inhibitor of choline kinase, analyses of the labellings in the choline-containing metabolites indicated that the conversion of choline to phosphocholine was not affected in the cells incubated with ethanolamine. Ethanolamine did not change the pool sizes of phosphocholine and CDP-choline. Based on the specific radioactivity of CDP-choline and the labelling of phosphatidylcholine, the rates of phosphatidylcholine biosynthesis were not significantly different between the control and the ethanolamine-treated cells. In view of the concentrations of amino acids (millimolar) and ethanolamine (micromolar) in most cell culture media, it appeared that only amino acids were important metabolites for the regulation of choline uptake in BHK-21 cells. We conclude that both amino acids and ethanolamine have no direct effect on the biosynthesis of phosphatidylcholine.Key words: choline uptake, phosphatidylcholine biosynthesis, amino acids, ethanolamine, BHK-21 cells.

Effect of amino acids on choline uptake and phosphatidylcholine biosynthesis in the isolated hamster heart

1988 ◽  
Vol 66 (5) ◽  
pp. 418-424 ◽  
Author(s):  
Grant M. Hatch ◽  
Willem K. Stevens ◽  
Patrick C. Choy
Keyword(s):  
Amino Acids ◽  
Direct Interaction ◽  
Choline Uptake ◽  
Choline Transport ◽  
Neutral Amino Acids ◽  
Acidic Amino Acids ◽  
Phosphatidylcholine Biosynthesis ◽  
Concentration Threshold ◽  
Hamster Heart ◽  
Dose Dependent

Choline uptake by the hamster heart has been shown to be enhanced by exogenous glycine. In this study, the effect of neutral, basic, and acidic amino acids on choline uptake was assessed. Hamster hearts were perfused with labelled choline, and in the presence of L-alanine, L-serine, or L-phenylalanine (≥0.1 mM), choline uptake was enhanced 20–38%. L-Arginine, L-lysine, L-aspartate, and L-glutamate did not influence choline uptake. The rate of phosphatidylcholine biosynthesis was unaffected by all amino acids tested. Enhancement of choline uptake by neutral amino acids was not additive or dose dependent but required a concentration threshold. The enhancement of choline uptake by neutral amino acids was not influenced by preperfusion with the same amino acid. Exogenous choline had no effect on the uptake of amino acids. We postulate that choline and the neutral amino acids are not cotransported and modulation of choline uptake is facilitated by direct interaction of the neutral amino acids with the choline transport system.

scholarly journals Effects of fasting on phosphatidylcholine biosynthesis in hamster liver: regulation of cholinephosphotransferase activity by endogenous argininosuccinate

1993 ◽  
Vol 289 (3) ◽  
pp. 727-733 ◽  
Author(s):  
K M O ◽  
P C Choy
Keyword(s):  
Enzyme Activity ◽  
Substantial Decrease ◽  
Compensatory Mechanism ◽  
Choline Uptake ◽  
Endogenous Inhibitor ◽  
Short Term ◽  
Phosphatidylcholine Biosynthesis ◽  
Choline Phosphotransferase ◽  
Pool Sizes

The control of phosphatidylcholine biosynthesis in the hamster liver was examined. Livers of hamsters fasted for 24 and 48 h were perfused with labelled choline. Under both fasting conditions, the incorporation of labelled choline into phosphatidylcholine was reduced. After 48 h of fasting, the 52% reduction in phosphatidylcholine biosynthesis was caused by changes in several factors including a diminishing rate of choline uptake and severe reductions in the pool sizes of ATP and CTP (to 33-37% control values) which resulted in a decrease in the pools of choline-containing metabolites. The activation of cytidylyltransferase after 48 h of fasting might be regarded as a compensatory mechanism for the maintenance of phosphatidylcholine biosynthesis. After 24 h of fasting, a 25% reduction in phosphatidylcholine biosynthesis was observed. The ATP and CTP levels were decreased but the reduction was not severe enough to affect the choline uptake or the labelling of the phosphocholine fraction. The activities of the cytidylyltransferase remained unchanged but an accumulation of labelled CDP-choline was detected. Although choline-phosphotransferase activity was not changed in the microsomes, the enzyme activity was attenuated in the postmitochondrial fraction. Further analysis revealed that cholinephosphotransferase in the liver was inhibited by an endogenous inhibitor in the cytosol which was later identified as argininosuccinate. The level of argininosuccinate was elevated during fasting and the change quantitatively accounted for the attenuation of cholinephosphotransferase activity. The inhibition of choline-phosphotransferase by argininosuccinate, coupled with a substantial decrease in the diacylglycerol level, would provide the hamster liver with an immediate mechanism for the transient modulation of phosphatidylcholine biosynthesis during short-term fasting.

scholarly journals Antagonism of phorbol-ester-stimulated phosphatidylcholine biosynthesis by the phospholipid analogue hexadecylphosphocholine

1993 ◽  
Vol 291 (2) ◽  
pp. 561-567 ◽  
Author(s):  
T Wieder ◽  
C C Geilen ◽  
W Reutter
Keyword(s):  
Cell Lines ◽  
Hela Cells ◽  
Mdck Cells ◽  
Fold Increase ◽  
Choline Uptake ◽  
Choline Incorporation ◽  
Contrast Enhanced ◽  
Phosphatidylcholine Biosynthesis ◽  
Membrane Bound ◽  
Stimulation Of

The antagonization of phorbol 12-myristate 13-acetate (PMA)-stimulated phosphatidylcholine (PtdCho) biosynthesis by the phospholipid analogue hexadecylphosphocholine (HePC) in MDCK cells was investigated and compared with the corresponding influence in HeLa cells. In both cell lines, PMA-stimulated PtdCho biosynthesis was antagonized by 50 microM HePC. However, subsequent experiments provided evidence that PMA enhances PtdCho biosynthesis by at least two mechanisms: (i) by stimulation of choline uptake and (ii) by translocation of CTP:choline phosphate cytidylyltransferase to membranes. In MDCK cells, 5 nM PMA caused a 4-fold increase in [methyl-3H]choline incorporation into PtdCho, which was paralleled by an approx. 2-fold stimulation of choline uptake. These data indicate that choline uptake might play an important role in the regulation of PtdCho biosynthesis in this cell line, especially since we could not detect any significant increase in membrane-bound cytidyltransferase activity in PMA-treated MDCK cells. In contrast, enhanced PtdCho biosynthesis in HeLa cells is achieved by a 2-fold increase in particulate cytidylyltransferase activity after PMA stimulation. Translocation of cytidylyltransferase from the cytosol to membranes is therefore important in HeLa cells. Nevertheless, in both cell lines, the main target of HePC seems to be the translocation process. In MDCK cells, addition of 50 microM HePC decreases membrane-bound cytidylyltransferase activity by about 45%, compared with control cells and PMA-treated cells. In HeLa cells, PMA-induced translocation of cytidylyltransferase to membranes is totally abolished by HePC.

Evidence that the transport-related proteins BAT and 4F2hc are not specific for amino acids: induction of Na+-dependent uridine and pyruvate transport activity by recombinant BAT and 4F2hc expressed in Xenopus oocytes

1998 ◽  
Vol 76 (5) ◽  
pp. 859-865 ◽  
Author(s):  
Sylvia YM Yao ◽  
William R Muzyka ◽  
Carol E Cass ◽  
Christopher I Cheeseman ◽  
James D Young
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Amino Acid Transport ◽  
Xenopus Oocytes ◽  
Transport Systems ◽  
Choline Uptake ◽  
Type I ◽  
Organic Substrates ◽  
Acid Transport ◽  
Cationic Amino Acids

Members of the BAT and 4F2hc gene family have one or, in the case of BAT, up to four transmembane domains and induce amino acid transport systems bo,+ (BAT) and y+L (4F2hc) when expressed in Xenopus oocytes. System bo,+ is a Na+-independent process with a broad tolerance for cationic and zwitterionic amino acids, whereas y+L exhibits Na+-independent transport of cationic amino acids (e.g., lysine) and Na+-dependent transport of zwitterionic amino acids (e.g., leucine). Mutations in the human BAT gene are associated with type I cystinuria, a genetic disease affecting the ability of intestinal and renal brush border membranes to transport cationic amino acids and cystine. An unresolved question is whether BAT and 4F2hc themselves have catalytic (i.e., transporting) activity or whether they operate as activators of other, as yet unidentified, transporter proteins. In this report, we have investigated the transport of representatives of four different classes of organic substrates in Xenopus oocytes following injection with rat BAT or 4F2hc RNA transcripts: leucine (a control amino acid substrate), uridine (a nucleoside), pyruvate (a monocarboxylate), and choline (an amine). Both recombinant proteins induced small, statistically significant Na+-dependent fluxes of uridine and pyruvate but had no effect on choline uptake. In contrast, control oocytes injected with transcripts for conventional nucleoside and cationic amino acid transporters (rat CNT1 and murine CAT1, respectively) showed no induction of transport of either leucine or pyruvate (CNT1) or uridine or pyruvate (CAT1). These findings support the idea that BAT and 4F2hc are transport activators and minimize the possibility that they have intrinsic transport capability. The transport-regulating functions of these proteins may extend to permeants other than amino acids.Key words: amino acid transport, uridine, pyruvate, BAT, 4F2hc, Xenopus oocytes.

scholarly journals Phosphatidylcholine biosynthesis and choline transport in the anaerobic protozoon Entodinium caudatum

1976 ◽  
Vol 160 (3) ◽  
pp. 481-490 ◽  
Author(s):  
F L Bygrave ◽  
R M C Dawson
Keyword(s):  
Cell Envelope ◽  
Choline Kinase ◽  
Choline Uptake ◽  
Choline Transport ◽  
Intact Cells ◽  
Phosphatidylcholine Biosynthesis ◽  
Free Choline ◽  
Choline Phosphate ◽  
Rate Limiting ◽  
Phosphatidylcholine Synthesis

Choline accumulation and phosphatidylcholine biosynthesis were investigated in the choline-requiring anaerobic protozoon Entodinium caudatum by incubating whole cells or subcellular fractions with [14C] choline, phosphoryl [14C] choline and CDP-[14C] choline. 2. All membrane fractions contained choline kinase (EC 2.7.1.32) and CDP-choline-1,2-diacylglycerol cholinephosphotransferase (EC 2.7.8.2), although the specific activities were less in the cell-envelope fraction. Choline phosphate cytidylyltransferase (EC 2.7.7.15) was limited to the supernatant, and this enzyme was rate-limiting for phosphatidylcholine synthesis in the whole cell. 3. Synthesis of phosphatidylcholine from free choline by membranes was only possible in the presence of supernatant. Such reconstituted systems required ATP (2.5 mM), CTP (1 mM) and Mg2+ (5 mM) for maximum synthesis of the phospholipid. CTP and Mg2+ were absolute requirements. 4. Hemicholinium-3 prevented choline uptake by the cells and was strongly inhibitory towards choline kinase; the other enzymes involved in phosphatidylcholine synthesis were minimally affected. 5. Ca2+ ions (0.5 mM) substantially inhibited CDP-choline-1,2-diacylglycerol cholinephosphotransferase in the presence of 15 mM-Mg2+, but choline phosphate cytidylyltransferase and choline kinase were less affected. 6. No free choline could be detected intact cells even after short (10-180s) incubations or at temperatures down to 10° C. The [14C] choline entering was mainly present as phosphorylcholine and to a lesser extent as phosphatidylcholine. 7. It is suggested that choline kinase effectively traps any choline within the cell, thus ensuring a supply of the base for future growth. At low choline concentrations the activity of choline kinase is rate-limiting for choline uptake, and the enzyme might possibly play an active role in the transport phenomenon. Thus the choline uptake by intact cells and choline kinase have similar Km values and show similar responses to temperature and hemicholinium-3.

Effect of cAMP on choline uptake and phosphatidylcholine biosynthesis in cultured chick heart cells

1988 ◽  
Vol 66 (3) ◽  
pp. 231-237 ◽  
Author(s):  
Paul S. Sunga ◽  
P. Haydn Pritchard ◽  
Simon W. Rabkin
Keyword(s):  
Phosphodiesterase Inhibitor ◽  
Cardiac Cells ◽  
Heart Cells ◽  
Choline Uptake ◽  
Ctp:Phosphocholine Cytidylyltransferase ◽  
Rate Limiting Step ◽  
Limiting Step ◽  
Phosphatidylcholine Biosynthesis ◽  
Chick Heart ◽  
Rate Limiting

The effect of an analogue of cAMP on the uptake and metabolism of choline in the heart was studied in isolated cardiac cells. The cells were obtained from 7-day-old chick embryos and maintained in culture. The effects of cAMP were studied using the dibutyryl cAMP analogue and the phosphodiesterase inhibitor 3-isobutyl-1-methylxanthine. After a 2-h incubation with [3H]choline, about 85% of the label was recovered in phosphocholine, with most of the rest in phospholipid. During a subsequent chase incubation, [3H]phosphocholine was transferred to phosphatidylcholine with little accumulation in CDP-choline. This suggests the rate-limiting step for the conversion of phosphocholine to phosphatidylcholine in these cells is the synthesis of CDP-choline. cAMP decreased the incorporation of choline into phosphatidylcholine, but did not change the flux of metabolites through the step catalyzed by CTP:phosphocholine cytidylyltransferase. cAMP had little effect on choline uptake at low (1–25 μM) extracellular choline concentrations, but significantly (p < 0.05) decreased choline uptake at higher (37.5–50 μM) extracellular choline concentrations. Thus, cardiac cells take up and metabolize choline to phosphocholine, with CTP:phosphocholine cytidylyltransferase being the rate-limiting step in phosphatidylcholine biosynthesis. cAMP decreases [3H]choline uptake and its subsequent incorporation into phosphocholine and phospholipid. However, the metabolism of choline within the cell is unaffected.

Sign in / Sign up

Export Citation Format

Share Document