Stimulation of phosphatidylcholine biosynthesis by hemicholinium-3, a potent inhibitor of choline uptake in human leukemic monocyte-like U937 cells

1994 ◽  
Vol 12 (2) ◽  
pp. 79-88
Author(s):  
Arthur J. Chu
Keyword(s):  
Potent Inhibitor ◽  
Choline Uptake ◽  
U937 Cells ◽  
Phosphatidylcholine Biosynthesis ◽  
Stimulation Of

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.

Enhancement of Plasminogen Binding to U937 Cells and Fibrin by Complestatin

1997 ◽  
Vol 77 (01) ◽  
pp. 137-142 ◽  
Author(s):  
Kiyoshi Tachikawa ◽  
Keiji Hasurni ◽  
Akira Endo
Keyword(s):  
Binding Site ◽  
Binding Affinity ◽  
Blood Cells ◽  
Aminocaproic Acid ◽  
U937 Cells ◽  
Biochemical Basis ◽  
Equilibrium Binding ◽  
Pharmacological Stimulation ◽  
Endogenous Fibrinolysis ◽  
Stimulation Of

SummaryPlasminogen binds to endothelial and blood cells as well as to fibrin, where the zymogen is efficiently activated and protected from inhibition by α2-antiplasmin. In the present study we have found that complestatin, a peptide-like metabolite of a streptomyces, enhances binding of plasminogen to cells and fibrin. Complestatin, at concentrations ranging from 1 to 5 μM, doubled 125I-plasminogen binding to U937 cells both in the absence and presence of lipoprotein(a), a putative physiological competitor of plasminogen. The binding of 125I-plasminogen in the presence of complestatin was abolished by e-aminocaproic acid, suggesting that the lysine binding site(s) of the plasminogen molecule are involved in the binding. Equilibrium binding analyses indicated that complestatin increased the maximum binding of 125I-plasminogen to U937 cells without affecting the binding affinity. Complestatin was also effective in increasing 125I-plasminogen binding to fibrin, causing 2-fold elevation of the binding at ~1 μM. Along with the potentiation of plasminogen binding, complestatin enhanced plasmin formation, and thereby increased fibrinolysis. These results would provide a biochemical basis for a pharmacological stimulation of endogenous fibrinolysis through a promotion of plasminogen binding to cells and fibrin.

scholarly journals A comparison of the effects of NN′-dicyclohexylcarbodi-imide, oligomycin A and aurovertin on energy-linked reactions in mitochondria and submitochondrial particles

1968 ◽  
Vol 108 (3) ◽  
pp. 445-456 ◽  
Author(s):  
A. M. Roberton ◽  
Caroline T. Holloway ◽  
I G Knight ◽  
R B Beechey
Keyword(s):  
Potent Inhibitor ◽  
Atp Synthesis ◽  
Mitochondrial Fraction ◽  
Optimum Concentration ◽  
Submitochondrial Particles ◽  
Nicotinamide Nucleotide Transhydrogenase ◽  
Oligomycin A ◽  
Submitochondrial Particle ◽  
Site Of Action ◽  
Stimulation Of

1. The effects of dicyclohexylcarbodi-imide, oligomycin A and aurovertin on enzyme systems related to respiratory-chain phosphorylation were compared. Dicyclohexylcarbodi-imide and oligomycin A have very similar functional effects, giving 50% inhibition of ATP-utilizing and ATP-generating systems at concentrations below 0·8nmole/mg. of submitochondrial-particle protein. Aurovertin is a more potent inhibitor of ATP synthesis, giving 50% inhibition at 0·2nmole/mg. of protein. However, aurovertin is a less potent inhibitor of ATP-utilizing systems: the ATP-driven energy-linked nicotinamide nucleotide transhydrogenase is 50% inhibited at 3·0nmoles/mg. of protein and the ATP-driven reduction of NAD+ by succinate is 50% inhibited at 0·95nmole/mg. of protein. 2. With EDTA-particles (prepared by subjecting mitochondria to ultrasonic radiation at pH9 in the presence of 2mm-EDTA) the maximum stimulation of the ATP-driven partial reactions is effected by similar concentrations of oligomycin A and dicylcohexylcarbodi-imide, but the latter is less effective. The stimulatory effects of suboptimum concentrations of dicyclohexylcarbodi-imide and oligomycin A are additive. Aurovertin does not stimulate these reactions or interfere with the stimulation by the other inhibitors. 3. Dicyclohexylcarbodi-imide and oligomycin A stimulate the aerobic energy-linked nicotinamide nucleotide transhydrogenase of EDTA-particles, but the optimum concentration is higher than that required for the ATP-driven partial reactions. Aurovertin has no effect on this reaction. 4. The site of action of dicyclohexylcarbodi-imide is in CF0, the mitochondrial fraction that confers oligomycin sensitivity on F1 mitochondrial adenosine triphosphatase.

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.

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.

scholarly journals Phosphorylation of choline and ethanolamine in Ehrlich ascites-carcinoma cells

1967 ◽  
Vol 105 (2) ◽  
pp. 497-503 ◽  
Author(s):  
Cheng-Po Sung ◽  
R. M. Johnstone
Keyword(s):  
Potent Inhibitor ◽  
Ehrlich Ascites Carcinoma ◽  
Carcinoma Cells ◽  
Detectable Effect ◽  
Ascites Cell ◽  
Cell Extracts ◽  
Ehrlich Ascites ◽  
Ehrlich Ascites Cell ◽  
Stimulation Of

1. Ehrlich ascites-cell extracts convert choline and ethanolamine approximately equally well into their respective phosphoryl derivatives. 2. Choline is a potent inhibitor of ethanolamine phosphorylation, but ethanolamine has little effect on choline phosphorylation. 3. 2,3-Dimercaptopropanol, cysteine and Ca2+ inhibit ethanolamine phosphorylation, but have no detectable effect on choline phosphorylation. 4. Choline-phosphorylating activity in Ehrlich ascites-cell extracts is more stable during storage than ethanolamine-phosphorylating activity. 5. Choline phosphorylation is stimulated in the presence of benzoylcholine, succinylcholine, butyrylcholine and propionylcholine, whereas ethanolamine phosphorylation is inhibited. This relationship is reciprocal: the compounds causing the greatest stimulation of choline phosphorylation bring about the greatest inhibition of ethanolamine phosphorylation.

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