Phospholipid metabolism of serine in Plasmodium-infected erythrocytes involves phosphatidylserine and direct serine decarboxylation
Phospholipid metabolism of serine in Plasmodium-infected erythrocytes involves phosphatidylserine and direct serine decarboxylation
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DOI：
10.1042/bj3240435
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发表时间：
1997-06-01
影响因子：
4.1
通讯作者：
Vial, HJ
中科院分区：
文献类型：
--
作者：
Elabbadi, N;Ancelin, ML;Vial, HJ
感染恶性疟原虫或诺氏疟原虫的红细胞有效地将放射性丝氨酸掺入磷脂酰丝氨酸（PtdSer）、磷脂酰乙醇胺（PtdEtn）和磷脂酰胆碱（PtdCho）中。丝氨酸还通过直接丝氨酸脱羧代谢为乙醇胺（Etn）和磷酸乙醇胺（P-Etn）;这是一种主要现象，因为这些代谢物占总放射性水溶性代谢物的60%。它们被确定为反相HPLC和两个TLC型分析，并确认碱性磷酸酶处理，这耗尽了放射性P-Etn峰完全与随之而来的增加，Etn。在5 μ M标记丝氨酸的存在下，放射性出现在Etn和P-Etn后25分钟的滞后期，并分别在40和95分钟达到同位素平衡。PtdEtn的形成，积累稳定至少180分钟有一个类似的滞后期。丝氨酸磷脂和水溶性代谢产物的掺入增加了高达500 μ M外部丝氨酸的存在下。然后，除了细胞内丝氨酸和Etn外，所有代谢产物均达到明显的平台期。外源性Etn（在20 μ M）诱导随之而来的丝氨酸掺入P-Etn和所有磷脂，但不进入Etn显着减少。增加外源性丝氨酸至100 μ M，放射性Etn掺入PtdEtn仅下降30%，PtdCho水平不受影响。2-羟乙基肼显着降低丝氨酸掺入P-Etn和PtdEtn，而Etn的积累。没有伴随抑制PtdSer或PtdCho标记丝氨酸发生，即使当PtdEtn形成减少了95%。这表明直接丝氨酸脱羧产生的PtdEtn库不同于PtdSer脱羧产生的PtdEtn库，后者似乎优先用于PtdCho生物合成。羟胺还抑制丝氨酸衍生的Etn的磷酸化，但不抑制外源性Etn的磷酸化。从10 μ L-丝氨酸合成PtdSer的速率为3.1 +/- 0.5和2.95 +/- 1.3 nmol/5 h/10（10）个感染细胞，而L-丝氨酸脱羧分别占恶性疟原虫和诺氏疟原虫每10（10）个感染细胞的7.1 +/-1.5和9.9 +/-3 nmol/5 h（平均值+/- S.E.M.）。在其他高等真核细胞（例如小鼠成纤维细胞和人类淋巴细胞）中未检测到丝氨酸脱羧反应。最后，这些结果也表明在疟原虫感染的红细胞中磷脂代谢的区室化。
Erythrocytes infected with Plasmodium falciparum or Plasmodium knowlesi efficiently incorporated radioactive serine into phosphatidylserine (PtdSer), phosphatidylethanolamine (PtdEtn) and phosphatidylcholine (PtdCho). Serine was also metabolized into ethanolamine (Etn) and phosphorylethanolamine (P-Etn) via direct serine decarboxylation; this is a major phenomenon since together these metabolites represent 60% of total radioactive water-soluble metabolites. They were identified by reverse-phase HPLC and two TLC-type analyses and confirmed by alkaline phosphatase treatment, which depleted the radioactive P-Etn peak completely with a concomitant increase in that of Etn. In the presence of 5 mu M labelled serine, radioactivity appeared in Etn and P-Etn after a 25 min lag period, and isotopic equilibrium was reached at 40 and 95 min respectively. There was a similar lag period for PtdEtn formation, which accumulated steadily for at least 180 min. Incorporation of serine into phospholipids and water-soluble metabolites increased in the presence of up to 500 mu M external serine. An apparent plateau was then reached for all metabolites except intracellular serine and Etn. Exogenous Etn (at 20 mu M) induced a concomitant dramatic decrease in serine incorporation into P-Etn and all phospholipids, but not into Etn. Increasing exogenous serine to 100 mu M decreased the incorporation of radioactive Etn into PtdEtn by only 30%, and the PtdCho level was not affected. 2-Hydroxyethylhydrazine significantly decreased serine incorporation into P-Etn and PtdEtn, whereas Etn was accumulated. No concomitant inhibition of PtdSer or PtdCho labelling from serine occurred, even when PtdEtn formation was decreased by 95%. This indicates that the PtdEtn pool derived from direct serine decarboxylation differed from that derived from PtdSer decarboxylation, and the latter appeared to be preferentially used for PtdCho biosynthesis. Hydroxylamine also inhibited phosphorylation of serine-derived Etn but not that of exogenous Etn. The rate of PtdSer synthesis from 10 mu L-serine was 3.1 +/- 0.5 and 2.95 +/- 1.3 nmol/5 h per 10(10) infected cells, whereas L-serine decarboxylation accounted for 7.1 +/- 1.5 and 9.9 +/- 3 nmol/5 h per 10(10) infected cells for P. falciparum and P. knowlesi respectively (means +/- S.E.M.). The serine decarboxylating reaction was not detected in other higher eukaryotic cells such as mouse fibroblasts and human lymphocytes. Finally, these results also indicate compartmentalization of phospholipid metabolism in Plasmodium-infected erythrocytes.