Athamena Ahmed, Trajkovic-Bodennec Selena, Brichon Gérard, Zwingelstein Georges, Bodennec Jacques
Université de Lyon, France.
Lipids. 2011 Dec;46(12):1141-54. doi: 10.1007/s11745-011-3590-9. Epub 2011 Jul 19.
We previously demonstrated the importance of upregulation of phosphatidylethanolamine N-methylation pathway in euryhaline fish and crustaceans facing hyperosmotic conditions. In marine molluscs phosphatidylcholine synthesis through N-methylation of phosphatidylethanolamine has not been described until now. In vivo labeling of the mussel Mytilus galloprovincialis with [1-(3)H]-ethanolamine showed that the digestive gland is the tissue expressing the highest incorporation into lipids. A sustained increase in lipid labeling was observed up to 72 h following label injection with 79-92% of radioactivity concentrated into phosphatidylethanolamine and phosphatidylcholine. A direct correlation (r = 0.47, p < 0.01) between the specific radioactivities of phosphatidylcholine in plasma and the digestive gland was observed. Moreover, the phosphatidylcholine fatty acid compositions of plasma and the digestive gland were similar but differed from those of phosphatidylcholine purified from other tissues. In vitro incubation of tissues with [1-(3)H]-ethanolamine or L-[3-(3)H]-serine showed that a significant labeling of the choline moiety of phosphatidylcholine was observed in the digestive gland and hemocytes. Pulse-chase experiments with [1-(3)H]-ethanolamine also demonstrated that hemocytes are exchanging the newly formed phospholipids with plasma. Finally, phosphatidylethanolamine N-methyltransferase assays demonstrated salinity-dependent activities in the digestive gland and hemocytes. We conclude that in M. galloprovincialis an active phosphatidylcholine synthesis through N-methylation of phosphatidylethanolamine occurs in the digestive gland and hemocytes and that this newly formed phosphatidylcholine is partly exchanged with plasma.
我们之前证明了在广盐性鱼类和甲壳类动物面临高渗环境时，磷脂酰乙醇胺N-甲基化途径上调的重要性。直到现在，在海洋软体动物中，通过磷脂酰乙醇胺的N-甲基化合成磷脂酰胆碱的过程尚未被描述。用[1-(3)H]-乙醇胺对加利福尼亚贻贝进行体内标记，结果表明消化腺是脂质掺入率最高的组织。在注射标记物后长达72小时内，观察到脂质标记持续增加，79-92%的放射性集中在磷脂酰乙醇胺和磷脂酰胆碱中。观察到血浆和消化腺中磷脂酰胆碱的比放射性之间存在直接相关性（r = 0.47，p < 0.01）。此外，血浆和消化腺中磷脂酰胆碱的脂肪酸组成相似，但与从其他组织纯化的磷脂酰胆碱不同。用[1-(3)H]-乙醇胺或L-[3-(3)H]-丝氨酸对组织进行体外孵育，结果表明在消化腺和血细胞中观察到磷脂酰胆碱胆碱部分有显著标记。用[1-(3)H]-乙醇胺进行的脉冲追踪实验也表明，血细胞正在将新形成的磷脂与血浆进行交换。最后，磷脂酰乙醇胺N-甲基转移酶测定表明，消化腺和血细胞中的活性与盐度有关。我们得出结论，在加利福尼亚贻贝中，消化腺和血细胞中通过磷脂酰乙醇胺的N-甲基化发生了活跃的磷脂酰胆碱合成，并且这种新形成的磷脂酰胆碱部分与血浆进行了交换。
