Zufferey Rachel, Mamoun Choukri Ben
Department of Pathology, University of Connecticut Health Center, 263 Farmington Ave., Farmington, CT 06030, USA.
Mol Biochem Parasitol. 2002 Nov-Dec;125(1-2):127-34. doi: 10.1016/s0166-6851(02)00220-7.
Phosphatidylcholine is the most abundant phospholipid in the membranes of the human parasite Leishmania. The metabolic pathways leading to its biosynthesis are likely to play a critical role in parasite development and survival and may offer a good target for antileishmanial chemotherapy. Phosphatidylcholine synthesis via the CDP-choline pathway requires transport of the choline precursor from the host. Here, we report the first characterization of choline transport in this parasite, which is carrier-mediated and exhibits Michaelis-Menten kinetics with an apparent K(m) value of 2.5 microM for choline. This process is Na(+)-independent and requires an intact proton gradient to be fully functional. Choline transport into Leishmania is highly specific for choline and is inhibited by the choline carrier inhibitor hemicholinium-3, the channel blocker quinacrine, the antimalarial aminoquinolines quinine and quinidine, the antileishmanial phosphocholine analogs, miltefosine and edelfosine, and by choline analogs, most of which have antimalarial activities. Most importantly, choline analogs kill the promastigote form of the parasite in vitro in the low micromolar range. These results set the stage for the use of choline analogs in antileishmanial chemotherapy and shed new lights on the mechanism of action of the leishmanicidal phosphocholine analogs.
磷脂酰胆碱是人类寄生虫利什曼原虫细胞膜中含量最丰富的磷脂。其生物合成的代谢途径可能在寄生虫的发育和存活中起关键作用，并且可能为抗利什曼病化疗提供一个良好的靶点。通过CDP - 胆碱途径合成磷脂酰胆碱需要从宿主转运胆碱前体。在此，我们报道了该寄生虫中胆碱转运的首次特征描述，它是载体介导的，对胆碱表现出米氏动力学，胆碱的表观K(m)值为2.5微摩尔。这个过程不依赖于Na(+)，并且需要完整的质子梯度才能完全发挥功能。胆碱转运进入利什曼原虫对胆碱具有高度特异性，并受到胆碱载体抑制剂半胱氨酸 - 3、通道阻滞剂奎纳克林、抗疟氨基喹啉奎宁和奎尼丁、抗利什曼病的磷酸胆碱类似物米替福新和依地福新以及胆碱类似物的抑制，其中大多数具有抗疟活性。最重要的是，胆碱类似物在低微摩尔范围内可在体外杀死寄生虫的前鞭毛体形式。这些结果为胆碱类似物在抗利什曼病化疗中的应用奠定了基础，并为利什曼杀菌磷酸胆碱类似物的作用机制提供了新的线索。
