Salmon Didier, Paturiaux-Hanocq Françoise, Poelvoorde Philippe, Vanhamme Luc, Pays Etienne
Department of Medical Biochemistry, Institute of Biomedical Sciences, Federal University of Rio de Janeiro, Rio de Janeiro, 21941-590, Brazil.
Exp Parasitol. 2005 Mar;109(3):188-94. doi: 10.1016/j.exppara.2004.11.010. Epub 2005 Jan 7.
The heterodimeric transferrin receptors of Trypanosoma brucei (Tf-Rs) are encoded by two genes termed ESAG7 and ESAG6. These genes belong to polycistronic transcription units contained in the multiple expression sites for the variant surface glycoprotein (VSG ESs), only one of which is active at a time. Each VSG ES carries a different copy of these genes, leading to alternative expression of Tf-Rs with quite distinct binding affinities for transferrins from various mammals. T. brucei clones exhibit marked growth differences depending on the species-specificity of the serum. Since transferrin is a vital growth factor for the parasite, we investigated whether it could be responsible for these observations. We analyzed the cases of Tf-Rs from two ESs preferentially selected for expression in man and mouse, respectively. We show that serum-dependent growth variations of trypanosomes expressing these receptors are independent of transferrin, and that both high- and low-affinity Tf-Rs allow efficient trypanosome growth in various sera, either in vivo or in vitro.
布氏锥虫的异源二聚体转铁蛋白受体（Tf-Rs）由两个基因ESAG7和ESAG6编码。这些基因属于多顺反子转录单元，包含在可变表面糖蛋白的多个表达位点（VSG ESs）中，其中只有一个在任何时候是活跃的。每个VSG ES携带这些基因的不同拷贝，导致Tf-Rs的交替表达，对来自各种哺乳动物的转铁蛋白具有截然不同的结合亲和力。布氏锥虫克隆根据血清的物种特异性表现出明显的生长差异。由于转铁蛋白是寄生虫的一种重要生长因子，我们研究了它是否能解释这些观察结果。我们分析了分别优先选择在人和小鼠中表达的两个ESs的Tf-Rs情况。我们表明，表达这些受体的锥虫的血清依赖性生长变化与转铁蛋白无关，并且高亲和力和低亲和力的Tf-Rs都能使锥虫在各种血清中在体内或体外高效生长。
