The role of transferrin-receptor variation in the host range of Trypanosoma brucei
The role of transferrin-receptor variation in the host range of Trypanosoma brucei
复制标题
作者：
Bitter, W;Gerrits, H;Borst, P
布鲁氏锥虫(1)是一种单细胞寄生虫，通过采采蝇在非洲哺乳动物之间传播。布鲁氏杆菌在许多不同哺乳动物的血液中自由繁殖，并通过其表面外壳的主要成分变异表面糖蛋白（VSG）的抗原变异而存活（2,3）。锥虫通过异二聚体转铁蛋白受体吸收转铁蛋白（4-9），该基因与VSG基因一起在端粒表达位点表达。每个锥虫核有多达20个这样的表达位点（3,10-15），但通常一次只有一个是活跃的。不同的表达位点编码的转铁蛋白受体相似但不完全相同（16）。本研究表明，转铁蛋白受体之间的这些微小差异可能对不同哺乳动物转铁蛋白的结合亲和力以及锥虫在这些哺乳动物血清中的生长能力产生深远的影响。我们的研究结果表明，在不同转铁蛋白受体基因之间切换的能力使布鲁氏体能够应对宿主转铁蛋白序列的巨大多样性（17）。
Trypanosoma brucei(1) is a unicellular parasite transmitted between African mammals by tsetse flies. T. brucei multiplies freely in the bloodstream of many different mammals, and survives by antigenic variation of the main component of its surface coat, variant surface glycoprotein (VSG)(2,3). Trypanosomes take up transferrin through a heterodimeric transferrin receptor(4-9), the genes for which are expressed in telomeric expression sites along with the VSG gene. There are up to 20 of these expression sites per trypanosome nucleus(3,10-15), but usually only one is active at a time. Different expression sites encode transferrin receptors that are similar but not identical(16). Here we show that these small differences between transferrin receptors can have profound effects on the binding affinity for transferrins from different mammals, and an the ability of trypanosomes to grow in the sera of these mammals. Our results suggest that the ability ro switch between different transferrin-receptor genes allows T. brucei to cope with the large sequence diversity in the transferrins of its hosts(17).