Department of Biochemistry and Molecular Biology, Oregon Health & Science University, Portland, OR 97239-3098, USA.
Mol Microbiol. 2010 Apr;76(1):78-91. doi: 10.1111/j.1365-2958.2010.07081.x. Epub 2010 Feb 10.
Whereas mammalian cells and most other organisms can synthesize polyamines from basic amino acids, the protozoan parasite Trypanosoma cruzi is incapable of polyamine biosynthesis de novo and therefore obligatorily relies upon putrescine acquisition from the host to meet its nutritional requirements. The cell surface proteins that mediate polyamine transport into T. cruzi, as well as most eukaryotes, however, have by-in-large eluded discovery at the molecular level. Here we report the identification and functional characterization of two polyamine transporters, TcPOT1.1 and TcPOT1.2, encoded by alleles from two T. cruzi haplotypes. Overexpression of the TcPOT1.1 and TcPOT1.2 genes in T. cruzi epimastigotes revealed that TcPOT1.1 and TcPOT1.2 were high-affinity transporters that recognized both putrescine and cadaverine but not spermidine or spermine. Furthermore, the activities and subcellular locations of both TcPOT1.1 and TcPOT1.2 in intact parasites were profoundly influenced by extracellular putrescine availability. These results establish TcPOT1.1 and TcPOT1.2 as key components of the T. cruzi polyamine transport pathway, an indispensable nutritional function for the parasite that may be amenable to therapeutic manipulation.
虽然哺乳动物细胞和大多数其他生物能够从碱性氨基酸合成多胺，但原生动物寄生虫克氏锥虫却不能从头合成多胺，因此必须从宿主中获取腐胺来满足其营养需求。然而，介导多胺进入克氏锥虫以及大多数真核生物的细胞表面蛋白在分子水平上基本上仍未被发现。在这里，我们报告了两个多胺转运蛋白 TcPOT1.1 和 TcPOT1.2 的鉴定和功能特征，它们由两个克氏锥虫单倍型的等位基因编码。在克氏锥虫的前鞭毛体中转基因表达 TcPOT1.1 和 TcPOT1.2 基因表明，TcPOT1.1 和 TcPOT1.2 是高亲和力的转运蛋白，可识别腐胺和尸胺，但不识别亚精胺或精胺。此外，在完整的寄生虫中，TcPOT1.1 和 TcPOT1.2 的活性和亚细胞定位都受到细胞外腐胺可用性的深刻影响。这些结果确立了 TcPOT1.1 和 TcPOT1.2 为克氏锥虫多胺转运途径的关键组成部分，这是寄生虫不可或缺的营养功能，可能适合治疗干预。
