GMP synthase is essential for viability and infectivity of Trypanosoma brucei despite a redundant purine salvage pathway.
GMP synthase is essential for viability and infectivity of Trypanosoma brucei despite a redundant purine salvage pathway.
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DOI：
10.1111/mmi.13083
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发表时间：
2015-09
影响因子：
3.6
通讯作者：
Phillips MA
中科院分区：
文献类型：
--
作者：
Li Q;Leija C;Rijo-Ferreira F;Chen J;Cestari I;Stuart K;Tu BP;Phillips MA
人类非洲锥虫病的病原体布鲁氏锥虫缺乏新的嘌呤生物合成，依赖于宿主的嘌呤回收。嘌呤回收途径是冗余的，包含两种途径形成鸟嘌呤-5′-单磷酸（GMP）：通过GMP合成酶（GMPS）从5′-单磷酸黄嘌呤（XMP）转化或通过次黄嘌呤-鸟嘌呤磷酸核糖基转移酶（HGPRT）直接回收鸟嘌呤。我们发现重组布鲁氏菌GMPS能有效催化GMP的形成。血液寄生虫GMPS基因敲除导致鸟嘌呤核苷酸池耗竭，具有致命性。只有超生理鸟嘌呤浓度（100 μM）或gmps染色体外拷贝的表达才能恢复gmps缺失细胞的生长。次黄嘌呤是一种竞争性的鸟嘌呤救援抑制剂，与常见的摄取/代谢转化机制一致。在小鼠中，没有gmp的寄生虫无法建立感染，这表明gmp对毒力是必不可少的，血浆鸟嘌呤不足以支持寄生虫的嘌呤需求。这些数据验证了GMPS作为治疗HAT的潜在治疗靶点。通过利用途径通量的本质和寄生虫细胞外生态位有限的营养环境，有策略地抑制嘌呤途径中关键代谢酶的能力出乎意料地绕过了其功能冗余。
The causative agent of human African trypanosomiasis, Trypanosoma brucei, lacks de novo purine biosynthesis and depends on purine salvage from the host. The purine salvage pathway is redundant and contains two routes to guanosine-5′-monophosphate (GMP) formation: conversion from xanthosine-5′-monophosphate (XMP) by GMP synthase (GMPS) or direct salvage of guanine by hypoxanthine-guanine phosphoribosyltransferase (HGPRT). We show recombinant T. brucei GMPS efficiently catalyzes GMP formation. Genetic knockout of GMPS in bloodstream parasites led to depletion of guanine nucleotide pools and was lethal. Growth of gmps null cells was only rescued by supraphysiological guanine concentrations (100 μM) or by expression of an extrachromosomal copy of GMPS. Hypoxanthine was a competitive inhibitor of guanine rescue, consistent with a common uptake/metabolic conversion mechanism. In mice, gmps null parasites were unable to establish an infection demonstrating that GMPS is essential for virulence and that plasma guanine is insufficient to support parasite purine requirements. These data validate GMPS as a potential therapeutic target for treatment of HAT. The ability to strategically inhibit key metabolic enzymes in the purine pathway unexpectedly bypasses its functional redundancy by exploiting both the nature of pathway flux and the limited nutrient environment of the parasite's extracellular niche.