Loureiro Inês, Faria Joana, Clayton Christine, Macedo-Ribeiro Sandra, Santarém Nuno, Roy Nilanjan, Cordeiro-da-Siva Anabela, Tavares Joana
Parasite Disease Group, Instituto de Biologia Molecular e Celular da Universidade do Porto, Porto, Portugal.
Zentrum für Molekulare Biologie der Universität Heidelberg, DKFZ-ZMBH cv Alliance, Heidelberg, Germany.
PLoS Negl Trop Dis. 2015 Jan 8;9(1):e3430. doi: 10.1371/journal.pntd.0003430. eCollection 2015 Jan.
Ribose 5-phosphate isomerase is an enzyme involved in the non-oxidative branch of the pentose phosphate pathway, and catalyzes the inter-conversion of D-ribose 5-phosphate and D-ribulose 5-phosphate. Trypanosomatids, including the agent of African sleeping sickness namely Trypanosoma brucei, have a type B ribose-5-phosphate isomerase. This enzyme is absent from humans, which have a structurally unrelated ribose 5-phosphate isomerase type A, and therefore has been proposed as an attractive drug target waiting further characterization. In this study, Trypanosoma brucei ribose 5-phosphate isomerase B showed in vitro isomerase activity. RNAi against this enzyme reduced parasites' in vitro growth, and more importantly, bloodstream forms infectivity. Mice infected with induced RNAi clones exhibited lower parasitaemia and a prolonged survival compared to control mice. Phenotypic reversion was achieved by complementing induced RNAi clones with an ectopic copy of Trypanosoma cruzi gene. Our results present the first functional characterization of Trypanosoma brucei ribose 5-phosphate isomerase B, and show the relevance of an enzyme belonging to the non-oxidative branch of the pentose phosphate pathway in the context of Trypanosoma brucei infection.
5-磷酸核糖异构酶是一种参与磷酸戊糖途径非氧化分支的酶，催化5-磷酸-D-核糖和5-磷酸-D-核酮糖之间的相互转化。包括非洲昏睡病病原体布氏锥虫在内的锥虫具有B型5-磷酸核糖异构酶。人类没有这种酶，人类具有结构上不相关的A型5-磷酸核糖异构酶，因此，B型5-磷酸核糖异构酶被认为是一个有吸引力的药物靶点，有待进一步研究。在本研究中，布氏锥虫5-磷酸核糖异构酶B表现出体外异构酶活性。针对该酶的RNA干扰降低了寄生虫的体外生长，更重要的是，降低了血流形式的感染力。与对照小鼠相比，感染诱导RNA干扰克隆的小鼠表现出较低的寄生虫血症和更长的生存期。通过用克氏锥虫基因的异位拷贝补充诱导RNA干扰克隆实现了表型回复。我们的结果首次对布氏锥虫5-磷酸核糖异构酶B进行了功能表征，并表明在布氏锥虫感染的背景下，属于磷酸戊糖途径非氧化分支的一种酶具有相关性。
