Abstract：
Protozoan parasites cause life-threatening infections in both humans and animals, including agriculturally significant livestock. Available treatments are typically narrow spectrum and are complicated by drug toxicity and the development of resistant parasites. Protozoan tubulin is an attractive target for the development of broad-spectrum antimitotic agents. The Medicines for Malaria Pathogen Box compound MMV676477 was previously shown to inhibit replication of kinetoplastid parasites, such as Leishmania amazonensis and Trypanosoma brucei, and the apicomplexan parasite Plasmodium falciparum by selectively stabilizing protozoan microtubules. In this report, we show that MMV676477 inhibits intracellular growth of the human apicomplexan pathogen Toxoplasma gondii with an EC50 value of ~50 nM. MMV676477 does not stabilize vertebrate microtubules or cause other toxic effects in human fibroblasts. The availability of tools for genetic studies makes Toxoplasma a useful model for studies of the cytoskeleton. We conducted a forward genetics screen for MMV676477 resistance, anticipating that missense mutations would delineate the binding site on protozoan tubulin. Unfortunately, we were unable to use genetics to dissect target interactions because no resistant parasites emerged. This outcome suggests that future drugs based on the MMV676477 scaffold would be less likely to be undermined by the emergence of drug resistance.
摘要：
原生动物寄生虫会在人类和动物中引起威胁生命的感染，包括农业上重要的牲畜。可用的治疗通常是窄谱的,并且由于药物毒性和抗性寄生虫的发展而复杂化。原生动物微管蛋白是开发广谱抗有丝分裂剂的有吸引力的靶标。用于疟疾病原体盒化合物MMV676477的药物先前被证明可以抑制动体寄生虫的复制，如亚马逊利什曼原虫和布鲁氏锥虫，通过选择性地稳定原生动物微管，和顶复体寄生虫恶性疟原虫。在这份报告中,我们显示MMV676477抑制人尖丛病原体弓形虫的细胞内生长，EC50值为约50nM。MMV676477不稳定脊椎动物微管或在人成纤维细胞中引起其他毒性作用。遗传研究工具的可用性使弓形虫成为研究细胞骨架的有用模型。我们对MMV676477抗性进行了正向遗传学筛选，预期错义突变会描绘原生动物微管蛋白上的结合位点。不幸的是,我们无法使用遗传学来剖析目标相互作用,因为没有出现抗药性寄生虫.该结果表明，基于MMV676477支架的未来药物不太可能因耐药性的出现而受到破坏。
