Matovu Enock, Stewart Mhairi L, Geiser Federico, Brun Reto, Mäser Pascal, Wallace Lynsey J M, Burchmore Richard J, Enyaru John C K, Barrett Michael P, Kaminsky Ronald, Seebeck Thomas, de Koning Harry P
Institute of Cell Biology, CH-3012 Bern, Switzerland.
Eukaryot Cell. 2003 Oct;2(5):1003-8. doi: 10.1128/EC.2.5.1003-1008.2003.
Sleeping sickness, caused by Trypanosoma brucei spp., has become resurgent in sub-Saharan Africa. Moreover, there is an alarming increase in treatment failures with melarsoprol, the principal agent used against late-stage sleeping sickness. In T. brucei, the uptake of melarsoprol as well as diamidines is thought to be mediated by the P2 aminopurine transporter, and loss of P2 function has been implicated in resistance to these agents. The trypanosomal gene TbAT1 has been found to encode a P2-type transporter when expressed in yeast. Here we investigate the role of TbAT1 in drug uptake and drug resistance in T. brucei by genetic knockout of TbAT1. Tbat1-null trypanosomes were deficient in P2-type adenosine transport and lacked adenosine-sensitive transport of pentamidine and melaminophenyl arsenicals. However, the null mutants were only slightly resistant to melaminophenyl arsenicals and pentamidine, while resistance to other diamidines such as diminazene was more pronounced. Nevertheless, the reduction in drug sensitivity might be of clinical significance, since mice infected with tbat1-null trypanosomes could not be cured with 2 mg of melarsoprol/kg of body weight for four consecutive days, whereas mice infected with the parental line were all cured by using this protocol. Two additional pentamidine transporters, HAPT1 and LAPT1, were still present in the null mutant, and evidence is presented that HAPT1 may be responsible for the residual uptake of melaminophenyl arsenicals. High-level arsenical resistance therefore appears to involve the loss of more than one transporter.
由布氏锥虫属引起的昏睡病在撒哈拉以南非洲地区再度流行。此外，用于治疗晚期昏睡病的主要药物美拉胂醇的治疗失败情况惊人地增加。在布氏锥虫中，美拉胂醇以及双脒类药物的摄取被认为是由P2氨基嘌呤转运体介导的，P2功能的丧失与对这些药物的耐药性有关。当在酵母中表达时，已发现锥虫基因TbAT1编码一种P2型转运体。在这里，我们通过对TbAT1进行基因敲除来研究TbAT1在布氏锥虫药物摄取和耐药性中的作用。TbAT1基因缺失的锥虫在P2型腺苷转运方面存在缺陷，并且缺乏对喷他脒和美拉明苯基胂剂的腺苷敏感性转运。然而，基因缺失突变体对美拉明苯基胂剂和喷他脒仅有轻微耐药性，而对其他双脒类药物如地美硝唑的耐药性则更为明显。尽管如此，药物敏感性的降低可能具有临床意义，因为感染了TbAT1基因缺失锥虫的小鼠连续四天给予2mg/kg体重的美拉胂醇无法治愈，而感染亲代株的小鼠使用该方案全部治愈。另外两种喷他脒转运体HAPT1和LAPT1在基因缺失突变体中仍然存在，并且有证据表明HAPT1可能负责美拉明苯基胂剂的残余摄取。因此，高水平的胂剂耐药性似乎涉及不止一种转运体的丧失。
