Callahan H L, Beverley S M
Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, Massachusetts 02115.
J Biol Chem. 1991 Oct 5;266(28):18427-30.
P-glycoproteins are responsible for multidrug resistance in tumor cell lines and are thought to have a physiologic role in exporting cellular metabolites. We now report that a P-glycoprotein gene in the H region of the trypanosomatid protozoan Leishmania confers resistance to heavy metals when present in multiple copies. The Leishmania H region is frequently amplified in drug-resistant lines and is associated with metal resistance. Leishmania expression vectors were used to introduce multiple copies of segments of the Leishmania major H region into wild-type L. major promastigotes. Only constructs bearing a segment of L. major DNA containing the P-glycoprotein lmpgpA conferred arsenite resistance. Deletional analysis of the arsenite-resistant construct mapped resistance to the lmpgpA protein coding region. Lines expressing lmpgpA showed resistance to arsenite and trivalent antimonials, but not to pentavalent antimonials, zinc, cadmium, or the typical multidrug-resistant P-glycoprotein substrates vinblastine and puromycin. Transfection of the Leishmania tarentolae P-glycoprotein homologue ltpgpA resulted in a similar resistance profile. Thus, these pgpAs represent a functionally distinct group of P-glycoproteins which exhibit a substrate specificity similar to prokaryotic heavy metal pumps. Additionally, several arguments suggest that pgpAs may play a role in the susceptibility of Leishmania to clinically utilized antimonials.
P-糖蛋白与肿瘤细胞系中的多药耐药性有关，并且被认为在细胞代谢产物的输出中具有生理作用。我们现在报告，锥虫原生动物利什曼原虫H区域中的一个P-糖蛋白基因在以多拷贝形式存在时赋予对重金属的抗性。利什曼原虫的H区域在耐药株中经常扩增，并且与金属抗性相关。利什曼原虫表达载体被用于将大利什曼原虫H区域片段的多个拷贝导入野生型大利什曼原虫前鞭毛体中。只有携带包含P-糖蛋白lmpgpA的大利什曼原虫DNA片段的构建体赋予对亚砷酸盐的抗性。对亚砷酸盐抗性构建体的缺失分析将抗性定位到lmpgpA蛋白编码区域。表达lmpgpA的株系对亚砷酸盐和三价锑剂表现出抗性，但对五价锑剂、锌、镉或典型的多药耐药性P-糖蛋白底物长春碱和嘌呤霉素没有抗性。转染大利什曼原虫P-糖蛋白同源物ltpgpA产生了类似的抗性谱。因此，这些pgpA代表了一组功能上不同的P-糖蛋白，它们表现出与原核重金属泵相似的底物特异性。此外，一些证据表明pgpA可能在利什曼原虫对临床使用的锑剂的敏感性中起作用。
