ABCI3 Is a New Mitochondrial ABC Transporter from Leishmania major Involved in Susceptibility to Antimonials and Infectivity.

We have identified and characterized ABCI3 as a new mitochondrial ABC transporter from Localization studies using confocal microscopy, a surface biotinylation assay, and trypsin digestion after digitonin permeabilization suggested that ABCI3 presents a dual localization in both mitochondria and the plasma membrane. From studies using parasites with a single knockout of (), we provide evidence that ABCI3 is directly involved in susceptibility to the trivalent form of antimony (SbIII) and metal ions. Attempts to obtain parasites with a double knockout of were unsuccessful, suggesting that could be an essential gene in promastigotes were 5-fold more resistant to Sb than the wild type, while amastigotes were approximately 2-fold more resistant to pentavalent antimony (Sb). This resistance phenotype was associated with decreased Sb accumulation due to decreased Sb uptake. parasites presented higher ATP levels and generated less mitochondrial superoxide after Sb incubation. Finally, we observed that parasites showed a slightly higher infection capacity than wild-type and add-back ::3×FABCI3 parasites; however, after 72 h the number of intracellular parasites per macrophage increased significantly. Our results show that ABCI3 is responsible for Sb transport inside mitochondria, where it contributes to enhancement of the general toxic effects caused by Sb To our knowledge, ABCI3 is the first ABC transporter which is involved in susceptibility toward antimony, conferring Sb resistance to parasites when it is partially deleted.