title: Quinone-amino acid conjugates targeting Leishmania amino acid transporters.
abstract: The aim of the present study was to investigate the feasibility of targeting Leishmania transporters via appropriately designed chemical probes. Leishmania donovani, the parasite that causes visceral leishmaniasis, is auxotrophic for arginine and lysine and has specific transporters (LdAAP3 and LdAAP7) to import these nutrients. Probes 1-15 were originated by conjugating cytotoxic quinone fragments (II and III) with amino acids (i.e. arginine and lysine) by means of an amide linkage. The toxicity of the synthesized conjugates against Leishmania extracellular (promastigotes) and intracellular (amastigotes) forms was investigated, as well their inhibition of the relevant amino acid transporters. We observed that some conjugates indeed displayed toxicity against the parasites; in particular, 7 was identified as the most potent derivative (at concentrations of 1 µg/mL and 2.5 µg/mL residual cell viability was reduced to 15% and 48% in promastigotes and amastigotes, respectively). Notably, 6, while retaining the cytotoxic activity of quinone II, displayed no toxicity against mammalian THP1 cells. Transport assays indicated that the novel conjugates inhibited transport activity of lysine, arginine and proline transporters. Furthermore, our analyses suggested that the toxic conjugates might be translocated by the transporters into the cells. The non-toxic probes that inhibited transport competed with the natural substrates for binding to the transporters without being translocated. Thus, it is likely that 6, by exploiting amino acid transporters, can selectively deliver its toxic effects to Leishmania cells. This work provides the first evidence that amino acid transporters of the human pathogen Leishmania might be modulated by small molecules, and warrants their further investigation from drug discovery and chemical biology perspectives.
authors.affiliation: Department of Pharmacy and Biotechnology, Alma Mater Studiorum University of Bologna, Bologna, Italy.
authors.forename: Federica
authors.initials: F
authors.lastname: Prati
authors.affiliation: Faculty of Biology, Technion-Israel Institute of Technology, Haifa, Israel.
authors.forename: Adele
authors.initials: A
authors.lastname: Goldman-Pinkovich
authors.affiliation: Department of Pharmacy and Biotechnology, Alma Mater Studiorum University of Bologna, Bologna, Italy.
authors.forename: Federica
authors.initials: F
authors.lastname: Lizzi
authors.affiliation: Department of Pharmacy and Biotechnology, Alma Mater Studiorum University of Bologna, Bologna, Italy.
authors.forename: Federica
authors.initials: F
authors.lastname: Belluti
authors.affiliation: Faculty of Biology, Technion-Israel Institute of Technology, Haifa, Israel.
authors.forename: Roni
authors.initials: R
authors.lastname: Koren
authors.affiliation: Faculty of Biology, Technion-Israel Institute of Technology, Haifa, Israel.
authors.forename: Dan
authors.initials: D
authors.lastname: Zilberstein
authors.affiliation: Department of Pharmacy and Biotechnology, Alma Mater Studiorum University of Bologna, Bologna, Italy.
authors.forename: Maria Laura
authors.initials: ML
authors.lastname: Bolognesi
mesh_terms: D026905:Amino Acid Transport Systems / Q000378:metabolism*; D000981:Antiprotozoal Agents / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology / Q000633:toxicity; D001120:Arginine / Q000737:chemistry*; D001667:Binding, Competitive; D001692:Biological Transport / Q000187:drug effects; D002460:Cell Line; D015195:Drug Design; D005240:Feasibility Studies; D006801:Humans; D007893:Leishmania donovani / Q000187:drug effects* / Q000378:metabolism*; D008239:Lysine / Q000737:chemistry*; D009285:Naphthoquinones / Q000737:chemistry* / Q000378:metabolism / Q000494:pharmacology* / Q000633:toxicity
chemical_list: D026905:Amino Acid Transport Systems; D000981:Antiprotozoal Agents; D009285:Naphthoquinones; D001120:Arginine; D008239:Lysine