title: Trypanosoma brucei eflornithine transporter AAT6 is a low-affinity low-selective transporter for neutral amino acids.
abstract: Amino acid transporters are crucial for parasite survival since the cellular metabolism of parasitic protozoa depends on the up-take of exogenous amino acids. Amino acid transporters are also of high pharmacological relevance because they may mediate uptake of toxic amino acid analogues. In the present study we show that the eflornithine transporter AAT6 from Trypanosoma brucei (TbAAT6) mediates growth on neutral amino acids when expressed in Saccharomyces cerevisiae mutants. The transport was electrogenic and further analysed in Xenopus laevis oocytes. Neutral amino acids, proline analogues, eflornithine and acivicin induced inward currents. For proline, glycine and tryptophan the apparent affinities and maximal transport rates increased with more negative membrane potentials. Proline-induced currents were dependent on pH, but not on sodium. Although proline represents the primary energy source of T. brucei in the tsetse fly, down-regulation of TbAAT6-expression by RNAi showed that in culture TbAAT6 is not essential for growth of procyclic form trypanosomes in the presence of glucose or proline as energy source. TbAAT6-RNAi lines of both bloodstream and procyclic form trypanosomes showed reduced susceptibility to eflornithine, whereas the sensitivity to acivicin remained unchanged, indicating that acivicin enters the cell by more than one transporter.
authors.affiliation: *Institute of Plant Sciences, University of Bern, Altenbergrain 21, 3013 Bern, Switzerland.
authors.forename: Christoph
authors.initials: C
authors.lastname: Mathieu
authors.affiliation: †Institute of Biochemistry and Molecular Medicine, University of Bern, Bühlstrasse 28, 3012 Bern, Switzerland.
authors.forename: Amaia
authors.initials: A
authors.lastname: González Salgado
authors.affiliation: *Institute of Plant Sciences, University of Bern, Altenbergrain 21, 3013 Bern, Switzerland.
authors.forename: Corina
authors.initials: C
authors.lastname: Wirdnam
authors.affiliation: *Institute of Plant Sciences, University of Bern, Altenbergrain 21, 3013 Bern, Switzerland.
authors.forename: Stefan
authors.initials: S
authors.lastname: Meier
authors.affiliation: *Institute of Plant Sciences, University of Bern, Altenbergrain 21, 3013 Bern, Switzerland.
authors.forename: Marianne Suter
authors.initials: MS
authors.lastname: Grotemeyer
authors.affiliation: ‡Faculty of Biology, Technion-Israel Institute of Technology, Haifa 32000, Israel.
authors.forename: Ehud
authors.initials: E
authors.lastname: Inbar
authors.forename: Pascal
authors.initials: P
authors.lastname: Mäser
authors.affiliation: ‡Faculty of Biology, Technion-Israel Institute of Technology, Haifa 32000, Israel.
authors.forename: Dan
authors.initials: D
authors.lastname: Zilberstein
authors.affiliation: †Institute of Biochemistry and Molecular Medicine, University of Bern, Bühlstrasse 28, 3012 Bern, Switzerland.
authors.forename: Erwin
authors.initials: E
authors.lastname: Sigel
authors.affiliation: †Institute of Biochemistry and Molecular Medicine, University of Bern, Bühlstrasse 28, 3012 Bern, Switzerland.
authors.forename: Peter
authors.initials: P
authors.lastname: Bütikofer
authors.affiliation: *Institute of Plant Sciences, University of Bern, Altenbergrain 21, 3013 Bern, Switzerland.
authors.forename: Doris
authors.initials: D
authors.lastname: Rentsch
mesh_terms: D026921:Amino Acid Transport Systems, Neutral / Q000235:genetics / Q000378:metabolism*; D000596:Amino Acids / Q000235:genetics / Q000378:metabolism; D000818:Animals; D001693:Biological Transport, Active / Q000187:drug effects; D015536:Down-Regulation / Q000187:drug effects / Q000235:genetics; D004351:Drug Resistance / Q000187:drug effects / Q000235:genetics; D000518:Eflornithine / Q000493:pharmacokinetics* / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006863:Hydrogen-Ion Concentration; D007555:Isoxazoles / Q000494:pharmacology; D008564:Membrane Potentials / Q000187:drug effects; D015800:Protozoan Proteins / Q000235:genetics / Q000378:metabolism*; D014344:Trypanocidal Agents / Q000493:pharmacokinetics* / Q000494:pharmacology; D014346:Trypanosoma brucei brucei / Q000235:genetics / Q000378:metabolism*; D014981:Xenopus
chemical_list: D026921:Amino Acid Transport Systems, Neutral; D000596:Amino Acids; D004791:Enzyme Inhibitors; D007555:Isoxazoles; D015800:Protozoan Proteins; D014344:Trypanocidal Agents; C006303:acivicin; D000518:Eflornithine