title: The Uptake of GABA in Trypanosoma cruzi.
abstract: Gamma aminobutyric acid (GABA) is widely known as a neurotransmitter and signal transduction molecule found in vertebrates, plants, and some protozoan organisms. However, the presence of GABA and its role in trypanosomatids is unknown. Here, we report the presence of intracellular GABA and the biochemical characterization of its uptake in Trypanosoma cruzi, the etiological agent of Chagas' disease. Kinetic parameters indicated that GABA is taken up by a single transport system in pathogenic and nonpathogenic forms. Temperature dependence assays showed a profile similar to glutamate transport, but the effect of extracellular cations Na(+) , K(+) , and H(+) on GABA uptake differed, suggesting a different uptake mechanism. In contrast to reports for other amino acid transporters in T. cruzi, GABA uptake was Na(+) dependent and increased with pH, with a maximum activity at pH 8.5. The sensitivity to oligomycin showed that GABA uptake is dependent on ATP synthesis. These data point to a secondary active Na(+) /GABA symporter energized by Na(+) -exporting ATPase. Finally, we show that GABA occurs in the parasite's cytoplasm under normal culture conditions, indicating that it is regularly taken up from the culture medium or synthesized through an still undescribed metabolic pathway.
authors: Departamento de Parasitologia, Instituto de Ciências Biomédicas, Universidade de São Paulo, São Paulo, Brazil.
authors: Robert L
authors: RL
authors: Galvez Rojas
authors: Departamento de Parasitologia, Instituto de Ciências Biomédicas, Universidade de São Paulo, São Paulo, Brazil.
authors: Il-Young
authors: IY
authors: Ahn
authors: Departamento de Parasitologia, Instituto de Ciências Biomédicas, Universidade de São Paulo, São Paulo, Brazil.
authors: Brian
authors: B
authors: Suárez Mantilla
authors: Instituto Nacional de Metrologia (INMetro), Rio de Janeiro, Brazil.
authors: Celso
authors: C
authors: Sant'Anna
authors: Departamento de Parasitologia, Instituto de Ciências Biomédicas, Universidade de São Paulo, São Paulo, Brazil.
authors: Elizabeth Mieko Furusho
authors: EM
authors: Pral
authors: Departamento de Parasitologia, Instituto de Ciências Biomédicas, Universidade de São Paulo, São Paulo, Brazil.
authors: Ariel Mariano
authors: AM
authors: Silber
mesh_terms: D000255:Adenosine Triphosphate / Q000096:biosynthesis; D000596:Amino Acids / Q000378:metabolism; D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D005455:Fluorescent Antibody Technique; D018698:Glutamic Acid / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D009840:Oligomycins / Q000494:pharmacology; D011188:Potassium / Q000378:metabolism; D012964:Sodium / Q000378:metabolism; D014349:Trypanosoma cruzi / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D005680:gamma-Aminobutyric Acid / Q000378:metabolism*
chemical_list: D000596:Amino Acids; D009840:Oligomycins; D018698:Glutamic Acid; D005680:gamma-Aminobutyric Acid; D000255:Adenosine Triphosphate; D012964:Sodium; D011188:Potassium
keywords: Active metabolite transporters; Na+/metabolite symporter; amino acids metabolism; chemotherapy