Cationic amino acid uptake constitute a metabolic regulation mechanisms and occurs in the flagellar pocket of Trypanosoma Cruzi

MARIANA MIRANDA; MELISA SAYE; LEON BOUVIER; MARÍA CAMARA; JAVIER MONTSERRAT; CLAUDIO PEREIRA

PLOS ONE

PUBLIC LIBRARY SCIENCE

Lugar: San Francisco; Año: 2012 vol. 7 p. 32760 - 32766

1932-6203

Trypanosomatids´ amino acid permeases are key proteins in parasite metabolism sincethey participate in the adaptation of parasites to different environments. Here, wereport that TcAAP3, a member of a Trypanosoma cruzi multigene family of permeases,is a bona fide arginine transporter. Most of higher eukaryotic cells incorporate cationicamino acids through a single transporter. In contrast, T. cruzi can recognize andtransport cationic amino acids by mono-specific permeases since, a 100-fold molarexcess of lysine could not affect the arginine transport in parasites that over-expressthe arginine permease (TcAAP3 epimastigotes). In order to test if the permease activityregulates downstream processes of the arginine metabolism, the expression of thesingle T. cruzi enzyme that uses arginine as substrate, arginine kinase, was evaluatedin TcAAP3 epimastigotes. In this parasite model, intracellular arginine concentrationincreases 4-folds and ATP level remains constant until cultures reach the stationaryphase of growth, when decrease about 6-folds respect to the controls. Interestingly,Western Blot analysis demonstrated that arginine kinase is significantly down-regulated during the stationary phase of growth in TcAAP3 epimastigotes. Thisdecrease could represent a compensatory mechanism for the increase in ATPconsumption as a consequence of the displacement of the reaction equilibrium ofarginine kinase, when the intracellular arginine concentration augments and theglucose from the medium is exhausted. Using immunofluorescence techniques we alsodetermined that TcAAP3 and the specific lysine transporter TcAAP7 co-localize in aspecialized region of the plasma membrane named flagellar pocket, staining a singlelocus close to the flagellar pocket collar. Taken together these data suggest thatarginine transport is closely related to arginine metabolism and cell energy balance.The clinical relevance of studying trypanosomatids´ permeases relies in the possibilityof using these molecules as a route of entry of therapeutic drugs.