title: Na+-dependent and Na+-independent mechanisms for inorganic phosphate uptake in Trypanosoma rangeli.
abstract: BACKGROUND
  Trypanosoma rangeli is dependent on the presence of exogenous orthophosphate (Pi) for maximal growth and ecto-phosphatase activity is responsible for Pi supply under low Pi. Here we investigated the mechanisms of Pi uptake.
  
  
  METHODS
  We investigated the kinetics of 32Pi transport, its Na+ and H+ dependence, its correlation with the Na+-ATPase and H+-ATPase, and gene expression of the Na+:Pi cotransporter and Na+-ATPase.
  
  
  RESULTS
  T. rangeli grown under limiting Pi transports this anion to the cytosol in the absence and presence of Na+, suggesting that influx is mediated by both Na+-independent and Na+-dependent transporters. Cloning studies demonstrated that this parasite expresses a Pi transporter not previously studied in trypanosomatids. The H+ ionophore, carbonylcyanide-p-trifluoromethoxyphenylhydrazone, decreased both components of 32Pi influx by 80-95%. The H+-ATPase inhibitor, bafilomycin A1, inhibited the Na+-independent mechanism. Furosemide, an inhibitor of ouabain-insensitive Na+-ATPase, decreased both uptake mechanisms of 32Pi to the same extent, whereas ouabain had no effect, indicating that the former is the pump responsible for inwardly directed Na+ and the electric gradients required by the transporters. Parasite growth in high Pi had a lower Pi influx than that found in those grown in low Pi, without alteration in TrPho89 expression, showing that turnover of the transporters is stimulated by Pi starvation.
  
  
  CONCLUSIONS
  Two modes of Pi transport, one coupled to Na+-ATPase and other coupled to H+-ATPase seem to be responsible for Pi acquisition during development of T. rangeli.
  
  
  CONCLUSIONS
  This study provides the first description of the mechanism of Pi transport across the plasma membrane of trypanosomatids.
authors.affiliation: Instituto de Microbiologia Professor Paulo de Góes, Centro de Ciências da Saúde, Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ, Brazil.
authors.forename: C F
authors.initials: CF
authors.lastname: Dick
authors.forename: A L A
authors.initials: AL
authors.lastname: Dos-Santos
authors.forename: D
authors.initials: D
authors.lastname: Majerowicz
authors.forename: K C
authors.initials: KC
authors.lastname: Gondim
authors.forename: C
authors.initials: C
authors.lastname: Caruso-Neves
authors.forename: I V
authors.initials: IV
authors.lastname: Silva
authors.forename: A
authors.initials: A
authors.lastname: Vieyra
authors.forename: J R
authors.initials: JR
authors.lastname: Meyer-Fernandes
mesh_terms: D000251:Adenosine Triphosphatases / Q000037:antagonists & inhibitors / Q000378:metabolism; D000818:Animals; D001692:Biological Transport; D027682:Cation Transport Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D018942:Macrolides / Q000494:pharmacology; D010042:Ouabain / Q000494:pharmacology; D010710:Phosphates / Q000378:metabolism*; D006180:Proton-Translocating ATPases / Q000037:antagonists & inhibitors / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics; D060888:Real-Time Polymerase Chain Reaction; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012239:Rhodnius / Q000378:metabolism / Q000469:parasitology*; D012964:Sodium / Q000378:metabolism*; D014345:Trypanosoma / Q000254:growth & development / Q000378:metabolism*
chemical_list: D027682:Cation Transport Proteins; D004791:Enzyme Inhibitors; D018942:Macrolides; D010710:Phosphates; D012333:RNA, Messenger; D010042:Ouabain; C040929:bafilomycin A1; D012964:Sodium; D000251:Adenosine Triphosphatases; C021838:sodium-translocating ATPase; D006180:Proton-Translocating ATPases