Transport of inorganic phosphate in Leishmania infantum and compensatory regulation at low inorganic phosphate concentration.

BACKGROUND

Proliferation of Leishmania infantum depends on exogenous inorganic phosphate (P) but little is known about energy metabolism and transport of P across the plasma membrane in Leishmania sp.

METHODS

We investigated the kinetics of P transport, the influence of H and K ionophores and inhibitors, and expression of the genes for the Na:P and H:P cotransporters.

RESULTS

The proton ionophore FCCP, bafilomycin A (vacuolar ATPase inhibitor), nigericin (K ionophore) and SCH28080 (an inhibitor of H, K-ATPase) all inhibited the transport of P. This transport showed Michaelis-Menten kinetics with K and V values of 0.016±0.002mM and 564.9±18.06pmol×h×10cells, respectively. These values classify the P transporter of L. infantum among the high-affinity transporters, a group that includes Pho84 of Saccharomyces cerevisiae. Two sequences were identified in the L. infantum genome that code for phosphate transporters. However, transcription of the PHO84 transporter was 10-fold higher than the PHO89 transporter in this parasite. Accordingly, P transport and LiPho84 gene expression were modulated by environmental P variations.

CONCLUSIONS

These findings confirm the presence of a P transporter in L. infantum, similar to PHO84 in S. cerevisiae, that contributes to the acquisition of inorganic phosphate and could be involved in growth and survival of the promastigote forms of L. infantum.

GENERAL SIGNIFICANCE

This work provides the first description of a PHO84-like P transporter in a Trypanosomatide parasite of the genus Leishmania, responsible for many infections worldwide.