Assessment of Plasmodium falciparum PfMDR1 transport rates using Fluo-4.
Bottom Line: Although it is generally accepted that drug resistance in P. falciparum is partly associated with PfMDR1 transport activity situated in the membrane of the digestive vacuole, direct estimates of the pump rate of this transport process in the natural environment of the intact host-parasite system have never been analysed.The fluorochrome Fluo-4 is a well-documented surrogate substrate of PfMDR1 and has been found to accumulate by actively being transported into the digestive vacuole of several parasitic strains.With this assay, we provide a powerful method to selectively measure the effect of PfMDR1 mutations on substrate transport kinetics.
Affiliation: Institute of Medical Biotechnology, Friedrich-Alexander-University Erlangen-Nuremberg, Erlangen, Germany; SAOT, Erlangen Graduate School of Advanced Optical Technologies, Friedrich-Alexander-University Erlangen-Nuremberg, Erlangen, Germany.Show MeSH
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Mentions: Understanding the bioenergetics of PfMDR1 sheds light on general mechanisms of action for this superfamily of transporters. Unlike artificial systems, such as PfMDR1 embedded in artificial liposomes, it is desirable to study transport rates in the natural environment of the transporter, i.e. within the DV of the intact P. falciparum-infected erythrocyte and to have tools at hand to differentiate between pump rates and diffusional uptake. Therefore, the aim of the present study was to investigate the transport kinetics of PfMDR1 in the host–parasite system using the Fluo-4 fluorochrome and live-cell imaging. We describe a detailed investigation of the transporter in relation to Fluo-4 solute uptake applied in all compartments of the host–parasite system (Fig. 1). This is the first estimate of overall transport rates of PfMDR1 in the intact host–parasite system. Using a ligand-binding model, we were able to estimate a maximum overall pump rate of ∼50,000 Fluo-4 molecules/min.—or 820/sec.—for the complete set of PfMDR1 molecules found on the DV membrane of the Dd2 parasite.
Affiliation: Institute of Medical Biotechnology, Friedrich-Alexander-University Erlangen-Nuremberg, Erlangen, Germany; SAOT, Erlangen Graduate School of Advanced Optical Technologies, Friedrich-Alexander-University Erlangen-Nuremberg, Erlangen, Germany.