The intraerythrocytic malaria parasite, Plasmodium falciparum, maintains a low cytosolic Na+ concentration and the plasma membrane P-type cation translocating ATPase ‘PfATP4’ has been implicated as playing a key role in this process PfATP4 has been the subject of significant attention in recent years as mutations in this protein confer resistance to a growing number of new antimalarial compounds, including the spiroindolones, the pyrazoles, the dihydroisoquinolones, and a number of the antimalarial agents in the Medicines for Malaria Venture's ‘Malaria Box’ On exposure of parasites to these compounds there is a rapid disruption of cytosolic Na+ Whether, and if so how, such chemically distinct compounds interact with PfATP4, and how such interactions lead to parasite death, is not yet clear The fact that multiple different chemical classes have converged upon PfATP4 highlights its significance as a potential target for new generation antimalarial agents A spiroindolone (KAE609, now known as cipargamin) has progressed through Phase I and IIa clinical trials with favourable results In this review we consider the physiological role of PfATP4, summarise the current repertoire of antimalarial compounds for which PfATP4 is implicated in their mechanism of action, and provide an outlook on translation from target identification in the laboratory to patient treatment in the field

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The malaria parasite cation ATPase PfATP4 and its role in the mechanism of action of a new arsenal of antimalarial drugs

The intraerythrocytic malaria parasite relies primarily on glycolysis to fuel its rapid growth and reproduction. The major byproduct of this metabolism, lactic acid, is extruded into the external medium. In this study, we show that the human malaria parasite Plasmodium falciparum expresses at its surface a member of the microbial formate-nitrite transporter family (PfFNT), which, when expressed in Xenopus laevis oocytes, transports both formate and lactate. The transport characteristics of PfFNT in oocytes (pH-dependence, inhibitor-sensitivity and kinetics) are similar to those of the transport of lactate and formate across the plasma membrane of mature asexual-stage P. falciparum trophozoites, consistent with PfFNT playing a major role in the efflux of lactate and hence in the energy metabolism of the intraerythrocytic parasite.

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A lactate and formate transporter in the intraerythrocytic malaria parasite, Plasmodium falciparum

Identification of novel parasitophorous vacuole proteins in P. falciparum parasites using BioID.

https://eprints.ncl.ac.uk/file_store/production/250606/81E87612-0F40-4093-B4A9-8C26160F43BC.pdf

Efficient Hydrogen-Dependent Carbon Dioxide Reduction by Escherichia coli.

Bacterial formate–nitrite transporters (FNTs) regulate the metabolic flow of small, weak mono‐acids. Recently, the eukaryotic PfFNT was identified as the malaria parasite9s lactate transporter and novel drug target. Despite crystal data, central mechanisms of FNT gating and transport remained unclear. Here, we show elucidation of the FNT transport mechanism by single‐step substrate protonation involving an invariant lysine in the periplasmic vestibule. Opposing earlier gating hypotheses and electrophysiology reports, quantification of total uptake by radiolabeled substrate indicates a permanently open conformation of the bacterial formate transporter, FocA, irrespective of the pH. Site‐directed mutagenesis, heavy water effects, mathematical modeling, and simulations of solvation imply a general, proton motive force‐driven FNT transport mechanism: Electrostatic attraction of the acid anion into a hydrophobic vestibule decreases substrate acidity and facilitates protonation by the bulk solvent. We define substrate neutralization by proton transfer for transport via a hydrophobic transport path as a general theme of the Amt/Mep/Rh ammonium and formate–nitrite transporters.

/pdf/mechanism-of-formate-nitrite-transporters-by-dielectric-1o5yylmo2x.pdf

Mechanism of formate–nitrite transporters by dielectric shift of substrate acidity

Malaria parasites generate metabolic energy through anaerobic glycolysis, yielding lactate and protons that are then secreted out of the parasite cell by an unknown transporter. Here, the authors identify and characterize a lactate/proton transporter that may be carrying out such function in Plasmodium.

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Identity of a Plasmodium lactate/H + symporter structurally unrelated to human transporters

Resistance against all available antimalarial drugs calls for novel compounds that hit unexploited targets in the parasite. Here, we show that the recently discovered Plasmodium falciparum lactate/proton symporter, PfFNT, is a valid druggable target, and describe a new class of fluoroalkyl vinylogous acids that potently block PfFNT and kill cultured parasites. The original compound, MMV007839, is derived from the malaria box collection of potent antimalarials with unknown targets and contains a unique internal prodrug principle that reversibly switches between a lipophilic transport form and a polar, substrate-analogous active form. Resistance selection of cultured P. falciparum parasites with sub-lethal concentrations of MMV007839 produced a single nucleotide exchange in the PfFNT gene; this, and functional characterization of the resulting PfFNT G107S validated PfFNT as a novel antimalarial target. From quantitative structure function relations we established the compound binding mode and the pharmacophore. The pharmacophore largely circumvents the resistance mutation and provides the basis for a medicinal chemistry program that targets lactate and proton transport as a new mode of antimalarial action.

/pdf/substrate-analogous-inhibitors-exert-antimalarial-action-by-37egfmmgkp.pdf

Substrate-analogous inhibitors exert antimalarial action by targeting the Plasmodium lactate transporter PfFNT at nanomolar scale.

Bacterial formate-nitrite transporters (FNT) regulate the metabolic flow of small weak mono-acids derived from anaerobic mixed-acid fermentation, such as formate, and further transport nitrite, and hydrosulfide The eukaryotic Plasmodium falciparum FNT is vital for the malaria parasite by its ability to release the larger l-lactate substrate as the metabolic end product of anaerobic glycolysis in symport with protons preventing cytosolic acidification However, the molecular basis for substrate discrimination by FNTs has remained unclear Here, we identified a size-selective FNT substrate filter region around an invariant lysine at the bottom of the periplasmic/extracellular vestibule The selectivity filter is reminiscent of the aromatic/arginine constriction of aquaporin water and solute channels regarding composition, location in the protein, and the size-selection principle Bioinformatics support an adaptation of the eukaryotic FNT selectivity filter to accommodate larger physiologically relevant substrates Mutations that affect the diameter at the filter site predictably modulated substrate selectivity The shape of the vestibule immediately above the filter region further affects selectivity This study indicates that eukaryotic FNTs evolved to transport larger mono-acid substrates, especially l-lactic acid as a product of energy metabolism

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https://febs.onlinelibrary.wiley.com/doi/pdf/10.1111/febs.14117

A widened substrate selectivity filter of eukaryotic formate-nitrite transporters enables high-level lactate conductance.

The discovery that the Escherichia coli focA gene product facilitates the transmembrane exchange of formate1 sparked research on proteins that turned out to be functionally situated between classic...

Marie Wiechert

Papers

Identity of a Plasmodium lactate/H + symporter structurally unrelated to human transporters

Mechanism of formate–nitrite transporters by dielectric shift of substrate acidity

Substrate-analogous inhibitors exert antimalarial action by targeting the Plasmodium lactate transporter PfFNT at nanomolar scale.

A widened substrate selectivity filter of eukaryotic formate-nitrite transporters enables high-level lactate conductance.

Formate-nitrite transporters: Monoacids ride the dielectric slide.