Biochemical characterization and chemical inhibition of PfATP4-associated Na+-ATPase activity in Plasmodium falciparum membranes.
J Biol Chem
; 293(34): 13327-13337, 2018 08 24.
Article
em En
| MEDLINE
| ID: mdl-29986883
ABSTRACT
The antimalarial activity of chemically diverse compounds, including the clinical candidate cipargamin, has been linked to the ATPase PfATP4 in the malaria-causing parasite Plasmodium falciparum The characterization of PfATP4 has been hampered by the inability thus far to achieve its functional expression in a heterologous system. Here, we optimized a membrane ATPase assay to probe the function of PfATP4 and its chemical sensitivity. We found that cipargamin inhibited the Na+-dependent ATPase activity present in P. falciparum membranes from WT parasites and that its potency was reduced in cipargamin-resistant PfATP4-mutant parasites. The cipargamin-sensitive fraction of membrane ATPase activity was inhibited by all 28 of the compounds in the "Malaria Box" shown previously to disrupt ion regulation in P. falciparum in a cipargamin-like manner. This is consistent with PfATP4 being the direct target of these compounds. Characterization of the cipargamin-sensitive ATPase activity yielded data consistent with PfATP4 being a Na+ transporter that is sensitive to physiologically relevant perturbations of pH, but not of [K+] or [Ca2+]. With an apparent Km for ATP of 0.2 mm and an apparent Km for Na+ of 16-17 mm, the protein is predicted to operate at below its half-maximal rate under normal physiological conditions, allowing the rate of Na+ efflux to increase in response to an increase in cytosolic [Na+]. In membranes from a cipargamin-resistant PfATP4-mutant line, the apparent Km for Na+ is slightly elevated. Our study provides new insights into the biochemical properties and chemical sensitivity of an important new antimalarial drug target.
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Texto completo:
1
Base de dados:
MEDLINE
Assunto principal:
Plasmodium falciparum
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Sódio
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Malária Falciparum
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ATPases Transportadoras de Cálcio
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Adenosina Trifosfatases
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Proteínas de Transporte de Cátions
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Eritrócitos
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Antimaláricos
Tipo de estudo:
Risk_factors_studies
Limite:
Animals
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Humans
Idioma:
En
Ano de publicação:
2018
Tipo de documento:
Article