Portal de Periódicos da CAPES

Biochemical characterization and chemical inhibition of PfATP4-associated Na+-ATPase activity in Plasmodium falciparum membranes

2018; Elsevier BV; Volume: 293; Issue: 34 Linguagem: Inglês

10.1074/jbc.ra118.003640

1083-351X

James E. O. Rosling, Melanie C. Ridgway, Robert L. Summers, Kiaran Kirk, Adele M. Lehane,

Traditional and Medicinal Uses of Annonaceae

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 [Ca 2+ ]. With an apparent K m for ATP of 0.2 mm and an apparent K m 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 K m for Na + is slightly elevated. Our study provides new insights into the biochemical properties and chemical sensitivity of an important new antimalarial drug target.