Gene disruptions demonstrate independent roles for the four falcipain cysteine proteases of Plasmodium falciparum

Sijwali, Puran Singh; Koo, Jamie; Singh, Naresh; Rosenthal, Philip J.

doi:10.1016/j.molbiopara.2006.06.013

Cited by 143 publications

(141 citation statements)

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“…In any event, in our study the aspartic protease inhibitor pepstatin had a relatively small impact on artemisinin activity compared to cysteine protease inhibitors, consistent with aspartic proteases playing a redundant role in hemoglobin digestion (26). Falcipain-2 is the only cysteine protease hemoglobinase expressed early in erythrocytic parasite development, and knockout parasites have markedly diminished hemoglobinase activity in the early trophozoite stage (25). These parasites exhibit a swollen vacuole phenotype, consistent with defective hemoglobin digestion, but the deletion is not lethal, apparently due to rescue by the expression of falcipain-2′ and falcipain-3 beginning at the mid trophozoite stage (25).…”

Section: Discussionsupporting

confidence: 70%

“…4B). The effects of deletion of falcipain-3 could not be assessed, as erythrocytic parasites cannot tolerate the deletion (25). Our data strongly suggest that flux of a hemoglobin degradation product, presumably heme or ferrous iron, is needed for the potent antimalarial activity of artemisinin.…”

Section: Resultsmentioning

confidence: 91%

“…These parasites exhibit a swollen vacuole phenotype, consistent with defective hemoglobin digestion, but the deletion is not lethal, apparently due to rescue by the expression of falcipain-2′ and falcipain-3 beginning at the mid trophozoite stage (25). By contrast, falcipain-2′ deletion parasites show no defect, presumably due to the expression of other falcipains in mature parasites (25). As would be expected if hemoglobin digestion is needed for artemisinin action, falcipain-2 deletion parasites showed substantial protection against a pulse of artemisinin in early to mid trophozoites, whereas falcipain-2′ deletion parasites showed an artemisinin sensitivity profile similar to that of wild type parasites.…”

Section: Discussionmentioning

confidence: 99%

“…Falcipain cysteine proteases play important roles in hemoglobin degradation, both directly and as activators of plasmepsin hemoglobinases (25,33). To confirm the importance of hemoglobin degradation in the action of artemisinin we examined the effect of pretreatment of parasites with the cysteine protease inhibitors ALLN and E-64.…”

Section: Discussionmentioning

confidence: 99%

“…Falcipain-2 is the only cysteine protease hemoglobinase expressed early in erythrocytic parasite development, and knockout parasites have markedly diminished hemoglobinase activity in the early trophozoite stage (25). These parasites exhibit a swollen vacuole phenotype, consistent with defective hemoglobin digestion, but the deletion is not lethal, apparently due to rescue by the expression of falcipain-2′ and falcipain-3 beginning at the mid trophozoite stage (25). By contrast, falcipain-2′ deletion parasites show no defect, presumably due to the expression of other falcipains in mature parasites (25).…”

Section: Discussionmentioning

confidence: 99%

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Artemisinin activity againstPlasmodium falciparumrequires hemoglobin uptake and digestion

Klonis

Crespo-Ortiz²,

Bottová³

et al. 2011

Proc. Natl. Acad. Sci. U.S.A.

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322

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Combination regimens that include artemisinin derivatives are recommended as first line antimalarials in most countries where malaria is endemic. However, the mechanism of action of artemisinin is not fully understood and the usefulness of this drug class is threatened by reports of decreased parasite sensitivity. We treated Plasmodium falciparum for periods of a few hours to mimic clinical exposure to the short half-life artemisinins. We found that drug treatment retards parasite growth and inhibits uptake of hemoglobin, even at sublethal concentrations. We show that potent artemisinin activity is dependent on hemoglobin digestion by the parasite. Inhibition of hemoglobinase activity with cysteine protease inhibitors, knockout of the cysteine protease falcipain-2 by gene deletion, or direct deprivation of host cell lysate, significantly decreases artemisinin sensitivity. Hemoglobin digestion is also required for artemisinin-induced exacerbation of oxidative stress in the parasite cytoplasm. Arrest of hemoglobin digestion by early stage parasites provides a mechanism for surviving short-term artemisinin exposure. These insights will help in the design of new drugs and new treatment strategies to circumvent drug resistance.erythrocyte | endoperoxide

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Section: Discussionsupporting

confidence: 70%

Section: Resultsmentioning

confidence: 91%