title: Plasmodium falciparum cysteine protease falcipain-1 is not essential in erythrocytic stage malaria parasites.
abstract: Among potential new targets for antimalarial chemotherapy are Plasmodium falciparum cysteine proteases, known as falcipains. Falcipain-2 and falcipain-3 are food vacuole hemoglobinases that may have additional functions. The function of falcipain-1 remains uncertain. To better characterize the role of falcipain-1 in erythrocytic parasites, we disrupted the falcipain-1 gene and characterized recombinant parasites. Disruption of the falcipain-1 gene was confirmed with Southern blots, and loss of expression of falcipain-1 was confirmed with immunoblots and by loss of labeling with a specific protease inhibitor. Compared with wild-type parasites, falcipain-1 knockout parasites developed normally, with the same morphology, multiplication rate, and invasion efficiency, and without significant differences in sensitivity to cysteine protease inhibitors. In wild-type and knockout parasites, cysteine protease inhibitors blocked hemoglobin hydrolysis in trophozoites, with a subsequent block in rupture of erythrocytes by mature schizonts, but they did not inhibit erythrocyte invasion by merozoites. Our results indicate that although falcipain-1 is expressed by erythrocytic parasites, it is not essential for normal development during this stage or for erythrocyte invasion.
authors.affiliation: Department of Medicine, San Francisco General Hospital, University of California, San Francisco, CA 94143-0811, USA.
authors.forename: Puran S
authors.initials: PS
authors.lastname: Sijwali
authors.forename: Kentaro
authors.initials: K
authors.lastname: Kato
authors.forename: Karl B
authors.initials: KB
authors.lastname: Seydel
authors.forename: Jiri
authors.initials: J
authors.lastname: Gut
authors.forename: Julie
authors.initials: J
authors.lastname: Lehman
authors.forename: Michael
authors.initials: M
authors.lastname: Klemba
authors.forename: Daniel E
authors.initials: DE
authors.lastname: Goldberg
authors.forename: Louis H
authors.initials: LH
authors.lastname: Miller
authors.forename: Philip J
authors.initials: PJ
authors.lastname: Rosenthal
mesh_terms: D000818:Animals; D001483:Base Sequence; D003546:Cysteine Endopeptidases / Q000235:genetics / Q000502:physiology*; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D016054:DNA, Protozoan / Q000235:genetics; D004912:Erythrocytes / Q000469:parasitology; D018390:Gene Targeting; D017125:Genes, Protozoan; D006801:Humans; D066298:In Vitro Techniques; D016778:Malaria, Falciparum / Q000188:drug therapy / Q000469:parasitology; D010963:Plasmodium falciparum / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development
chemical_list: D015853:Cysteine Proteinase Inhibitors; D016054:DNA, Protozoan; D003546:Cysteine Endopeptidases; C099607:falcipain