title: Falcipain cysteine proteases require bipartite motifs for trafficking to the Plasmodium falciparum food vacuole.
abstract: The Plasmodium falciparum cysteine proteases falcipain-2 and falcipain-3 hydrolyze hemoglobin in an acidic food vacuole to provide amino acids for erythrocytic malaria parasites. Trafficking to the food vacuole has not been well characterized. To study trafficking of falcipains, which include large membrane-spanning prodomains, we utilized chimeras with portions of the proteases fused to green fluorescent protein. The prodomains of falcipain-2 and falcipain-3 were sufficient to target green fluorescent protein to the food vacuole. Using serial truncations, deletions, and point mutations, we showed that both a 20-amino acid stretch of the lumenal portion and a 10-amino acid stretch of the cytoplasmic portion of the falcipain-2 prodomain were required for efficient food vacuolar trafficking. Mutants with altered trafficking were arrested at the plasma membrane, implicating trafficking via this structure. Our results indicate that falcipains utilize a previously undescribed bipartite motif-dependent mechanism for targeting to a hydrolytic organelle, suggesting inhibition of this unique mechanism as a new means of antimalarial chemotherapy.
authors.affiliation: Department of Medicine, Division of Infectious Disease, University of California, San Francisco, San Francisco, California 94143, USA.
authors.forename: Shoba
authors.initials: S
authors.lastname: Subramanian
authors.forename: Puran S
authors.initials: PS
authors.lastname: Sijwali
authors.forename: Philip J
authors.initials: PJ
authors.lastname: Rosenthal
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002462:Cell Membrane / Q000378:metabolism; D003546:Cysteine Endopeptidases / Q000737:chemistry* / Q000502:physiology; D004912:Erythrocytes / Q000378:metabolism / Q000469:parasitology; D049452:Green Fluorescent Proteins / Q000378:metabolism; D006454:Hemoglobins / Q000737:chemistry; D006801:Humans; D006868:Hydrolysis; D008954:Models, Biological; D008969:Molecular Sequence Data; D010963:Plasmodium falciparum; D017386:Sequence Homology, Amino Acid; D014617:Vacuoles / Q000378:metabolism
chemical_list: D006454:Hemoglobins; D049452:Green Fluorescent Proteins; D003546:Cysteine Endopeptidases; C099607:falcipain; C416224:falcipain 2; C443101:falcipain 3