title: Global identification of multiple substrates for Plasmodium falciparum SUB1, an essential malarial processing protease.
abstract: The protozoan pathogen responsible for the most severe form of human malaria, Plasmodium falciparum, replicates asexually in erythrocytes within a membrane-bound parasitophorous vacuole (PV). Following each round of intracellular growth, the PV membrane (PVM) and host cell membrane rupture to release infectious merozoites in a protease-dependent process called egress. Previous work has shown that, just prior to egress, an essential, subtilisin-like parasite protease called PfSUB1 is discharged into the PV lumen, where it directly cleaves a number of important merozoite surface and PV proteins. These include the essential merozoite surface protein complex MSP1/6/7 and members of a family of papain-like putative proteases called SERA (serine-rich antigen) that are implicated in egress. To determine whether PfSUB1 has additional, previously unrecognized substrates, we have performed a bioinformatic and proteomic analysis of the entire late asexual blood stage proteome of the parasite. Our results demonstrate that PfSUB1 is responsible for the proteolytic processing of a range of merozoite, PV, and PVM proteins, including the rhoptry protein RAP1 (rhoptry-associated protein 1) and the merozoite surface protein MSRP2 (MSP7-related protein-2). Our findings imply multiple roles for PfSUB1 in the parasite life cycle, further supporting the case for considering the protease as a potential new antimalarial drug target.
authors.affiliation: Division of Parasitology, MRC National Institute for Medical Research, Mill Hill, London NW7 1AA, United Kingdom.
authors.forename: Natalie C
authors.initials: NC
authors.lastname: Silmon de Monerri
authors.forename: Helen R
authors.initials: HR
authors.lastname: Flynn
authors.forename: Marta G
authors.initials: MG
authors.lastname: Campos
authors.forename: Fiona
authors.initials: F
authors.lastname: Hackett
authors.forename: Konstantinos
authors.initials: K
authors.lastname: Koussis
authors.forename: Chrislaine
authors.initials: C
authors.lastname: Withers-Martinez
authors.forename: J Mark
authors.initials: JM
authors.lastname: Skehel
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Blackman
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D015153:Blotting, Western; D004591:Electrophoresis, Polyacrylamide Gel; D008018:Life Cycle Stages / Q000502:physiology; D008969:Molecular Sequence Data; D010447:Peptide Hydrolases / Q000737:chemistry / Q000378:metabolism*; D010963:Plasmodium falciparum / Q000201:enzymology* / Q000254:growth & development; D017434:Protein Structure, Tertiary
chemical_list: D010447:Peptide Hydrolases