title: A single malaria merozoite serine protease mediates shedding of multiple surface proteins by juxtamembrane cleavage.
abstract: Erythrocyte invasion by the malaria merozoite is accompanied by the regulated discharge of apically located secretory organelles called micronemes. Plasmodium falciparum apical membrane antigen-1 (PfAMA-1), which plays an indispensable role in invasion, translocates from micronemes onto the parasite surface and is proteolytically shed in a soluble form during invasion. We have previously proposed, on the basis of incomplete mass spectrometric mapping data, that PfAMA-1 shedding results from cleavage at two alternative positions. We now show conclusively that the PfAMA-1 ectodomain is shed from the merozoite solely as a result of cleavage at a single site, just 29 residues away from the predicted transmembrane-spanning sequence. Remarkably, this cleavage is mediated by the same membrane-bound parasite serine protease as that responsible for shedding of the merozoite surface protein-1 (MSP-1) complex, an abundant, glycosylphosphatidylinositol-anchored multiprotein complex. Processing of MSP-1 is essential for invasion. Our results indicate the presence on the merozoite surface of a multifunctional serine sheddase with a broad substrate specificity. We further demonstrate that translocation and shedding of PfAMA-1 is an actin-independent process.
authors.affiliation: Division of Protein Structure, National Institute for Medical Research, Mill Hill, London NW7 1AA, United Kingdom.
authors.forename: Steven A
authors.initials: SA
authors.lastname: Howell
authors.forename: Isabelle
authors.initials: I
authors.lastname: Well
authors.forename: Suzanne L
authors.initials: SL
authors.lastname: Fleck
authors.forename: Catherine
authors.initials: C
authors.lastname: Kettleborough
authors.forename: Christine R
authors.initials: CR
authors.lastname: Collins
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Blackman
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000953:Antigens, Protozoan; D008565:Membrane Proteins / Q000378:metabolism; D020066:Merozoite Surface Protein 1 / Q000378:metabolism; D008969:Molecular Sequence Data; D010963:Plasmodium falciparum / Q000201:enzymology* / Q000502:physiology / Q000648:ultrastructure; D011499:Protein Processing, Post-Translational; D021381:Protein Transport; D015800:Protozoan Proteins / Q000378:metabolism*; D012697:Serine Endopeptidases / Q000378:metabolism / Q000502:physiology*; D021241:Spectrometry, Mass, Electrospray Ionization
chemical_list: D000953:Antigens, Protozoan; D008565:Membrane Proteins; D020066:Merozoite Surface Protein 1; D015800:Protozoan Proteins; C090077:apical membrane antigen I, Plasmodium; D012697:Serine Endopeptidases