A single malaria merozoite serine protease mediates shedding of multiple surface proteins by juxtamembrane cleavage.
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.
Howell
Steven A
SA
Division of Protein Structure, National Institute for Medical Research, Mill Hill, London NW7 1AA, United Kingdom.
Well
Isabelle
I
Fleck
Suzanne L
SL
Kettleborough
Catherine
C
Collins
Christine R
CR
Blackman
Michael J
MJ
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
D000953:Antigens, Protozoan; D008565:Membrane Proteins; D020066:Merozoite Surface Protein 1; D015800:Protozoan Proteins; C090077:apical membrane antigen I, Plasmodium; D012697:Serine Endopeptidases