Malaria proteases mediate inside-out egress of gametocytes from red blood cells following parasite transmission to the mosquito

Authors

  • Ludmilla Sologub,

    1. Research Center for Infectious Diseases, University of Würzburg, Josef-Schneider-Strasse 2/D15, 97080 Würzburg, Germany
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    • These authors contributed equally.

  • Andrea Kuehn,

    1. Research Center for Infectious Diseases, University of Würzburg, Josef-Schneider-Strasse 2/D15, 97080 Würzburg, Germany
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    • These authors contributed equally.

  • Selina Kern,

    1. Research Center for Infectious Diseases, University of Würzburg, Josef-Schneider-Strasse 2/D15, 97080 Würzburg, Germany
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  • Jude Przyborski,

    1. Department of Parasitology, Philipps University Marburg, Karl-von-Frisch-Strasse 8, 35043 Marburg, Germany
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  • Rebecca Schillig,

    1. Research Center for Infectious Diseases, University of Würzburg, Josef-Schneider-Strasse 2/D15, 97080 Würzburg, Germany
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  • Gabriele Pradel

    Corresponding author
    1. Research Center for Infectious Diseases, University of Würzburg, Josef-Schneider-Strasse 2/D15, 97080 Würzburg, Germany
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E-mail gabriele.pradel@uni-wuerzburg.de; Tel. (+49) 931 3182174; Fax (+49) 931 3182578.

Summary

Malaria parasites reside in human erythrocytes within a parasitophorous vacuole. The parasites are transmitted from the human to the mosquito by the uptake of intraerythrocytic gametocytes during a blood meal, which in the midgut become activated by external stimuli and subsequently egress from the enveloping erythrocyte. Gametocyte egress is a crucial step for the parasite to prepare for fertilization, but the molecular mechanisms of egress are not well understood. Via electron microscopy, we show that Plasmodium falciparum gametocytes exit the erythrocyte by an inside-out type of egress. The parasitophorous vacuole membrane (PVM) ruptures at multiple sites within less than a minute following activation, a process that requires a temperature drop and parasite contact with xanthurenic acid. PVM rupture can also be triggered by the ionophore nigericin and is sensitive to the cysteine protease inhibitor E-64d. Following PVM rupture the subpellicular membrane begins to disintegrate. This membrane is specific to malaria gametocytes, and disintegration is impaired by the aspartic protease inhibitor EPNP and the cysteine/serine protease inhibitor TLCK. Approximately 15 min post activation, the erythrocyte membrane ruptures at a single breaking point, which can be inhibited by inhibitors TLCK and TPCK. In all cases inhibitor treatment results in interrupted gametogenesis.

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