title: Malaria proteases mediate inside-out egress of gametocytes from red blood cells following parasite transmission to the mosquito.
abstract: 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.
authors.affiliation: Research Center for Infectious Diseases, University of Würzburg, Würzburg, Germany.
authors.forename: Ludmilla
authors.initials: L
authors.lastname: Sologub
authors.forename: Andrea
authors.initials: A
authors.lastname: Kuehn
authors.forename: Selina
authors.initials: S
authors.lastname: Kern
authors.forename: Jude
authors.initials: J
authors.lastname: Przyborski
authors.forename: Rebecca
authors.initials: R
authors.lastname: Schillig
authors.forename: Gabriele
authors.initials: G
authors.lastname: Pradel
mesh_terms: D000818:Animals; D009033:Culicidae / Q000469:parasitology*; D004852:Epoxy Compounds / Q000378:metabolism; D004912:Erythrocytes / Q000469:parasitology* / Q000648:ultrastructure; D006801:Humans; D007425:Intracellular Membranes / Q000648:ultrastructure; D007930:Leucine / Q000031:analogs & derivatives / Q000378:metabolism; D008854:Microscopy, Electron; D009550:Nigericin / Q000378:metabolism; D009596:Nitrophenols / Q000378:metabolism; D010963:Plasmodium falciparum / Q000254:growth & development* / Q000648:ultrastructure; D013696:Temperature; D014107:Tosyllysine Chloromethyl Ketone / Q000378:metabolism; D014617:Vacuoles / Q000469:parasitology / Q000648:ultrastructure; D014977:Xanthurenates / Q000378:metabolism
chemical_list: D004852:Epoxy Compounds; D009596:Nitrophenols; D014977:Xanthurenates; D014107:Tosyllysine Chloromethyl Ketone; C028330:xanthurenic acid; C007606:1,2-epoxy-3-(p-nitrophenoxy)propane; D007930:Leucine; C108192:aloxistatin; D009550:Nigericin