Glushakova Svetlana, Yin Dan, Li Tao, Zimmerberg Joshua
Laboratory of Cellular and Molecular Biophysics, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892, USA.
Curr Biol. 2005 Sep 20;15(18):1645-50. doi: 10.1016/j.cub.2005.07.067.
Three opposing pathways are proposed for the release of malaria parasites from infected erythrocytes: coordinated rupture of the two membranes surrounding mature parasites; fusion of erythrocyte and parasitophorus vacuolar membranes (PVM); and liberation of parasites enclosed within the vacuole from the erythrocyte followed by PVM disintegration. Rupture by cell swelling should yield erythrocyte ghosts; membrane fusion is inhibited by inner-leaflet amphiphiles of positive intrinsic curvature, which contrariwise promote membrane rupture; and without protease inhibitors, parasites would leave erythrocytes packed within the vacuole. Therefore, we visualized erythrocytes releasing P. falciparum using fluorescent microscopy of differentially labeled membranes. Release did not yield erythrocyte ghosts, positive-curvature amphiphiles did not inhibit release but promoted it, and release of packed merozoites was shown to be an artifact. Instead, two sequential morphological stages preceded a convulsive rupture of membranes and rapid radial discharge of separated merozoites, leaving segregated internal membrane fragments and plasma membrane vesicles or blebs at the sites of parasite egress. These results, together with the modulation of release by osmotic stress, suggest a pathway of parasite release that features a biochemically altered erythrocyte membrane that folds after pressure-driven rupture of membranes.
关于疟原虫从受感染红细胞中释放出来，提出了三种相反的途径：围绕成熟疟原虫的两层膜协同破裂；红细胞膜与疟原虫空泡膜（PVM）融合；空泡内的疟原虫从红细胞中释放出来，随后PVM解体。细胞肿胀导致的破裂应产生红细胞影；膜融合受到具有正固有曲率的内小叶两亲分子的抑制，相反，这些分子会促进膜破裂；并且在没有蛋白酶抑制剂的情况下，疟原虫会以包裹在空泡内的形式离开红细胞。因此，我们使用对不同标记膜进行荧光显微镜观察，来可视化红细胞释放恶性疟原虫的过程。释放过程并未产生红细胞影，具有正曲率的两亲分子并未抑制释放反而促进了释放，并且已证明包裹的裂殖子的释放是一种假象。相反，在膜的痉挛性破裂和分离的裂殖子的快速径向排出之前，有两个连续的形态学阶段，在疟原虫逸出部位留下分离的内膜碎片和质膜囊泡或小泡。这些结果，连同渗透压应激对释放的调节作用，提示了一种疟原虫释放途径，其特征是红细胞膜在压力驱动的膜破裂后发生折叠，生化性质发生改变。
