Institute of Laboratory Medicine, Ingolstadt Hospital, Krumenauerstr. 25, 85049, Ingolstadt, Germany.
Central Division of Microscopy, Biocenter, University of Wuerzburg, Am Hubland, 97094, Würzburg, Germany.
Parasitol Res. 2024 Aug 30;123(9):311. doi: 10.1007/s00436-024-08334-7.
Striking morphological transformations characterize the invasion of a red blood cell by the malaria parasite. Shortly after the infection, parasite-induced membranes appear in the cytosol of the affected host erythrocyte. One intensely investigated membrane type, commonly called Maurer's clefts, has a slit-like morphology and can be arranged in the form of extended three-dimensional membrane stacks or networks. Here we report the three-dimensional reconstruction of a second membrane type, giant or extended membrane rings/loops, that have only occasionally been described on single ultrathin sections, however that have never been systematically examined so far. Serial ultrathin sectioning of P. falciparum-infected red blood cells, subsequent three-dimensional reconstructions, and in addition examination of Giemsa-stained blood films revealed that intraerythrocytic membrane rings/loops are not isolated structures but are locally in contact with the parasite. They consist either of the parasitophorous vacuolar membrane alone or contain the parasitophorous vacuolar membrane including the plasma membrane of the parasite and small amounts of parasite cytoplasm. We demonstrate that membrane rings/loops represent surface extensions of the parasite that maybe involved in ring stage parasite formation and Maurer's cleft generation at least in a subset of infected red blood cells.
疟原虫入侵红细胞时会发生显著的形态变化。在感染后不久，受感染的宿主红细胞胞质中就会出现寄生虫诱导的膜。一种备受关注的膜类型，通常称为 Maurer 裂隙，具有狭缝状形态，可以排列成扩展的三维膜堆叠或网络。在这里，我们报告了第二种膜类型的三维重建，即巨大或扩展的膜环/环，这些膜在单个超薄切片上仅偶尔被描述过，但迄今为止从未被系统检查过。对感染疟原虫的红细胞进行连续超薄切片、三维重建，以及对吉姆萨染色血片的检查表明，红细胞内的膜环/环不是孤立的结构，而是与寄生虫局部接触。它们要么仅由滋养液泡膜组成，要么包含滋养液泡膜，包括寄生虫的质膜和少量寄生虫细胞质。我们证明，膜环/环是寄生虫表面的延伸部分，可能参与环早期寄生虫的形成和 Maurer 裂隙的产生，至少在一部分感染的红细胞中是这样。
