Department of Protozoology, Institute of Tropical Medicine (NEKKEN), Nagasaki University, Sakamoto, Nagasaki 852-8523, Japan.
Leading program, Graduate School of Biomedical Sciences, Nagasaki University, Sakamoto, Nagasaki 852-8523, Japan.
PLoS One. 2016 Oct 12;11(10):e0164272. doi: 10.1371/journal.pone.0164272. eCollection 2016.
The malaria parasite, Plasmodium, exports protein products to the infected erythrocyte to introduce modifications necessary for the establishment of nutrient acquisition and surface display of host interaction ligands. Erythrocyte remodeling impacts parasite virulence and disease pathology and is well documented for the human malaria parasite Plasmodium falciparum, but has been less described for other Plasmodium species. For P. falciparum, the exported protein skeleton-binding protein 1 (PfSBP1) is involved in the trafficking of erythrocyte surface ligands and localized to membranous structures within the infected erythrocyte, termed Maurer's clefts. In this study, we analyzed SBP1 orthologs across the Plasmodium genus by BLAST analysis and conserved gene synteny, which were also recently described by de Niz et al. (2016). To evaluate the localization of an SBP1 ortholog, we utilized the zoonotic malaria parasite, Plasmodium knowlesi. Immunofluorescence assay of transgenic P. knowlesi parasites expressing epitope-tagged recombinant PkSBP1 revealed a punctate staining pattern reminiscent of Maurer's clefts, following infection of either monkey or human erythrocytes. The recombinant PkSBP1-positive puncta co-localized with Giemsa-stained structures, known as 'Sinton and Mulligan' stipplings. Immunoelectron microscopy also showed that recombinant PkSBP1 localizes within or on the membranous structures akin to the Maurer's clefts. The recombinant PkSBP1 expressed in P. falciparum-infected erythrocytes co-localized with PfSBP1 at the Maurer's clefts, indicating an analogous trafficking pattern. A member of the P. knowlesi 2TM protein family was also expressed and localized to membranous structures in infected monkey erythrocytes. These results suggest that the trafficking machinery and induced erythrocyte cellular structures of P. knowlesi are similar following infection of both monkey and human erythrocytes, and are conserved with P. falciparum.
疟原虫，如恶性疟原虫，将蛋白产物输出到受感染的红细胞中，以引入建立营养获取和表面展示宿主相互作用配体所必需的修饰。红细胞重塑会影响寄生虫的毒力和疾病病理学，这在人类疟原虫恶性疟原虫中已有详细描述，但在其他疟原虫中描述较少。对于恶性疟原虫，分泌蛋白骨架结合蛋白 1（PfSBP1）参与红细胞表面配体的运输，并定位于感染红细胞内的膜状结构，称为 Maurer's clefts。在这项研究中，我们通过 BLAST 分析和保守基因同线性分析来分析整个疟原虫属的 SBP1 同源物，这也被 de Niz 等人（2016 年）最近描述过。为了评估 SBP1 同源物的定位，我们利用了动物源疟原虫，即疟原虫 knowlesi。转染了带有表位标记的重组 PkSBP1 的疟原虫 knowlesi 寄生虫的免疫荧光分析显示，在感染猴子或人类红细胞后，呈现出类似于 Maurer's clefts 的点状染色模式。重组 PkSBP1 阳性的点状结构与 Giemsa 染色的结构（称为“辛顿和马利根”点状染色）共定位。免疫电镜也显示重组 PkSBP1 定位于类似于 Maurer's clefts 的膜状结构内或其表面。在感染恶性疟原虫的红细胞中表达的重组 PkSBP1 与 PfSBP1 在 Maurer's clefts 共定位，表明存在类似的运输模式。疟原虫 knowlesi 2TM 蛋白家族的一个成员也在感染猴子的红细胞中表达并定位于膜状结构。这些结果表明，疟原虫 knowlesi 在感染猴子和人类红细胞后，其运输机制和诱导的红细胞细胞结构相似，并且与恶性疟原虫保守。
