Kagaya Wataru, Miyazaki Shinya, Yahata Kazuhide, Ohta Nobuo, Kaneko Osamu
Section of Environmental Parasitology, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, 1-5-45 Yushima, Bunkyo, Tokyo 113-0034, Japan; Department of Protozoology, Institute of Tropical Medicine (NEKKEN), Nagasaki University, Nagasaki, 1-12-4 Sakamoto, Nagasaki 852-8523, Japan.
Department of Protozoology, Institute of Tropical Medicine (NEKKEN), Nagasaki University , Nagasaki, 1-12-4 Sakamoto, Nagasaki 852-8523, Japan.
Trop Med Health. 2015 Dec;43(4):265-72. doi: 10.2149/tmh.2015-38. Epub 2015 Nov 5.
Plasmodium, the causative agent of malaria, exports many proteins to the surface of the infected red blood cell (iRBC) in order to modify it toward a structure more suitable for parasite development and survival. One such exported protein, SURFIN4.2, from the parasite of human malignant malaria, P. falciparum, was identified in the trypsin-cleaved protein fraction from the iRBC surface, and is thereby inferred to be exposed on the iRBC surface. SURFIN4.2 also localize to Maurer's clefts-parasite-derived membranous structures established in the RBC cytoplasm and tethered to the RBC membrane-and their role in trafficking suggests that they are a pathway for SURFIN4.2 transport to the iRBC surface. It has not been determined the participation of protein domains and motifs within SURFIN4.2 in transport from Maurer's clefts to the iRBC surface; and herein we examined if the SURFIN4.2 intracellular region containing tryptophan-rich (WR) domain is required for its exposure on the iRBC surface.
We generated two transgenic parasite lines which express modified SURFIN4.2, with or without a part of the intracellular region. Both recombinant SURFIN4.2 proteins were exported to Maurer's clefts. However, only SURFIN4.2 possessing the intracellular region was efficiently cleaved by surface treatment of iRBC with proteinase K.
These results indicate that SURFIN4.2 is exposed on the iRBC surface and that the intracellular region containing WR domain plays a role on the transport from Maurer's clefts to the iRBC membrane.
疟原虫是疟疾的病原体，它会向受感染红细胞（iRBC）表面输出多种蛋白质，以使红细胞结构发生改变，更适合寄生虫的发育和生存。其中一种输出蛋白SURFIN4.2是从人类恶性疟原虫——恶性疟原虫的寄生虫中鉴定出来的，它存在于iRBC表面经胰蛋白酶切割后的蛋白质组分中，因此推断其暴露于iRBC表面。SURFIN4.2也定位于毛氏小体——一种在红细胞细胞质中形成并与红细胞膜相连的寄生虫来源的膜性结构——并且其在运输中的作用表明它们是SURFIN4.2运输到iRBC表面的一条途径。尚未确定SURFIN4.2内的蛋白质结构域和基序在从毛氏小体运输到iRBC表面过程中的参与情况；在此我们研究了含有富含色氨酸（WR）结构域的SURFIN4.2细胞内区域是否是其暴露于iRBC表面所必需的。
我们构建了两个表达修饰后的SURFIN4.2的转基因寄生虫株系，一个含有部分细胞内区域，另一个没有。两种重组SURFIN4.2蛋白都被输出到毛氏小体。然而，只有含有细胞内区域的SURFIN4.2在用蛋白酶K对iRBC进行表面处理时能被有效切割。
这些结果表明SURFIN4.2暴露于iRBC表面，并且含有WR结构域的细胞内区域在从毛氏小体运输到iRBC膜的过程中发挥作用。
