Adisa Akinola, Frankland Sarah, Rug Melanie, Jackson Katherine, Maier Alexander G, Walsh Peter, Lithgow Trevor, Klonis Nectarios, Gilson Paul R, Cowman Alan F, Tilley Leann
Department of Biochemistry, La Trobe University, Melbourne 3086, Vic., Australia.
Int J Parasitol. 2007 Aug;37(10):1127-41. doi: 10.1016/j.ijpara.2007.02.009. Epub 2007 Mar 12.
The malaria parasite, Plasmodium falciparum, exports proteins beyond the confines of its own plasma membrane, however there is debate regarding the machinery used for these trafficking events. We have generated transgenic parasites expressing chimeric proteins and used immunofluorescence studies to determine the locations of plasmodial homologues of the COPII component, Sar1p, and the Golgi-docking protein, Bet3p. The P. falciparum Sar1p (PfSar1p) chimeras bind to the endoplasmic reticulum surface and define a network of membranes wrapped around parasite nuclei. As the parasite matures, the endomembrane systems of individual merozoites remain interconnected until very late in schizogony. Antibodies raised against plasmodial Bet3p recognise two foci of reactivity in early parasite stages that increase in number as the parasite matures. Some of the P. falciparum Bet3p (PfBet3p) compartments are juxtaposed to compartments defined by the cis Golgi marker, PfGRASP, while others are distributed through the cytoplasm. The compartments defined by the trans Golgi marker, PfRab6, are separate, suggesting that the Golgi is dispersed. Bet3p-green fluorescent protein (GFP) is partly associated with punctate structures but a substantial population diffuses freely in the parasite cytoplasm. By contrast, yeast Bet3p is very tightly associated with immobile structures. This study challenges the view that the COPII complex and the Golgi apparatus are exported into the infected erythrocyte cytoplasm.
疟原虫，恶性疟原虫，会将蛋白质输出到其自身质膜范围之外，然而对于这些运输事件所使用的机制存在争议。我们构建了表达嵌合蛋白的转基因寄生虫，并利用免疫荧光研究来确定COPII组分Sar1p和高尔基体对接蛋白Bet3p的疟原虫同源物的位置。恶性疟原虫Sar1p（PfSar1p）嵌合体与内质网表面结合，并界定了围绕寄生虫细胞核的膜网络。随着寄生虫成熟，单个裂殖子的内膜系统在裂体生殖后期之前一直保持相互连接。针对疟原虫Bet3p产生的抗体在寄生虫早期阶段识别出两个反应位点，随着寄生虫成熟，反应位点数量增加。一些恶性疟原虫Bet3p（PfBet3p）区室与顺面高尔基体标记PfGRASP所界定的区室并列，而其他区室则分布在细胞质中。反式高尔基体标记PfRab6所界定的区室是分开的，这表明高尔基体是分散的。Bet3p-绿色荧光蛋白（GFP）部分与点状结构相关，但大量群体在寄生虫细胞质中自由扩散。相比之下，酵母Bet3p与固定结构紧密相关。这项研究挑战了COPII复合体和高尔基体被输出到受感染红细胞细胞质中的观点。
