Sehgal Alfica, Kumar Nirbhay, Carruthers Vern B, Sharma Shobhona
Department of Biological Sciences, Tata Institute of Fundamental Research, Homi Bhabha Road, Mumbai 400 005, India.
Int J Parasitol. 2003 Dec;33(14):1589-94. doi: 10.1016/s0020-7519(03)00267-4.
A ribosomal phosphoprotein P0 detected on the surface of the human malarial parasite Plasmodium falciparum (PfP0) has been shown to be recognised by invasion blocking antibodies. Using cross-reactive polyclonal antibodies against PfP0, the surface localisation has also been demonstrated on certain mammalian cells, yeast and Toxoplasma gondii. We sought to characterise the phenomenon of surface localisation in Toxoplasma using T. gondii P0 protein. Sequence analysis of a cDNA clone isolated from a T. gondii library showed marked similarity to PfP0, suggesting that T. gondii expresses an orthologous gene, TgP0. The expression of TgP0 was corroborated by Northern blot analysis revealing a transcript of 1.8 kb in size. Immunofluorescence analysis using anti-PfP0 indicated surface localisation of TgP0. To confirm surface translocation of the TgP0, tachyzoites were transfected with the HA-tagged TgP0 gene followed by immunofluorescence detection of the HA-tag. Surface translocation of transiently expressed TgP0 and blocking of tachyzoite invasion of human foreskin fibroblasts by anti-PfP0 antibodies suggest that P0 protein plays an important role in T. gondii invasion of human cells.
在人类疟原虫恶性疟原虫（PfP0）表面检测到的一种核糖体磷蛋白P0已被证明能被入侵阻断抗体识别。使用针对PfP0的交叉反应性多克隆抗体，在某些哺乳动物细胞、酵母和刚地弓形虫上也证实了其表面定位。我们试图利用刚地弓形虫P0蛋白来表征刚地弓形虫中的表面定位现象。从刚地弓形虫文库中分离出的一个cDNA克隆的序列分析显示与PfP0有显著相似性，这表明刚地弓形虫表达一个直系同源基因TgP0。Northern印迹分析证实了TgP0的表达，显示出一个大小为1.8 kb的转录本。使用抗PfP0的免疫荧光分析表明TgP0定位于表面。为了证实TgP0的表面转运，用HA标签的TgP0基因转染速殖子，随后对HA标签进行免疫荧光检测。瞬时表达的TgP0的表面转运以及抗PfP0抗体对速殖子入侵人包皮成纤维细胞的阻断表明，P0蛋白在刚地弓形虫入侵人细胞中起重要作用。
