Singh Meha, Mukherjee Paushali, Narayanasamy Krishnamoorthy, Arora Reena, Sen Som Dutta, Gupta Shashank, Natarajan Krishnamurthy, Malhotra Pawan
Malaria Group, International Centre for Genetic Engineering and Biotechnology, Aruna Asaf Ali Marg, New Delhi 110067, India.
Mol Cell Proteomics. 2009 Sep;8(9):2102-18. doi: 10.1074/mcp.M900029-MCP200. Epub 2009 Jun 3.
The highly co-evolved relationship of parasites and their hosts appears to include modulation of host immune signals, although the molecular mechanisms involved in the host-parasite interplay remain poorly understood. Characterization of these key genes and their cognate proteins related to the host-parasite interplay should lead to a better understanding of this intriguing biological phenomenon. The malaria agent Plasmodium falciparum is predicted to export a cohort of several hundred proteins to remodel the host erythrocyte. However, proteins actively exported by the asexual intracellular parasite beyond the host red blood cell membrane (before merozoite egress) have been poorly investigated so far. Here we used two complementary methodologies, two-dimensional gel electrophoresis/MS and LC-MS/MS, to examine the extracellular secreted antigens at asexual blood stages of P. falciparum. We identified 27 novel antigens exported by P. falciparum in the culture medium of which some showed clustering with highly polymorphic genes on chromosomes, suggesting that they may encode putative antigenic determinants of the parasite. Immunolocalization of four novel secreted proteins confirmed their export beyond the infected red blood cell membrane. Of these, preliminary functional characterization of two novel (Sel1 repeat-containing) parasite proteins, PfSEL1 and PfSEL2 revealed that they down-regulate expression of cell surface Notch signaling molecules in host cells. Also a novel protein kinase (PfEK) and a novel protein phosphatase (PfEP) were found to, respectively, phosphorylate/dephosphorylate parasite-specific proteins in the extracellular culture supernatant. Our study thus sheds new light on malaria parasite extracellular secreted antigens of which some may be essential for parasite development and could constitute promising new drug targets.
寄生虫与其宿主高度协同进化的关系似乎包括对宿主免疫信号的调节，尽管宿主 - 寄生虫相互作用所涉及的分子机制仍知之甚少。对这些与宿主 - 寄生虫相互作用相关的关键基因及其同源蛋白进行表征，应该能够更好地理解这一有趣的生物学现象。疟原虫恶性疟原虫预计会输出数百种蛋白质，以重塑宿主红细胞。然而，到目前为止，对无性细胞内寄生虫在宿主红细胞膜之外（裂殖子逸出之前）主动输出的蛋白质研究甚少。在这里，我们使用了两种互补的方法，二维凝胶电泳/质谱和液相色谱 - 质谱联用，来检测恶性疟原虫无性血液阶段的细胞外分泌抗原。我们在培养基中鉴定出了27种由恶性疟原虫输出的新抗原，其中一些与染色体上的高度多态性基因聚集在一起，这表明它们可能编码寄生虫的假定抗原决定簇。对四种新分泌蛋白的免疫定位证实了它们输出到被感染的红细胞膜之外。其中，对两种新的（含Sel1重复序列的）寄生虫蛋白PfSEL1和PfSEL2的初步功能表征显示，它们下调宿主细胞中细胞表面Notch信号分子的表达。此外，还发现一种新的蛋白激酶（PfEK）和一种新的蛋白磷酸酶（PfEP）分别在细胞外培养上清液中对寄生虫特异性蛋白进行磷酸化/去磷酸化。因此，我们的研究为疟原虫细胞外分泌抗原提供了新的线索，其中一些可能对寄生虫发育至关重要，并可能构成有前景的新药物靶点。
