Export determinants and pathways in protein trafficking in the human malaria parasite Plasmodium falciparum

血液阶段的人类疟疾寄生虫恶性疟原虫是疟疾的罪魁祸首。在这个生命周期阶段，寄生虫在人类红细胞中繁殖。为了将这种细胞内生态位转变为适合生存和生长的环境，寄生虫通过大量输出的寄生虫蛋白介导了深刻的变化。因此，输出的蛋白质对寄生虫至关重要。这些蛋白质必须被运输到寄生虫边界之外，穿过周围的寄生液泡膜到达宿主细胞。最近的数据表明，这些步骤是由易位事件介导的，但个别步骤尚未得到解决。此外，已知有不同类型的输出蛋白，包括许多具有所谓的疟原虫输出元件（PEXEL）和其他没有这样的基元（PNEPs， PEXEL阴性输出蛋白）。这两类蛋白都包含可溶蛋白和跨膜蛋白，需要不同的转运模式才能出口。虽然PEXEL蛋白可以根据确定的输出基序的存在来预测，但PNEPs无法预测，因此不知道在恶性疟原虫基因组中编码了多少进一步的输出蛋白。在这个应用中，我们建议在最近发现的PNEPs和PEXEL蛋白之间共享的核心输出域中寻找输出介导序列决定因子，以预测和鉴定疟疾寄生虫的进一步（可能全部）输出蛋白。进一步，我们将鉴定介导最近发现的新型PNEPs输出的序列，并测试它们是否也包含PNEPs和PEXEL蛋白之间共享的核心输出结构域。最后，我们将分析这些蛋白质进入宿主细胞的途径，重点是解决寄生虫外周涉及寄生虫质膜和寄生虫液泡的易位步骤。用于修饰高度衍生的宿主细胞的蛋白质输出是寄生虫生存所必需的，也负责与寄生虫毒力直接相关的宿主细胞表面的变化。因此，了解哪些蛋白质被输出以及它们如何输出不仅是一个令人着迷的细胞生物学问题，而且可能最终为这种重要寄生虫的化疗干预提供新的靶点。

Blood stages of the human malaria parasite Plasmodium falciparum are responsible for the disease malaria. In this life cycle phase the parasites multiply in human red blood cells. To turn this intracellular niche into an environment suitable for survival and growth, the parasite induces profound changes mediated by a large number of exported parasite proteins. Hence, exported proteins are of crucial importance for the parasite. These proteins have to be trafficked beyond the parasite boundary and across the surrounding parasitophorous vacuole membrane to reach the host cell. Recent data indicates that these steps are mediated by translocation events but the individual steps have not been resolved. Further, there are different types of exported proteins known, including many with a so called Plasmodium export element (PEXEL) and others without such a motif (PNEPs, PEXEL negative exported proteins). Both these groups comprise soluble as well as transmembrane proteins, requiring different translocation modi for export. While PEXEL proteins can be predicted based on the presence of a defined export motif, PNEPs can not be predicted and it is therefore unknown how many further exported proteins are encoded in the P. falciparum genome. In this application it is proposed to find the export-mediating sequence determinants in a recently discovered core export domain shared between PNEPs and PEXEL proteins to predict and identify further (potentially all) exported proteins in malaria parasites. Further we will identify the sequences mediating export of recently discovered new types of PNEPs and test whether they also contain the core export domain shared between PNEPs and PEXEL proteins. Finally we will analyse the pathway these proteins take into the host cell, with a focus on resolving the translocation steps in the parasite periphery that involve the parasite plasma membrane and the parasitophorous vacuole. Protein export to modify the highly derived host cell is necessary for parasite survival and is also responsible for changes to the host cell surface directly linked to parasite virulence. Knowing which proteins are exported and how they are exported is therefore not only a fascinating cell biological problem but may ultimately also provide new targets for chemotherapeutic interventions for this important parasite.