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

人类疟疾寄生虫恶性疟原虫的血液阶段是导致疟疾的原因。在这个生命周期阶段，寄生虫在人类红细胞中繁殖。为了将这种细胞内的生态位转变为适合生存和生长的环境，寄生虫在大量输出寄生虫蛋白的介导下引发了深刻的变化。因此，出口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，穿过周围的寄生虫液泡膜才能到达宿主细胞。最近的数据表明，这些步骤是由易位事件介导的，但个别步骤尚未解决。此外，已知有不同类型的出口蛋白，包括许多带有所谓的疟原虫出口元件(PEXEL)的蛋白，以及其他没有这种基序的蛋白(PNEs，PEXEL阴性出口蛋白)。这两类蛋白都由可溶性蛋白和跨膜蛋白组成，需要不同的易位Modi才能出口。虽然PEXEL蛋白可以根据定义的出口基序的存在进行预测，但PNEs无法预测，因此尚不清楚恶性疟原虫基因组中还编码了多少进一步出口的蛋白。在这一应用中，建议在最近发现的PNEs和PEXEL蛋白共享的核心出口结构域中找到出口中介序列决定因素，以预测和进一步鉴定疟疾寄生虫中的出口蛋白(可能是全部)。此外，我们将鉴定介导新近发现的新型PNEs输出的序列，并测试它们是否也包含PNEs和PEXEL蛋白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围涉及寄生虫质膜和寄生虫空泡的易位步骤。蛋白质输出修饰高度衍生的宿主细胞是寄生虫生存所必需的，也是与寄生虫毒力直接相关的宿主细胞表面变化的原因。因此，了解哪些蛋白质被输出以及它们是如何输出的不仅是一个令人着迷的细胞生物学问题，而且最终还可能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.