Protein trafficking mechanisms in the human malarial parasite P. falciparum

恶性疟原虫是热带疟疾的病原体，它入侵了成熟的人类红细胞，将蛋白质排出自身质膜的边界，进入宿主红细胞。许多这些寄生虫编码的蛋白都与感染宿主细胞的结构和生理变化有关。其中一些蛋白质是疟疾病理中的重要因素。宿主红细胞本身没有必要的分子机制来将蛋白质运输到宿主细胞中的最终目的地。因此，寄生虫本身似乎将一个功能分泌系统输出到新陈代谢死亡的宿主细胞中，这是细胞生物学中一个有趣的范例。寄生虫分泌系统的不同寻常的性质被不寻常的蛋白质靶向基序进一步强调。因此，可以证明许多输出到宿主红细胞的寄生虫蛋白不具有典型的N末端ER靶向序列，这是进入分泌系统的先决条件。然而，这些蛋白质中的许多确实在其N末端含有一个凹陷的疏水结构域。这种信号被认为可以完成分泌信号序列的功能，然而，关于这种信号如何调节内质网转位的机械性数据仍然很少。在这个资金阶段，我们将解决这些疏水结构域如何调节内质网易位的问题。我们设计了进行内质网易位分析的实验策略，以便从机械上剖析寄生虫早期分泌途径的初始步骤。这项研究可能会揭示在其他细胞类型的内质网转位过程中发挥作用的新的内质网转位机制。此外，我们的目标是解决蛋白质的折叠状态如何影响它们运输到宿主红细胞的胞浆。

Having invaded mature human erythrocytes, Plasmodium falciparum the aetiological agent of malaria tropica, exports proteins beyond the boundaries of its own plasma membrane, into the host erythrocyte. Many of these parasite-encoded proteins have been implicated in structural and physiological changes in the infected host cell. Some of these proteins are important factors in the pathology of malaria. The host erythrocyte does not, itself, have the necessary molecular machinery to traffic proteins to their eventual destinations in the host cell. Thus, it appears that the parasite itself exports a functional secretory system into the metabolically ¿dead¿ host cell, an interesting paradigm in cell biology. The unusual nature of the parasites secretory system is further underlined by unusual protein targeting motifs. Thus, it can be shown that many parasite proteins exported into the host erythrocyte do not possess a canonical N¿terminal ER targeting sequence, a pre-requisite for entry into the secretory system. However, many of these proteins do contain a recessed hydrophobic domain towards their N-terminal end. This signal has been suggested to fulfil the function of a secretory signal sequence, however mechanistic data on how this signal mediates ER translocation remain sparse. In this funding period, we shall address the question as to how these hydrophobic domains mediate ER translocation. We have designed experimental strategies to perform an ER translocation assay in order to mechanistically dissect the initial steps in the parasites early secretory pathway. This study may uncover novel ER translocation mechanisms playing a role in ER translocation processes in other cell types. Furthermore, we aim to address how the folding state of proteins affects their trafficking to the cytosol of the host erythrocyte.