Survival strategies of Plasmodium berghei exoerythrocytic forms (EEF) in hepatocytes

细胞内寄生虫的存活取决于它们绕过宿主细胞凋亡的能力。以鼠类寄生虫伯氏疟原虫为模型系统，研究了从子孢子进入肝细胞到裂殖子释放的过程中，疟原虫在肝细胞中的生存策略。在我们正在进行的研究过程中，我们可以证明，在感染的头两天，寄生虫保护宿主细胞免受凋亡，而在裂殖子形成后的第三天，它会诱导细胞凋亡。它计划研究寄生虫对促进和抗凋亡的宿主信号通路的调节，以及在合并过程中导致宿主细胞戏剧性变化的分子事件。这项建议的另一个目标是确定肝细胞中裂殖子形成的特征。该项目的这一部分是基于我们的观察结果，即寄生的肝细胞在经历细胞凋亡之前，会在培养上清液中短暂漂浮。漂浮的感染细胞可以很容易地从非感染的贴壁细胞中分离出来，首次提供了详细研究肝源性疟原虫寄生虫的可能性。对裂殖子存活所需的寄生虫蛋白的鉴定和特异性抑制是设想的。除了更多的谷物方法来鉴定这些寄生虫蛋白外，我们还将重点研究寄生虫蛋白水解酶，它们参与了裂殖子从肝细胞释放过程中对宿主细胞膜的破坏。

Survival of intracellular parasites depends on their ability to circumvent apoptosis of the host cell. Using the rodent parasite Plasmodium berghei as a model system we investigate survival strategies of Plasmodium parasites in hepatocytes from entry of sporozoites to the release of merozoites. In course of our ongoing studies we could show that during the first two days of infection the parasite protects the host cell from apoptosis, where as it induces apoptosis on the third day upon formation of merozoites. It is planned to study parasite dependent regulation of pro- and anti-apoptotic host signalling pathways as well as the molecular events leading to the dramatic changes in the host cell during merogony. Another goal of this proposal is the characterisation of merozoite formation in hepatocytes. This part of the project is based on our observation that parasitised hepatic cells round off and float in the supernatant briefly before they undergo apoptosis. Floating infected cells can easily be separated from non-infected adherent cells offering for the first time the possibility to study liver-derived Plasmodium parasites in detail. The identification and specific inhibition of parasite proteins needed for merozoite survival is envisaged. Apart from a more gereal approach to identify those parasite proteins we will focus on parasite proteases which are involved in the destruction of host cell membranes during the release of merozoites from hepatocytes.