Host cell membrane perforation during invasion by Toxoplasma gondii

弓形虫是一种分布广泛的原生动物寄生虫，可引起危及生命的疾病。 免疫功能受损的个体和发育中的胎儿。虽然有治疗急性呼吸道感染的药物 弓形虫病，由于严重的不良反应，它们经常被停用。开发新的、更好的- 耐受药物需要更好地了解弓形虫的生物学和潜在的机制 它的毒性，以便能够识别和瞄准其生命周期中的脆弱性临界点。 弓形虫属于一组相关的人类病原体，尖端复合体，其中也包括致病原 疟疾(疟原虫)和隐孢子虫病(隐孢子虫)的病原体。蜂复合体寄生虫必须入侵 进入宿主的细胞中以求生存和繁殖。在入侵的早期阶段，蛋白质是 从被称为棒状体的顶端细胞器中排出。释放后，这些蛋白质被输送到 它们参与寄生虫内化的宿主细胞胞浆，使宿主的天然免疫防御失活， 并操纵宿主基因的表达，使其对寄生虫有利。因为注射的效应器蛋白 这种在寄生虫入侵和细胞内生存方面的关键作用，它们是最重要的 寄生虫的毒力因素。虽然我们对这些效应器蛋白的功能了解很多，但我们知道 几乎没有关于它们被输送到宿主细胞的过程。这个项目的目标是填补 在我们对顶端复合体寄生虫入侵宿主细胞的理解上存在这一重要差距。 我们以前已经证明，当弓形虫第一次接触宿主细胞时，它会引起瞬变(~200毫秒) 破坏宿主细胞质膜的屏障完整性。这个项目的中心假设是 这种宿主细胞膜的瞬时穿孔，我们可以用高速多波长检测到 荧光显微镜是将杆状病毒蛋白注入宿主细胞的管道。 该项目的主要目的是：(1)确定宿主细胞的物理性质和直接原因 以及(2)确定穿孔剂如何被输送到宿主细胞膜 以及它所造成的漏洞的功能。 在入侵期间，杆状病毒蛋白是如何注入宿主细胞的，这是一个有趣的细胞生物学问题， 目前的证据表明，潜在的机制是新颖的。更好地理解这些 机制可能导致治疗或预防弓形虫病的新方法，因为靶向注射 这一过程将同时扰乱许多寄生虫最关键的毒力进入宿主细胞的过程 各种因素。此外，由于棒状蛋白注射到宿主细胞中发生在所有被检查的顶端复合体中， 该项目的结果很可能直接适用于相关的人类病原体，如疟原虫 和隐孢子虫。

Toxoplasma gondii is a widespread protozoan parasite that can cause life-threatening disease in immunocompromised individuals and the developing fetus. While drugs are available to treat acute toxoplasmosis, they are frequently discontinued due to severe adverse effects. The development of new, better- tolerated drugs requires an improved understanding of the biology of T. gondii and the mechanisms underlying its virulence so that critical points of vulnerability in its life cycle can be identified and targeted. T. gondii belongs to a group of related human pathogens, the Apicomplexa, which also includes the causative agents of malaria (Plasmodium) and cryptosporidiosis (Cryptosporidium). Apicomplexan parasites must invade into cells of their hosts in order to survive and multiply. During the early stages of invasion, proteins are exocytosed from apical organelles known as the rhoptries. After their release, these proteins are delivered into the host cell cytosol where they participate in parasite internalization, inactivate host innate immune defenses, and manipulate host gene expression to the parasite’s advantage. Because the injected effector proteins play such critical roles in parasite invasion and intracellular survival, they are among the most important of the parasite’s virulence factors. While we know a great deal about the functions of these effector proteins, we know virtually nothing about the process by which they are delivered into the host cell. The goal of this project is to fill in this important gap in our understanding of host cell invasion by apicomplexan parasites. We have previously shown that when T. gondii first contacts a host cell, it causes a transient (~200msec) disruption in the barrier integrity of the host cell plasma membrane. The central hypothesis of this project is that this transient perforation of the host cell membrane, which we can detect using high-speed multiwavelength fluorescence microscopy, serves as the conduit through which rhoptry proteins are injected into the host cell. The major Aims of the project are to: (1) Determine the physical nature and proximate cause of host cell perforation during invasion and (2) Determine how the perforating agent is delivered to the host cell membrane and the function of the breach it creates. How rhoptry proteins are injected into the host cell during invasion is a fascinating cell biological problem, and current evidence suggests that the underlying mechanisms are novel. A greater understanding of these mechanisms may lead to new approaches to treating or preventing toxoplasmosis, since targeting the injection process will simultaneously disrupt the delivery into the host cell of many of the parasite’s most critical virulence factors. In addition, because rhoptry protein injection into the host cell occurs in all apicomplexans examined, the results of this project are likely to be directly applicable to related human pathogens such as Plasmodium and Cryptosporidium.