PTEX mechanism in malaria parasite effector protein export and host cell subversion

项目摘要 疟疾仍然是一个严重的公共卫生问题。疟疾控制进展缓慢 近年来，虽然在最受影响的地区出现了对一线抗疟药物的耐药性， 强调迫切需要破译基本的寄生虫生物学，以提供新的 治疗策略这种专性细胞内寄生虫输出一组效应蛋白 一个空泡生态位，以彻底改造其宿主细胞，这一过程取决于疟原虫 输出蛋白的转位子（PTEX）。PTEX是建立在一个液泡营养孔形成的， EXP 2，其被衔接子PTEX 150和AAA+伴侣HSP 101进一步功能化， 形成效应子转位子。PTEX由于其重要的作用而成为一种新的药物靶点 在血液阶段寄生虫存活和疾病发病机制，但不知道如何易位货物 或复合物如何组装和调节以执行其功能。最近的结果 建议HSP 101识别寄生虫ER中的出口目的地货物，然后将其带到 液泡中组装成PTEX复合物刺激HSP 101的展开活性，以驱动 膜移位进入红细胞。重要的是，虽然类似的出口过程是 预期发生在确定血液分期的初始肝脏感染中，仅EXP 2和 PTEX 150存在于肝内空泡中，而HSP 101不存在。这意味着PTEX 组分介导蛋白质输出到红细胞和肝细胞中， 为了满足破坏这些显著不同的宿主细胞的需求，已经进化出了这些差异。 为了支持这一点，我们最近确定EXP 2对肝内寄生虫至关重要， 开发，首次清楚地表明，PTEX组件也在 肝期空泡。我们假设EXP 2/PTEX 150构成最小效应子， 用于脊椎动物宿主细胞颠覆的易位子，其进一步被HSP 101适应以满足 对蛋白质输出以重塑红细胞的独特需求。这项提案将回答 关于PTEX输出机制的关键问题，以确定宿主细胞颠覆的基础 并为对抗这种毁灭性的病原体提供新的目标。目标1将确定 通过剖析HSP 101沿着的ER定位功能在血液阶段中选择PTEX货物 与新发现的HSP 101相互作用的ER蛋白的作用。目标2将定义功能 需要形成PTEX并鉴定刺激HSP 101在细胞中展开活性的相互作用。 使用光反应性非天然氨基酸交联系统组装的易位子复合物。 最后，目标3将揭示EXP 2/PTEX 150在肝脏中的HSP 101非依赖性功能， 鉴定使肝细胞颠覆能够建立血液阶段的新型输出效应物。

Project Summary Malaria disease remains a serious public health problem. Progress in Malaria control has slowed in recent years while resistance to frontline antimalarials is emerging in the most afflicted regions, underscoring a pressing need for deciphering fundamental parasite biology to provide novel therapeutic strategies. This obligate intracellular parasite exports a battery of effector proteins out of a vacuolar niche to drastically remodel its host cell, a process that depends on the Plasmodium Translocon of EXported proteins (PTEX). PTEX is built on a vacuole nutrient pore formed by EXP2 which is further functionalized by the adaptor PTEX150 and AAA+ chaperone HSP101 to form the effector translocon. PTEX has emerged as a novel drug target owing to its essential role in blood stage parasite survival and disease pathogenesis but it is unknown how translocon cargo is identified or how the complex is assembled and regulated to perform its function. Recent results suggest HSP101 identifies export-destine cargo in the parasite ER and then brings it to the vacuole where assembly into the PTEX complex stimulates HSP101’s unfolding activity to drive membrane translocation into the erythrocyte. Importantly, while a similar export process is expected to occur in the initial liver infection that establishes the blood stage, only EXP2 and PTEX150 are present in the intrahepatic vacuole but not HSP101. This implies that PTEX components mediate protein export into both erythrocytes and hepatocytes but that mechanistic distinctions have evolved to meet the demands of subverting these remarkably different host cells. In support of this, we recently determined that EXP2 is critical to intrahepatic parasite development, clearly showing for the first time that PTEX components are also functional in the liver stage vacuole. We hypothesize that EXP2/PTEX150 constitutes a minimal effector translocon for vertebrate host cell subversion that is further adapted by HSP101 to meet the unique demands on protein export to remodel the erythrocyte. This proposal will answer key questions about the PTEX export mechanism to determine the basis for host cell subversion and provide new targets to combat this devastating pathogen. Aim 1 will determine the basis for PTEX cargo selection in the blood stage by dissecting the ER-localized function of HSP101 along with the role of a newly discovered HSP101-interacting ER protein. Aim 2 will define features required to form PTEX and identify the interaction that stimulates HSP101 unfolding activity in the assembled translocon complex using a photoreactive unnatural amino acid crosslinking system. Finally, Aim 3 will uncover the HSP101-independent function of EXP2/PTEX150 in the liver and identify novel exported effectors that enable hepatocyte subversion to establish the blood stage.