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。疟疾控制工作进展缓慢 近年来，尽管在疫情最严重的地区出现了对一线抗疟疾药物的抗药性， 强调迫切需要破译基础寄生虫生物学，以提供新的 治疗策略。这种专属的细胞内寄生虫输出一组效应蛋白。 以彻底重塑其宿主细胞，这一过程依赖于疟原虫 出口蛋白转运子(PTEX)。PTEX建立在液泡营养孔上，由 通过适配器PTEX150和AAA+伴侣HSP101进一步功能化的EXP2，以 形成效应器移位。PTEX因其重要作用而成为一种新的药物靶点 在血液期寄生虫的存活和疾病的发病机制，但尚不清楚如何转位货物 确定或如何组装和调节复合体以履行其功能。最新结果 建议HSP101识别寄生虫ER中的出口目的地货物，然后将其带到 组装成PTEX复合体的空泡刺激热休克蛋白101的S展开活动以驱动 红细胞膜的移位。重要的是，虽然类似的出口过程是 预计会发生在建立血液阶段的初始肝脏感染中，只有EXP2和 PTEX150存在于肝内空泡中，而不存在于HSP101中。这意味着PTEX 调节蛋白质输出到红细胞和肝细胞的成分，但其机制是 为了满足颠覆这些截然不同的宿主细胞的需求，已经进化出了不同的细胞。 为了支持这一点，我们最近确定EXP2对肝内寄生虫是关键的 开发，第一次清楚地表明PTEX组件在 肝期空泡。我们假设EXP2/PTEX150构成一个最小效应器 脊椎动物宿主细胞颠覆的转位子，HSP101进一步调整以满足 对蛋白质输出的独特需求，以重塑红细胞。这项建议将会解决 关于确定宿主细胞颠覆基础的PTEX输出机制的关键问题 并提供新的靶点来对抗这种毁灭性的病原体。目标1将确定以下基础 HSP101内质网定位功能在血液期PTEX货物选择中的应用 与新发现的HSP101相互作用的ER蛋白的作用。目标2将定义功能 需要形成PTEX并确定刺激HSP101在 使用光反应性非天然氨基酸交联系统组装的转位蛋白复合体。 最后，Aim 3将揭示肝脏和肝脏中EXP2/PTEX150的HSP101不依赖的功能 确定新的出口效应物，使肝细胞颠覆建立血液阶段。

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.