ER-phagy in the functional conversion of the Brucella-containing vacuole

项目摘要 具有空泡生活方式的细胞内微生物具有重塑宿主细胞区室的能力， 支持其感染周期的特定阶段。细胞和分子的细节 微生物空泡在病原体的细胞内循环中功能性地进化以促进其毒力， 没有很好地理解。在这里，我们的目标是定义细胞过程驱动的功能进化的 人畜共患细菌流产布鲁氏菌的细胞内空泡，从复制生态位转变 出口细胞器B。流产杆菌主要感染吞噬细胞，并将其原始吞噬体改造成 复制性含布鲁氏菌空泡（replicative Brucella containing vacuole，rBCV），一种来源于宿主内质网的细胞器 支持细胞内增殖的内质网（ER）。rBCV随后转化为自噬体- 如介导复制后细菌外出的空泡（aBCVs）。自噬是一种保守的真核生物 在膜结合的自噬体内选择性或非选择性捕获细胞内容物的过程 对于溶酶体降解，包括通过专用的细胞器如ER的选择性降解， 自噬受体我们已经表明，来自rBCV的aBCV生物发生需要一个常规的亚组。 自噬机制和活性细菌VirB IV型分泌系统，但该过程，选择性 这种液泡转化的调节仍然是个谜。布鲁氏菌感染触发展开 通过先天免疫传感器STING在rBCV阶段期间的蛋白质应答（UPR），激发ER- 集中的应激反应，促进rBCV内的细菌复制。普遍定期审议是否也 对aBCV生物发生的贡献是未知的。STING依赖性UPR诱导ER-吞噬，其选择性 可以机械地驱动ER衍生的rBCV被自噬体捕获以形成aBCV。基于 初步证据表明：i）布鲁氏菌感染影响ER-吞噬; ii）rBCV募集不同的ER-吞噬 受体和iii）STING是aBCV生物发生所需的，在这里我们将测试总体假设， aBCV的生物发生是由rBCV的选择性ER-吞噬通过STING依赖性过程介导的。aim 1将 确定i）布鲁氏菌是否调节ER-吞噬，ii）是否需要特异性ER-吞噬受体 和iii）在aBCV生物发生期间参与的自噬级联。目标2将 确定STING在aBCV生物发生中的作用是否是通过诱导UPR或其活性作为一种诱导剂。 ER-吞噬受体。这些目标的成功实现将建立新的功能概念， 细菌空泡的进化，这是许多微生物病原体感染周期的共同特征， 是很难理解的。

Project Summary Intracellular microbes with a vacuolar lifestyle share an ability to remodel host cell compartments and functions to support specific stages of their infectious cycle. The cellular and molecular details of how microbial vacuoles functionally evolve during a pathogen’s intracellular cycle to promote their virulence are not well understood. Here we aim to define cellular processes driving the functional evolution of the intracellular vacuole of the zoonotic bacterium Brucella abortus, which transitions from a replicative niche to an egress organelle. B. abortus primarily infects phagocytes and remodels its original phagosome into the replicative Brucella-containing vacuole (rBCV), an organelle derived from the host endoplasmic reticulum (ER) that supports intracellular proliferation. rBCVs subsequently convert into autophagosome- like vacuoles (aBCVs) that mediate post-replication bacterial egress. Autophagy is a conserved eukaryotic process of selective or non-selective capture of cellular content within membrane-bound autophagosomes for lysosomal degradation, including the selective degradation of organelles such as the ER via dedicated autophagy receptors. We have shown that aBCV biogenesis from rBCVs requires a subset of conventional autophagic machineries and an active bacterial VirB Type IV secretion system, but the process, selectivity and regulation of this vacuolar conversion remain enigmatic. Brucella infection triggers the Unfolded Protein Response (UPR) during the rBCV stage via the innate immune sensor STING, provoking an ER- centered stress response that promotes bacterial replication within rBCVs. Whether the UPR also contributes to aBCV biogenesis is unknown. STING-dependent UPR induces ER-phagy, whose selectivity could mechanistically drive the capture of ER-derived rBCVs by autophagosomes to form aBCVs. Based on preliminary evidence that i) Brucella infection influences ER-phagy; ii) rBCVs recruit distinct ER-phagy receptors and iii) STING is required for aBCV biogenesis, here we will test the overall hypothesis that aBCV biogenesis is mediated by selective ER-phagy of rBCVs via a STING-dependent process. Aim1 will determine i) whether Brucella modulates ER-phagy, ii) whether specific ER-phagy receptors are required for aBCV biogenesis and iii) the autophagic cascade engaged during aBCV biogenesis. Aim 2 will determine whether the role of STING in aBCV biogenesis is via induction of the UPR or its activity as an ER-phagy receptor. The successful completion of these aims will establish new concepts of functional evolution of bacterial vacuoles, a common feature of the infectious cycle of many microbial pathogens that is poorly understood.