Impact of the cytoprotective chaperone HSP25/27 on the structural integrity and autophagic degradation of chlamydial compartments

衣原体是专性细胞内细菌，可引起性传播疾病、眼部感染和非典型肺炎。所有已知的衣原体物种都经历了一个独特的双相发育周期，该周期发生在非酸化的膜结合空泡内，称为包涵体。衣原体靶向宿主细胞骨架以调节其细胞内存活的各个方面，例如其内含物的结构稳定性和生理维持。为此，细菌用细胞骨架细丝的网状物包围它们的液泡，细胞骨架细丝作为支架在结构上稳定细菌区室。因此，宿主细胞防御机制的激活受到限制，因为防止了内含物渗漏到胞质溶胶中。我们最近证明，衣原体感染的免疫细胞和非免疫细胞能够分解包涵体，导致细菌的胞质释放。随后，衣原体被杀死并通过自噬降解，导致衣原体抗原的加工并将其展示给T细胞用于免疫监视。此外，我们发现，感染诱导表达的宿主细胞伴侣HSP 25/27，调节细胞骨架丝的重塑，似乎在破坏和降解衣原体室中发挥了关键作用。因此，详细阐明热休克蛋白25/27介导的过程中衣原体感染的细胞是至关重要的，以了解如何夹杂物在宿主细胞中的攻击和细胞机械是用来破坏细菌的车厢。我们的主要目标是解开HSP 25/27影响的分子和细胞过程，并评估这些过程如何决定衣原体感染的结果。我们将利用先进的国家最先进的方法在生物化学，显微镜，细胞生物学和分子生物学的功能特性感染诱导的HSP 25/27，并试图确定宿主细胞和病原体来源的HSP 25/27相互作用的合作伙伴。我们还将探讨HSP 25/27如何影响细菌细胞骨架效应蛋白，以及它如何破坏持久性和生产性内含物的完整性以及它们与宿主细胞骨架的相互作用。此外，我们将评估衣原体基因表达伴随着包含崩溃。我们的工作的另一个重点将解决衣原体车厢的解体和随后的降解之间的功能合作。在这里，我们将集中在NOD 1/2（核苷酸结合寡聚化结构域1/2）-途径和HMGB 1（高迁移率族蛋白1）控制的HSP 25/27表达和自噬过程。我们对细胞保护性HSP 25/27及其对细菌隔室的影响的研究将有助于更深入地了解衣原体的细胞内生命周期和开发新的治疗策略。

Chlamydiae are obligate intracellular bacteria that cause sexually transmitted disease, ocular infections, and atypical pneumonia. All known chlamydia species undergo a unique biphasic developmental cycle that takes place within a non-acidified membrane-bound vacuole, termed inclusion. Chlamydiae target the host cytoskeleton to regulate diverse aspects of their intracellular survival such as the structural stability and physiological maintenance of their inclusions. To this end, the bacteria surround their vacuole with a mesh of cytoskeletal filaments, which serve as a scaffold structurally stabilizing the bacterial compartment. As a consequence, the activation of host cell defense mechanisms is limited as leakage of inclusion contents into the cytosol is prevented. We recently demonstrated that chlamydia-infected immune and non-immune cells are able to break down inclusions resulting in the cytosolic release of bacteria. Subsequently, chlamydiae are killed and degraded via autophagy leading to the processing of chlamydial antigens and their display to T cells for immunosurveillance. Moreover, we found that the infection-induced expression of the host cell chaperone HSP25/27, which regulates the remodeling of cytoskeletal filaments, seems to play a critical role in disrupting and degrading chlamydial compartments. Therefore, the detailed elucidation of HSP25/27-mediated processes in chlamydia-infected cells is crucial to understand how inclusions are attacked in host cells and which cellular machinery is used to destroy the bacterial compartments. Our key goal is to unravel the molecular and cellular processes that HSP25/27 impacts and to assess how these processes determine the outcome of chlamydial infections. We will utilize advanced state-of-the-art methods in biochemistry, microscopy, cell biology, and molecular biology to functionally characterize infection-induced HSP25/27 and attempt to identify both host cellular and pathogen-derived HSP25/27 interaction partners. We will also explore how HSP25/27 affects bacterial cytoskeleton effector proteins, and how it disrupts the integrity of persistent and productive inclusions as well as their interaction with the host cytoskeleton. Moreover, we will assess the chlamydial gene expression accompanying inclusion breakdown. Another focus of our work will address the functional cooperation between the disintegration of chlamydial compartments and their subsequent degradation. Here, we will concentrate on NOD1/2 (Nucleotide-Binding Oligomerization Domain 1/2)-pathways and on HMGB1 (High Mobility Group Box 1)-controlled processes of HSP25/27 expression and autophagy. Our studies on cytoprotective HSP25/27 and its effects on bacterial compartments will aid the deeper understanding of the intracellular life cycle of chlamydia and the development of novel therapeutic strategies against chlamydial infections.