Host actin cytoskeleton rearrangements induced by Salmonella

性状（由申请方提供）：侵入非吞噬宿主细胞的能力对沙门氏菌的毒力至关重要。SipA、SipC、SopB、SopE和SopE 2是已知通过直接和间接调节宿主肌动蛋白动力学来促进沙门氏菌入侵的五种III型效应物。SipA和SipC通过模拟宿主肌动蛋白结合蛋白的功能直接调节肌动蛋白动力学。间接地，SopB，SopE，和SopE 2颠覆宿主细胞信号转导途径，诱导肌动蛋白细胞骨架重排和膜皱褶。这些细菌效应蛋白的协同作用最终导致细菌的有效摄取。SipA、SipC、SopB是多功能效应子，也参与效应子移位和诱导宿主炎症反应。尽管这些效应子和它们在沙门氏菌诱导的肌动蛋白细胞骨架重排中的单独作用的理解有所提高，但很少有人分离它们的多功能活性，并研究这些活性在功能上如何相互作用以促进沙门氏菌的入侵。在这项研究中，我们建议调查各自的贡献，他们的肌动蛋白调节活动，以及它们是如何在细菌入侵的功能协调。我们的初步数据表明，SipC发挥其肌动蛋白成核活性，通过瞬时二聚体的形成和SipA和SipC可能在功能上合作，以促进细菌进入。我们还证明了SopB依赖的VAMP 8招募沙门氏菌诱导的膜皱褶，VAMP 8是有效的细菌入侵所必需的。我们进一步确定SipA和SipC可能介导SopB和SopE独立的沙门氏菌进入。我们假设，SipA，SipC，SopB，和SopE功能合作和独立调节宿主肌动蛋白动力学，以促进沙门氏菌进入。为了验证这一假设，我们将：（i）表征的贡献SipA，SipC肌动蛋白调节活动在沙门氏菌的入侵;（ii）定义的分子机制，SopB促进肌动蛋白细胞骨架重排和沙门氏菌的入侵;（iii）研究SipA，SipC，SopB，和SopE如何协调他们的肌动蛋白调节活动，以促进沙门氏菌的入侵。本研究的结果将为SipA、SipC和SopB如何独立或协同利用宿主肌动蛋白细胞骨架促进沙门氏菌进入提供分子基础。 项目叙述：尽管我们长期以来对沙门氏菌的研究取得了一定的认识，但沙门氏菌病仍然是世界范围内的医学问题，即使在发达国家也仍然是食源性疾病的头号原因。沙门氏菌毒力蛋白的宿主细胞靶点的鉴定将有助于临床治疗药物的设计和多重耐药细菌的治疗。这项研究的结果不仅将拓宽我们对沙门氏菌致病机理的理解，而且还将为基础宿主细胞生物学提供重要的见解。

DESCRIPTION (provided by applicant): The ability to invade non-phagocytic host cells is essential for Salmonella virulence. SipA, SipC, SopB, SopE, and SopE2 are five type III effectors that are known to promote Salmonella invasion by modulating host actin dynamics both directly and indirectly. SipA and SipC regulate actin dynamics directly by mimicking functions of host actin-binding proteins. Indirectly, SopB, SopE, and SopE2 subvert host cell signal transduction pathways to induce actin cytoskeletal rearrangements and membrane ruffling. The concerted actions of these bacterial effector proteins eventually lead to the efficient uptake of the bacterium. SipA, SipC, SopB are multifunctional effectors also involved in effector translocation and in inducing host inflammatory responses. Despite improved understanding of these effectors and their individual roles in Salmonella-induced actin cytoskeleton rearrangements, little has been done to separate their multifunctional activities and to examine how these activities functionally interact to promote Salmonella invasion. In this study, we propose to investigate the individual contributions of their actin-modulating activities and how they are functionally coordinated during bacterial invasion. Our preliminary data showed that SipC exerts its actin-nucleation activity through transient dimer formation and that SipA and SipC may functionally cooperate to promote bacterial entry. We also demonstrated SopB-dependent VAMP8 recruitment to Salmonella-induced membrane ruffles and that VAMP8 is required for efficient bacterial invasion. We further determined that SipA and SipC may mediate SopB- and SopE-independent Salmonella entry. We hypothesize that SipA, SipC, SopB, and SopE function both cooperatively and independently to regulate host actin dynamics to promote Salmonella entry. To test this hypothesis, we will: (i) characterize the contributions of SipA, SipC actin-modulating activities in Salmonella invasion; (ii) define the molecular mechanism by which SopB promotes actin cytoskeleton rearrangements and Salmonella invasion; (iii) study how SipA, SipC, SopB, and SopE coordinate their actin-modulating activities to promote Salmonella invasion. Results from this study will provide a molecular basis for how SipA, SipC and SopB exploit the host actin cytoskeleton both independently and cooperatively to promote Salmonella entry. Project Narrative: Despite the understanding gained by our long-standing interest in studying Salmonella, salmonellosis continues to pose worldwide medical concerns and remains the number one cause of food-borne diseases even in developed countries. The identification of host cellular targets of Salmonella virulence proteins will aid clinical therapeutic drug designs and treatment of multidrug-resistant bacteria. Results from this study will not only broaden our understanding of Salmonella pathogenesis but will also provide vital insights into basic host cell biology.