Actin-Cytoskeleton Rearrangements by Salmonella

尽管公共卫生有所改善，但沙门氏菌病仍然每年给世界经济造成数十亿美元的损失，仍然是已报告的食源性疾病的头号原因。沙门氏菌感染涉及细菌和宿主细胞之间复杂和高度协调的相互作用。沙门氏菌通过细菌III型分泌系统将蛋白质注入宿主细胞。我们的工作假设是，这些细菌蛋白与宿主蛋白结合进行肌动蛋白聚合和解聚，这两个过程是沙门氏菌诱导的肌动蛋白细胞骨架重排和细菌入侵非吞噬细胞所必需的。该项目的目标是通过使用微生物学、生化和细胞方法来识别和表征在体外和体内调节肌动蛋白动态的细菌和宿主蛋白(S)。这项建议侧重于沙门氏菌诱导的涉及SipA的肌动蛋白重排的分子机制。我们已经证明，SIPA通过降低肌动蛋白聚合的临界浓度和抑制肌动蛋白细丝的解聚来结合肌动蛋白并调节肌动蛋白动力学。我们还发现，SIPA增加了T-纤溶酶的结合活性，从而增加了肌动蛋白束的稳定性。初步结果表明，SipA-肌动蛋白复合体中存在更多的宿主蛋白，SipA活性必须被其他细菌或宿主因素关闭。我们建议研究沙门氏菌诱导的肌动蛋白细胞骨架重排是如何启动、维持和随后逆转的。我们已经开发了必要的分析和试剂来研究肌动蛋白的结构，并研究了SipA和宿主蛋白在调节沙门氏菌诱导的肌动蛋白细胞骨架重排中的作用。这项研究的结果将有助于我们了解沙门氏菌如何截获正常的细胞成分来调节宿主肌动蛋白细胞骨架。更好地了解这些过程将有助于开发用于治疗和预防沙门氏菌病的新的化疗药物。这些实验还将为宿主细胞的基本功能提供新的见解，包括细胞骨架重排和细胞运动。

Despite improvements in public hygiene, salmonellosis continues to cost the world economy billions of dollars each year and remains to be the number one cause of reported foodborne diseases. The Salmonella infection involves complex and highly orchestrated interactions between the bacterium and host cells. Salmonella injects proteins into host cells via a bacterial type III secretion system. Our working hypothesis is that these bacterial proteins engage host proteins for actin polymerization as well as depolymerization, two processes that are required for Salmonella-induced actin cytoskeleton rearrangements and invasion of non-phagocytic cells by the bacterium. The goal of this project is to identify and characterize bacterial and host proteins that play a role(s) in modulating actin dynamics both in vitro and in vivo by using microbiological, biochemical and cellular approaches. This proposal focuses on the molecular mechanism of Salmonella-induced actin rearrangements involving SipA. We have shown that SipA binds actin and modulates actin dynamics by decreasing the critical concentration for actin polymerization and by inhibiting depolymerization of actin filaments. We also showed that SipA increases the bundling activity of T-plastin, which increases the stability of actin bundles. Preliminary results indicate that additional host proteins are present in the SipA-actin complex and SipA activities must be turned off by other bacterial or host factors. We propose to investigate how Salmonella-induced actin cytoskeleton rearrangements are initiated, maintained and subsequently reversed. We have developed assays and reagents necessary to examine the actin architecture and investigate roles of SipA and host proteins in modulating Salmonella-induced actin cytoskeleton rearrangements. Results from this study will help us understand how Salmonella intercepts normal cellular constituents to modulate host actin cytoskeleton. A better understanding of these processes will facilitate the development of new chemotherapeutic agents for the treatment and prevention of salmonellosis. These experiments will also provide new insights into basic host cellular functions, including cytoskeletal rearrangements and cell movement.