Actin Based Motility of a Bacterial Pathogen

描述（由申请方提供）：单核细胞增生李斯特菌是一种普遍存在的革兰氏阳性菌，可导致孕妇、新生儿和免疫功能低下的成人发生严重的食源性感染。细菌直接生长在受感染宿主细胞的细胞质中，并使用基于肌动蛋白的运动形式在受感染细胞中和受感染细胞之间快速移动。洛杉矶单核细胞增多症表面蛋白ActA以极化方式表达，并与宿主细胞骨架因子相互作用以诱导肌动蛋白“彗星尾”结构的聚合，该结构推动细菌通过宿主细胞质。本课题的总体目标是了解L.单核细胞增多症我们使用三种互补方法的组合来研究这种形式的运动-生物物理，生物化学和细胞生物学。L.肌动蛋白为基础的运动所需的全套基本蛋白质组分。单核细胞增多症现在已经被确定，并且该领域开始就理解稳态运动期间力产生的一般物理框架达成一致。下一组概念和实验挑战在于重建和掌握生物行为全部复杂性的机制。我们将集中我们的机械研究细菌肌动蛋白为基础的运动在两个领域，没有充分解决现有的稳态模型：了解细菌运动启动的生化和生物物理机制，探索负责调节路径持久性和曲率的决定因素。在细菌细胞间传播的背景下检查感染的细胞生物学，我们将开发新技术，用于直接观察组织培养中完全极化的上皮单层中的细菌传播以及上皮细胞和巨噬细胞之间的异型传播。此外，我们将解决细菌细胞的细胞生物学在确定ActA蛋白极化的机制。我们的研究目标的成功完成将使我们对致病菌如L。单核细胞增多症特异性地与它们的人类宿主的细胞通信。此外，自L.基于肌动蛋白的单核细胞增生运动是肌动蛋白聚合产生力的简单模型系统，我们的研究结果将有助于我们理解涉及基于肌动蛋白的细胞运动的各种基本生物过程，包括伤口愈合，炎症，胚胎发育和癌症转移。

DESCRIPTION (provided by applicant): Listeria monocytogenes is a ubiquitous Gram-positive bacterium that can cause serious food-borne infections in pregnant women, newborns and immunocompromised adults. The bacterium grows directly in the cytoplasm of infected host cells and moves rapidly throughout and between infected cells using a form of actin-based motility. The L. monocytogenes surface protein, ActA, is expressed in a polarized fashion and interacts with host cell cytoskeletal factors to induce the polymerization of an actin "comet tail" structure that pushes the bacterium through the host cell cytoplasm. The overall goal of this project is to understand the mechanism and biological significance of the actin-based motility of L. monocytogenes. We use a combination of three complementary approaches to studying this form of motility-biophysical, biochemical, and cell biological. The full set of basic protein components required for actin-based motility by L. monocytogenes have now been identified and the field is beginning to agree on a general physical framework for understanding force generation during steady-state movement. The next set of conceptual and experimental challenges lie in rebuilding and coming to grips with the mechanisms underlying the full complexity of the biological behavior. We will focus our mechanistic studies on bacterial actin-based motility in two areas that are not adequately addressed by the existing steady-state models: understanding the biochemical and biophysical mechanism of bacterial movement initiation and exploring the determinants responsible for regulating path persistence and curvature. In examining the cell biology of infection in the context of bacterial cell-to-cell spread, we will develop new techniques for direct observation of bacterial spread in fully polarized epithelial monolayers in tissue culture and heterotypic spread between epithelial cells and macrophages. In addition, we will address the cell biology of the bacterial cell in determining the mechanism of ActA protein polarization. Successful completion of our research goals would give significant insight into the mechanisms by which pathogenic bacteria such as L. monocytogenes communicate specifically with the cells of their human hosts. In addition, since L. monocytogenes actin-based motility is a simple model system for force generation by actin polymerization, the results of our research would contribute to our understanding of a wide variety of basic biological processes involving actin-based cell movement, including wound healing, inflammation, embryonic development, and cancer metastasis.