IQGAP1 in microbial pathogenesis

病原体已经开发出复杂的机制来进入细胞，逃避真核细胞内的破坏并繁殖。宿主细胞的细胞骨架是细菌为促进感染而操纵的常见目标。侵袭性细菌控制宿主细胞的细胞骨架，以加快对正常非吞噬细胞的摄取，并避免吞噬和破坏。主要的细胞骨架成分，特别是肌动蛋白和微管，与几种蛋白质结合并受其调节。本研究的重点是IQGAP1，它通过直接结合肌动蛋白和通过与许多靶点相互作用间接调节细胞骨架，包括CDC42、rac1和微管结合蛋白CLIP-170。我们观察到IQGAP1在CDC42细胞骨架功能和细胞运动中起着重要作用。基于这些数据，我们假设IQGAP1是某些病原微生物诱导的细胞骨架改变的组成部分。这项提案的重点是沙门氏菌。具体目的是：(1)为了验证IQGAP1是沙门氏菌进入细胞机制的一个元件的假设，我们将确定IQGAP1是否通过将CDC42/rac1偶联到肌动蛋白细胞骨架来调节沙门氏菌的侵袭。分析将使用突变的和显性的负IQGAP1结构和特定的抑制物肽。(2)为了验证IQGAP1参与细菌吞噬和细胞内转运的假说，我们将评估IQGAP1功能受到明显负结构、过表达和特异性敲除的巨噬细胞对沙门氏菌的摄取和转运。这些研究应该表明IQGAP1是否参与沙门氏菌感染。此外，这些数据可能会加深我们对CDC42和rac1在沙门氏菌发病机制中的理解，有助于理解沙门氏菌的生物学。阐明病原体-宿主相互作用的机制可以为诊断、治疗和疫苗提供新的靶点。

Pathogens have developed sophisticated mechanisms to enter cells, evade destruction inside the eukaryotic cell and multiply. The cytoskeleton of the host cell is a common target that is manipulated by bacteria to facilitate infection. Invasive bacteria control the host cell's cytoskeleton to expedite uptake into cells that are normally nonphagocytic and to evade phagocytosis and destruction. The major cytoskeletal elements, particularly actin and microtubules, associate with and are regulated by several proteins. This proposal focuses on IQGAP1, which regulates the cytoskeleton both directly by binding actin and indirectly by interacting with a number of targets, including Cdc42, Rac1 and the microtubule-binding protein CLIP-170. We observed that IQGAP1 has a fundamental role in Cdc42 cytoskeletal function and cell motility. Based on these data we hypothesize that IQGAP1 is an integral component of the cytoskeletal alterations induced by some pathogenic microbes. This proposal focuses on Salmonella. The Specific Aims are: (1) To test the hypothesis that IQGAP1 is an element of the mechanism by which Salmonella enter cells, we shall determine whether IQGAP1 modulates Salmonella invasion by coupling Cdc42/Rac1 to the actin cytoskeleton. Analysis will be performed using mutant and dominant negative IQGAP1 constructs and a specific inhibitor peptide. (2) To test the hypothesis that IQGAP1 participates in phagocytosis and intracellular trafficking of bacteria, uptake and trafficking of Salmonella will be assessed in macrophages in which IQGAP1 function has been manipulated with dominant negative constructs, overexpression and specific knockdown. These studies should indicate whether IQGAP1 participates in Salmonella infection. In addition, the data are likely to enhance our comprehension of Cdc42 and Rac1 in Salmonella pathogenesis, contributing to an understanding of Salmonella biology. Elucidation of the mechanisms of pathogen-host interactions could reveal new targets for diagnosis, therapy and vaccines.