IQGAP1 in microbial pathogenesis

病原体已经发展出复杂的机制来进入细胞，在真核细胞内逃避破坏并繁殖。宿主细胞的细胞骨架是细菌操纵以促进感染的常见靶标。侵入性细菌控制宿主细胞的细胞骨架，以加速吸收进入通常非吞噬细胞的细胞，并逃避吞噬和破坏。主要的细胞骨架元件，特别是肌动蛋白和微管，与几种蛋白质结合并受其调节。该提案的重点是IQGAP 1，它通过结合肌动蛋白直接调节细胞骨架，并通过与一些靶点（包括Cdc 42，Rac 1和微管结合蛋白CLIP-170）相互作用间接调节细胞骨架。我们观察到IQGAP 1在Cdc 42细胞骨架功能和细胞运动中具有重要作用。基于这些数据，我们假设IQGAP 1是由某些病原微生物诱导的细胞骨架改变的组成部分。该提案侧重于沙门氏菌。具体目标是：（1）为了验证IQGAP 1是沙门氏菌进入细胞机制的一个要素这一假设，我们将确定IQGAP 1是否通过将Cdc 42/Rac 1偶联到肌动蛋白细胞骨架来调节沙门氏菌的侵袭。将使用突变体和显性阴性IQGAP 1构建体和特异性抑制剂肽进行分析。(2)为了检验IQGAP 1参与细菌的吞噬作用和细胞内运输的假设，将在巨噬细胞中评估沙门氏菌的摄取和运输，其中IQGAP 1功能已通过显性阴性构建体、过表达和特异性敲减进行操纵。这些研究应该表明IQGAP 1是否参与沙门氏菌感染。此外，这些数据可能会增强我们对Cdc 42和Rac 1在沙门氏菌发病机制中的理解，有助于理解沙门氏菌生物学。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.