Small GTPase signalling networks and subversion by pathogenic bacteria

哺乳动物细胞在细胞膜上聚合肌动蛋白细丝，为细胞移动、重塑结构和分裂创造动力，并提供定义细胞形状和极性的结构框架。肌动蛋白结构在膜上的形成需要肌动蛋白机制的网络，这些网络通过被称为Rho GTP酶(20种异构体)的肌动蛋白细胞骨架的主调节器来控制。细菌致病性的一个中心范例是Rho GTP酶被注入目标宿主细胞的大量病原体编码的毒力蛋白谱系所颠覆。我们最近发现了细菌效应器如何劫持协同促进感染的脂质和GTPase信号，例如沙门氏菌进入宿主细胞(Humphreys等人，Cell host Microbe，2012，Humphreys等人，PNAS，2013)。这让我意识到，虽然我们知道许多Rho靶标，但我们不知道这些组分如何相互作用，也不知道毒力蛋白如何在膜环境中操纵复杂的Rho细胞骨架网络。这项跨学科的博士项目将结合肌动蛋白细胞骨架的活细胞成像、感染生物学和毒力驱动的肌动蛋白聚合的生化重建，以了解毒力效应器在感染过程中如何在膜上发挥作用并劫持Rho细胞骨架网络。鉴于细菌病原体继续产生多重耐药性，对人类和饲养的食物链动物构成健康威胁，这一点尤其重要。了解疾病的基础有可能确定新的治疗靶点，并增加我们的抗感染药物武器库。

Mammalian cells polymerise actin filaments at the membrane to create a driving force for cells to move, remodel their architecture and divide, and to provide a structural framework that defines cell shape and polarity. The formation of actin structures at the membrane requires a network of actin machineries that are controlled through master regulators of the actin cytoskeleton known as Rho GTPases (20 isoforms). A central paradigm in bacterial pathogenicity is Rho GTPase subversion by an enormous repertoire of pathogen-encoded virulence proteins that are injected into the target host cell. We recently uncovered how bacterial effectors hijack co-incident lipid and GTPase signals that cooperate to facilitate infection, e.g. Salmonella uptake into host cells (Humphreys et al, Cell Host Microbe, 2012, Humphreys et al, PNAS, 2013). This has opened my eyes to the fact that while we know many of the Rho targets, we do not know how the components interact with each other nor how virulence proteins manipulate the complex Rho cytoskeleton networks in the membrane environment. The interdisciplinary PhD project will combine live cell imaging of the actin cytoskeleton, infection biology and biochemical reconstitution of virulence-driven actin polymerisation to understand how virulence effectors function at the membrane and hijack Rho cytoskeleton networks during infection. This is especially important given the health threat posed to humans and farmed food chain animals by bacterial pathogens that continue to develop multidrug resistance. Understanding the basis of disease has the potential to identify new therapeutic targets and augment our anti-infectives arsenal.