Annexin A2 and the regulation of actin cytoskeletal dynamics

PI(4,5)P2富集的膜微结构域主要参与细胞信号传导、膜运输、细胞运动和极性。在细胞外刺激下，这些结构域（通常称为筏）聚集形成信号平台，招募和积累包括调节肌动蛋白细胞骨架的信号成分，从而提供一个连接细胞信号传导和肌动蛋白动力学调节的环境。膜联蛋白A2是src-酪氨酸激酶和几种受体酪氨酸激酶的底物，是最具特征的筏相关蛋白之一。它最近作为PI(4,5)P2结合蛋白出现，并诱导膜脂的侧向分离，这表明它在更大的筏聚集体的形成和稳定中起作用。目前的证据表明，膜联蛋白A2在肌动蛋白筏的动态组装中的因果作用，影响粘连和运动性。我们提出膜联蛋白A2酪氨酸磷酸化作为调节基于肌动蛋白的细胞运动的分子开关，导致更具运动性的表型。我们想从机制层面阐明膜联蛋白A2的作用。首先，我们将描述膜联蛋白A2酪氨酸磷酸化的时间和空间控制。其次，我们将探索哪些途径是酪氨酸磷酸化膜联蛋白A2的目标。第三，我们将研究膜联蛋白A2的酪氨酸磷酸化是否在肿瘤生物学中发挥作用。我们将通过生物化学和基于细胞的方法，辅以活细胞成像技术，在体外和体内解决这些关键问题。

PI(4,5)P2 enriched membrane microdomains are essentially involved in cell signalling, membrane trafficking, cell motility and polarity. Upon extracellular stimulation, these domains, often called rafts, cluster to form signalling platforms that recruit and accumulate signalling components including those regulating the actin cytoskeleton, thus providing an environment which links cellular signalling and the regulation of actin dynamics. Annexin A2, a substrate of the src-tyrosine kinase and several receptor tyrosine kinases, is one of the best characterized raft-associated proteins. It has recently emerged as a PI(4,5)P2 binding protein and induces the lateral segregation of membrane lipids, suggesting a role in the formation and stabilization of larger raft aggregates. Current evidence indicates a causal role for annexin A2 in the dynamic assembly of actin at rafts, which affects adhesion and motility. We propose that annexin A2 tyrosine phosphorylation functions as a molecular switch that modulates actin-based cellular motility, leading to a more motile phenotype. We want to elucidate the annexin A2 action at a mechanistic level. Firstly, we will characterize the temporal and spatial control of annexin A2 tyrosine phosphorylation. Secondly, we will explore which pathways are targeted by tyrosine phosphorylated annexin A2. Thirdly, we will investigate whether tyrosine phosphorylation of annexin A2 plays a role in tumour biology.We will address these key questions both in vitro and in vivo by biochemical and cell-based approaches, complemented by live cell imaging techniques.