Intercellular adhesion and morphogenesis: role of actin-regulatory proteins

描述（申请人提供）：细胞形态变化和细胞间粘附的协调调节对发育过程中的形态发生、细胞迁移、存活和生长至关重要。这些过程的不耦合导致发育缺陷，从而导致毁灭性的病理状况，包括心血管异常。本研究的目的是确定Abi蛋白复合物和相关的Abl激酶在发育形态发生过程中调节粘附和生长因子受体下游的肌动蛋白动力学的机制。我们发现Abl激酶在细胞表面受体下游肌动蛋白结构的形成和转换中发挥作用。这些过程是由局部肌动蛋白聚合驱动的，我们已经证明这涉及Abi蛋白的活性。我们已经证明Abi/Nap1复合体是细胞-细胞接触形成和稳定所必需的，并且Abi存在于不同的蛋白质复合体中：一个复合体由两个Abi结合蛋白Abi和Wave以及Nap1， Sra1和Arp2/3组成，第二个复合体由不同的新型Abi结合蛋白组成，这是细胞-细胞粘附所必需的。值得注意的是，缺乏Abl家族激酶、Wave2、Abi1和Nap1的小鼠表现出显著的发育缺陷，与细胞骨架动力学改变和细胞间粘附缺陷一致，导致心血管异常。关于连接细胞间粘附和肌动蛋白聚合的信号通路，存在一个基本的知识缺口。本研究的具体目的是：1)利用体外模型和敲除小鼠阐明Abi复合物调节粘附受体下游形态发生的机制，重点是我们最近发现的Abi/ nap1依赖和Arp2/3-独立通路，这对细胞-细胞连接的完整性至关重要；2)明确Abl激酶调控内皮细胞增殖、存活和粘附的机制，重点研究粘附受体的转运。意义：拟议研究的结果将为肌动蛋白聚合机制的组成部分调节内皮细胞生长和存活的关键粘附过程的机制提供新的见解。此外，我们的发现将为阐明发育异常（如先天性心血管疾病和其他由肌动蛋白动力学失调引起的病理）的分子基础提供急需的知识。

DESCRIPTION (provided by applicant): Coordinate regulation of cell shape changes and intercellular adhesion is critical for morphogenesis, cell migration, survival and growth during development. Uncoupling of these processes results in developmental defects that lead to devastating pathological conditions, including cardiovascular abnormalities. The goal of this research is to define the mechanisms employed by Abi protein complexes and associated Abl kinases to regulate actin dynamics downstream of adhesion and growth factor receptors during developmental morphogenesis. We showed that Abl kinases play a role in the formation and turnover of actin structures downstream of cell surface receptors. These processes are driven by localized actin polymerization, which we have demonstrated involves the activity of the Abi proteins. We have shown that the Abi/Nap1 complex is required for the formation and stability of cell-cell contacts, and that Abi exists in distinct protein complexes: one, which is comprised of two Abl-binding proteins, Abi and Wave, as well as Nap1, Sra1 and Arp2/3, and a second complex comprised of distinct novel Abi-binding proteins, which is required for cell-cell adhesion. Notably, mice deficient for Abl family kinases, Wave2, Abi1, and Nap1 exhibit striking developmental defects consistent with altered cytoskeletal dynamics and defective intercellular adhesion, leading to cardiovascular abnormalities. A fundamental gap in knowledge exists regarding the signaling pathways linking intercellular adhesion to actin polymerization. The specific aims of this proposal are: 1) to elucidate the mechanisms employed by Abi complexes to regulate morphogenesis downstream of adhesion receptors using in vitro models and knockout mice, with emphasis on our recently discovered Abi/Nap1-dependent and Arp2/3- independent pathway, which is critical for the integrity of cell-cell junctions; and 2) to define the mechanisms whereby the Abl kinases regulate cell proliferation, survival and adhesion in endothelial cells, with emphasis on trafficking of adhesion receptors. Significance: Results from the proposed studies will provide novel insights into the mechanisms whereby components of the actin polymerization machinery regulate adhesion processes critical for endothelial cell growth and survival. Moreover, our findings will provide much needed knowledge for elucidating the molecular basis of develomental abnormalities such as congenital cardiovascular disease and other pathologies induced by disregulated actin dynamics.