Ephrin B reverse signaling in endothelial cells

描述（由申请人提供）：血管生成是一个多步骤过程，需要信号来诱导内皮细胞增殖、迁移和组装。Eph受体酪氨酸激酶（RTK）及其配体ephrin是内皮细胞迁移和附着的重要介质。作为膜栓系配体，肝配蛋白能够双向传递信号。我们实验室以前的研究表明，肝配蛋白-B1被缺乏胞质结构域的EphB 1-Fc受体的可溶形式激活，因此不能传递正向信号。此外，内皮细胞的可溶性EphB 1-Fc刺激诱导细胞迁移、附着和体内血管生成。这些细胞变化需要肝配蛋白B1的PDZ结合结构域。基于这些数据，我们假设（1）肝配蛋白-B1反向信号传导是由PDZ衔接蛋白介导的，通过PDZ衔接蛋白激活下游信号传导途径，以及（2）表面肝配蛋白-B1的内化代表了肝配蛋白-B1介导的反向信号传导被调节的机制。为了验证这些假设，我们建议通过鉴定肝配蛋白B1接头蛋白和影响内皮细胞迁移和粘附的信号传导途径来研究肝配蛋白B1下游的信号传导成分。我们还将确定ephrin-B1内化在调节ephrin B1激活和信号转导中的作用。

DESCRIPTION (provided by applicant): Angiogenesis is a multi-step process requiring signals to induce endothelial cell proliferation, migration, and assembly. The Eph receptor tyrosine kinases (RTKs) and their ligands, ephrins, are important mediators of endothelial cell migration and attachment. As membrane tethered ligands, ephrins are capable of transmitting signals bi-directionally. Previous studies from our laboratory have shown that ephrin-B1 is activated by a soluble form of the EphB1-Fc receptor which lacks a cytoplasmic domain and thus is incapable of transmitting forward signals. In addition, soluble EphB1-Fc stimulation of endothelial cells induces cell migration, attachment, and in vivo angiogenesis. These cellular changes require the PDZ binding domain of ephrin B1. Based on these data, we hypothesize that (1) ephrin-B1 reverse signaling is mediated by PDZ adapter proteins through which downstream signaling pathways are activated, and (2) internalization of surface ephrin-B1 represents a mechanism by which ephrin-B1-mediated reverse signaling is regulated. To test these hypotheses, we propose to investigate signaling components downstream of ephrin-B1 by identifying ephrin B1 adapter proteins and pathways that transduce signals affecting endothelial cell migration and adhesion. We will also determine the role of ephrin-B1 internalization in regulating ehrin B1 activation and signal transduction.