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的过程，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（RTKs）及其配体ephrin是内皮细胞迁移和附着的重要介质。作为膜系链配体，ephrin具有双向传递信号的能力。我们实验室之前的研究表明，ephrin-B1被一种可溶性形式的EphB1-Fc受体激活，该受体缺乏细胞质结构域，因此无法向前传递信号。此外，可溶性EphB1-Fc刺激内皮细胞可诱导细胞迁移、附着和体内血管生成。这些细胞变化需要ephrin B1的PDZ结合域。基于这些数据，我们假设(1)ephrin-B1反向信号是由PDZ适配器蛋白介导的，下游信号通路通过PDZ适配器蛋白被激活；(2)表面ephrin-B1的内化代表了ephrin-B1介导的反向信号调控机制。为了验证这些假设，我们建议通过鉴定ephrin B1适配蛋白和传导影响内皮细胞迁移和粘附的信号通路来研究ephrin-B1下游的信号成分。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.