Molecular mechanisms of Tie2/Angiopoietin signaling initiation

摘要 血管生成素是一小类分泌性糖蛋白，在成熟中起关键作用 以及维持哺乳动物的血管和淋巴系统。它们通过 Tie受体酪氨酸激酶。所有四种血管生成素（Ang 1 -4）都直接结合Tie 2，而它们都不结合Tie 2。 相关的Tie 1，尽管后者已被证明可调节Ang/Tie 2信号传导。整合素， 特别是a5 b1，参与调节Ang 1依赖性血管生成，并显示直接 与Tie 2互动。Ang/Tie信号传导在受体激酶-配体系统中是独特的， 血管生成素配体，尽管都是高度同源的，但在某些情况下可以作为激动剂或拮抗剂起作用 依赖的方式。详细了解血管生成素/Tie信号转导机制及其在血管生成中的作用。 在血管生成过程中的精确功能需要对血管生成的细胞进行全面的结构和生物物理分析。 血管生成素、Tie受体和它们的共受体以及它们的相互作用。我们将使用X光 晶体学，结合其他生物物理，生物化学和细胞生物学技术，研究这些 分子。我们以前已经确定了Tie 2，Ang 1，Ang 2以及Tie 2/Ang 1的结构 和Tie 2/Ang 2复合物，揭示了Tie 2信号起始的重要和独特的特征。我们 还对活细胞进行了基于FRET的研究，以监测细胞表面上的Tie 1/Tie 2相互作用。 我们实验的一个重要结论是，个体的独特信号特性 血管生成素可能是Tie 2共受体对不同配体的不同反应的结果。 因此，我们现在建议研究共受体调节的分子机制， 调节和细胞/环境依赖性的方式，Ang/Tie 2信号传导事件。我们特别建议， 研究Tie 1和整合素a5 b1的作用。最后，我们的最终目标是确定 完整的Tie 2受体，包括其跨膜区，单独的和与配体和共- 受体，我们将致力于生产和功能全长Tie的结构表征 proteins. + PHS 398/2590（Rev.05/01）

Abstract The angiopoietins are a small class of secreted glycoproteins that play key roles in the maturation and maintenance of the mammalian vascular and lymphatic systems. They exert their effects through the Tie receptor tyrosine kinases. All four angiopoietins (Ang1-4) directly bind Tie2, while none of them binds the related Tie1, although the latter has been shown to modulate the Ang/Tie2 signaling. Integrins, and in particular a5b1, are involved in regulating Ang1-dependent angiogenesis and were shown to directly interact with Tie2. The Ang/Tie signaling is unique among receptor kinase-ligand systems in that distinct angiopoietin ligands, although all highly homologous, may function as agonist or antagonist in a context dependent manner. A detailed understanding of the mechanisms of Angiopoietin/Tie signaling and their precise function during angiogenesis requires a comprehensive structural and biophysical analysis of the angiopoietins, of the Tie receptors and their co-receptors, as well as of their interactions. We will use X-ray crystallography, combined with other biophysical, biochemical and cell-biological techniques, to study these molecules. We have previously determined the structures of Tie2, Ang1, Ang2, as well as of the Tie2/Ang1 and Tie2/Ang2 complexes, revealing important and unique characteristics of Tie2 signaling initiation. We also performed FRET-based studies on live cells to monitor the Tie1/Tie2 interactions on the cell surface. An important conclusion of our experiments is that the distinct signaling properties of the individual angiopoietins are likely the result of Tie2 co-receptors that respond differently to the different ligands. Therefore, we now propose to study the molecular mechanisms by which co-receptors modulate, in a regulated and cell/context-dependent manner, the Ang/Tie2 signaling events. We specifically propose to investigate the roles of Tie1 and intergrin a5b1. Finally, our ultimate goal is to determine crystal structures of the complete Tie2 receptor, including its transmembrane region, alone and in complex with ligands and co- receptors, and we will work on the production and structural characterization of functional full-length Tie proteins. + PHS 398/2590 (Rev. 05/01)