Molecular mechanisms of Tie2/Angiopoietin signaling initiation

摘要 血管生成素是一小类分泌的糖蛋白，在成熟过程中起关键作用。 以及维持哺乳动物的血管和淋巴系统。它们通过以下方式发挥作用 领带受体酪氨酸激酶。所有四种血管生成素(Ang1-4)都直接与Tie2结合，而没有一种与Tie2结合 相关的Tie1，尽管后者已被证明调制Ang/Tie2信号。整合素，以及在 特别是a5b1，参与调节Ang1依赖的血管生成，并被证明直接 与Tie2互动。Ang/Tie信号在受体激酶-配体系统中是独一无二，因为 血管生成素配体，虽然都是高度同源的，但在某种情况下可以作为激动剂或拮抗剂发挥作用 依赖的态度。详细了解Angiopoietin/Tie信号转导机制及其相互关系 血管生成过程中的精确功能需要全面的结构和生物物理分析 血管生成素、TiE受体和它们的辅助受体以及它们之间的相互作用。我们将使用X光 结晶学，结合其他生物物理、生化和细胞生物学技术来研究这些 分子。我们之前已经确定了Tie2，Ang1，Ang2以及Tie2/Ang1的结构 和Tie2/Ang2复合体，揭示了Tie2信号启动的重要而独特的特征。我们 还对活细胞进行了基于FRET的研究，以监测细胞表面的Tie1/Tie2相互作用。 我们实验的一个重要结论是，个体的不同信号特性 血管生成素可能是Tie2辅助受体对不同配体反应不同的结果。 因此，我们现在建议研究辅受体在一种 调节和细胞/上下文依赖的方式，Ang/Tie2信号事件。我们特别建议 研究Tie1和整合素a5b1的作用。最后，我们的最终目标是确定晶体结构 完整的Tie2受体，包括其跨膜区，单独的以及与配体和共刺激分子形成的复合体。 受体，我们将致力于功能性全长Tie的生产和结构表征 蛋白质。 PHS 398/2590(05/01版)

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)