Angiopoietins in Angiogenesis

描述(申请人提供)：血管生成过多或不足往往在许多疾病的发展中起着关键作用，如心脏和肢体缺血，以及肿瘤的生长和转移。血管生成是指在原有血管的基础上长出新血管的过程。这项建议的长期目标是阐明血管生成素在血管生成中的作用，并确定这些作用是如何调节的。血管生成素是三种密切相关的蛋白质，它们是Tie-2受体酪氨酸激酶的配体。血管生成素-Tie-2通路在胚胎血管生成中发挥重要作用。然而，血管生成素在肿瘤血管生成中的作用还不是很清楚，这些作用的细胞和分子机制以及调控机制还不是很清楚。我们已经证明Ang-1与细胞外基质(ECM)结合，Ang-3通过分别调节Ang-1或Ang-3功能的硫酸乙酰肝素蛋白多糖(HSPGs)保留在细胞表面。我们推测，Ang-1和Ang-3在体内调节内皮细胞行为和血管生成中起着重要的拮抗作用，Ang-1的促血管生成作用是通过与ECM的结合而负调控的，而Ang-3的抗血管生成作用是通过与细胞表面的HSPGs结合来实现的。为了验证这一假说，我们计划：1)确定Ang-1与ECM相互作用的分子基础；2)Ang-3与细胞表面HSPGs的相互作用；3)研究Ang-1与ECM的结合以及Ang-3与细胞表面HSPGs的结合如何影响它们在调节内皮细胞行为和血管生成中的作用；4)体内血管生成，我们计划利用已建立的生化、分子和细胞生物学手段，以及Lewis肺癌细胞的体内自发肺转移模型来实现这些目标。这些研究的完成将对Ang-1和Ang-3在内皮细胞生物学和肿瘤血管生成中的作用以及Ang-1和Ang-3如何分别受ECM或细胞表面热休克蛋白G调控产生新的见解。这些结果将有助于我们从总体上理解血管生成，并有助于为血管生成相关疾病的治疗开发潜在的新的有效靶点，具有很高的生物学和治疗意义。

DESCRIPTION (provided by applicant): Over or insufficient angiogenesis often plays essential roles in the progression of many diseases, such as ischemic heart and limb, and tumor growth and metastasis. Angiogenesis is a process of formation of new blood vessels by sprouting from pre-existing ones. The long-term objective of this proposal is to elucidate the roles of angiopoietins in angiogenesis and determine how these roles are regulated. Angiopoietins are three closely related proteins that serve as ligands of Tie-2 receptor tyrosine kinase. Angiopoietin-Tie-2 pathway has been shown to play important role in embryonic angiogenesis. However, the roles of angiopoietins in tumor angiogenesis, which is essential for tumor growth and metastasis, is not well established, and the underlying cellular and molecular mechanism and the regulation of these roles are not well understood. We have demonstrated that Ang-1 binds to the extracellular matrix (ECM) and Ang-3 is retained to the cell surface via heparan sulfate proteoglycans (HSPGs), which modulate the function of Ang-1 or Ang-3, respectively. We hypothesize that Ang-1 and Ang-3 play important antagonistic roles in regulating endothelial cell behavior and angiogenesis in vivo and the pro-angiogenic role of Ang-1 is negatively regulated by its binding to the ECM and the anti-angiogenic role of Ang-3 is facilitated by its binding to cell surface HSPGs. The following specific aims are designed to test this hypotheses: To determine the molecular bases of the interactions between 1) Ang-1 and the ECM and 2) Ang-3 and the cell surface HSPGs; 3) to investigate how the binding of Ang-1 to the ECM and the binding of Ang-3 to the cell surface HSPGs affect their roles in regulating endothelial cell behavior and; 4) angiogenesis in vivo, We plan to accomplish the aims by using the established biochemical, molecular and cell biology approaches, the transfected cells, and the in vivo spontaneous pulmonary metastatic models of Lewis lung carcinoma cells. The completion of the proposed studies will generate new insights on the roles of Ang-1 and Ang-3 in endothelial cell biology and tumor angiogenesis and on how these functions of Ang-1 and -3 are regulated by the ECM or cell surface HSPGs, respectively. These results would contribute to our understanding of angiogenesis in general and help to develop potential novel and effective targets for therapies of the angiogenesis-related diseases, and are of high biologic and therapeutic relevance.