Annexin 2 in Angiogenesis

描述（由申请人提供）：新生血管的发育不仅是心肌梗死、中风和周围血管功能不全等血管闭塞事件恢复的基础，也是良性和恶性肿瘤生长和进展的基础。在这个建议中，我们假设纤溶受体复合物，即膜联蛋白2/p11系统，通过支持血管细胞及其前体表面关键蛋白酶活性的发展来促进新血管生成。具体来说，我们计划关注膜联蛋白2 （A2）在血管壁细胞募集和分化中的作用，以稳定正在发育的新血管。A2属于60个钙调节磷脂结合蛋白家族，在整个系统发育树中表达。我们和其他人已经确定A2是主要的内皮细胞纤维蛋白溶解受体，它结合组织纤溶酶原激活剂及其生理底物纤溶酶原。这种组合极大地加速了纤溶蛋白的产生，并促进了纤维蛋白的溶解。最近，我们证明了A2完全缺乏的小鼠的新生血管生成明显受损。新的初步数据证实并扩展了这些发现，证明了由于肿瘤血管生成受损，a2缺失小鼠的肿瘤异体移植物生长失败。我们特别注意到新生血管的缺乏、新生血管的扩张和壁细胞的缺乏。携带肿瘤的A2-null小鼠显示循环骨髓来源的VEGFR1+/CD11+造血前体减少，移植A2-/-小鼠A2+/+骨髓后，肿瘤生长可以恢复。因此，我们假设A2在血管细胞和血管前体细胞表面的表达对于有效的新生血管生成至关重要。我们的目标是[1]确定A2是否通过促进壁细胞（周细胞和平滑肌细胞）在肿瘤小鼠和癌症患者血管生成部位的招募来支持新血管的稳定；[2]确定PDGF-BB是否通过刺激A2/p11复合物向壁细胞前体表面的易位来招募壁细胞以形成新血管；[3]确定A2支持的血管生成是否也需要其辅助因子的参与。p11和[4]决定高同型半胱氨酸血症是否通过衍生A2和阻断其蛋白酶诱导活性来损害血管生成反应。可以预见，从这些研究中获得的新见解可能会导致新血管疾病的诊断和治疗的新模式。

DESCRIPTION (provided by applicant): While fundamental to recovery from vascular occlusive events such as myocardial infarction, stroke, and peripheral vascular insufficiency, neovascular development also underlies the growth and progression of both benign and malignant tumors. In this proposal, we postulate that that the fibrinolytic receptor complex, known as the annexin 2/p11 system, promotes neoangiogenesis by supporting the development of key protease activities at the surface of vascular cells and their precursors. Specifically, we plan to focus on the role of annexin 2 (A2) in the recruitment and differentiation of vascular mural cells for stabilization of the developing neovessel. A2 belongs to a 60-member family of calcium-regulated, phospholipid-binding proteins expressed throughout the phylogenetic tree. We and others have identified A2 as the major endothelial cell fibrinolytic receptor that binds tissue plasminogen activator and its physiologic substrate, plasminogen. This assembly greatly accelerates plasmin generation, and promotes the dissolution of fibrin. Recently, we demonstrated that mice completely deficient in A2 have markedly impaired neoangiogenesis. New preliminary data substantiate and extend these findings by demonstrating a failure of tumor allograft growth in A2-null mice due to impaired tumor angiogenesis. We note specifically a paucity of neovessels, neovascular dilatation, and a deficiency of mural cells. Tumor-bearing A2-null mice display reduced circulating bone marrow derived VEGFR1+/CD11+ hematopoietic precursors, and tumor growth can be restored upon transplantation of A2-/- mice with A2+/+ marrow. We, therefore, hypothesize that expression of A2 on the surface of vascular cells and vascular precursor cells is essential for effective neoangiogenesis. Our aims are to [1] determine whether A2 supports stabilization of new blood vessels by promoting recruitment of mural cells (pericytes and smooth muscle cells) to sites of angiogenesis in tumor-bearing mice and in humans with cancer, [2] determine whether PDGF-BB recruits mural cells to developing neovessels by stimulating translocation of the A2/p11 complex to the surface of mural cell precursors, [3] determine whether A2-supported angiogenesis also requires participation of its cofactor, p11, and [4] determine whether hyperhomocysteinemia impairs the angiogenic response by derivatizing A2 and blocking its protease-inducing activity. It is anticipated that new insights derived from these studies may lead to novel modalities in the diagnosis and treatment of neovascular disorders.