The Role of ADAM15 in sTie2 shedding in Ischemic Angiogenesis

描述（由申请人提供）：Tie2是生理和病理性血管生成所需的内皮受体酪氨酸激酶（RTK）。Tie 2的配体，血管生成素，对血管生成和血管维持具有环境依赖性作用。最近的证据表明，金属蛋白酶介导的可溶性Tie2（sTie2）蛋白的脱落调节Tie2/Ang系统，尽管其产生和功能的机制尚不清楚。在人类中，sTie 2在健康对照受试者的血清中是可检测的，并且其在与血管消退相关的疾病状态中增加，例如充血性心力衰竭和高血压，表明sTie 2的潜在抗血管生成功能。与这些发现一致，工程化的可溶性Tie2蛋白的过表达阻断了临床前模型中的生理性和病理性血管生成。sTie 2从内皮细胞脱落是由VEGF诱导的，并且依赖于磷酸肌醇（PI）3-激酶/Akt途径。此外，在具有最严重的外周动脉疾病（PAD）表现的患者中，sTie 2和VEGF的血浆浓度显著增加。这些发现表明sTie 2调节血管生成反应。负责Tie2切割的效应蛋白酶先前尚未被鉴定，尽管sTie2脱落的主要候选介质是ADAM（去整合素和金属蛋白酶）蛋白。已显示ADAM 15是病理性血管生成所需的，并且本提案中的初步研究将证明ADAM 15是sTie 2从内皮细胞脱落所需的。迄今为止，尚不清楚sTie2升高在CLI和其他疾病状态中的作用，并且ADAM15是否参与体内sTie2脱落仍不清楚。在这个建议中，我们假设，ADAM 15是主要的蛋白酶Tie2切割内皮细胞和ADAM 15诱导的sTie2所需的缺血性血管生成。为了验证这一假设，本提案的具体目的是：1）鉴定ADAM 15在sTie 2脱落中的作用和ADAM 15活化的分子机制;和2）确定体内缺血性血管生成中对ADAM 15的需求。实现这些特定目标将提供对调节sTie 2脱落的机制以及其在缺血性血管生成（例如PAD）中的作用的关键见解。

DESCRIPTION (provided by applicant): Tie2 is an endothelial receptor tyrosine kinase (RTK) that is required for physiological and pathological angiogenesis. The ligands for Tie2, the Angiopoietins, have context-dependent effects on angiogenesis and vascular maintenance. Recent evidence suggests that metalloprotease-mediated shedding of a soluble Tie2 {sTie2) protein regulates the Tie2/Ang system, although the mechanisms of its production and function are not known. In humans, sTie2 is detectable in the serum of healthy control subjects, and it is increased in disease states associated with vascular regression, such as congestive heart failure and hypertension, suggesting a potential anti-angiogenic function for sTie2. Consistent with these findings, overexpression of an engineered soluble Tie2 protein blocks both physiological and pathological angiogenesis in preclinical models. sTie2 shedding from endothelial cells is induced by VEGF and is dependent on the phosphoinositide (PI) 3-kinase/Akt pathway. Furthermore, plasma concentrations of sTie2 and VEGF are significantly increased in patients with the most severe manifestation of peripheral arterial disease (PAD). These findings suggest that sTie2 modulates the angiogenic response. The effector protease responsible for Tie2 cleavage has not previously been identified, although the primary candidate mediators of sTie2 shedding are the ADAM (a disintegrin and metalloprotease) proteins. ADAM15 has been shown to be required for pathological angiogenesis, and preliminary studies in this proposal will demonstrate that ADAM15 is required for sTie2 shedding from endothelial cells. To date, the role of elevated sTie2 in CLI and other disease states is not known, and whether ADAM15 is involved in sTie2 shedding in vivo remains unclear. In this proposal, we hypothesize that ADAM15 is the principal protease for Tie2 cleavage in endothelial cells and that ADAM15-induced sTie2 is required for ischemic angiogenesis. To test this hypothesis, the Specific Aims of this proposal are to: 1) Identify the role of ADAM15 in sTie2 shedding and the molecular mechanism of ADAM15 activation; and 2) Determine the requirement for ADAM 15 in ischemic angiogenesis in vivo. Accomplishing these Specific Aims will provide key insights into the mechanisms regulating sTie2 shedding as well as its role in ischemic angiogenesis such as in PAD.