The Role of ADAM15 in sTie2 shedding in Ischemic Angiogenesis

描述（由申请人提供）：Tie2是一种内皮受体酪氨酸激酶（RTK），是生理和病理血管生成所必需的。Tie2的配体，血管生成素，在血管生成和血管维持中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，sTie2在健康对照者的血清中可检测到，并且在与血管退化相关的疾病状态（如充血性心力衰竭和高血压）中升高，这表明sTie2具有潜在的抗血管生成功能。与这些发现一致，在临床前模型中，工程可溶性Tie2蛋白的过表达会阻断生理性和病理性血管生成。内皮细胞的sTie2脱落是由VEGF诱导的，并依赖于磷酸肌苷（PI） 3-激酶/Akt通路。此外，在表现最严重的外周动脉疾病（PAD）患者中，血浆中sTie2和VEGF浓度显著升高。这些发现表明，sTie2调节血管生成反应。虽然sTie2脱落的主要候选介质是ADAM（一种崩解素和金属蛋白酶）蛋白，但负责Tie2切割的效应蛋白酶尚未被确定。ADAM15已被证明是病理性血管生成所必需的，本提案的初步研究将证明ADAM15是内皮细胞中sTie2脱落所必需的。迄今为止，sTie2升高在CLI和其他疾病状态中的作用尚不清楚，ADAM15是否参与体内sTie2的脱落仍不清楚。在这一提议中，我们假设ADAM15是内皮细胞中Tie2切割的主要蛋白酶，ADAM15诱导的sTie2是缺血性血管生成所必需的。为了验证这一假设，本提案的具体目的是：1)确定ADAM15在sTie2脱落中的作用和ADAM15激活的分子机制；2)确定体内缺血性血管生成对adam15的需求。实现这些特定目标将为研究sTie2脱落的调节机制及其在缺血性血管生成（如PAD）中的作用提供关键见解。

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.