Urokinase-type Plasminogen Activator in the Ischemic Brain

项目摘要/摘要 在过去的二十年里，急性缺血性中风的死亡率显著下降，这反过来又 导致在不同程度的缺血性中风中存活的患者数量大幅增加 残疾。不幸的是，尽管这个问题很严重，但到目前为止， 缺血性损伤后神经修复的过程知之甚少，也没有有效的治疗方法 促进缺血性卒中幸存者神经康复的策略。脑缺血具有危害性 神经功能障碍对突触结构和功能的影响。因此， 缺血性中风后的神经恢复需要形成新的突触接触和/或 修复因缺血损伤而受损的组织。这是一个高度动态的过程，从 轴突与突触后粘连接触的重建和/或从头形成 通过膜结合的黏附蛋白之间的相互作用来调节。神经元钙粘附素 (N-钙粘附素或NCAD)是一种在突触中大量存在的粘附性蛋白质，它在突触形成粘连接触 在突触前和突触后终末之间。尿激酶型纤溶酶原激活物(UPA)是一种丝氨酸蛋白酶 与其受体(UPAR)结合后催化纤溶酶原转化为纤溶酶并激活细胞 促进细胞存活、增殖和运动的信号通路。在本项目的上一个资金周期中 应用我们发现，uPA是从大脑皮层神经元的突触前终末释放出来的 缺血性卒中恢复期，这种uPA与其受体(UPAR)结合促进修复 因缺血损伤而受损的轴突和树突。在此续订申请中，我们将检验假设 内源性或重组uPA与uPAR的结合通过诱导 NCAD介导的突触前和突触后终末之间粘连接触的形成 因缺血损伤而受损。为了实现这一目标，我们首先将研究uPA的机制 调节NCAD在突触中的表达和功能，并验证uPA促进的假设 通过诱导NCAD介导的新的粘连接触的重建和/或形成来恢复突触 在遭受缺血损伤的神经元的轴突和突触后终末之间。然后，我们 将研究uPA对典型的Wnt-β-Catenin途径的影响。最后，我们将使用一个动物模型 研究uPA是否诱导NCAD介导的Wnt-β-Catenin通路的激活 促进脑缺血损伤后突触修复和神经功能恢复。

PROJECT SUMMARY/ABSTRACT The last two decades have witnessed a significant decrease in acute ischemic stroke mortality, that in turn has caused a substantial increase in the number of patients that survive an ischemic stroke with different degrees of disability. Unfortunately, despite the magnitude of this problem, to this date the mechanisms that underlie the process of neurorepair following an ischemic injury are poorly understood, and there is no effective therapeutic strategy to promote neurological recovery among ischemic stroke survivors. Cerebral ischemia has a harmful impact on synaptic structure and function associated with the development of neurological deficits. Hence, neurological recovery following an ischemic stroke requires the formation of new synaptic contacts and/or the repair of those damaged by the ischemic injury. This is a highly dynamic process that begins with the reestablishment and/or de novo formation of adhesive contacts between axonal boutons and postsynaptic terminals, and is mediated by the interaction between membrane-bound adherent proteins. Neuronal cadherin (N-Cadherin or NCAD) is an adherent protein abundantly found in the synapse, where it forms adhesive contacts between the pre- and postsynaptic terminals. Urokinase-type plasminogen activator (uPA) is a serine proteinase that upon binding to its receptor (uPAR) catalyzes the conversion of plasminogen into plasmin and activates cell signaling pathways that promote cell survival, proliferation and motility. In the previous funding cycle of this application we found that uPA is released from the presynaptic terminal of cerebral cortical neurons during the recovery phase from an ischemic stroke, and that binding of this uPA to its receptor (uPAR) promotes the repair of axons and dendrites damaged by the ischemic injury. In this renewal application we will test the hypothesis that binding of either endogenous or recombinant uPA to uPAR promotes synaptic repair by inducing the formation of NCAD-mediated adhesive contacts between the pre- and postsynaptic terminals that have been damaged by an ischemic injury. To accomplish this goal, first we will study the mechanism whereby uPA regulates the expression and function of NCAD in the synapse, and test the hypothesis that uPA promotes synaptic recovery by inducing NCAD-mediated reestablishment and/or formation of new adhesive contacts between axonal boutons and postsynaptic terminals of neurons that have suffered an ischemic injury. Then, we will investigate the effect of uPA on the canonical Wnt-β-Catenin pathway. Finally, we will use an animal model of cerebral ischemia to investigate if uPA-induced NCAD-mediated activation of the Wnt-β-Catenin pathway promotes synaptic repair and neurological recovery after an ischemic injury.