TISSUE PLASMINOGEN ACTIVATOR AND NEURONAL DEGENERATION

描述（研究者摘要）：细胞外蛋白酶已被 参与哺乳动物中枢神经系统的各种功能 （CNS）。 然而，分析这些可能的功能一直很困难 in vivo. 利用实验模型诱导小鼠神经元损伤 在海马体中，我们发现丝氨酸蛋白酶tPA缺陷小鼠 (tPA-/-）对神经元变性具有显著的抗性。 缺陷的小鼠 对于纤溶酶原，经典的tPA底物，表现出相同的耐药性， 表型为tPA-/-小鼠。 tPA和纤溶酶原都是在 海马，蛋白水解活性的表达似乎是 由内源性抑制剂调节。 最后，输注tPA/纤溶酶 抑制剂进入野生型小鼠的海马体也可以赋予耐药性 神经元死亡 从这些结果中出现了一个中心假设， 在其他实验室工作： tPA和纤溶酶的细胞外蛋白水解级联介导神经元 哺乳动物中枢神经系统中的细胞死亡。 在本申请中，我们提出研究的机制， tPA/纤溶酶在CNS中的功能，通过解决以下问题：1） tPA和纤溶酶的结构和催化特性是什么 严重退化吗 蛋白酶抑制剂是否能被鉴定为 参与调节神经元死亡，并具有治疗作用， 延缓退化的潜力 2)是否存在内源性蛋白酶 有助于调节tPA和纤溶酶活性的抑制剂？ 3)有哪些 神经元和小胶质细胞产生的tPA各自的作用？ 4)有哪些 被tPA和/或纤溶酶裂解的特异性底物介导神经元 退化？ 提出这些问题将有助于通过以下方式确定机制： tPA和纤溶酶原在海马中起作用， 这对许多神经退行性疾病的治疗具有重要意义。

DESCRIPTION (Investigator's Abstract): Extracellular proteases have been implicated in various functions in the mammalian central nervous system (CNS). However, it has been difficult to analyze these possible functions in vivo. Using an experimental model to induce neuronal damage in the mouse hippocampus, we have shown that mice deficient for the serine protease tPA (tPA-/-) are strikingly resistant to neuronal degeneration. Mice deficient for plasminogen, the classical tPA substrate, exhibit the same resistant phenotype as the tPA-/- mice. Both tPA and plasminogen are synthesized in the hippocampus, and the expression of proteolytic activity appears to be modulated by endogenous inhibitors. Finally, infusion of tPA/plasmin inhibitors into the hippocampus of wild-type mice can also confer resistance to neuronal death. A central hypothesis emerges from these results and from work in other laboratories: An extracellular proteolytic cascade of tPA and plasmin mediates neuronal cell death in the mammalian CNS. In this application, we propose to investigate the mechanism by which tPA/plasmin function in the CNS by addressing the following questions: 1) What structural and catalytic characteristics of tPA and plasmin are critical for degeneration? Can protease inhibitors be identified that participate in regulating neuronal death, and that have therapeutic potential in retarding degeneration? 2) Are there endogenous protease inhibitors that help regulate tPA and plasmin activity? 3) What are the respective roles of tPA produced by neurons and microglia? 4) What are the specific substrates whose cleavage by tPA and/or plasmin mediates neuronal degeneration? Answering these questions will help define the mechanism by which tPA and plasminogen function in the hippocampus, and could have implications for the treatment of many neurodegenerative disorders.