The Molecular Mechanism and Therapeutics in Axon Regeneration

摘要 周围神经损伤很常见，但恢复很差。目前没有非- 可以进行手术治疗。脑源性神经营养因子(BDNF)和其他生长因子是已知的 促进周围神经损伤后轴突再生。这项建议的目标是：1) 研究这种作用的分子机制是否通过稳定 轴突微管相关蛋白，Tau在再生轴突中；2)检查治疗 设计用来模拟这些细胞效应的两种靶向药物的疗效。天冬酰胺 内肽酶(AEP)是一种半胱氨酸蛋白酶，在切断的周围神经中被强烈激活并介导 Tau的裂解，降低了其对轴突细胞骨架的稳定作用。因为这样的稳定是 周围神经损伤后成功再生轴突的一个基本特征是抑制AEP 生长因子信号在周围神经损伤后的重要作用。我们假设阿克特， 被生长因子激活，如BDNF(或小分子BDNF模拟物，7，8DHF)，磷酸化 AEP并抑制其酶活性，从而阻止牛磺酸的降解，导致增强 轴突再生。我们将结合体外和体内实验来评估这一关键方面 前两个具体目标中的假设。我们已经开发出一种前药，可以提高口服生物利用度 7，8-二氢呋喃。我们还发现了AEP的一种小的变构抑制剂，它可以阻断小鼠体内的Tau裂解。我们 将探讨前药或/和AEP抑制剂治疗促进 特定目的的轴突再生和功能恢复3.拟议研究的圆满完成 将有助于更好地理解生长因子介导的轴突再生的分子机制 并确定一种治疗周围神经损伤的新药物靶点。

Summary Injuries to peripheral nerves are common, but recovery from them is very poor. There is currently no non- surgical treatment available. Brain-derived neurotrophic factor (BDNF), and other growth factors, are known to promote axon regeneration following peripheral nerve injury. The objectives of this proposal are to: 1) investigate whether the molecular mechanism by which this effect is achieved is through stabilization of the axonal microtubule-associated protein, Tau in the regenerating axons; and 2) to examine the therapeutic efficacy of two targeted pharmacological agents designed to mimic these cellular effects. Asparagine endopeptidase (AEP), a cysteine protease, is robustly activated in cut peripheral nerves and mediates cleavage of Tau that degrades its stabilizing effect on the axonal cytoskeleton. Because such stabilization is an essential feature of successful axon regeneration after peripheral nerve injury, inhibiting AEP could be an important effect of growth factor signaling after peripheral nerve injury. We hypothesize that Akt, activated by growth factors such as BDNF (or the small molecule BDNF mimetic, 7,8 DHF), phosphorylates AEP and suppresses its enzymatic activity, thereby preventing degradation of Tau, leading to enhanced axon regeneration. We will combine in vitro and in vivo experiments to evaluate critical aspects of this hypothesis in the first two Specific Aims. We have developed a prodrug that elevates oral bioavailability of 7,8-DHF. We also have identified a small allosteric inhibitor of AEP, which blocks Tau cleavage in mice. We will explore the therapeutic efficacy of treatments with the prodrug or/and the AEP inhibitor in promoting axon regeneration and functional recovery in Specific Aim 3. Successful completion of the proposed studies will lead to better understanding of the molecular mechanisms of growth factor-mediated axon regeneration and identification of a novel drug target for treatment of peripheral nerve injury.