The molecular mechanism and therapeutics in axon regeneration

总结 周围神经损伤是常见的，但从他们的恢复是非常差的。目前没有非- 可进行手术治疗。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。本提案的目标是：1） 研究实现这种效果的分子机制是否是通过稳定 轴突微管相关蛋白Tau在再生轴突中的作用;以及2）检查治疗性 两种靶向药理学试剂设计来模拟这些细胞效应的功效。天冬酰胺 内肽酶（AEP）是一种半胱氨酸蛋白酶，在切断的外周神经中被强烈激活，并介导 Tau的裂解降低了其对轴突细胞骨架的稳定作用。因为这种稳定性是 周围神经损伤后成功轴突再生的一个基本特征，抑制AEP可以是 周围神经损伤后生长因子信号传导的重要作用。我们假设Akt， 由生长因子如BDNF（或小分子BDNF模拟物，7，8 DHF）激活，磷酸化 AEP并抑制其酶活性，从而防止Tau的降解，导致增强的 轴突再生我们将联合收割机在体外和体内实验，以评估这一关键方面 在前两个具体目标的假设。我们已经开发了一种前药， 7，8-DHF。我们还鉴定了AEP的小变构抑制剂，其阻断小鼠中的Tau裂解。我们 将探索用前药或/和AEP抑制剂治疗在促进 轴突再生和功能恢复的具体目标3。成功完成拟议的研究 将有助于更好地了解生长因子介导的轴突再生的分子机制 以及确定治疗周围神经损伤的新的药物靶点。

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.