Spastin泛素化修饰的调控机制及其在脊髓损伤修复中的作用

Spastin可通过切割微管调控突起分支及生长，但Spastin自身的翻译后修饰调控，特别是泛素化修饰及其在脊髓损伤修复中的作用尚不清楚，亟待阐明。我们的预实验结果表明，Spastin存在泛素化修饰；介导该修饰的关键位点位于Spastin的C端；Cullin环状泛素连接酶可能是介导该修饰的E3连接酶；泛素化修饰影响Spastin蛋白稳定性，使其被泛素-蛋白酶体系统降解，丧失微管切割活性，丧失调控神经元突起分支及生长的能力。据此，我们提出科学假设：脊髓损伤时，抑制Spastin的泛素化修饰，可提升Spastin蛋白稳定性，增强微管切割从而促进轴突再生及功能恢复。本项目拟通过形态学、分子生物学、电生理学、转基因等技术，从体外细胞培养和体内动物模型阐明Spastin泛素化修饰的分子机制，明确该修饰在微管切割、轴突再生及脊髓损伤修复中的作用，为脊髓损伤的临床治疗提供切实的科学依据及新思路。

Spastin regulates neurite growth via microtubule severing. Until now, no evidence shows the existence of Spastin ubiquitination and its potential role in axonal regeneration and spinal cord injury (SCI). Our preliminary results showed that Spastin interacted with ubiquitin protein and can be ubiquitinated. The critical motif that mediated this modification located in the C terminal of Spastin and Cullin-RING ubiquitin ligase could be the E3 ligase. When ubiquitinated, the protein stability of Spastin was affected and Spastin was degraded via the ubiquitin-proteasome system, losing microtubule severing activity and the ability to regulate neurite growth. Thus, we propose the hypothesis: inhibition of Spastin ubiquitin could increase its protein stability, enhance the microtubule severing and promote axonal regeneration during SCI recovery. By morphological, molecular biological, physiological approaches and transgenic technology, via neuronal cultures in vitro and SCI rat/mouse model in vivo, this project aims to elucidate the detailed molecular mechanism of Spastin ubiquitination and to reveal its role in microtubule severing, axonal regeneration and SCI, thus, to provide solid evidences and new ideas for the clinical treatment of SCI.