Ma Chao, Wang Junpei, Tu Qifeng, Bo Weijuan, Hu Zunlu, Zhuo Run, Wu Ronghua, Dong Zhangji, Qiang Liang, Liu Yan, Liu Mei
Key Laboratory of Neuroregeneration of Jiangsu and Ministry of Education, Co-innovation Center of Neuroregeneration, NMPA Key Laboratory for Research and Evaluation of Tissue Engineering Technology Products, Nantong University; Medical School of Nantong University, Nantong, Jiangsu Province, China.
Key Laboratory of Neuroregeneration of Jiangsu and Ministry of Education, Co-innovation Center of Neuroregeneration, NMPA Key Laboratory for Research and Evaluation of Tissue Engineering Technology Products, Nantong University, Nantong, Jiangsu Province, China.
Neural Regen Res. 2023 Dec;18(12):2727-2732. doi: 10.4103/1673-5374.373716.
Fidgetin, a microtubule-severing enzyme, regulates neurite outgrowth, axonal regeneration, and cell migration by trimming off the labile domain of microtubule polymers. Because maintenance of the microtubule labile domain is essential for axon initiation, elongation, and navigation, it is of interest to determine whether augmenting the microtubule labile domain via depletion of fidgetin serves as a therapeutic approach to promote axonal regrowth in spinal cord injury. In this study, we constructed rat models of spinal cord injury and sciatic nerve injury. Compared with spinal cord injury, we found that expression level of tyrosinated microtubules in the labile portion of microtubules continuously increased, whereas fidgetin decreased after peripheral nerve injury. Depletion of fidgetin enhanced axon regeneration after spinal cord injury, whereas expression level of end binding protein 3 (EB3) markedly increased. Next, we performed RNA interference to knockdown EB3 or fidgetin. We found that deletion of EB3 did not change fidgetin expression. Conversely, deletion of fidgetin markedly increased expression of tyrosinated microtubules and EB3. Deletion of fidgetin increased the amount of EB3 at the end of neurites and thereby increased the level of tyrosinated microtubules. Finally, we deleted EB3 and overexpressed fidgetin. We found that fidgetin trimmed tyrosinated tubulins by interacting with EB3. When fidgetin was deleted, the labile portion of microtubules was elongated, and as a result the length of axons and number of axon branches were increased. These findings suggest that fidgetin can be used as a novel therapeutic target to promote axonal regeneration after spinal cord injury. Furthermore, they reveal an innovative mechanism by which fidgetin preferentially severs labile microtubules.
凝溶胶蛋白是一种微管切割酶，它通过切除微管聚合物的不稳定结构域来调节神经突生长、轴突再生和细胞迁移。由于微管不稳定结构域的维持对于轴突起始、伸长和导航至关重要，因此确定通过消耗凝溶胶蛋白来增加微管不稳定结构域是否可作为促进脊髓损伤后轴突再生的治疗方法具有重要意义。在本研究中，我们构建了脊髓损伤和坐骨神经损伤的大鼠模型。与脊髓损伤相比，我们发现微管不稳定部分的酪氨酸化微管表达水平持续升高，而周围神经损伤后凝溶胶蛋白减少。消耗凝溶胶蛋白可增强脊髓损伤后的轴突再生，而末端结合蛋白3（EB3）的表达水平显著增加。接下来，我们进行RNA干扰以敲低EB3或凝溶胶蛋白。我们发现缺失EB3不会改变凝溶胶蛋白的表达。相反，缺失凝溶胶蛋白会显著增加酪氨酸化微管和EB3的表达。缺失凝溶胶蛋白会增加神经突末端的EB3量，从而提高酪氨酸化微管的水平。最后，我们缺失EB3并过表达凝溶胶蛋白。我们发现凝溶胶蛋白通过与EB3相互作用来切割酪氨酸化微管蛋白。当凝溶胶蛋白缺失时，微管的不稳定部分会延长，结果轴突长度和轴突分支数量增加。这些发现表明，凝溶胶蛋白可作为促进脊髓损伤后轴突再生的新型治疗靶点。此外，它们揭示了一种凝溶胶蛋白优先切割不稳定微管的创新机制。
