中国神经再生研究(英文版)

中国神经再生研究(英文版) ›› 2023, Vol. 18 ›› Issue (11): 2526-2534.doi: 10.4103/1673-5374.371372

• 原著:视神经损伤修复保护与再生 • 上一篇    下一篇

S6K1和4E-BP1磷酸化在组成型活性Rheb介导视网膜神经节细胞存活和轴突再生中的作用

  

  • 出版日期:2023-11-15 发布日期:2023-05-05
  • 基金资助:
    国家自然科学基金项目（82070967，81770930），湖南省自然科学基金项目（2020jj4788）

Phosphorylated S6K1 and 4E-BP1 play different roles in constitutively active Rheb-mediated retinal ganglion cell survival and axon regeneration after optic nerve injury

Jikuan Jiang1, 2, Lusi Zhang1, 2, Jingling Zou1, 2, Jingyuan Liu1, 2, Jia Yang1, 2, Qian Jiang1, 2, Peiyun Duan1, 2, Bing Jiang1, 2, *   

  1. 1Department of Ophthalmology, Second Xiangya Hospital, Central South University, Changsha, Hunan Province, China; 2Hunan Clinical Research Center of Ophthalmic Disease, Changsha, Hunan Province, China
  • Online:2023-11-15 Published:2023-05-05
  • Contact: Bing Jiang, MD, PhD, drjiangb@csu.edu.cn.
  • Supported by:
    This study was supported by the National Natural Science Foundation of China, Nos. 82070967, 81770930, and the Natural Science Foundation of Hunan Province, No. 2020jj4788 (all to BJ).

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摘要：

Rheb是一种能激活mTORC1的小GTPase。有研究显示，组成性活性Rheb可通过激活mTOR下游的蛋白质，增强脊髓损伤后感觉轴突的再生。S6K1和4E-BP1就是mTORC1下游的重要效应子。为了解Rheb/mTOR及其下游效应子S6K1和4E-BP1在视网膜神经节细胞保护中的作用，实验以腺病毒相关病毒介导组成性活性Rheb转染视神经挤压小鼠模型，观察其对视网膜神经节细胞存活和轴突再生的作用。结果可见，组成性活性Rheb过表达可有效促进损伤急性期（14d）和慢性期（21和42d）视网膜神经节细胞的存活，且显性负性S6K1突变体或组成性活性4E-BP1突变体与组成性活性Rheb共表达均能显著抑制视网膜神经节细胞轴突的再生，表明mTORC1介导的S6K1激活和4E-BP1抑制是组成性活性Rheb诱导轴突再生的必要因素。然而玻璃体内单独转染显性负性S6K1突变体或组成性活性4E-BP1突变体时，则只有S6K1激活而不是4E-BP1敲除才能诱导轴突再生。S6K1激活还能促进视网膜神经节细胞在损伤后14d时的存活，而4E-BP1敲低则意外地轻微抑制了视网膜神经节细胞的存活，组成性活性4E-BP1过表达也能促进视网膜神经节细胞的存活。与组成性活性Rheb单独表达相比，共表达组成性活性Rheb和组成性活性4E-BP1可显著提高视网膜神经节细胞的存活率。因此认为，4E-BP1和S6K1有神经保护作用，且4E-BP1可能至少部分独立于Rheb/mTOR通路发挥作用。上述结果提示，组成性活性Rheb可通过调节S6K1和4E-BP1活性促进视网膜神经节细胞的存活和轴突再生，且S6K1磷酸化（活化）和4E-BP1磷酸化（失活）可协同促进轴突再生，但在两者在视网膜神经节细胞存活中起拮抗作用。

https://orcid.org/0000-0001-6594-4019 (Bing Jiang)

关键词: 神经变性, 基因治疗, 神经保护, Rheb, 轴突再生, 视网膜, 中枢神经系统, mRNA翻译, 翻译启动, 视神经挤压

Abstract: Ras homolog enriched in brain (Rheb) is a small GTPase that activates mammalian target of rapamycin complex 1 (mTORC1). Previous studies have shown that constitutively active Rheb can enhance the regeneration of sensory axons after spinal cord injury by activating downstream effectors of mTOR. S6K1 and 4E-BP1 are important downstream effectors of mTORC1. In this study, we investigated the role of Rheb/mTOR and its downstream effectors S6K1 and 4E-BP1 in the protection of retinal ganglion cells. We transfected an optic nerve crush mouse model with adeno-associated viral 2-mediated constitutively active Rheb and observed the effects on retinal ganglion cell survival and axon regeneration. We found that overexpression of constitutively active Rheb promoted survival of retinal ganglion cells in the acute (14 days) and chronic (21 and 42 days) stages of injury. We also found that either co-expression of the dominant-negative S6K1 mutant or the constitutively active 4E-BP1 mutant together with constitutively active Rheb markedly inhibited axon regeneration of retinal ganglion cells. This suggests that mTORC1-mediated S6K1 activation and 4E-BP1 inhibition were necessary components for constitutively active Rheb-induced axon regeneration. However, only S6K1 activation, but not 4E-BP1 knockdown, induced axon regeneration when applied alone. Furthermore, S6K1 activation promoted the survival of retinal ganglion cells at 14 days post-injury, whereas 4E-BP1 knockdown unexpectedly slightly decreased the survival of retinal ganglion cells at 14 days post-injury. Overexpression of constitutively active 4E-BP1 increased the survival of retinal ganglion cells at 14 days post-injury. Likewise, co-expressing constitutively active Rheb and constitutively active 4E-BP1 markedly increased the survival of retinal ganglion cells compared with overexpression of constitutively active Rheb alone at 14 days post-injury. These findings indicate that functional 4E-BP1 and S6K1 are neuroprotective and that 4E-BP1 may exert protective effects through a pathway at least partially independent of Rheb/mTOR. Together, our results show that constitutively active Rheb promotes the survival of retinal ganglion cells and axon regeneration through modulating S6K1 and 4E-BP1 activity. Phosphorylated S6K1 and 4E-BP1 promote axon regeneration but play an antagonistic role in the survival of retinal ganglion cells. 

Key words: axon regeneration, central nervous system, gene therapy, mRNA translation, neurodegeneration, neuroprotection, optic nerve crush, Ras homolog enriched in the brain, retina, translation initiation