中国神经再生研究(英文版) ›› 2015, Vol. 10 ›› Issue (12): 1912-1913.doi: 10.4103/1673-5374.169627

• 观点:神经损伤修复保护与再生 • 上一篇    下一篇

多能干细胞至纹状体投射神经元:还差“激活素A”的距离

  

  • 收稿日期:2015-09-18 出版日期:2015-12-30 发布日期:2015-12-30

Regenerative potential of targeting glycogen synthase kinase-3 signaling in neural tissues

Eui-Man Jung, Jeffrey J. Moffat, Woo-Yang Kim*   

  1. Department of Developmental Neuroscience, Munroe-Meyer Institute, University of Nebraska Medical Center, Omaha, NE, USA
  • Received:2015-09-18 Online:2015-12-30 Published:2015-12-30
  • Contact: Woo-Yang Kim, Ph.D., wooyang.kim@unmc.edu.

摘要:

糖原合酶激酶3(GSK-3)是一种高度保守的丝氨酸/苏氨酸蛋白激酶,是胰岛素依赖性糖原合成的重要调节因子,广泛表达于真核生物。研究发现,GSK-3除参与糖代谢外,还参与细胞生长、增殖和凋亡等重要生理过程。GSK-3在神经系统中具有高表达,参与神经极性、突触可塑性、神经炎症和神经稳态调控等特性。GSK-3为活跃在新生轴突尖端的分子,其极性分布和活性调控神经元的极性建立和轴突分化。体外培养的神经元发育成熟分为5个阶段:(1)伪足形成;(2)未成熟神经突形成;(3)选择性轴突形成;(4)树突形成;(5)突触形成。GSK-3β存在于2,3期的所有突起中,磷酸化后非活性的GSK-3β聚集于3期极化的轴突末梢。在已建立极性的神经细胞中,采用多种化学抑制剂以及RNA沉默抑制GSK-3β的活性后,神经细胞分化出多个轴突,且轴突数目的增加伴随树突数目的减少。相反,持续激活GSK-3β时,神经细胞仅能分化出树突,没有轴突形成。进一步研究发现Akt激酶和PTEN磷酸酶是GSK-3β控制神经细胞极性的上游分子。该研究揭示了GSK-3β极性分布和活性改变是神经极性和轴突分化的调控基础。同时,上调的GSK-3活性与神经元死亡相关。例如,GSK-3β的过表达显著提高了神经元细胞的死亡,因而药理抑制GSK-3可以促进几种类型的神经细胞存活。因此,GSK-3在神经细胞调节的许多方面都是主要因素之一,如神经发生,神经干细胞增殖,神经细胞死亡,神经元分化等。

Abstract:

Glycogen synthase kinase-3 (GSK-3) is a serine/threonine kinase that has two isoforms encoded by two different genes, GSK-3α and GSK-3β, in mammals. GSK-3 has several sites of serine and tyrosine phosphorylation. Its activity is negatively regulated by phosphorylation of serine 21 for GSK-3α and serine 9 for GSK-3β, while it is positively regulated by phosphorylation of tyrosine 279 for GSK-3α and tyrosine 216 for GSK-3β. GSK-3 was initially found to be an important component of glycogen metabolism. However, recent studies have revealed that GSK-3 is a multifunctional kinase in various cell types, including neural cells. GSK-3α and GSK-3β are highly expressed in neural tissues such as the cerebral cortex, the hippocampus, the cerebellum, and the spinal cord. In particular, GSK-3β is elevated in the aged hippocampus, and more abundant than GSK-3α in rodents. Also, GSK-3β is highly expressed in neurons and astrocytes in the developing brain and spinal cord. Localized inhibitionof GSK-3 activity at the axon terminal is required for axon growth during development and regeneration after injury. Meanwhile, phosphorylation by GSK-3 activates some unprimed-substrates such as MAP1B, which stabilizes microtubules for axon extension. This is why global inhibition of GSK-3 at a high degree using pharmacological inhibitors or genetic elimination of both isoforms suppresses axon growth also a master regulator of neural stem cell proliferation and differentiation. Elevated GSK-3 activity is correlated with neuronal death. For example, overexpression of GSK-3β significantly increases neuronal cell death, and pharmacological inhibition of GSK-3 promotes the survival of several types of neural cells. Therefore, GSK-3 is a major factor in many facets of neural cell regulation, such as neurogenesis, neural stem cell proliferation, neural cell death, neuronal differentiation, and gliogenesis.