Elucidation of molecular signaling mechanism of axonal guidance

信号蛋白在轴突引导中起着至关重要的作用，排斥因子和CRMP家族蛋白被认为参与了信号蛋白的信号传导。我们发现了一种新的GTPase CRAG，它含有一个核定位信号序列（NLS）作为塌陷反应介质蛋白（CRMP）相关分子（CRAM ICRMP-51）的结合蛋白。在神经元中，CRAG在活性氧（ROS）介导的应激反应（包括semaphorin3A信号）中起重要作用。有趣的是，在信号蛋白3a刺激后，CRAG形成与PML小体相关的独特核包涵体。这一结果支持了信号蛋白利用氧化还原信号的观点，并提供了信号蛋白可能通过激活crg来调控裸体转录调控的新概念。另一方面，发现CRAG参与了多聚谷氨酰胺病的分子机制。实际上，CRAG与PML相关，导致PML体呈大铃状结构，泛素化，这是聚谷氨酰胺病的特征。重要的是，CRAG通过泛素-蛋白酶体途径促进核包涵体中错误折叠的聚谷氨酰胺蛋白的快速降解，并减弱其细胞毒性。最近，我们发现慢速载体介导的CRAG在小脑神经元中的表达清除了PolyQ聚集体，并显著改善了多谷氨酰胺病模型小鼠的严重共济失调。在不久的将来，靶向表达CRAG是治疗人类多谷氨酰胺疾病的潜在基因疗法。

Semaphorins play a critical role in axon guidance as repulsive factors and CRMP family proteins are believed to be involved in semaphorin signaling. We have identified a novel GTPase named CRAG containing a nuclear localization signal sequence (NLS) as a binding protein of collapsin response mediator protein (CRMP) -associated molecule (CRAM ICRMP-51) . In neurons, CRAG plays an important role for reactive oxygen species (ROS) -mediated stress response including semaphorin3A signaling. Interestingly, CRAG forms unique nuclear inclusion associated with PML bodies after stimulation of semaphorin3A. This result supports that semaphorins utilize redox signaling and provides new concept that semaphorins may regulate transcriptional regulation in nudes by activation of CRAG.On the other hand, CRAG was found to be involved in the molecular mechanism of polyglutamine disease. Actually, CRAG associates with and PML, leading to a large ling-like stnicture of PML body with ubiquitination which is characteristic of polyglutamine diseases. Importantly, CRAG promoted a rapid degradation of misfolded polyglutamine proteins in the nuclear inclusions through ubiquitin-proteasome pathway and attenuated their cell toxicity. Most recently, we showed that lentivector-mediated CRAG expression in cerebellar neurons cleared PolyQ aggregates and strikingly ameliorated severe ataxia in model mice of polyglutamine disease.In the near future, targeted expression of CRAG is a potential gene therapy for human polyglutamine diseases.