Cdc42介导的神经元树突重塑在帕金森病发生中的作用

Parkinson's disease (PD) is a debilitating neurological disorder marked by progressive slowing of movements and difficulty in initiating them, and is caused by the degeneration of dopamine neurons in the midbrain and their axonal projections to the striatum. A key alteration that has been reported in various rodent models and PD patients is a significant reduction in striatal spine density. The striatal spine loss is an early pathological feature of PD, tightly linked with the degree of stratal DA deneration. Importantly,mainining normal strital pine density improves the therapeutic benefit induced by graftedDA neurons. The Rho family of small GTPases, including Rac, RhoA and Cdc42, are important regulators of the actin rearrangement which play key roles in dendritic morphogenesis. Althrough many investigations illustrate the importance of Rho family GTPase in dendritic morphogenesis, it remains unclear whether they also function to regulate the dendritic reorganization in PD. Our recent findings indicate that the induction of Cdc42 and Rac1 in the Cpu is important for cocaine exposure-induced remodeling of dendritic spines and behavioral plasticity. Meanwhile we found that activation of Cdc42 GTPase may restore the spine loss in PD mouse model. However, the precise molecular mechanisms leading to these morphological changes have yet to be fully investigated. These preliminary results lead us to hypothesize that Cdc42 plays key role in dendritic remodeling in PD. By using a complex methods, including the construction of striatum specific Rac1 knockout mice and the gain of function Cdc42 GAP gene targeted mice, we aimed at answer the following questions: whether Cdc42 GTPase signaling is involved in the structural plasticity in PD? And by what downstream effectors, the Cdc42 GTPase signaling regulate dendritic remodeling? The answers to these questions will provide further insight into the molecular and cellular mechanism of PD and may provide new leads to the development of novel therapeutics targeting Cdc42 GTPase signaling.

神经元树突重塑异常在多种疾病发生发展中起重要作用。帕金森病(PD)核心问题是中脑多巴胺能神经元进行性变性。神经递质多巴胺匮乏导致PD患者纹状体区呈现异常树突重塑，表现为神经元树突棘密度显著下降等。小GTP酶Cdc42是Rho家族最受关注的分子之一。我们近期研究提示Cdc42在PD纹状体神经元树突重塑中发挥作用，但具体分子机制不清楚。为进一步探讨Cdc42在PD神经元树突重塑中的作用，本研究应用Cdc42功能获得性突变小鼠与纹状体特异性Cdc42基因敲除小鼠，集中探讨PD发生中，Cdc42是否调控神经元树突重塑及相关行为学变化；进一步，Cdc42通过何种下游效应分子发挥生物学效应。我们提出假说：PD发生中，多巴胺匮乏通过抑制Cdc42表达及活性，进一步影响Cdc42相关下游分子而诱导神经元树突重塑。上述问题的回答为进一步阐明Cdc42通路在PD中的作用，寻找新的治疗PD靶点和药物奠定基础。

帕金森病(PD)主要发病机制是黑质纹状体（CPu）多巴胺系统中多巴胺能神经元进行性丢失。PD患者临床表现为运动迟缓、肌肉强直和姿势步态异常为特征的运动功能障碍。有研究表明，PD小鼠和PD病人CPu中型多棘神经元（MSNs）呈现异常的形态与功能的重塑，然而其相关的分子机制却知之甚少。Cdc42作为Ras超家族中小G蛋白家族的成员，在维持树突棘成熟和树突棘功能方面起到关键作用。. 我们构建了PD小鼠模型，并利用其探讨了PD小鼠中CPu区Cdc42及下游效应分子NWASP/PAK1/LIMK/Cofilin的活性改变，发现PD小鼠Cdc42信号通路活性下降。通过Cdc42组成型活性突变体慢病毒和显性负效突变体慢病毒升高或降低Cdc42-GTPase活性，验证Cdc42参与调节PD小鼠模型CPu区MSNs的树突棘重塑和行为学改变。进一步，利用CPu区特异性D1R基因敲除小鼠和D2R基因敲除小鼠构建PD模型，发现多巴胺D2受体敲除后Cdc42活性进一步降低；同时激活D2R基因敲除小鼠D2-MSNs中Cdc42-GTPase能够明显改善PD模型小鼠中因D2敲除导致的树突棘可塑性改变和行为学异常。进一步，采用CPu区D2-MSNs特异性Cdc42基因敲除小鼠，探讨PD模型小鼠D2-MSNs中D2R对Cdc42的特异性调控作用，发现D2-MSNs中特异性Cdc42基因敲除能够诱导小鼠产生类PD小鼠样改变。. 另一方面，针对帕金森病的治疗，我们从新型生物材料入手，联合对神经元具有保护作用的活化素B和BMSCs，探讨治疗帕金森病的新的治疗策略。结果发现新型温敏型水凝胶联合活化素B和新型导电水凝胶联合BMSCs对帕金森病的运动障碍具有很好的治疗作用。上述研究部分已发表在Biomaterials、Toxicology Letters、Neurobiology of Disease等杂志。.