APP-NCAM选择性相互作用调节神经突生长的分子机制研究

Alzheimer's disease (AD) is characterized by senile plaques and neurofibrillary tangles in the brain, and the senile plaques are composed of β-amyloid peptide (Aβ). Most of previous studies have focused primarily on a pathophysiological role of Aβ peptides that are generated via the amyloidogenic pathway of the amyloid precursor protein (APP) processing. However, the physiological roles of APP family members remain to be fully elucidated. So understanding APP function is important for therapeutic strategy in AD. Neural cell adhesion molecule (NCAM) is implicated in various functions such as regeneration, neurite outgrowth, transmembrane signaling transduction, learning and memory and so on. In our previous studies, the selective interaction of APP and NCAM was found, and the co-expresssion of the proteins could obviously increase the phosphorylation levels of ERK in the MAPK signaling pathway. So the interaction could involve in the modulation of neurite outgrowth and neural development. Here, with the help of various biotechnologies such as molecular biology, cell biology and genetics, the effects of the interaction on the neurite outgrowth would be first studies in hippocampal neurons, PC12 cells and deficient mice. On the other hand, the signaling pathway involved in the process would be also discussed. These studies will enable us to have a better understanding of normal physiological function of APP and its role in diseases of the nervous system, providing new drug target and new perspectives for AD treatment.

阿尔茨海默氏病(AD)患者脑组织内淀粉样斑块主要成分为Aβ。大量的研究主要关注Aβ的病理生理功能，对其前体蛋白APP的正常生理功能知之甚少。APP的功能研究对AD治疗具有重要意义。神经细胞粘附分子（NCAM）在神经再生、神经突生长、跨膜信号的传导、学习和记忆等方面均起着一定的作用。我们的前期工作首次发现APP与NCAM存在选择性相互作用，并且两种蛋白共表达时可以显著提高MAPK信号通路中ERK磷酸化水平。据此，我们推测此相互作用参与了神经突生长发育的调控。本项目拟在预实验结果基础上，以海马神经元、PC12细胞及基因敲除小鼠等为研究对象，采用分子生物学、细胞生物学、遗传学等多种技术观察APP与NCAM相互作用对神经突生长发育的调控，并探讨了参与其中的信号通路。这将使我们更深入理解APP正常的生理功能及其在神经系统疾病中扮演的角色，并为AD的药物研发提供新的靶点，为AD的治疗提供新的思路。

阿尔茨海默氏病(AD)患者脑组织内淀粉样斑块主要成分为Aβ。大量的研究主要关注Aβ的病理生理功能，对其前体蛋白APP 的正常生理功能知之甚少。APP 的功能研究对AD 治疗具有重要意义。神经细胞粘附分子（NCAM）在神经再生、神经突生长、跨膜信号的传导、学习和记忆等方面均起着一定的作用。课题组发现APP 与NCAM 存在选择性相互作用，并且两种蛋白共表达时可显著提高MAPK 信号通路ERK 磷酸化水平。因此这种相互作用可能通过调控MAPK 信号通路，从而参与AD发生发展。采用基因敲除、基因敲入鼠与基因表达PCR芯片等技术，本项目主要研究APP与NCAM-140相互作用对APP水解代谢的调控；这种相互作用对神经突生长发育的调控及对MAPK信号通路信号分子的调控。研究结果表明：1.APP与NCAM的胞内段调控了这种选择性相互作用；2.这种相互作用可调节APP水解代谢即Aβ40与Aβ42的生成；3.无论在PC12E2细胞系还是野生型小鼠中均发现，APP与NCAM-140共存时可促进神经突生长发育。利用基因敲除与基因敲入鼠也证实在APP与NCAM-140共存时，原代海马神经元的神经突生长发育明显增强；4.利用基因表达谱PCR芯片研究MAPK信号通路，APP与NCAM-140共转至HEK293细胞，除引起MAPK8、MAP2K4与MAP2K6表达变化外，还可引起FASLG表达显著变化。APP与NCAM-140相互作用促进神经突生长发育以及引起FASLG表达变化的研究结果，为AD的研究开辟了新的视角，将使我们更深入理解APP 正常的生理功能及其在神经系统疾病中扮演的角色，并为AD 的药物研发提供新的靶点，为AD 的治疗提供新的思路。