The role of NECAB2 in brain physiology and in Huntington s disease

NECAB2 在脑生理学和亨廷顿病中的作用

• 批准号: 281465568
• 负责人: Professor Dr. Axel Methner
• 金额: --
• 依托单位: Institut für Molekulare Medizin
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2015
• 资助国家: 德国
• 起止时间: 2014-12-31 至 2018-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/281465568?language=en
• 关键词: role; NECAB2; brain; physiology; Huntington

NECAB2 is a Neuronal Ca2+-binding protein characterized by the combination of Ca2+-binding domains and a monooxygenase domain which interacts with metabotropic glutamate and adenosine receptors thereby increasing their constitutive signaling. We investigated a potential role of NECAB2 in Huntington's disease (HD), a hereditary neurodegenerative disease, based on the following reasoning: First, NECAB2 is predominantly expressed in the striatum, the predilection site for neuronal degeneration in this disease. Second, NECAB2 interacts with membrane receptors that are over-active in HD. Third, the function of NECAB2 is altered by Ca2+ and disturbed Ca2+ signaling plays a major role in HD pathophysiology. Fourth, prokaryotic homologs of NECAB2 possess monooxygenase activity and are involved in the detoxification of reactive oxygen species, suggesting a similar function in eukaryotes distinct from the interaction with membrane receptors. Oxidative stress plays an important role in the pathophysiology of HD. In preliminary studies, we found that NECAB2 is downregulated in mouse models of HD, preceding the degeneration of striatal neurons. We also showed that mammalian NECAB2 dimerizes in a Ca2+-dependent manner and protects against oxidative stress similar to its prokaryotic orthologs. We know that NECAB2 resides at the plasma membrane where it interacts with metabotropic glutamate and adenosine receptors and increases their basal constitutive signaling. This interaction is inhibited by increased Ca2+ concentrations that occur upon synaptic stimulation when Ca2+ enters the cell through ionotropic NMDA channels and is released from intracellular stores. We think that this increase in the cytosolic Ca2+ concentration causes homodimerization of NECAB2, resulting in subsequent receptor desensitization in a negative feedback loop. The dimerization also activates its monooxygenase activity, which probably serves to process reactive oxygen species generated in active, stimulated neurons. As it is a well-established fact that metabotropic glutamate receptor signaling is over-active in Huntington's disease, I hypothesize that NECAB2 is downregulated as an adaptive process to stall or slow-down receptor signaling, which probably has the side effect that NECAB2 is less able to exert its enzymatic activity. This then accelerates the degeneration of medium spiny neurons in Huntington's disease. To test these hypotheses, I propose studies with the following aims: 1) To clarify the role of NECAB2 on neuronal viability, receptor signaling, synaptic transmission and behavior by studying NECAB2-deficient mice; and 2) to clarify the role of NECAB2 in Huntington's disease by studying expression in human HD and the phenotype of double transgenic NECAB2 -/- x HD mice. This work is of high relevance as it aims to elucidate fundamental aspects of neurobiology and the pathophysiology of a human disease.

NECAB 2是一种神经元Ca 2+结合蛋白，其特征在于Ca 2+结合结构域和单加氧酶结构域的组合，所述单加氧酶结构域与代谢型谷氨酸和腺苷受体相互作用，从而增加其组成性信号传导。我们基于以下推理研究了NECAB 2在亨廷顿病（HD）（一种遗传性神经变性疾病）中的潜在作用：首先，NECAB 2主要在纹状体中表达，纹状体是这种疾病中神经元变性的好发部位。其次，NECAB 2与HD中过度活跃的膜受体相互作用。第三，NECAB 2的功能被Ca 2+改变，Ca 2+信号传导紊乱在HD病理生理学中发挥重要作用。第四，NECAB 2的原核同源物具有单加氧酶活性，并参与活性氧的解毒，这表明在真核生物中与膜受体的相互作用不同的类似功能。氧化应激在HD的病理生理学中起重要作用。在初步研究中，我们发现NECAB 2在HD小鼠模型中下调，先于纹状体神经元的变性。我们还表明，哺乳动物NECAB 2二聚化的Ca 2+依赖性的方式，并防止氧化应激类似于其原核直系同源物。我们知道NECAB 2位于质膜上，在那里它与代谢型谷氨酸和腺苷受体相互作用，并增加它们的基础组成性信号传导。当Ca 2+通过离子型NMDA通道进入细胞并从细胞内储存释放时，突触刺激后发生的Ca 2+浓度增加抑制了这种相互作用。我们认为，这种增加的胞质Ca 2+浓度的原因同源二聚体的NECAB 2，导致随后的受体脱敏的负反馈回路。二聚化还激活其单加氧酶活性，其可能用于处理活性的、受刺激的神经元中产生的活性氧。由于代谢型谷氨酸受体信号传导在亨廷顿病中过度活跃是一个公认的事实，因此我假设NECAB 2作为一种适应性过程被下调，以停止或减缓受体信号传导，这可能具有NECAB 2不太能够发挥其酶活性的副作用。这加速了亨廷顿病中中型多刺神经元的退化。为了验证这些假设，我提出了以下目的的研究：1）通过研究NECAB 2缺陷小鼠来阐明NECAB 2对神经元活力、受体信号传导、突触传递和行为的作用; 2）通过研究人类HD中的表达和双转基因NECAB 2-/- x HD小鼠的表型来阐明NECAB 2在亨廷顿病中的作用。这项工作是高度相关的，因为它旨在阐明神经生物学和人类疾病的病理生理学的基本方面。