Synaptic Structure Laboratory, Instituto de Investigación en Discapacidades Neurológicas (IDINE), Departamento de Ciencias Médicas, Facultad de Medicina, Universidad de Castilla-La Mancha, Campus Biosanitario, C/Almansa 14, 02006 Albacete, Spain.
Department of Inorganic, Organic and Biochemistry, Faculty of Chemical and Technological Sciences, Universidad de Castilla-La Mancha, School of Medicine of Ciudad Real, Regional Center of Biomedical Research (CRIB), 13071 Ciudad Real, Spain.
Int J Mol Sci. 2021 May 30;22(11):5867. doi: 10.3390/ijms22115867.
Metabotropic glutamate receptor subtype 5 (mGlu) is implicated in the pathophysiology of Alzheimer´s disease (AD). However, its alteration at the subcellular level in neurons is still unexplored. Here, we provide a quantitative description on the expression and localisation patterns of mGlu in the APP/PS1 model of AD at 12 months of age, combining immunoblots, histoblots and high-resolution immunoelectron microscopic approaches. Immunoblots revealed that the total amount of mGlu protein in the hippocampus, in addition to downstream molecules, i.e., G and PLCβ, was similar in both APP/PS1 mice and age-matched wild type mice. Histoblots revealed that mGlu expression in the brain and its laminar expression in the hippocampus was also unaltered. However, the ultrastructural techniques of SDS-FRL and pre-embedding immunogold demonstrated that the subcellular localisation of mGlu was significantly reduced along the neuronal surface of hippocampal principal cells, including CA1 pyramidal cells and DG granule cells, in APP/PS1 mice at 12 months of age. The decrease in the surface localisation of mGlu was accompanied by an increase in its frequency at intracellular sites in the two neuronal populations. Together, these data demonstrate, for the first time, a loss of mGlu at the plasma membrane and accumulation at intracellular sites in different principal cells of the hippocampus in APP/PS1 mice, suggesting an alteration of the excitability and synaptic transmission that could contribute to the cognitive dysfunctions in this AD animal model. Further studies are required to elucidate the specificity of mGlu-associated molecules and downstream signalling pathways in the progression of the pathology.
代谢型谷氨酸受体 5 型（mGlu）参与阿尔茨海默病（AD）的病理生理学。然而，其在神经元亚细胞水平的改变仍未被探索。在这里，我们结合免疫印迹、组织印迹和高分辨率免疫电镜方法，提供了 APP/PS1 型 AD 模型中 mGlu 在 12 个月时的表达和定位模式的定量描述。免疫印迹显示，海马体中的 mGlu 总蛋白量，除了下游分子，即 G 和 PLCβ，在 APP/PS1 小鼠和同龄野生型小鼠中相似。组织印迹显示，大脑中的 mGlu 表达及其在海马体中的分层表达也没有改变。然而，SDS-FRL 和预包埋免疫金的超微结构技术表明，mGlu 的亚细胞定位在 APP/PS1 小鼠 12 个月时沿海马体主细胞（包括 CA1 锥体和 DG 颗粒细胞）的神经元表面显著减少。mGlu 表面定位的减少伴随着其在两个神经元群体的细胞内部位的频率增加。总之，这些数据首次表明，APP/PS1 小鼠海马体不同主细胞的 mGlu 从质膜丢失并在细胞内部位积累，表明兴奋性和突触传递的改变可能导致该 AD 动物模型中的认知功能障碍。需要进一步的研究来阐明 mGlu 相关分子和下游信号通路在病理进展中的特异性。
