Martín-Belmonte Alejandro, Aguado Carolina, Alfaro-Ruíz Rocío, Itakura Makoto, Moreno-Martínez Ana Esther, de la Ossa Luis, Molnár Elek, Fukazawa Yugo, Luján Rafael
Synaptic Structure Laboratory, Departamento de Ciencias Médicas, Facultad de Medicina, Instituto de Investigación en Discapacidades Neurológicas (IDINE), Universidad de Castilla-La Mancha, Albacete, Spain.
Department of Biochemistry, Kitasato University School of Medicine, Sagamihara-shi, Japan.
Front Aging Neurosci. 2020 Oct 6;12:577996. doi: 10.3389/fnagi.2020.577996. eCollection 2020.
Synapse loss occurs early in Alzheimer's disease (AD) patients and animal models. Alterations at synaptic level are a major morphological correlate of the memory deficits and related symptoms of AD. Given the predominant roles of synaptic AMPA receptors (AMPARs) in excitatory synaptic transmission in the brain, changes in their dynamic regulation are also implicated in the pathophysiology of AD. Here, we used immunolocalization techniques to analyze the expression and subcellular distribution of AMPARs in the hippocampal region of APP/PS1 mouse model of AD. Immunoblots and histoblots revealed that the total amount of AMPARs and their regional expression pattern in the hippocampus was similar in APP/PS1 mice and in age-matched wild type mice. At the ultrastructural level, two synapse populations were examined using SDS-digested freeze-fracture replica labeling in the in mice: (i) on spines of CA1 pyramidal cells; and (ii) on randomly found dendritic shafts of CA1 interneurons. While 1- and 6-months-old APP/PS1 mice exhibited no change, we observed a significant reduction at 12 months in AMPAR density at synapses in both pyramidal cells and interneurons, compared to wild-type. This reduction of AMPARs in dendritic spines was accompanied by a significant increase in AMPAR subunit proteins identified in intracellular compartments. Our data demonstrate an age-dependent reduction of synaptic AMPARs in APP/PS1 mice, which may contribute to impaired learning and memory at later stages of AD.
在阿尔茨海默病（AD）患者和动物模型中，突触丢失在疾病早期就会发生。突触水平的改变是AD记忆缺陷及相关症状的主要形态学关联因素。鉴于突触α-氨基-3-羟基-5-甲基-4-异恶唑丙酸受体（AMPARs）在大脑兴奋性突触传递中起主要作用，其动态调节的变化也与AD的病理生理学有关。在此，我们使用免疫定位技术分析了AD的APP/PS1小鼠模型海马区中AMPARs的表达和亚细胞分布。免疫印迹和组织印迹显示，APP/PS1小鼠与年龄匹配的野生型小鼠海马中AMPARs的总量及其区域表达模式相似。在超微结构水平上，我们使用十二烷基硫酸钠消化的冷冻断裂复制品标记法在小鼠中检测了两类突触群体：（i）CA1锥体细胞的棘突上；（ii）CA1中间神经元随机发现的树突干上。虽然1个月和6个月大的APP/PS1小鼠没有表现出变化，但与野生型相比，我们观察到12个月大的APP/PS1小鼠锥体细胞和中间神经元突触处的AMPAR密度显著降低。树突棘中AMPARs的这种减少伴随着细胞内区室中鉴定出的AMPAR亚基蛋白的显著增加。我们的数据表明APP/PS1小鼠中突触AMPARs存在年龄依赖性减少，这可能导致AD后期学习和记忆受损。
