The effect of GBA1 L444P heterozygous mutation on synaptic morphology in the hippocampus and cognition related to Lewy body dementias

项目摘要/摘要： 近80%的帕金森氏症(PD)患者会患上痴呆症。帕金森病的病理特征是 错误折叠的α-Synn的不溶性聚集体积累，称为路易小体和路易突起。最常见的 帕金森病的遗传危险因素是编码溶酶体酶的GBA1基因的突变 葡萄糖脑苷酶(GCase)。具有GBA1突变(GBA1-PD)的帕金森病患者患痴呆症的风险增加 和丰富的路易氏病理。模型系统显示突变的GCase的表达增加了 病理性α-SYN。这些数据表明突变的GCase、α-SYN包涵体的形成和 认知缺陷。严重GBA1 L444P突变(GBA+/L444P)杂合子的PD患者具有 患痴呆症的风险最高(与非GBA突变携带者相比是5.6倍)。生产的GCase 来自GBA1的L444P没有正确折叠或从内质网运输到溶酶体，并且数据 提示溶酶体功能受损导致α-SYN积聚，形成病理性包涵体。 突变型GBA1引起的溶酶体活性异常也可能影响突触结构。溶酶体酶， 组织蛋白酶B(CatB)与GBA1-PD有遗传关系。GBA+/L444P小鼠脑组织中CatB水平降低 老鼠。CatB对α-SYN的切割损伤可能导致α-SYN的蓄积。因此，这一计划的总体目标是 该项目旨在评估突触退行性变并确定CatB活动背后的机制作用 增强GbA1+/L444P小鼠海马区α-SYN聚集和突触变化。我们有 发现GbA1+/L444P小鼠仅在海马区表现出明显增加的α-SYN包涵体形成。 我的实验室发现，在原代海马神经元和野生型小鼠体内，α-SYN包涵体的早期形成 导致兴奋性突触的严重缺失。我认为，海马区α-SYN包裹体的形成导致 突触结构的主要变化，GBA1+/L444P的表达增强。我的中心假设是 GbA1+/L444P导致的CatB表达和活性降低增加α-SYN的形成 包涵体，导致突触变性和认知障碍。我将通过确定以下内容来检验这一假设 如果GbA1+/L444P突变加剧突触变性并导致α-突触核蛋白引起的认知功能障碍 海马体中的包裹体。我还将确定GBA+/L444P海马区CatB活性是否降低 小鼠增强α-SYN聚集。了解这些机制将导致旨在调节 帕金森病和其他联核病的酶活性。通过这项拟议的工作，我将继续学习 有价值的技术，如用于分析突触结构细节的扩张显微镜，以及AAV的使用 病毒增加GCase和CatB的水平，这将使我们更好地了解分子机制 这导致了警局。我还将与GBA1突变和神经变性方面的专家合作。

Project Summary/Abstract: Nearly 80% of Parkinson’s disease (PD) patients develop dementia. PD is pathologically characterized by the accumulation of insoluble aggregates of misfolded α-syn called Lewy bodies and Lewy neurites. The most common genetic risk factor of PD is mutations in the GBA1 gene, which encodes for the lysosomal enzyme glucocerebrosidase (GCase). PD patients with GBA1 mutations (GBA1-PD) show increased risk of dementia and abundant Lewy pathology. Model systems show that expression of mutant GCase increases formation of pathologic α-syn. These data suggest an interaction among mutant GCase, α-syn inclusion formation, and cognitive deficits. PD patients heterozygous for the severe GBA1 L444P mutation (GBA+/L444P) have one of the highest risks of developing dementia (5.6-fold compared to noncarrier of the GBA mutation). GCase produced from GBA1 L444P is not properly folded or trafficked from the endoplasmic reticulum to lysosomes, and data suggest that impaired lysosome function leads to an accumulation of α-syn, which forms pathologic inclusions. Abnormal lysosome activity caused by mutant GBA1 may also impact synaptic structure. The lysosomal enzyme, Cathepsin B (CatB) has been genetically linked to GBA1-PD. Levels of CatB are reduced in the brains of GBA+/L444P mice. Impaired cleavage of α-syn by CatB may lead to an accumulation of α-syn. Thus, the overall goal of this project is to evaluate synaptic degeneration and identify the mechanistic role of CatB activity behind enhanced α-syn aggregation and synaptic changes in the hippocampus of GBA1+/L444P mice. We have found that GBA1+/L444P mice show significantly increased formation of α-syn inclusions, only in the hippocampus. My lab found that early formation of α-syn inclusions in primary hippocampal neurons and in wildtype mice leads to a major loss of excitatory synapses. I propose that α-syn inclusions formation in the hippocampus causes major changes in synaptic structure, enhanced by expression of GBA1+/L444P. My central hypothesis is that decreased CatB expression and activity caused by GBA1+/L444P expression increases the formation of α-syn inclusions, which leads to synaptic degeneration and cognitive impairments. I will test this hypothesis by determining if the GBA1+/L444P mutation enhances synaptic degeneration and leads to cognitive deficits caused by α-synuclein inclusions in the hippocampus. I will also determine if reduced activity of CatB in the hippocampus of GBA+/L444P mice enhances α-syn aggregation. Understanding these mechanisms will lead to therapies designed to modulate enzymatic activity in PD and other synucleinopathies. Through this proposed work, I will continue to learn valuable techniques, such as expansion microscopy to analyze details of synaptic structure, and the use of AAV viruses to increase levels of GCase and CatB, which will allow us to better understand molecular mechanisms that lead to PD. I will also collaborate with experts in GBA1 mutations and neurodegeneration.