Department of Biochemistry and Molecular Biology, Dalhousie University, Halifax, Nova Scotia B3H 1X5, Canada.
J Neurochem. 2010 Jul;114(1):311-22. doi: 10.1111/j.1471-4159.2010.06768.x. Epub 2010 Apr 23.
Imbalances in brain cholesterol homeostasis have been observed in several neurodegenerative diseases. In Niemann-Pick Type C (NPC) disease, mutations in NPC1 or NPC2 lead to endosomal cholesterol accumulation, neuronal dysfunction and death. Cholesterol in synaptic plasma membranes influences membrane fluidity, curvature, and protein function, and its depletion may adversely affect synaptic vesicle cycling. We have investigated pre-synaptic function in primary hippocampal neurons with altered cholesterol distribution because of NPC1 deficiency or cyclodextrin treatment. In NPC1-deficient neurons grown in serum-free medium, plasma membrane cholesterol was reduced and total synaptic vesicle release during prolonged stimulation was attenuated. In NPC1-deficient neurons cultured in the presence of high-density lipoproteins, plasma membrane cholesterol markedly increased, but the defects in synaptic vesicle release in NPC1-deficient neurons were exacerbated. Treatment with 1 mM methyl-beta-cyclodextrin acutely depleted plasma membrane cholesterol in wild-type neurons to levels below those in NPC1 deficiency, but did not alter synaptic vesicle exo- or endocytosis. Defects only became apparent when higher methyl-beta-cyclodextrin concentrations were used. Our data indicate that synaptic vesicle release can tolerate some degree of plasma membrane cholesterol depletion and suggest that the pre-synaptic defects in NPC1-deficient neurons are not solely caused by a reduction of plasma membrane cholesterol.
脑胆固醇动态平衡失衡在几种神经退行性疾病中都有观察到。在尼曼-匹克 C 型（NPC）疾病中，NPC1 或 NPC2 的突变导致内体胆固醇积累、神经元功能障碍和死亡。突触质膜中的胆固醇会影响膜流动性、曲率和蛋白质功能，其耗竭可能会对突触小泡循环产生不利影响。我们研究了由于 NPC1 缺乏或环糊精处理而改变胆固醇分布的原代海马神经元的前突触功能。在无血清培养基中培养的 NPC1 缺乏神经元中，质膜胆固醇减少，长时间刺激期间的总突触小泡释放减弱。在存在高密度脂蛋白的 NPC1 缺乏神经元中培养时，质膜胆固醇明显增加，但 NPC1 缺乏神经元中突触小泡释放的缺陷加剧。用 1mM 甲基-β-环糊精处理野生型神经元会使质膜胆固醇急性耗竭至低于 NPC1 缺乏的水平，但不会改变突触小泡外排或内吞作用。只有当使用更高浓度的甲基-β-环糊精时，缺陷才会变得明显。我们的数据表明，突触小泡释放可以耐受一定程度的质膜胆固醇耗竭，并表明 NPC1 缺乏神经元的前突触缺陷不仅仅是由质膜胆固醇减少引起的。
