Simultaneous single-molecule fluorescence and conductivity studies reveal distinct classes of Abeta species on lipid bilayers.
Simultaneous single-molecule fluorescence and conductivity studies reveal distinct classes of Abeta species on lipid bilayers.
复制标题
同时进行的单分子荧光和电导率研究揭示了脂质双层上不同类别的 Abeta 物种。
DOI：
10.1021/bi901444w
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发表时间：
2010
期刊：
影响因子：
2.9
通讯作者：
Gafni,Ari
中科院分区：
文献类型：
--
作者：
Schauerte,JosephA;Wong,PamelaT;Wisser,KathleenC;Ding,Hao;Steel,DuncanG;Gafni,Ari
阿尔茨海默病(AD)患者脑组织中普遍存在的细胞外老年斑是由Aβ多肽形成的淀粉样蛋白纤维组成的。这些原纤维传统上被认为是神经毒性的特征；然而，最近的许多研究表明，AD的细胞毒性可能与Aβ的低分子寡聚体有关，这种寡聚体与神经细胞膜相关，并可能导致细胞膜通透性和细胞内离子平衡的破坏。导致膜破裂的潜在机制是最近许多研究的主题。在这里，我们报告了单分子光学检测的应用，使用荧光标记的人Αβ40，结合膜电导测量，监测单个寡聚肽结构与模型平面黑色类脂膜(BLM)的相互作用。在定性研究中，我们发现Αβ与膜的结合可以用三种截然不同的行为来描述，这取决于Αβ单体的浓度。对于远低于10 nm的浓度，单体在膜表面形成均匀的结合，没有低聚物形成或膜渗透的证据。在10 nm到几百纳摩尔之间，均匀的单体结合伴随着从二聚体到小寡聚体的各种多肽的存在。未发现二聚体对膜有通透性，但较大的低聚体导致透过性，单个低聚体产生的离子电导为<；10ps/孔。在较高的浓度下，可能超过生理上相关的浓度，发现具有大电导的更大的延伸和动态结构(数百个皮西姆)，这表明细胞膜发生了重大的破坏。
The extracellular senile plaques prevalent in brain tissue in Alzheimer’s disease (AD) are composed of amyloid fibrils formed by the Aβ peptide. These fibrils have been traditionally believed to be featured in neurotoxicity; however, numerous recent studies provide evidence that cytotoxicity in AD may be associated with low-molecular weight oligomers of Aβ that associate with neuronal membranes and may lead to membrane permeabilization and disruption of the ion balance in the cell. The underlying mechanism leading to disruption of the membrane is the subject of many recent studies. Here we report the application of single-molecule optical detection, using fluorescently labeled human Αβ40, combined with membrane conductivity measurements, to monitor the interaction of single-oligomeric peptide structures with model planar black lipid membranes (BLMs). In a qualitative study, we show that the binding of Αβ to the membrane can be described by three distinctly different behaviors, depending on the Αβ monomer concentration. For concentrations much below 10 nM, there is uniform binding of monomers over the surface of the membrane with no evidence of oligomer formation or membrane permeabilization. Between 10 nM and a few hundred nanomolar, the uniform monomer binding is accompanied by the presence of peptide species ranging from dimers to small oligomers. The dimers are not found to permeabilize the membrane, but the larger oligomers lead to permeabilization with individual oligomers producing ion conductances of <10 pS/pore. At higher concentrations, perhaps beyond physiologically relevant concentrations, larger extended and dynamic structures are found with large conductances (hundreds of picosiemens), suggesting a major disruption of the membrane.