Medin Oligomer Membrane Pore Formation: A Potential Mechanism of Vascular Dysfunction.
Medin Oligomer Membrane Pore Formation: A Potential Mechanism of Vascular Dysfunction.
复制标题
Medin 寡聚物膜孔形成：血管功能障碍的潜在机制。
DOI：
10.1016/j.bpj.2020.04.026
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发表时间：
2020
影响因子：
3.4
通讯作者：
Arce,FernandoT
中科院分区：
文献类型：
--
作者：
Younger,Scott;Jang,Hyunbum;Davies,HannahA;Niemiec,MartinJ;Garcia,JoeGN;Nussinov,Ruth;Migrino,RaymondQ;Madine,Jillian;Arce,FernandoT
Medin是一种由50个氨基酸组成的乳脂球-EGF因子8蛋白的裂解产物，是在50岁以上的人的血管系统中发现的最常见的局限性淀粉样蛋白之一。梅丁可导致内皮功能障碍和血管炎症，然而，尽管它在人的大动脉和多个动脉床中流行，但人们对其病理本质知之甚少。Medin寡聚体与主动脉瘤、主动脉夹层以及最近的血管性痴呆的病理有关。最近的体外生物力学测量发现，主动脉壁完整性改变的动脉瘤患者寡聚体水平增加。我们的结果提示低聚物介导的毒性机制在Medin病理中。利用脂质双层电生理学，我们证明了Medin低聚物通过形成孔来诱导离子膜通透性。主要观察到生长阶段的预聚集Medin物种的孔隙活动，而很少观察到滞后阶段的物种。原子力显微镜(AFM)对不同聚集阶段的Medin聚集体的成像显示，逐渐形成的扁平结构域类似于支撑的脂质双层的形态。透射电子显微镜图像显示，与AFM数据基本一致的致密低聚物和较大的原纤维结构共存。圆二色谱揭示了大部分无序物种的存在，并暗示了β-Sheet的存在。这一观察结果以及与淀粉样蛋白-β纤维相比，Medin聚集体发出的硫代黄素T荧光显著降低，同时在原子力显微镜和透射电子显微镜图像中没有淀粉样纤维，表明Medin聚集到毛孔中遵循非淀粉样蛋白生成途径。在分子动力学的计算机模拟中，模拟提供了Medin孔的原子级结构细节，其中CNpNC桶拓扑和直径与根据实验孔电导估计的值相当。
Medin, a 50-amino-acid cleavage product of the milk fat globule-EGF factor 8 protein, is one of the most common forms of localized amyloid found in the vasculature of individuals older than 50 years. Medin induces endothelial dysfunction and vascular inflammation, yet despite its prevalence in the human aorta and multiple arterial beds, little is known about the nature of its pathology. Medin oligomers have been implicated in the pathology of aortic aneurysm, aortic dissection, and more recently, vascular dementia. Recent in vitro biomechanical measurements found increased oligomer levels in aneurysm patients with altered aortic wall integrity. Our results suggest an oligomer-mediated toxicity mechanism for medin pathology. Using lipid bilayer electrophysiology, we show that medin oligomers induce ionic membrane permeability by pore formation. Pore activity was primarily observed for preaggregated medin species from the growth-phase and rarely for lag-phase species. Atomic force microscopy (AFM) imaging of medin aggregates at different stages of aggregation revealed the gradual formation of flat domains resembling the morphology of supported lipid bilayers. Transmission electron microscopy images showed the coexistence of compact oligomers, largely consistent with the AFM data, and larger protofibrillar structures. Circular dichroism spectroscopy revealed the presence of largely disordered species and suggested the presence ofβ-sheets. This observation and the significantly lower thioflavin T fluorescence emitted by medin aggregates compared to amyloid-βfibrils, along with the absence of amyloid fibers in the AFM and transmission electron microscopy images, suggest that medin aggregation into pores follows a nonamyloidogenic pathway. In silico modeling by molecular dynamics simulations provides atomic-level structural detail of medin pores with the CNpNC barrel topology and diameters comparable to values estimated from experimental pore conductances.