Mechanical properties of the high cholesterol-containing membrane: An AFM study.
Mechanical properties of the high cholesterol-containing membrane: An AFM study.
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DOI：
10.1016/j.bbamem.2021.183625
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发表时间：
2021-08-01
期刊：
影响因子：
--
通讯作者：
Mainali L
中科院分区：
文献类型：
--
作者：
Khadka NK;Timsina R;Rowe E;O'Dell M;Mainali L
胆固醇（Chol）在大多数细胞膜中的含量不超过50 mol%，仅在眼透镜的纤维细胞质膜中，其含量超过50 mol%。在此高浓度下，Chol诱导纯胆固醇双层结构域（CBD）的形成，该结构域与周围的磷脂胆固醇结构域（PCD）共存。在这里，我们应用原子力显微镜研究的机械性能的胆固醇/磷脂酰胆碱膜的胆固醇含量从0增加到75摩尔%，相关的眼睛透镜膜。膜的表面粗糙度随着Chol含量的增加而减小，直到它达到60摩尔%，并且粗糙度随着Chol含量的进一步增加而增加。我们建议，增加粗糙度在较高的胆固醇含量的结果从CBD的形成。力谱上的膜与胆固醇含量为50摩尔%或更少表现出单一的突破事件，而两个不同的穿刺事件，观察到的膜与胆固醇含量大于50摩尔%。我们提出，第一次穿刺力对应于含有共存PCD和CBD的膜。相比之下，第二穿刺力对应于由于共存的CBD和PCD而形成的“CBD水囊”。膜面积压缩模量（KA）随着Chol含量的增加而增加，直到其达到60mol%，并且随着Chol含量的进一步增加，形成CBD，并且KA开始减小。我们的研究结果报告了在与眼睛透镜膜相关的非常高的Chol含量（> 60 mol %）下膜粗糙度的增加和KA的降低。
Cholesterol (Chol) content in most cellular membranes does not exceed 50 mol%, only in the eye lens’s fiber cell plasma membrane, its content surpasses 50 mol%. At this high concentration, Chol induces the formation of pure cholesterol bilayer domains (CBDs), which coexist with the surrounding phospholipid-cholesterol domain (PCD). Here, we applied atomic force microscopy to study the mechanical properties of Chol/phosphatidylcholine membranes where the Chol content was increased from 0 to 75 mol%, relevant to eye lens membranes. The surface roughness of the membrane decreases with an increase of Chol content until it reaches 60 mol%, and roughness increases with a further increment in Chol content. We propose that the increased roughness at higher Chol content results from the formation of CBDs. Force spectroscopy on the membrane with Chol content of 50 mol% or lesser exhibited single breakthrough events, whereas two distinct puncture events were observed for membranes with the Chol content greater than 50 mol%. We propose that the first puncture force corresponds to the membranes containing coexisting PCD and CBDs. In contrast, the second puncture force corresponds to the “CBD water pocket” formed due to coexisting CBDs and PCD. Membrane area compressibility modulus (KA) increases with an increase in Chol content until it reaches 60 mol%, and with further increment in Chol content, CBDs are formed, and KA starts to decrease. Our results report the increase in membrane roughness and decrease KA at very high Chol content (> 60 mol %) relevant to the eye lens membrane.
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