Widomska Justyna, Subczynski Witold K, Mainali Laxman, Raguz Marija
Department of Biophysics, Medical University of Lublin, Lublin, Poland.
Department of Biophysics, Medical College of Wisconsin, Milwaukee, USA.
Cell Biochem Biophys. 2017 Dec;75(3-4):387-398. doi: 10.1007/s12013-017-0812-7. Epub 2017 Jun 29.
The most unique biochemical characteristic of the eye lens fiber cell plasma membrane is its extremely high cholesterol content, the need for which is still unclear. It is evident, however, that the disturbance of Chol homeostasis may result in damages associated with cataracts. Electron paramagnetic resonance methods allow discrimination of two types of lipid domains in model membranes overloaded with Chol, namely, phospholipid-cholesterol domains and pure Chol bilayer domains. These domains are also detected in human lens lipid membranes prepared from the total lipids extracted from lens cortices and nuclei of donors from different age groups. Independent of the age-related changes in phospholipid composition, the physical properties of phospholipid-Chol domains remain the same for all age groups and are practically identical for cortical and nuclear membranes. The presence of Chol bilayer domains in these membranes provides a buffering capacity for cholesterol concentration in the surrounding phospholipid-Chol domains, keeping it at a constant saturating level and thus keeping the physical properties of the membrane consistent with and independent of changes in phospholipid composition. It seems that the presence of Chol bilayer domains plays an integral role in the regulation of cholesterol-dependent processes in fiber cell plasm membranes and in the maintenance of fiber cell membrane homeostasis.
眼晶状体纤维细胞质膜最独特的生化特性是其极高的胆固醇含量，但其原因尚不清楚。然而，很明显，胆固醇稳态的紊乱可能会导致与白内障相关的损害。电子顺磁共振方法能够区分在胆固醇超载的模型膜中的两种脂质结构域，即磷脂 - 胆固醇结构域和纯胆固醇双层结构域。在从不同年龄组供体的晶状体皮质和核中提取的总脂质制备的人晶状体脂质膜中也检测到了这些结构域。与磷脂组成的年龄相关变化无关，磷脂 - 胆固醇结构域的物理性质在所有年龄组中保持相同，并且在皮质膜和核膜中实际上是相同的。这些膜中胆固醇双层结构域的存在为周围磷脂 - 胆固醇结构域中的胆固醇浓度提供了缓冲能力，使其保持在恒定的饱和水平，从而使膜的物理性质与磷脂组成的变化一致且不受其影响。似乎胆固醇双层结构域的存在在纤维细胞质膜中胆固醇依赖性过程的调节以及纤维细胞膜稳态的维持中起着不可或缺的作用。
