Cholesterol Crystalline Domain Function in Eye Lens: EPR Spin-Labeling Studies

摘要 人眼透镜的纤维细胞膜被胆固醇饱和（显示胆固醇对 磷脂摩尔比从皮质中的1到核中高达4），这导致形成 这些膜内的不混溶胆固醇结晶域（CCD）。在胆固醇含量最高的时候， 高达50%的细胞膜表面可以被CCD占据。这些条件存在于透镜核中， 其中胆固醇含量可显著超过膜的溶解度阈值。的 CCD的出现通常是病理学的标志;然而，只有在眼睛的透镜中，CCD才能起到积极的作用。 生理功能，保持透镜透明度，并可能防止白内障 阵 这项建议的长期目标是更好地了解胆固醇的功能， 纤维细胞膜在短期内，我们将（i）研究高胆固醇含量如何影响横向 磷脂透镜膜的组织，特别注意CCD的形成，和（ii）测试 假设CCD的存在决定了周围大量磷脂的性质- 胆固醇膜。(iii)另外，实验将揭示透镜的磷脂成分是否 膜影响CCD的形成、尺寸和稳定性。(iv)最后，开发的方法和 在模型膜系统中进行测试，将应用于检测和表征共存的胆固醇结晶 成熟、老化和白内障过程中透镜纤维细胞膜中的大量磷脂-胆固醇结构域 阵对于从眼透镜分离的膜中共存域的研究，以及在眼晶状体模型中共存域的研究， 纤维细胞膜，将使用氧转运（DOT）方法的区别。DOT方法， 该方法基于电子顺磁共振（EPR）自旋标记技术， 不同的膜域，并提供有关结构和分子动力学的信息， 在共存域中的膜深度，而不需要它们的分离。它还允许信息 关于氧在膜域内和跨膜域的运输。

ABSTRACT Fiber-cell membranes of the human eye lens are saturated with cholesterol (showing cholesterol-to- phospholipid mole ratios from 1 in the cortex to as high as 4 in the nucleus), which leads to the formation of immiscible cholesterol crystalline domains (CCDs) within these membranes. At the highest cholesterol content, up to 50% of the cell-membrane surface can be occupied by CCDs. These conditions exist in the lens nucleus, where the cholesterol content can significantly exceed the solubility threshold of the membrane. The appearance of CCDs is usually a sign of pathology; however, only in the eye lens can CCDs play a positive physiological function, maintaining lens transparency and possibly protecting against cataract formation. The long-term objective of this proposal is to achieve a greater understanding of cholesterol's function in fiber-cell membranes. In the short-term, we will (i) examine how high cholesterol content affects the lateral organization of phospholipid lens membranes, with special attention paid to the formation of CCDs, and (ii) test the hypothesis that the presence of CCDs determines the properties of the surrounding bulk phospholipid- cholesterol membranes. (iii) Additionally, experiments will reveal if the phospholipid composition of the lens membrane affects the formation, size, and stability of CCDs. (iv) Finally, the methodology developed and tested in model-membrane systems will be applied to detect and characterize coexisting cholesterol crystalline and bulk phospholipid-cholesterol domains in lens fiber-cell membranes during maturation, aging, and cataract formation. For studies of coexisting domains in membranes isolated from the eye lens, as well as in models of fiber-cell membranes, the discrimination by oxygen transport (DOT) method will be used. The DOT method, which is based on electron paramagnetic resonance (EPR) spin-labeling techniques, permits discrimination of different membrane domains and gives information about structure and molecular dynamics as a function of the membrane depth in coexisting domains without the need for their separation. It also allows information about oxygen transport within and across membrane domains to be obtained.