FUNCTIONAL ORGANIZATION OF MEMBRANE DOMAINS IN THE LENS

晶状体纤维细胞是体内最长的上皮细胞。尽管纤维细胞的长度很长，但在离散的基膜、侧膜和顶膜区，纤维细胞维持膜蛋白的极化分布。这些结构域的独特组成是在发育早期建立的，并积极保持，即使在伴随纤维细胞分化的快速细胞伸长期间也是如此。这一建议利用一种综合的方法来研究活的晶状体中的膜动力学。最初的研究将集中在晶状体不同区域的膜合成控制和细胞膜囊泡在细胞内的运输机制。开发了一种简单、一步法纯化基膜结构域成分的技术。使用这种方法，将识别基膜结构域的成分。基膜结构域上的膜和细胞骨架元件的排列表明了在调节和/或迁移中的新作用。实验将测试基膜结构域在这些功能中的作用。晶状体侧膜的一个显著特征是存在异常丰富的缝隙连接。提出了检测晶状体缝隙连接斑块的形成和稳定性的实验。此外，在中心纤维细胞中发现了一条新的扩散途径，并将对这一途径进行表征。当纤维细胞到达缝合线时，侧膜底物的酪氨酸磷酸化就会发生。将鉴定被磷酸化的蛋白质，并确定触发膜磷酸化的发育线索。这些研究将提供有关晶状体内膜动力学的重要数据。这些研究特别及时，因为最近发现晶状体膜缺陷(遗传和生化)是人类多种类型白内障的基础。

Lens fiber cells are the longest epithelial cells in the body. Despite their length, fiber cells maintain a polarized distribution of membrane proteins in discrete basal, lateral and apical membrane domains. The unique composition of these domains is established early in development and actively maintained, even during the rapid cellular elongation that accompanies fiber cell differentiation. This proposal utilizes an integrated approach to study membrane dynamics in the living lens. Initial studies will focus on the control of membrane synthesis in various regions of the lens and mechanisms underlying intracellular transport of membrane vesicles. A simple, one-step, technique for purifying components of the basal membrane domain has been developed. Using this method, components of the basal membrane domain will be identified. The arrangement of membrane and cytoskeletal elements at the basal membrane domain suggests a novel role in accommodation and/or migration. Experiments will test the role of the basal membrane domain in these functions. A striking feature of the lateral membranes in the lens is the presence of an extraordinary abundance of gap junctions. Experiments are proposed that examine the formation and stability of lens gap junction plaques. In addition a novel diffusion pathway has been identified in central fiber cells and this pathway will be characterized. Tyrosine phosphorylation of lateral membrane substrates occurs when fiber cells reach the sutures. The phosphorylated proteins will be identified and the developmental cues that trigger membrane phosphorylation will be determined. These studies will provide important data on membrane dynamics in the lens. These studies are particularly timely because lens membrane defects (both genetic and biochemical) have recently been shown to underlie many types of cataract in humans.