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。尽管纤维细胞很长，但它们的膜蛋白在离散的基膜、侧膜和顶膜结构域中保持极化分布。这些结构域的独特组成是在发育早期建立并积极维持的，即使在伴随纤维细胞分化的快速细胞伸长期间也是如此。本方案采用一种综合的方法来研究活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膜囊胞内运输的机制。开发了一种简单的一步纯化基膜结构域组分的技术。使用这种方法，基底膜结构域的成分将被识别。膜和细胞骨架元件在基膜结构域的排列表明在调节和/或迁移中起着新的作用。实验将测试基底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间隙连接。提出了检测晶状体间隙连接斑块形成和稳定性的实验。此外，在中央纤维细胞中发现了一种新的扩散途径，并将对其进行表征。当纤维细胞到达缝合线时，侧膜底物发生酪氨酸磷酸化。磷酸化蛋白将被鉴定，并确定触发膜磷酸化的发育线索。这些研究将为晶状体膜动力学提供重要的数据。这些研究是非常及时的，因为晶状体膜缺陷（遗传的和生物化学的）最近被证明是人类许多类型白内障的基础。

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.