Intercellular Communication in the Eye Lens

描述（由申请人提供）：连接蛋白形成的间隙连接细胞间通讯（GJIC）对晶状体的代谢稳态至关重要。除了间隙连接外，连接蛋白还形成半通道，允许分子在细胞内交换。然而，人们对晶状体中半通道的功能和调控知之甚少。此外，晶状体连接蛋白受到翻译后修饰；分化晶状体纤维的磷酸化和成熟晶状体纤维的蛋白水解截断。我们的长期目标是了解连接蛋白分子在晶状体稳态和透明度中的分子机制和功能意义。目的是阐明间隙连接和半通道的独特机制作用，以及连接蛋白（Cx） 50在正常和氧化应激条件下的翻译后修饰作用。主要假设是：(1)GJIC和半通道在晶状体中起着不同的作用；(2) PKA对分化纤维中Cx50的磷酸化增加了GJIC和/或半通道功能，成熟纤维中Cx50截断对间隙连接/半通道的适应性调节增强了晶状体对氧化损伤的抗性。本研究将有三个具体目标：1)确定间隙连接和半通道在分化晶状体纤维中的独特作用。2)确定PKA磷酸化Cx50在晶状体中的功能重要性。3)确定成熟晶状体纤维中发育相关的Cx50截断的机制作用。其中一个创新之处在于，本研究旨在剖析间隙连接和半通道的独特作用，以及翻译后修饰在晶状体纤维分化和成熟中的作用。此外，我们将使用我们新开发的离体方法来解剖Cx50及其截断在晶状体皮层和中央核中的作用。我们期望通过对晶状体连接蛋白及其形成的通道调控的分子机制的阐明，可以更好地理解晶状体在正常和病理条件下的一般稳态过程。我们的研究结果将具有重要意义，因为新发现的知识将为治疗晶状体疾病（如年龄相关性白内障）的新策略做出新的有益贡献，并为药物发现和开发铺平道路。

DESCRIPTION (provided by applicant): Connexin-forming gap junction intercellular communication (GJIC) is essential for the metabolic homeostasis of the lens. In addition to gap junctions, connexins forms hemichannels, permitting exchange of molecules across the cell. However, little is known regarding the function and regulation of hemichannels in the lens. In addition, lens connexin is subjected to posttranslational modifications; phosphorylation in differentiating lens fibers and proteolytic truncation in mature lens fibers. Our long-range goal i to understand the molecular mechanism(s) and functional significance of connexin molecules in lens homeostasis and transparency. The objective is to elucidate the distinctive, mechanistic roles of gap junctions and hemichannels, and role of posttranslational modifications of connexin (Cx) 50 under normal and oxidative stress conditions. The central hypotheses are: (1) GJIC and hemichannels play distinctive roles in the lens; (2) Increased GJIC and/or hemichannel function due to Cx50 phosphorylation by PKA in differentiating fibers and adaptive-regulation of gap junctions/hemichannels due to Cx50 truncation in mature fibers enhance lens resistance to oxidative damages. Three specific aims will be pursued: 1) Determine the distinctive roles of gap junctions and hemichannels in the differentiating lens fibers. 2) Determine the functional importance of PKA phosphorylation of Cx50 in the lens. 3) Determine the mechanistic role of developmentally associated truncation of Cx50 in mature lens fibers. One of the innovative aspects is that this proposal aims to dissect distinctive roles of gap junctions and hemichannels, and posttranslational modifications in differentiating and mature lens fibers. Moreover, we will use our newly developed ex vivo approach to dissect the roles of Cx50 and its truncation in cortex and center core of the lens. It is our expectation that elucidation of the molecular mechanism(s) involved in the regulation of lens connexins and the channels formed by them will provide a better understanding of the general homeostatic process of lens under normal and pathological conditions. The outcomes of our research will be significant because the newly discovered knowledge should make novel and beneficial contributions to new strategies for the treatment of lens disorders, e.g. age-related cataracts, and pave way for drug discovery and development. PUBLIC HEALTH RELEVANCE: Cataracts are one of the most common eye diseases and also one of the leading causes for blindness worldwide. Connexins play important roles in lens homeostasis and mutations in connexin genes lead to human congenital cataracts. The proposed research activity will help in understanding the molecular mechanism underlying the function of connexins under physiological and pathological conditions, and should make novel contributions to new ideas and strategies for drug discovery and development in treatment of cataracts.