Trace element dynamics in the vertebrate eye

白内障是一个全球性的重大健康和经济问题。氧化损伤被认为是白内障形成的一个致病因素，铁催化的自由基反应几乎是所有氧化组织损伤的原因。除了催化氧化损伤和作为关键酶的重要组成部分外，铁在细胞生理中的新作用正在出现。例如，我们观察到铁调节了包括晶状体在内的许多细胞类型的谷氨酸的产生。此外，其他研究表明，铁通过控制关键铁调节蛋白的转录，调节转录因子缺氧诱导因子（hif - 1a）的可用性，对铁代谢有重要影响。所有细胞都小心地控制铁的摄取、利用和储存。大多数细胞内的铁被安全地储存在铁蛋白中或并入铁依赖性酶中。然而，细胞中存在一种可螯合的铁池，称为不稳定铁池（LIP）。LIP可能是细胞中铁代谢的关键调节因子，我们的实验旨在确定它是如何被调节的及其在晶状体中的作用。因此，我们假设细胞铁代谢和储存的改变导致LIP大小的显著变化，并伴随谷氨酸和谷胱甘肽的产生和分泌以及HIF-1活性的生理变化。以下具体目标将得到解决：SA #1。假设：不同年龄的晶状体上皮细胞中铁蛋白H:L链组成的年龄相关改变，以及纤维中铁蛋白结构的改变对铁蛋白功能有深远的影响。这些包括铁蛋白隔离铁的能力，以及铁从这些修饰的铁蛋白分子中长期储存和释放的能力。SA # 2。假设：细胞内铁分布的改变显著影响谷氨酸的合成和分泌，导致胱氨酸摄取和谷胱甘肽合成的改变。SA # 3。假设：谷氨酸囊泡、谷氨酸/胱氨酸反转运蛋白和铁转运蛋白在晶状体内具有特异性定位，这与其功能有关。SA # 4。假设：氧水平和细胞内铁分布的变化改变了转录调节因子HIF-1的活性。SA # 5。假设：HIF-1活性的改变改变了铁代谢，并对谷氨酸和谷胱甘肽的产生产生下游影响。

DESCRIPTION: Cataract is a significant health and economic problem worldwide. Oxidative damage has been implicated as a causative factor in cataract formation and iron-catalyzed free radical reactions are responsible for virtually all oxidative tissue damage. In addition to catalyzing oxidative damage and serving as an essential component of key enzymes, new roles for iron in cellular physiology are emerging. For example, we have made the novel observation that iron regulates glutamate production in a number of cell types, including the lens. Furthermore, others have shown that iron regulates the availability of the transcription factor, hypoxia inducible factor (HIF-1 a) which exerts significant effects on iron metabolism by controlling transcription of key iron regulatory proteins. All cells carefully control iron uptake, utilization and storage. Most intracellular iron is safely stored in ferritin or incorporated into iron-dependent enzymes. However, there is a pool of iron in cells that is chelatable and is called the labile iron pool (LIP). The LIP may be the key regulator of iron metabolism in cells and our experiments are designed to determine how it is regulated and its role in the lens. Therefore we have hypothesized that alterations in cellular iron metabolism and storage result in significant changes in the size of the LIP with concomitant physiological changes including glutamate and glutathione production and secretion as well as the activity of HIF-1. The following specific aims will be addressed: SA #1. Hypothesis: Age-related alterations in ferritin H:L chain makeup, as seen in lens epithelial cells of varying age, and modification of ferritin structure as found in ferritin from fiber have profound effects on ferritin function. These include the ability of ferritin to sequester iron as well as long term storage and release of iron from these modified ferritin molecules. SA #2. Hypothesis: Changes in intracellular iron distribution significantly impact glutamate synthesis and secretion resulting in alterations in cystine uptake and glutathione synthesis. SA #3. Hypothesis: Glutamate vesicles, glutamate/cystine antiporter and ferroportin have specific localization within the lens which is related to their function. SA #4. Hypothesis: Changes in oxygen levels and intracellular iron distribution alter the activity of the transcriptional regulator HIF-1. SA #5. Hypothesis: Alterations in the activity of HIF-1 modify iron metabolism with downstream effects on glutamate and glutathione production.