Modifications of Small Heat Shock Proteins in the Lens

晶体α蛋白和热休克蛋白27 （Hsp27）是在晶状体中发现的两种小的热休克蛋白（Hsps），被认为可以保护晶状体蛋白免受氧化和紫外线等应激。除了作为伴侣蛋白外，它们还是多功能的抗凋亡蛋白。在晶状体中，甲基乙二醛（MGO）作为糖酵解过程中的代谢副产物产生，其浓度比血浆中至少高20倍。糖尿病患者的晶状体MGO浓度远高于非糖尿病患者的晶状体。氧化石墨烯很容易与蛋白质中的赖氨酸、精氨酸和半胱氨酸残基反应，形成稳定的加合物，其中一些已在人类晶体中被鉴定出来。我们最近对MGO修饰的研究提供了令人惊讶的结果，MGO修饰增强了sHsps的伴侣功能。我们最近的研究表明，白内障晶状体含有高水平的磷酸化Hsp27 (pHsp27)，而pHsp27极易被MGO修饰。我们还发现mgo修饰的α -晶体蛋白是一种比天然未修饰的蛋白更好的抗凋亡蛋白。这些有趣的观察结果促使我们进一步研究mgo诱导的sHsps结构改变，并确定这种改变如何改变其功能。我们有四个目标。在目标1中，我们将详细研究由于sHsps暴露于MGO而导致的结构变化。我们将重点关注精氨酸残基，因为它们最容易被MGO修饰。在目的2中，我们将确定mgo诱导的修饰如何改变sHsps的抗凋亡功能。在目标3中，我们将研究mgo诱导的修饰对sHsps与其他晶状体蛋白相互作用的影响。最后，在目的4中，我们将确定mgo修饰sHsps是否会影响它们在细胞应激增加时进入细胞核的运输。这些研究将提高我们对sHsps与代谢途径之间相互作用的理解，并将帮助我们确定sHsps在晶状体上皮细胞凋亡中的作用以及对白内障形成的影响。

Alpha-crystallin and heat shock protein-27 (Hsp27), the two small heat shock proteins (Hsps) found in the lens are thought to protect lens proteins from the stress, such as, oxidation and ultra violet light. In addition to functioning as chaperone proteins, they are versatile anti-apoptotic proteins. In the lens methylglyoxal (MGO) is produced as a metabolic by-product during glycolysis and its concentration is at least 20 times higher than in plasma. Lenses from diabetics have far greater MGO concentrations than lenses from nondiabetic individuals. MGO readily reacts with lysine, arginine and cysteine residues in proteins to form stable adducts, several of which have been identified in the human lens. Our recent studies on MGO modifications provided the surprising results that MGO-modification enhances the chaperone function of sHsps. Our most recent studies demonstrate that cataractous lenses contain high levels of phosphorylated Hsp27 (pHsp27) and pHsp27 is highly susceptible for modification by MGO. We also found MGO-modified alpha-crystallin is a better anti-apoptotic protein than the native unmodified protein. These intriguing observations prompted us to examine further on the MGO-induced structural alterations in sHsps, and to determine how such alterations change their functions. We have four aims. In aim 1, we will examine in detail the structural changes resulting from exposure of sHsps to MGO. We will focus on arginine residues, because these are the most vulnerable to modification by MGO. In aim 2, we will determine how MGO-induced modifications alter the anti-apoptotic functions of sHsps. In aim 3, we will study the impact of MGO-induced modifications on the interaction of sHsps with other lens proteins. Finally, in aim 4, we will determine whether MGO-modification of sHsps influence their transportation into the nucleus during increased cellular stress. These studies will improve our understanding of the interplay between sHsps and metabolic pathways, and they will help us to define the role of sHsps in apoptosis of lens epithelial cells and the implications for cataract formation.