Proteinase Inhbitors & Crystallin Fragments in Cataract

描述：在老化过程中，由于聚集和/或交联，越来越多的晶状体总蛋白变成不溶于水的(WL)。这些物种进一步交联成共价多聚体被认为在年龄相关(老年性)白内障的发展过程中导致混浊。文献中描述了多种晶状体蛋白的翻译后修饰作为导致交联机制的因素，但它们的相关作用尚不清楚。由于老年性白内障的发展是一个缓慢的过程，有时需要数年时间，因此很少有特定的修饰可能会作为触发因素加速交叉连接机制，并导致晶状体混浊。结果表明，修饰后的晶状体蛋白片段在晶状体蛋白的交联过程中起到了积极的作用。要了解晶体蛋白片段的这种作用，必须确定它们的来源、翻译后修饰和交联机制，以便将它们作为致病因素。根据我们的结果，我们推测Ba3/A1-晶状体蛋白含有蛋白酶活性，但由于该酶的活性需要被激活，所以该活性在体内是受调节的，并且该活性酶被α-晶状体蛋白抑制。Ba3/A1-晶状体蛋白水解酶降解a-、b-和g-晶状体蛋白，晶状体蛋白片段经过翻译后修饰，导致它们本身以及与phakinin和细丝蛋白(晶状体珠状细丝蛋白)形成共价多聚体。这些共价多聚体会导致晶状体混浊。为了验证上述假设，拟议的研究将集中回答以下三个主要问题：(A)Ba3/A1-晶体蛋白的Arg-键水解酶活性激活的分子机制是什么？(B)bA3/A1-晶体蛋白水解酶活性在体内是如何调节的？(C)翻译后修饰的晶体蛋白片段本身以及与phakinin和细丝蛋白的共价交联机制是什么？上述研究将提供一个核心问题的答案，即在年龄相关性白内障发展过程中混浊是如何发展的。由于这些研究将使用人类的晶状体，这些发现将有助于阐明bA3/A1-晶体蛋白水解酶在晶体蛋白的蛋白分解中的作用，它们在体内的调节，特别是晶体蛋白片段本身以及与phakinin和细丝蛋白的交联机制。

DESCRIPTION: During aging, an increasing proportion of total lens proteins becomes water insoluble (Wl), either due to aggregation and/or cross-linking. A further cross-linking of these species into covalent multimers is believed to cause opacity during age-related (senile) cataract development. A variety of post-translational modifications of crystallins are described in the literature as causative factors for cross-linking mechanism, but their relative roles remain unclear. Because the senile cataract development is a slow process and sometimes takes years, few specific modifications might act as triggers to accelerate the cross-linking mechanism and cause lens opacity. Our results show that modified crystallin fragments play an active role in the crystallin cross-linking process. To understand such a role of crystallin fragments, one must determine their origin, post-translational modifications and cross-linking mechanism in order to implicate them as a causative factor. Based on our results, we have hypothesized that bA3/A1 -crystallin contains proteinase activity, but the activity is regulated in vivo because the enzyme activity needed activation, and the active enzyme is inhibited by a-crystallin. The bA3/A1-crystallin proteinase proteolyses a-, b- and g-crystallins, and the crystallin fragments undergo post-translational modifications, leading to their cross-linking per se and with phakinin and filensin (lens beaded filament proteins) to form covalent multimers. These covalent multimers cause lens opacity. To test the above hypothesis, the proposed studies will be focused to answer the following three major questions: (A) What is the molecular mechanism of activation of an Arg-bond hydrolyzing proteinase activity of bA3/ A1-crystallin? (B) How is the b A3/A1-crystaltin proteinase activity regulated in vivo? (C) What is the covalent crosslinking mechanism of post-translationally modified crystallin fragments per se and with phakinin and filensin? The above studies will provide an answer to the central question of how opacity develops during age-related cataract development. Because human lenses will be used in these studies, the findings will be relevant in elucidating the role of b A3/A1-crystallin proteinase in the proteolysis of crystallins, their regulation in vivo, and in particular the mechanism of cross-linking of crystallin fragments per se and with phakinin and filensin.