Mechanisms and consequences of impaired glutathione homeostasis in the aging Lens.

透镜谷胱甘肽的年龄相关性下降与人类白内障的形成密切相关 以及谷胱甘肽耗竭的实验小鼠模型，正如我们最近的研究所证实的那样。年龄- 已经记录了透镜谷胱甘肽生物合成酶活性的相关损伤，尽管 这种与年龄有关的变化背后的机制知之甚少。在初步研究中， 范式转换观察表明，透镜谷胱甘肽生物合成的关键酶，γ谷氨酰半胱氨酸 连接酶催化亚基（Gclc）经历翻译后截短，并且这种截短的蛋白质形式 随着年龄的增长，特别是在透镜皮质和核心纤维区域。进一步的研究表明， 截短与caspase-3和6样切割基序的存在有关，其触发C-末端13 kD 截短和积累N-末端60 kD稳定的蛋白形式（本文称为Gclc 60）。后者似乎 参与与细胞骨架蛋白的强相互作用和深刻的细胞质分布 与全长Gclc蛋白相比，我们假设Gclc的截短是一个关键事件， 年龄相关性白内障的发病机制，Gclc 60的形成机制， 其积累的分子生物学后果是设计新型抗白内障药物的重要目标 疗法因此，本申请的三个具体目的是目的1：确定Gclc的机制 截断及其对透镜GSH稳态影响。特别是，我们将测试Gclc 60将 抑制GSH合成，导致GSH含量降低，并将鉴定 负责与年龄相关的分裂。在目标2中，我们将确定对GCLC截短的体内影响， 通过检测抗裂解敲入（KI）小鼠模型的Gclc 60蓄积。特别是我们假设 KI小鼠透镜在老化过程中将显著保持其GSH水平和生物学功能。在AIM 3中，我们将 确定Gclc 60与细胞骨架蛋白相互作用产生的生物学效应，假设 Gclc蓄积导致细胞骨架基质紊乱。 !一个！

The age-related decline of lens glutathione is strongly correlated with cataract formation in the human and in experimental mouse models of glutathione depletion, as recently confirmed in our own studies. The age- related impairment of lens glutathione biosynthesis enzyme activity has been documented, though the mechanisms underlying this age-related change are poorly understood. In preliminary studies we made the paradigm shifting observation that the lens glutathione biosynthesis key enzyme, gamma glutamylcysteine ligase, catalytic subunit (Gclc) is subject to posttranslational truncation, and that this truncated proteoform accumulates with age, particularly in the lens cortical and core fiber region. Further studies revealed that the truncation is linked to the presence of a caspase-3 and 6 like cleavage motif triggering a C-terminal 13kD truncation and accumulation of a N-terminal 60kD stable proteoform (herein named Gclc60). The latter appears to engage in strong interaction with cell cytoskeleton proteins and profound cytoplasmic distribution discrepancies compared to the full length Gclc protein. We hypothesize that truncation of Gclc is a key event in the pathogenesis of age-related cataract, and that understanding the mechanism of formation of Gclc60 and the molecular biological consequences of its accumulation are important goals for the design of novel anti-cataract therapy. Accordingly, the three Specific Aims of this application are Aim 1: to determine the mechanism of Gclc truncation and its impact on lens GSH homeostasis. In particular, we will test the hypothesis that Gclc60 will suppresses GSH synthesis resulting in lowered GSH content and will identify the proteases that are responsible for age-related cleavage. In Aim 2, we will determine the in vivo effects on GCLC truncation and Gclc60 accumulation by testing a cleavage resistant knockin (KI) mouse model. In particular we hypothesize that KI mouse lens will significantly retain its GSH levels and biological functions during aging. In Aim3, we will determine the biological effects resulting from Gclc60 interaction with cytoskeletal proteins, hypothesizing that Gclc accumulation results in cytoskeletal matrix disorganization. ! 1!