Molecular Genetics of Open Angle Glaucoma

描述（由申请人提供）：青光眼是一种异质性眼病，是全球双侧失明的第二大原因。由于人口老龄化，开角型青光眼（OAG）是最常见的青光眼，在美国的患病率正在上升。心肌蛋白是第一个确定与遗传性OAG相关的基因，但杂合心肌蛋白突变导致显性青光眼表型的机制尚不清楚。在上一个资助期内完成的工作中，我们发现突变心肌蛋白错误折叠并在细胞内质网（ER）内聚集。长时间表达突变心肌可导致培养的人小梁网细胞死亡。在较低的温度下培养细胞，这种条件可以促进蛋白质折叠，增加突变蛋白的分泌，并改善其对HTM细胞的有害影响。对多种突变型心肌蛋白的检测表明，温敏分泌是一种普遍特性，特定突变型心肌蛋白的生化特性与其相关青光眼表型的严重程度之间存在相关性。我们的研究结果表明，肌素相关性青光眼是一种蛋白质构象疾病，并提示了一系列事件的进展，在这些事件中，错误折叠、非分泌肌素的慢性表达导致内质网应激延长、HTM细胞功能障碍和死亡，并最终成为显性青光眼表型。我们现在试图确定影响HTM细胞对突变心肌蛋白表达易感性的因素。我们将利用心肌蛋白突变体、热媒细胞系和培养温度条件之间的差异来确定细胞中心肌蛋白突变表达的关键应激诱导后果。这些途径的知识将用于测试关于可能保护HTM细胞免受突变心肌蛋白有害影响的操作的定义假设。该项目的成功将为心肌素相关性青光眼的治疗干预指明方向，并可能揭示HTM细胞生理学的各个方面，这些方面与这种致盲的神经退行性疾病的更广泛范围有关。

DESCRIPTION (provided by applicant): Glaucoma is a heterogeneous eye disease that is the second leading cause of bilateral blindness worldwide. The prevalence of open angle glaucoma (OAG), the most common form of the disease, is increasing in the United States because of an aging population. Myocilin is the first gene to be conclusively associated with inherited OAG, but the mechanism(s) by which heterozygous myocilin mutations cause a dominant glaucoma phenotype is not known. In work accomplished during the last funding period, we found that mutant myocilin proteins are misfolded and accumulate as aggregates within the endoplasmic reticulum (ER) of cells. Prolonged expression of mutant myocilin resulted in death of cultured human trabecular meshwork (HTM) cells. Culturing cells at a lower temperature, a condition known to promote protein folding, increased secretion of the mutant protein and ameliorated its deleterious effects on HTM cells. Testing of a variety of mutant myocilins showed that temperature sensitive secretion is a general property and that there is a correlation between the biochemical properties of particular mutant myocilins and the severity of their associated glaucoma phenotypes. Our findings indicate that myocilin-associated glaucoma is a protein conformational disease, and suggest a progression of events in which chronic expression of misfolded, non- secreted myocilin leads to prolonged ER-stress, HTM cell dysfunction and death, and, ultimately, a dominant glaucoma phenotype. We now seek to identify the factors that influence HTM cell susceptibility to mutant myocilin expression. We will exploit differences among myocilin mutants, HTM cell lines, and culture temperature conditions to identify critical stress-induced consequences of mutant myocilin expression in cells. Knowledge of these pathways will be used to test defined hypotheses regarding manipulations that may protect HTM cells from the deleterious effects of mutant myocilin. Success of this project will indicate points for therapeutic intervention for myocilin-associated glaucoma, and may uncover aspects of HTM cell physiology that are relevant to a wider spectrum of this blinding, neurodegenerative disease.