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）的患病率在美国正在增加，OAG是该疾病的最常见形式。肌球蛋白是第一个明确与遗传性青光眼相关的基因，但杂合肌球蛋白突变导致显性青光眼表型的机制尚不清楚。在上一个资助期完成的工作中，我们发现突变的myocilin蛋白错误折叠并在细胞的内质网（ER）内聚集。突变型myocilin的长期表达导致培养的人小梁网（HTM）细胞死亡。在较低的温度下培养细胞，已知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。对多种突变型肌球蛋白的测试表明，温度敏感性分泌是一种一般性质，并且在特定突变型肌球蛋白的生化性质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，肌球蛋白相关性青光眼是一种蛋白质构象疾病，并表明其中错误折叠的非分泌型肌球蛋白的慢性表达导致延长的ER-应激、HTM细胞功能障碍和死亡，并最终导致显性青光眼表型的事件进展。我们现在试图确定影响HTM细胞对突变型肌钙蛋白表达敏感性的因素。我们将利用肌钙蛋白突变体，HTM细胞系，和培养温度条件之间的差异，以确定关键的应力诱导的突变肌钙蛋白在细胞中表达的后果。这些途径的知识将被用来测试定义的假设有关的操作，可以保护HTM细胞从突变型肌球蛋白的有害影响。该项目的成功将为肌球蛋白相关青光眼的治疗干预指明方向，并可能揭示与更广泛的致盲性神经退行性疾病相关的HTM细胞生理学方面。

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.