Molecular Genetics of Open Angle Glaucoma

描述(申请人提供)：青光眼是一种异质性眼病，是全世界导致双眼失明的第二大原因。开角型青光眼(OAG)是最常见的一种疾病，由于人口老龄化，在美国的患病率正在上升。Myocin是第一个与遗传性OAG明确相关的基因，但Myocin杂合突变导致显性青光眼表型的机制(S)尚不清楚。在上一次资助期间完成的工作中，我们发现突变的myocin蛋白错误折叠，并在细胞的内质网(ER)内聚集。突变的myoclin长时间表达可导致培养的人眼小梁细胞死亡。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，增加突变蛋白质的分泌，并改善其对HTM细胞的有害影响。对各种突变型myocilins的测试表明，温度敏感的分泌物是一种普遍特性，并且特定突变型myocilins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。我们的发现表明，肌球蛋白相关的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，错误折叠的、不分泌的肌球蛋白的慢性表达会导致长时间的内质网应激、HTM细胞功能障碍和死亡，最终导致主导的青光眼表型。我们现在试图确定影响HTM细胞对突变的myocin表达的敏感性的因素。我们将利用myocin突变体、HTM细胞系和培养温度条件之间的差异来确定突变体myoclin在细胞中表达的关键应激诱导后果。这些途径的知识将被用来测试关于可能保护HTM细胞免受突变的myoclin有害影响的操纵的明确假设。该项目的成功将指明治疗霉菌素相关青光眼的要点，并可能揭示HTM细胞生理学的一些方面，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.