Grp94-selective inhibitors to treat heredity glaucoma

描述(申请人提供)：美国有超过10万人患有由MYOC基因突变引起的原发性开角型青光眼(POAG)。这种形式的POAG是由称为小梁网络(TM)的保护性细胞网络死亡引起的视神经损伤引起的。在这些情况下，TM细胞死亡是因为突变的肌红素异常地积聚成有毒的聚集体。这种机制让人想起阿尔茨海默氏症、亨廷顿氏症和帕金森氏症等神经退行性疾病，这些疾病的异常蛋白质会在神经元中积聚，导致细胞死亡。事实上，TM细胞就像神经元一样寿命很长。此外，导致POAG发病较早的突变也使肌球蛋白更容易聚集，类似于与神经退行性疾病相关的蛋白质。因此，这两种疾病都可以被认为是“蛋白质平衡”紊乱，这意味着长寿命的细胞(神经元和TM)随着年龄的增长逐渐失去阻止突变蛋白有毒积累的能力。因此，旨在恢复TM细胞蛋白平衡的策略可能对青光眼有利，就像它们已被证明对神经退行性疾病一样。通过一系列研究，我们确定了内质网中的Grp94伴侣(一种Hsp90亚型)错误地将突变的myoclin保存在细胞中。重要的是，Grp94只影响错误折叠的肌球蛋白：正确折叠和功能的肌球蛋白不受Grp94操作的影响。Grp94只识别由于突变或糖基化受损而错误折叠的myoclin：但Grp94无法清除这种错误折叠的myoclin，而是保留它，导致其毒性积累。因此，Myocin的错误折叠通过错误地与Grp94伴侣结合来扰乱蛋白平衡。我们已经证明，仅通过抑制Grp94就可以加速有毒霉菌素的清除！我们的团队已经开发出第一个名为BnIm的异构体选择性Grp94抑制剂。由于Grp94依赖底物的列表很少，与其他Hsp90亚型相比，这种Grp94抑制剂的毒性曲线似乎也很低。因此，我们建议通过建立Grp94抑制剂的构效关系来验证和改进该Grp94抑制剂用于治疗霉菌素相关性POAG的有效性，以阐明错误折叠的myoclin分类的机制。我们还将评估Grp94抑制剂对疾病相关系统中突变的myoclin的生物学效果，然后努力开发对错误折叠的myoclin具有更高疗效和生物活性的Grp94抑制剂。这些研究将产生一套新的Grp94调节剂，并证明Grp94是治疗由错误折叠的肌球蛋白引起的青光眼的一个新的临床靶点。此外，本文确定的阐明Grp94如何调节myocin分流的机制可能为其他蛋白沉积性疾病提供新的见解。

DESCRIPTION (provided by applicant): Over 100,000 people in the US suffer from primary open-angle glaucoma (POAG) caused by mutations in the MYOC gene. This form of POAG results from optic nerve damage caused by the death of a protective cell network called the trabecular meshwork (TM). TM cell death occurs in these cases because mutant myocilin abnormally accumulates into toxic aggregates. This mechanism is reminiscent of neurodegenerative diseases, such as Alzheimer's, Huntington's and Parkinson's, where abnormal proteins accumulate in neurons and lead to cell death. In fact, TM cells are long-lived just like neurons. Moreover, mutations that cause earlier POAG onset also make myocilin aggregate more readily, similar to proteins associated with neurodegenerative diseases. Thus, both types of diseases can be considered "proteostasis" disorders, meaning that long-lived cells (neurons and TM) progressively lose their ability to prevent the toxic accumulation of mutant proteins with age. Thus, strategies aimed at restoring proteostasis in TM cells could be beneficial for glaucoma, just as they have proven for neurodegenerative disease. Through a series of studies, we determined that the Grp94 chaperone (an Hsp90 isoform) that resides in the endoplasmic reticulum, mistakenly preserves mutant myocilin in cells. Importantly, Grp94 only affects misfolded myocilin: Properly folded and functioning myocilin is unaffected by Grp94 manipulation. Grp94 recognizes only myocilin that is misfolded due to either mutations or impaired glycosylation: But Grp94 is unable to clear this misfolded myocilin, and instead, preserves it, causing its toxic accumulation. Thus, myocilin misfolding disrupts proteostasis by mistakenly engaging the Grp94 chaperone. We have shown that the clearance of toxic myocilin can be accelerated simply by inhibiting Grp94! Our team has developed the first isoform selective Grp94 inhibitor termed BnIm. Because the list of Grp94-dependent substrates is small, compared to other Hsp90 isoforms, the toxicity profile for this Grp94 inhibitor also appears low. Therefore, we propose to validate and improve upon this Grp94 inhibitor for the treatment of myocilin-associated POAG by establishing structure-activity relationships of Grp94 inhibitors to elucidate mechanisms of misfolded myocilin triage. We will also evaluate the biological efficacy of Grp94 inhibitors towards mutant myocilin in disease relevant systems and then work to develop Grp94 inhibitors with greater efficacy and biological activity towards misfolded myocilin. These studies will result in a new suite of Grp94 modulators and demonstrate that Grp94 is a novel clinical target to treat glaucoma caused by misfolded myocilin. In addition, mechanisms identified herein that clarify how Grp94 regulates myocilin triage could provide new insights for other proteostasis diseases.