Grp94-selective inhibitors to treat heredity glaucoma

描述（由申请人提供）：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是由视神经损伤引起的，这种损伤是由称为小梁网（TM）的保护性细胞网络死亡引起的。在这些病例中，由于突变心肌异常地积聚成毒性聚集体，会发生TM细胞死亡。这种机制让人想起神经退行性疾病，如阿尔茨海默氏症、亨廷顿氏症和帕金森氏症，在这些疾病中，异常蛋白质在神经元中积聚并导致细胞死亡。事实上，TM细胞和神经元一样寿命很长。此外，导致POAG早期发病的突变也使心肌蛋白更容易聚集，类似于与神经退行性疾病相关的蛋白质。因此，这两种类型的疾病都可以被认为是“蛋白质停滞”疾病，这意味着长寿的细胞（神经元和TM）随着年龄的增长逐渐失去阻止突变蛋白毒性积累的能力。因此，旨在恢复TM细胞中蛋白质平衡的策略可能对青光眼有益，正如它们已被证明对神经退行性疾病有益一样。通过一系列研究，我们确定位于内质网中的Grp94伴侣（Hsp90亚型）错误地保留了细胞中的突变心肌蛋白。重要的是，Grp94只影响错误折叠的心肌：正确折叠和功能正常的心肌不受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心肌蛋白，但Grp94不能清除这种错误折叠的心肌蛋白，而是保留它，导致其毒性积累。因此，心肌蛋白错误折叠通过错误地参与Grp94伴侣蛋白而破坏了蛋白质的静止。我们已经证明，仅通过抑制Grp94就可以加速毒性心肌蛋白的清除！我们的团队已经开发出了第一个被称为BnIm的Grp94亚型选择性抑制剂。由于Grp94依赖性底物列表较少，与其他Hsp90亚型相比，该Grp94抑制剂的毒性谱也较低。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这种Grp94抑制剂对心肌素相关性POAG的治疗作用，以阐明错误折叠的心肌分诊机制。我们还将在疾病相关系统中评估Grp94抑制剂对突变肌素的生物学功效，然后努力开发对错误折叠的肌素具有更大功效和生物活性的Grp94抑制剂。这些研究将产生一套新的Grp94调节剂，并证明Grp94是治疗错误折叠心肌引起的青光眼的新的临床靶点。此外，本文确定的阐明Grp94如何调节心肌蛋白分类的机制可能为其他蛋白酶抑制疾病提供新的见解。

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.