Grp94-selective inhibitors to treat heredity glaucoma

描述（由申请人提供）：在美国，超过100，000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（TM）的保护细胞网络死亡引起的视神经损伤引起的。TM细胞死亡发生在这些情况下，因为突变myocilin异常积累成有毒的聚集体。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，其中异常蛋白质在神经元中积累并导致细胞死亡。事实上，TM细胞就像神经元一样长寿。此外，导致早期POAG发作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，这两种类型的疾病都可以被认为是“蛋白质稳态”疾病，这意味着长寿细胞（神经元和TM）随着年龄的增长逐渐失去防止突变蛋白毒性积累的能力。因此，旨在恢复TM细胞中蛋白质稳态的策略可能对青光眼有益，就像他们已经证明的神经退行性疾病一样。 通过一系列的研究，我们确定了存在于内质网中的Grp 94分子伴侣（一种Hsp 90同种型）错误地将突变型myocilin保留在细胞中。重要的是，Grp 94只影响错误折叠的myocilin：正确折叠和发挥功能的myocilin不受Grp 94操作的影响。Grp 94只识别由于突变或糖基化受损而错误折叠的myocilin：但Grp 94无法清除这种错误折叠的myocilin，而是保留它，导致其毒性积累。因此，myocilin错误折叠通过错误地接合Grp 94分子伴侣而破坏蛋白质稳态。我们已经证明，毒性myocilin的清除可以简单地通过抑制Grp 94来加速！ 我们的团队已经开发出第一种亚型选择性Grp 94抑制剂，称为BnIm。由于Grp 94依赖性底物的列表较小，与其他Hsp 90同种型相比，该Grp 94抑制剂的毒性特征也较低。因此，我们建议通过建立Grp 94抑制剂的结构-活性关系来验证和改进这种Grp 94抑制剂用于治疗肌球蛋白相关的POAG，以阐明错误折叠的肌球蛋白分类的机制。我们还将评估Grp 94抑制剂对疾病相关系统中突变型myocilin的生物学功效，然后致力于开发对错误折叠myocilin具有更大功效和生物学活性的Grp 94抑制剂。这些研究将产生一套新的Grp 94调节剂，并证明Grp 94是治疗由错误折叠的肌球蛋白引起的青光眼的新的临床靶点。此外，本文确定的阐明Grp 94如何调节肌球蛋白分类的机制可以为其他蛋白质代谢停滞疾病提供新的见解。

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.