Crosstalk Between Unfolded Protein Response and Autophagy for the Treatment of Glaucoma

 描述(申请人提供)：原发性开角型青光眼是不可逆性失明的主要原因，通常与由于小梁网(TM)房水流出阻力增加而引起的眼内压(IOP)升高有关。导致流出阻力增加和眼压升高的病理机制尚不清楚。我们最近将蛋白质错误折叠和内质网(ER)应激与青光眼TM损伤和眼压升高联系起来。TM细胞激活保护性未折叠蛋白反应(UPR)途径以消除异常蛋白积聚。然而，慢性内质网应激导致末端UPR信号的诱导，包括已知的诱导细胞死亡的ATF4和CHOP。有趣的是，人类青光眼TM组织也显示ATF4和CHOP显著增加。此外，CHOP基因的缺失对青光眼小鼠模型的内质网应激和眼压升高具有保护作用。目前尚不清楚ATF4和CHOP如何导致TM功能障碍和眼压升高。在我们的初步研究中，我们发现ATF4或CHOP的增加与自噬受损有关，自噬是人类和小鼠青光眼TM中的一种溶酶体降解途径。此外，通过自噬特异性激活剂Tat-beclin1肽纠正受损的自噬，可降低青光眼小鼠模型的高眼压。基于这些发现，我们推测，在眼部慢性内质网应激期间，促细胞死亡ATF4和CHOP之间的平衡以及促生存的纠正自噬通路决定了青光眼TM疾病的进展。这项建议的具体目的是：(1)确定ATF4和CHOP是否损害WT小鼠的自噬功能，诱导TM细胞死亡和升高眼压；(2)确定ATF-4或CHOP缺乏是否通过改善TG-MYOCY437H小鼠的自噬功能来防止眼压升高；以及(3)确定Tat-beclin 1肽增强自噬通量是否能降低青光眼小鼠模型和人眼前节灌注培养模型的高眼压。这些研究将利用培养的人TM细胞、小鼠青光眼模型和人眼前节器官培养模型来研究ATF4、CHOP和自噬在TM介导的眼压调节中的相互作用。这项拟议的研究将提供UPR和自噬之间的联系，并调查操纵这些途径是否可以提供对青光眼的保护。这些研究将进一步探索利用Tat-beclin 1肽降解异常蛋白积聚治疗青光眼的可能性。

 DESCRIPTION (provided by applicant): Primary open angle glaucoma, a major cause of irreversible blindness, is often associated with elevated intraocular pressure (IOP) due to increased aqueous humor outflow resistance at the trabecular meshwork (TM). The pathological mechanisms leading to increased outflow resistance and IOP elevation are poorly understood. We recently linked protein misfolding and endoplasmic reticulum (ER) stress to the development of glaucomatous TM damage and IOP elevation. TM cells activate protective unfolded protein response (UPR) pathway to eliminate abnormal protein accumulation. However chronic ER stress leads to induction of terminal UPR signals including ATF4 and CHOP that are known to induce cell death. Interestingly, human glaucomatous TM tissues also show significantly increased ATF4 and CHOP. Moreover, deletion of Chop protects from ER stress and IOP elevation in mouse models of glaucoma. It is not clear how ATF4 and CHOP cause TM dysfunction and IOP elevation. In our preliminary studies, we discovered that increased ATF4 or CHOP is associated with impaired autophagy, a lysosomal degradation pathway in the TM of human and murine glaucoma. Moreover, correction of impaired autophagy via specific activator of autophagy Tat-beclin1 peptide reduces elevated IOP in mouse model of glaucoma. Based on these findings, we hypothesize that during ocular chronic ER stress, the balance between pro-cell death ATF4 and CHOP and pro-survival corrective autophagic pathways determine glaucomatous TM disease progression. The specific aims of this proposal are: (1) To determine whether ATF4 and CHOP impair autophagic function, induce TM cell death and elevate IOP in WT mice, (2) Determine whether ATF-4 or CHOP deficiency prevents IOP elevation by improving autophagic function in the TM of Tg-MYOCY437H mice, and (3) Determine whether enhancing autophagic flux by Tat-beclin 1 peptide reduces elevated IOP in mouse models of glaucoma and in the human anterior segment perfusion culture model. These studies will utilize cultured human TM cells, mouse models of glaucoma and human anterior segment organ culture model to examine the interactions between ATF4, CHOP and autophagy in TM mediated IOP regulation. The proposed study will provide a link between UPR and autophagy and investigate whether manipulation of these pathways can provide protection against glaucoma. These studies will further explore the possibility of treating glaucoma using Tat-beclin 1 peptide in degradation of abnormal protein accumulation.