GRP78 signaling and retinal angiogenesis

视网膜新生血管（RNV）是视力丧失的主要因素之一，尤其是在糖尿病患者中。在 事实上，世卫组织报告说，到2040年，全球6.42亿糖尿病患者中，35%（2.24亿） 将发展成某种形式的糖尿病视网膜病变，11%（7000万）的人将受到视力威胁。 视网膜病变模拟视网膜血管病的动物模型确定了VEGF的主导作用，它 随后导致靶向RNV的抗VEGF疗法的发展。然而，这些抗VEGF 治疗在单独抑制RNV方面不是选择性的，因为它们也影响发育和修复， 血管生成此外，长期使用抗VEGF药物会导致正常血液变性 视网膜和脉络膜的血管和血管纤维化导致玻璃体出血。因此有 因此，有必要找到仅靶向VEGF的病理性而非生理性信号传导的治疗剂。本 最后，我们发现GRP 78被OIR强烈诱导，并具有影响RNV的能力。GRP78 是内质网应激诱导的未折叠蛋白反应（UPR）的主要调节因子。除了在普遍定期审议中的作用外， GRP 78已被证明参与肿瘤细胞存活、增殖和耐药性。此外， 还报道了GRP 78水平和RNV之间的相关性。然而，这两者之间的因果关系 两个事件是未知的。在这方面，我们的初步结果表明，GRP 78不仅是诱导 OIR及其在EC中的条件性缺失降低了缺氧诱导的RNV。此外，我们观察到， GRP 78通过触发非Wnt依赖性b-连环蛋白从粘附连接释放及其复合物形成 与STAT 3的结合导致细胞周期蛋白D1的表达增强EC增殖和迁移。与b-连环蛋白平行- STAT 3-细胞周期蛋白D1信号传导，GRP 78通过非经典NF κ B RelB激活也介导IL-8/Cxcl 1/2 在调控EC发芽中的表达。基于这些新的观察，我们假设GRP 78 在RNV中起着关键作用。我们将通过测试以下三个具体目标来解决这个主要假设。 目标1。不依赖于UPR的ATF 6-GRP 78信号转导激活对于VEGF/OIR诱导的视网膜病变是必需的 新生血管形成;目的2. GRP 78介导的非Wnt依赖性的b-连环蛋白激活是 VEGFA/OIR诱导的细胞周期蛋白D1表达和视网膜新生血管形成;目的3.非典型NF κ B， RelB介导的IL-8表达是VEGFA/OIR诱导的视网膜新生血管形成所必需的。的结果 这些研究可以确定治疗RNV的选择性药物靶点，包括增殖性糖尿病 视网膜病变

Retinal neovascularization (RNV) is one of the major factors in vision loss, particularly in diabetic patients. In fact, WHO reported that by 2040, out of 642 million people with diabetes globally, 35% (224 million) of them will develop some form of diabetic retinopathy, and 11% (70 million) will suffer with sight-threatening retinopathy. The animal models mimicking retinal vasculopathies identified a dominant role for VEGF, which subsequently led to the development of anti-VEGF therapies targeting RNV. However, these anti-VEGF therapies are not selective in inhibiting RNV alone, as they also affect developmental and reparative angiogenesis. Furthermore, long-term use of anti-VEGF regiments can cause degeneration of normal blood vessels and angiofibrosis of neural retina and choroid resulting in vitreous hemorrhage. Therefore, it is necessary to find therapeutics that target only pathological but not physiological signaling of VEGF. To this end, we found that GRP78 was induced robustly by OIR and possessed the capacity to influence RNV. GRP78 is the main regulator of ER stress-induced unfolded protein response (UPR). In addition to its role in UPR, GRP78 has been shown to be involved in tumor cell survival, proliferation, and drug resistance. Besides, a correlation between GRP78 levels and RNV has also been reported. However, a causal link between these two events is unknown. In this regard, our preliminary results revealed that GRP78 not only was induced by OIR but also its conditional deletion in ECs reduced hypoxia-induced RNV. Furthermore, we observed that GRP78 by triggering Wnt-independent release of b-catenin from adherent junctions and its complex formation with STAT3 leads to cyclin D1 expression in enhancing EC proliferation and migration. Parallel to b-catenin- STAT3-Cyclin D1 signaling, GRP78 via non-canonical NFkB RelB activation also mediates IL-8/Cxcl1/2 expression in the modulation EC sprouting. Based on these novel observations, we hypothesized that GRP78 plays a crucial role in RNV. We will address this major hypothesis by testing the following three specific aims. Aim 1. UPR-independent activation of ATF6-GRP78 signaling is essential for VEGF/OIR-induced retinal neovascularization; Aim 2. GRP78-mediated Wnt-independent activation of b-catenin is required for VEGFA/OIR-induced cyclin D1 expression and retinal neovascularization; and Aim 3. Non-canonical NFkB, RelB-mediated IL-8 expression is required for VEGFA/OIR-induced retinal neovascularization. The outcome of these studies may identify selective drug targets for the treatment of RNV, including proliferative diabetic retinopathy.