Banerjee Kalpita, Keasey Matt P, Razskazovskiy Vladislav, Visavadiya Nishant P, Jia Cuihong, Hagg Theo
Department of Biomedical Sciences, Quillen College of Medicine, East Tennessee State University, PO Box 70582, Johnson City, TN 37614, USA.
Department of Biomedical Sciences, Quillen College of Medicine, East Tennessee State University, PO Box 70582, Johnson City, TN 37614, USA.
Cell Signal. 2017 Aug;36:154-162. doi: 10.1016/j.cellsig.2017.05.007. Epub 2017 May 8.
Excessive endoplasmic reticulum (ER) stress leads to cell loss in many diseases, e.g., contributing to endothelial cell loss after spinal cord injury. Here, we determined whether ER stress-induced mitochondrial dysfunction could be explained by interruption of the focal adhesion kinase (FAK)-mitochondrial STAT3 pathway we recently discovered. ER stress was induced in brain-derived mouse bEnd5 endothelial cells by thapsigargin or tunicamycin and caused apoptotic cell death over a 72h period. In concert, ER stress caused mitochondrial dysfunction as shown by reduced bioenergetic function, loss of mitochondrial membrane potential and increased mitophagy. ER stress caused a reduction in mitochondrial phosphorylated S727-STAT3, known to be important for maintaining mitochondrial function. Normal activation or phosphorylation of the upstream cytoplasmic FAK was also reduced, through mechanisms that involve tyrosine phosphatases and calcium signaling, as shown by pharmacological inhibitors, bisperoxovanadium (bpV) and 2-aminoethoxydiphenylborane (APB), respectively. APB mitigated the reduction in FAK and STAT3 phosphorylation, and improved endothelial cell survival caused by ER stress. Transfection of cells rendered null for STAT3 using CRISPR technology with STAT3 mutants confirmed the specific involvement of S727-STAT3 inhibition in ER stress-mediated cell loss. These data suggest that loss of FAK signaling during ER stress causes mitochondrial dysfunction by reducing the protective effects of mitochondrial STAT3, leading to endothelial cell death. We propose that stimulation of the FAK-STAT3 pathway is a novel therapeutic approach against pathological ER stress.
内质网（ER）应激过度在许多疾病中会导致细胞损失，例如，它会促使脊髓损伤后内皮细胞的损失。在此，我们确定了内质网应激诱导的线粒体功能障碍是否可以通过我们最近发现的粘着斑激酶（FAK）-线粒体信号转导和转录激活因子3（STAT3）通路的中断来解释。通过毒胡萝卜素或衣霉素在源自脑的小鼠bEnd5内皮细胞中诱导内质网应激，并在72小时内导致细胞凋亡死亡。与此同时，内质网应激导致线粒体功能障碍，表现为生物能量功能降低、线粒体膜电位丧失和线粒体自噬增加。内质网应激导致线粒体磷酸化S727-STAT3减少，已知其对维持线粒体功能很重要。上游细胞质FAK的正常激活或磷酸化也减少，分别通过涉及酪氨酸磷酸酶和钙信号的机制，如药理学抑制剂双过氧钒（bpV）和2-氨基乙氧基二苯硼（APB）所示。APB减轻了FAK和STAT3磷酸化的减少，并改善了内质网应激引起的内皮细胞存活。使用CRISPR技术用STAT3突变体转染使STAT3缺失的细胞，证实了S727-STAT3抑制在ER应激介导的细胞损失中的特异性参与。这些数据表明，内质网应激期间FAK信号的丧失通过降低线粒体STAT3的保护作用导致线粒体功能障碍，从而导致内皮细胞死亡。我们提出，刺激FAK-STAT3通路是一种针对病理性内质网应激的新型治疗方法。
