Honrath Birgit, Metz Isabell, Bendridi Nadia, Rieusset Jennifer, Culmsee Carsten, Dolga Amalia M
Institute of Pharmacology and Clinical Pharmacy, University of Marburg, Marburg, Germany.
Faculty of Science and Engineering, Groningen Research Institute of Pharmacy (GRIP), Department of Molecular Pharmacology, University of Groningen, Groningen, The Netherlands.
Cell Death Discov. 2017 Nov 6;3:17076. doi: 10.1038/cddiscovery.2017.76. eCollection 2017.
The crosstalk between different organelles allows for the exchange of proteins, lipids and ions. Endoplasmic reticulum (ER) and mitochondria are physically linked and signal through the mitochondria-associated membrane (MAM) to regulate the transfer of Ca from ER stores into the mitochondrial matrix, thereby affecting mitochondrial function and intracellular Ca homeostasis. The chaperone glucose-regulated protein 75 (GRP75) is a key protein expressed at the MAM interface which regulates ER-mitochondrial Ca transfer. Previous studies revealed that modulation of GRP75 expression largely affected mitochondrial integrity and vulnerability to cell death. In the present study, we show that genetic ablation of GRP75, by weakening ER-mitochondrial junctions, provided protection against mitochondrial dysfunction and cell death in a model of glutamate-induced oxidative stress. Interestingly, GRP75 silencing attenuated both cytosolic and mitochondrial Ca overload in conditions of oxidative stress, blocked the formation of reactive oxygen species and preserved mitochondrial respiration. These data revealed a major role for GRP75 in regulating mitochondrial function, Ca and redox homeostasis. In line, GRP75 overexpression enhanced oxidative cell death induced by glutamate. Overall, our findings suggest weakening ER-mitochondrial connectivity by GRP75 inhibition as a novel protective approach in paradigms of oxidative stress in neuronal cells.
不同细胞器之间的相互作用允许蛋白质、脂质和离子的交换。内质网（ER）和线粒体在物理上相互连接，并通过线粒体相关膜（MAM）发出信号，以调节Ca从内质网储存库向线粒体基质的转移，从而影响线粒体功能和细胞内Ca稳态。伴侣蛋白葡萄糖调节蛋白75（GRP75）是在MAM界面表达的关键蛋白，它调节内质网-线粒体Ca转移。先前的研究表明，GRP75表达的调节在很大程度上影响线粒体的完整性和对细胞死亡的易感性。在本研究中，我们表明，通过削弱内质网-线粒体连接对GRP75进行基因敲除，在谷氨酸诱导的氧化应激模型中可提供针对线粒体功能障碍和细胞死亡的保护作用。有趣的是，在氧化应激条件下，GRP75沉默可减轻细胞质和线粒体的Ca过载，阻止活性氧的形成并维持线粒体呼吸。这些数据揭示了GRP75在调节线粒体功能、Ca和氧化还原稳态中的主要作用。同样，GRP75的过表达增强了谷氨酸诱导的氧化细胞死亡。总体而言，我们的研究结果表明，通过抑制GRP75来削弱内质网-线粒体连接性，是神经元细胞氧化应激范式中的一种新型保护方法。
