Molecular Cell Manuscript_Zhiwei et al., 2017

Ca2+ dynamics and oxidative signaling are fundamental mechanisms for mitochondrial bioenergetics and cell function. The Mitochondrial Calcium Uniporter (MCU) complex is the major pathway by which these signals are integrated in the mitochondria. Whether and how these coactive elements interact with MCU has not been established. As an approach towards understanding the regulation of MCU channel activity by oxidative milieu, we adapted inflammatory and hypoxia model systems. Our studies identified the conserved cysteine at position 97 to be the only reactive thiol in human MCU that undergoes S-glutathionylation. Furthermore, biochemical, structural and superresolution imaging analysis revealed that MCU oxidation promotes MCU higher-order oligomer formation in the inner mitochondrial membrane. Both oxidation and mutation of MCU Cys-97 exhibited persistent activation of the MCU channel with higher [Ca2+]m uptake rate, increased IMCU, elevated mitochondrial ROS and enhanced [Ca2+]m overload-induced cell death. In contrast, these effects were largely independent of MCU interaction with its regulatory components. These findings reveal a distinct functional role for Cys-97 in ROS sensing and regulation of MCU activity.

钙离子动态变化和氧化信号传导是线粒体生物能量学和细胞功能的基本机制。线粒体钙单通道蛋白（Mitochondrial Calcium Uniporter，简称MCU）复合体是这些信号在细胞器中整合的主要途径。这些协同作用的元素是否以及如何与MCU相互作用尚未得到明确。为了深入理解氧化环境对MCU通道活性的调控，我们采用了炎症和缺氧模型系统。我们的研究揭示了位于97位点的保守半胱氨酸是人类MCU中唯一的反应性硫醇，经历S-谷胱甘肽化。此外，通过生化、结构和超分辨率成像分析发现，MCU的氧化促进了其在内质膜上的高阶寡聚体形成。氧化和MCU中Cys-97的突变均表现出MCU通道的持续激活，伴随着更高的[Ca2+]m摄取率、增加的IMCU、升高的线粒体活性氧（ROS）和增强的[Ca2+]m超负荷诱导的细胞死亡。相比之下，这些效应在很大程度上与MCU与其调节成分的相互作用无关。这些发现揭示了Cys-97在ROS感知和调控MCU活性中具有独特的功能作用。