线粒体ATP酶Msp1识别错误定位的尾锚定蛋白的分子机理

Mitochondrion performs essential metabolic and signaling functions and is a key mediator of cell death. Mitochondrial protein quality control mechanisms are critical for mitochondrial proteostasis and function. We utilize yeast to study mitochondrial outer-membrane associated degradation pathways. The conserved ATPase Msp1 on mitochondrial outer-membrane detects and clears mistargeted tail-anchored proteins to protect mitochondrial morphology and respiratory functions. How Msp1 distinguishes between mislocalized and authentic mitochondrial tail-anchored proteins remains unclear. In our preliminary studies, we identified conserved Msp1 residues critical for substrate binding. These residues localize to Msp1 domains in the cytoplasm and in mitochondrial inter-membrane space. Based on the localization and property of these residues, we propose Msp1 recognizes substrates through a dual-recognition mechanism. To prove and develop this hypothesis, we will combine genetic, imaging, biochemistry and chemical tools to determine the key Msp1 domain and residues involved in substrate recognition, identify new Msp1 substrates, analyze and define the key region and properties of substrates that are recognized by Msp1, and obtain the high quality interaction surface information between Msp1 and substrates. This study will reveal the molecular mechanisms that how Msp1 recognizes mislocalized tail-anchored proteins, and deepen our understandings of mitochondrial protein quality control mechanisms.

线粒体是细胞主要的能量代谢细胞器，也是细胞死亡的重要执行者。线粒体蛋白质量控制机制对维持线粒体健康十分关键。本课题组以酵母为模型研究线粒体外膜蛋白的清除降解机制。Msp1是线粒体外膜上序列和功能都高度保守的ATP酶。近几年的研究表明它能够直接识别并清除错误定位到外膜的尾锚定蛋白。但一个关键问题，即Msp1是如何特异识别错误定位的底物，仍不清楚。在前期研究中，我们发现Msp1跨膜区两侧都含有参与底物识别的关键并保守的氨基酸位点。基于这些位点的特性，我们提出了Msp1识别底物的双重识别假说。为了验证这一假说，我们将综合遗传，成像，生化和化学等技术，鉴定Msp1参与底物识别的关键结构域和位点，发现新底物，分析底物被Msp1识别的关键区域和特征，获取Msp1与底物互作界面的高精度信息。本课题将阐明Msp1识别错误定位的尾锚定蛋白的分子机制，深化和完善线粒体蛋白质量控制体系的理论基础。

线粒体是细胞主要的能量代谢细胞器，也是细胞死亡的重要执行者。线粒体蛋白质量控制和稳态维持对线粒体健康十分关键，但其分子机制仍不完整，需要进一步探索和研究。本项目围绕线粒体外膜蛋白质量控制通路的核心科学问题，阐明线粒体外膜ATP酶Msp1识别并清除错误定位到线粒体的尾锚定蛋白的双重识别分子机制，发现UBXD8-VCP复合物介导泛素化线粒体外膜蛋白的降解，并通过降解底物Noxa和Bnip3调控细胞凋亡和线粒体自噬。此项目的研究成果加深了我们对线粒体蛋白质量控制机制及其生物学功能的理解。