He Yunfan, Tang Zhining, Zhu Gao, Cai Luhang, Chen Chao, Guan Min-Xin
Center for Mitochondrial Biomedicine and Department of Otolaryngology-Head and Neck Surgery, The Fourth Affiliated Hospital, Zhejiang University School of Medicine, Yiwu, Zhejiang, China; Institute of Genetics, Zhejiang University International School of Medicine, Hangzhou, Zhejiang, China; Center for Genetic Medicine, Zhejiang University International Institute of Medicine, Yiwu, Zhejiang, China.
Clinical Laboratory, Huzhou Central Hospital, Affiliated Central Hospital of Huzhou University, Huzhou, Zhejiang, China.
J Biol Chem. 2025 Feb;301(2):108124. doi: 10.1016/j.jbc.2024.108124. Epub 2024 Dec 22.
Human mitochondrial 12S ribosomal RNA (rRNA) 1555A>G mutation has been associated with aminoglycoside-induced and nonsyndromic deafness in many families worldwide. Our previous investigation revealed that the m.1555A>G mutation impaired mitochondrial translation and oxidative phosphorylation (OXPHOS). However, the mechanisms by which mitochondrial dysfunctions induced by m.1555A>G mutation regulate intracellular signaling for mitochondrial and cellular integrity remain poorly understood. Here, we demonstrated that the m.1555A>G mutation downregulated the expression of nucleus-encoded subunits of complexes I and IV but upregulated the expression of assemble factors for OXPHOS complexes, using cybrids derived from one hearing-impaired Chinese subject bearing the m.1555A>G mutation and from one hearing normal control lacking the mutation. These alterations resulted in the aberrant assembly, instability, and reduced activities of respiratory chain enzyme complexes I, IV, and V, rate of oxygen consumption, and diminished ATP production. Furthermore, the mutant cell lines carrying the m.1555A>G mutation exhibited decreased membrane potential and increased the production of reactive oxygen species. The aberrant assembly and biogenesis of OXPHOS impacted mitochondrial quality controls, including the imbalance of mitochondrial dynamics via increasing fission with abnormal mitochondrial morphology and impaired mitophagy. Strikingly, the cells bearing the m.1555A>G mutation revealed the upregulation of both ubiquitin-dependent and independent mitophagy pathways, evidenced by increasing levels of Parkin, Pink, BNIP3 and NIX, respectively. The m.1555A>G mutation-induced deficiencies ameliorate the cell homeostasis via elevating the autophagy process and upregulating apoptotic pathways. Our findings provide new insights into pathophysiology of mitochondrial deafness arising from reshaping mitochondrial and cellular homeostasis due to 12S rRNA 1555A>G mutation.
人类线粒体12S核糖体RNA（rRNA）1555A>G突变与全球许多家庭中氨基糖苷类药物诱导的非综合征性耳聋有关。我们之前的研究表明，m.1555A>G突变会损害线粒体翻译和氧化磷酸化（OXPHOS）。然而，m.1555A>G突变诱导的线粒体功能障碍调节线粒体和细胞完整性的细胞内信号传导机制仍知之甚少。在这里，我们使用来自一名携带m.1555A>G突变的听力受损中国受试者和一名没有该突变的听力正常对照的胞质杂种，证明m.1555A>G突变下调了复合物I和IV的核编码亚基的表达，但上调了OXPHOS复合物组装因子的表达。这些改变导致呼吸链酶复合物I、IV和V的异常组装、不稳定性和活性降低，耗氧率降低以及ATP生成减少。此外，携带m.1555A>G突变的突变细胞系表现出膜电位降低和活性氧生成增加。OXPHOS的异常组装和生物合成影响线粒体质量控制，包括通过增加裂变和异常线粒体形态以及受损的线粒体自噬来破坏线粒体动力学的平衡。引人注目的是，携带m.1555A>G突变的细胞显示泛素依赖性和非依赖性线粒体自噬途径均上调，分别通过Parkin、Pink、BNIP3和NIX水平的增加来证明。m.1555A>G突变诱导的缺陷通过增强自噬过程和上调凋亡途径来改善细胞稳态。我们的研究结果为12S rRNA 1555A>G突变重塑线粒体和细胞稳态导致的线粒体耳聋的病理生理学提供了新的见解。
