雷帕霉素挽救携带线粒体 tRNA m.8344A > G 突变的细胞中线粒体功能障碍。

Rapamycin rescues mitochondrial dysfunction in cells carrying the m.8344A > G mutation in the mitochondrial tRNA.

机构信息

IRCCS Istituto delle Scienze Neurologiche di Bologna, Programma di Neurogenetica, via Altura 3, 40139, Bologna, Italy.

Department of Biomedical and NeuroMotor Sciences, University of Bologna, via Altura 3, 40139, Bologna, Italy.

出版信息

Mol Med. 2022 Aug 3;28(1):90. doi: 10.1186/s10020-022-00519-z.

DOI:10.1186/s10020-022-00519-z

PMID:35922766

原文链接:https://pmc.ncbi.nlm.nih.gov/articles/PMC9347137/

Abstract

BACKGROUND

Myoclonus, Epilepsy and Ragged-Red-Fibers (MERRF) is a mitochondrial encephalomyopathy due to heteroplasmic mutations in mitochondrial DNA (mtDNA) most frequently affecting the tRNA gene at position m.8344A > G. Defective tRNA severely impairs mitochondrial protein synthesis and respiratory chain when a high percentage of mutant heteroplasmy crosses the threshold for full-blown clinical phenotype. Therapy is currently limited to symptomatic management of myoclonic epilepsy, and supportive measures to counteract muscle weakness with co-factors/supplements.

METHODS

We tested two therapeutic strategies to rescue mitochondrial function in cybrids and fibroblasts carrying different loads of the m.8344A > G mutation. The first strategy was aimed at inducing mitochondrial biogenesis directly, over-expressing the master regulator PGC-1α, or indirectly, through the treatment with nicotinic acid, a NAD precursor. The second was aimed at stimulating the removal of damaged mitochondria through prolonged rapamycin treatment.

RESULTS

The first approach slightly increased mitochondrial protein expression and respiration in the wild type and intermediate-mutation load cells, but was ineffective in high-mutation load cell lines. This suggests that induction of mitochondrial biogenesis may not be sufficient to rescue mitochondrial dysfunction in MERRF cells with high-mutation load. The second approach, when administered chronically (4 weeks), induced a slight increase of mitochondrial respiration in fibroblasts with high-mutation load, and a significant improvement in fibroblasts with intermediate-mutation load, rescuing completely the bioenergetics defect. This effect was mediated by increased mitochondrial biogenesis, possibly related to the rapamycin-induced inhibition of the Mechanistic Target of Rapamycin Complex 1 (mTORC1) and the consequent activation of the Transcription Factor EB (TFEB).

CONCLUSIONS

Overall, our results point to rapamycin-based therapy as a promising therapeutic option for MERRF.

摘要

背景

肌阵挛性癫痫伴破碎红纤维（MERRF）是一种由线粒体 DNA（mtDNA）异质突变引起的线粒体脑肌病，最常影响 tRNA 基因位置 m.8344A>G。当大量突变异质体超过完全临床表型的阈值时，缺陷 tRNA 会严重损害线粒体蛋白合成和呼吸链。目前的治疗方法仅限于肌阵挛性癫痫的对症治疗，以及用辅因子/补充剂来对抗肌肉无力的支持措施。

方法

我们测试了两种治疗策略，以挽救携带不同 m.8344A>G 突变负荷的细胞系和纤维母细胞中的线粒体功能。第一种策略旨在直接诱导线粒体生物发生，过表达主调控因子 PGC-1α，或通过治疗烟酰胺，一种 NAD 前体，间接诱导。第二种方法旨在通过延长雷帕霉素治疗来刺激清除受损线粒体。

结果

第一种方法略微增加了野生型和中间突变负荷细胞中线粒体蛋白的表达和呼吸，但对高突变负荷细胞系无效。这表明，诱导线粒体生物发生可能不足以挽救高突变负荷 MERRF 细胞中的线粒体功能障碍。第二种方法，当长期（4 周）给药时，可诱导高突变负荷纤维母细胞中线粒体呼吸的轻微增加，以及中间突变负荷纤维母细胞的显著改善，完全挽救了生物能量缺陷。这种作用是通过增加线粒体生物发生介导的，可能与雷帕霉素诱导的 Mechanistic Target of Rapamycin Complex 1 (mTORC1) 抑制和随后的 Transcription Factor EB (TFEB) 激活有关。