Autosomal dominant retinitis pigmentosa-associated gene PRPF8 is essential for hypoxia-induced mitophagy through regulating ULK1 mRNA splicing

Aged and damaged mitochondria can be selectively degraded by specific autophagic elimination, termed mitophagy. Defects in mitophagy have been increasingly linked to several diseases including neurodegenerative diseases, metabolic diseases and other aging-related diseases. However, the molecular mechanisms of mitophagy are not fully understood. Here, we identify PRPF8 (pre-mRNA processing factor 8), a core component of the spliceosome, as an essential mediator in hypoxia-induced mitophagy from an RNAi screen based on a fluorescent mitophagy reporter, mt-Keima. Knockdown of PRPF8 significantly impairs mitophagosome formation and subsequent mitochondrial clearance through the aberrant mRNA splicing of ULK1, which mediates macroautophagy/autophagy initiation. Importantly, autosomal dominant retinitis pigmentosa (adRP)-associated PRPF8 mutant R2310K is defective in regulating mitophagy. Moreover, knockdown of other adRP-associated splicing factors, including PRPF6, PRPF31 and SNRNP200, also lead to ULK1 mRNA mis-splicing and mitophagy defects. Thus, these findings demonstrate that PRPF8 is essential for mitophagy and suggest that dysregulation of spliceosome-mediated mitophagy may contribute to pathogenesis of retinitis pigmentosa.

衰老和受损的线粒体可通过一种被称为线粒体自噬的特异性自噬清除过程被选择性降解。线粒体自噬缺陷与多种疾病的关联日益受到关注，这些疾病包括神经退行性疾病、代谢性疾病以及其他衰老相关疾病。然而，线粒体自噬的分子机制尚未完全阐明。在此，我们通过基于一种荧光线粒体自噬报告基因mt - Keima的RNA干扰筛选，鉴定出前体mRNA加工因子8（PRPF8）——剪接体的一个核心组分，是缺氧诱导的线粒体自噬的关键介质。敲低PRPF8会通过异常剪接介导巨自噬/自噬起始的ULK1的mRNA，显著损害线粒体自噬体的形成以及后续的线粒体清除。重要的是，常染色体显性遗传性视网膜色素变性（adRP）相关的PRPF8突变体R2310K在调节线粒体自噬方面存在缺陷。此外，敲低其他与adRP相关的剪接因子，包括PRPF6、PRPF31和SNRNP200，也会导致ULK1 mRNA的错误剪接和线粒体自噬缺陷。因此，这些研究结果表明PRPF8对线粒体自噬至关重要，并提示剪接体介导的线粒体自噬失调可能有助于视网膜色素变性的发病机制。