Department of Biochemistry, The University of Western Ontario, London, ON N6A 5C1, Canada.
Department of Chemistry, The University of Western Ontario, London, ON N6A 5C1, Canada.
Genes (Basel). 2023 Feb 18;14(2):518. doi: 10.3390/genes14020518.
High-fidelity protein synthesis requires properly aminoacylated transfer RNAs (tRNAs), yet diverse cell types, from bacteria to humans, show a surprising ability to tolerate errors in translation resulting from mutations in tRNAs, aminoacyl-tRNA synthetases, and other components of protein synthesis. Recently, we characterized a tRNA G35A mutant (tRNA) that occurs in 2% of the human population. The mutant tRNA decodes phenylalanine codons with serine, inhibits protein synthesis, and is defective in protein and aggregate degradation. Here, we used cell culture models to test our hypothesis that tRNA-dependent mistranslation will exacerbate toxicity caused by amyotrophic lateral sclerosis (ALS)-associated protein aggregation. Relative to wild-type tRNA, we found cells expressing tRNA showed slower but effective aggregation of the fused in sarcoma (FUS) protein. Despite reduced levels in mistranslating cells, wild-type FUS aggregates showed similar toxicity in mistranslating cells and normal cells. The aggregation kinetics of the ALS-causative FUS R521C variant were distinct and more toxic in mistranslating cells, where rapid FUS aggregation caused cells to rupture. We observed synthetic toxicity in neuroblastoma cells co-expressing the mistranslating tRNA mutant and the ALS-causative FUS R521C variant. Our data demonstrate that a naturally occurring human tRNA variant enhances cellular toxicity associated with a known causative allele for neurodegenerative disease.
高保真的蛋白质合成需要正确氨酰化的转移 RNA（tRNA），然而从细菌到人类的各种细胞类型都表现出一种惊人的能力，可以容忍由于 tRNA、氨酰-tRNA 合成酶和蛋白质合成其他成分的突变而导致的翻译错误。最近，我们对一种在 2%的人类中出现的 tRNA G35A 突变体（tRNA）进行了特征描述。突变 tRNA 将苯丙氨酸密码子解码为丝氨酸，抑制蛋白质合成，并在蛋白质和聚集体降解方面存在缺陷。在这里，我们使用细胞培养模型来检验我们的假设，即 tRNA 依赖性错译将加剧肌萎缩侧索硬化症（ALS）相关蛋白聚集引起的毒性。与野生型 tRNA 相比，我们发现表达 tRNA 的细胞中融合肉瘤（FUS）蛋白的聚集速度较慢，但效果更好。尽管在错译细胞中水平降低，但野生型 FUS 聚集体在错译细胞和正常细胞中表现出相似的毒性。ALS 致病 FUS R521C 变体的聚集动力学不同，在错译细胞中更具毒性，其中快速的 FUS 聚集导致细胞破裂。我们在共表达错译 tRNA 突变体和 ALS 致病 FUS R521C 变体的神经母细胞瘤细胞中观察到了合成毒性。我们的数据表明，一种自然发生的人类 tRNA 变体增强了与神经退行性疾病已知致病等位基因相关的细胞毒性。
