Aminoacyl-tRNA synthetases (ARSs) catalyze the charging of specific amino acids onto cognate tRNAs, an essential process for protein synthesis. Mutations in ARSs are frequently associated with a variety of human diseases. The human EPRS1 gene encodes a bifunctional glutamyl-prolyl-tRNA synthetase (EPRS) with two catalytic cores and appended domains that contribute to nontranslational functions. In this study, we report compound heterozygous mutations in EPRS1, which lead to amino acid substitutions P14R and E205G in two patients with diabetes and bone diseases. While neither mutation affects tRNA binding or association of EPRS with the multisynthetase complex, E205G in the glutamyl-tRNA synthetase (ERS) region of EPRS is defective in amino acid activation and tRNAGlu charging. The P14R mutation induces a conformational change and altered tRNA charging kinetics in vitro. We propose that the altered catalytic activity and conformational changes in the EPRS variants sensitize patient cells to stress, triggering an increased integrated stress response (ISR) that diminishes cell viability. Indeed, patient-derived cells expressing the compound heterozygous EPRS show heightened induction of the ISR, suggestive of disruptions in protein homeostasis. These results have important implications for understanding ARS-associated human disease mechanisms and development of new therapeutics.

中文翻译：

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双功能氨酰基-tRNA 合成酶基因中与疾病相关的突变会引发综合应激反应。

氨酰基-tRNA 合成酶 (ARS) 催化将特定氨基酸装载到同源 tRNA 上，这是蛋白质合成的重要过程。ARS 突变经常与多种人类疾病相关。人类 EPRS1 基因编码双功能谷氨酰-脯氨酰-tRNA 合成酶 (EPRS)，具有两个催化核心和有助于非翻译功能的附加结构域。在这项研究中，我们报告了 EPRS1 的复合杂合突变，该突变导致两名患有糖尿病和骨病的患者出现氨基酸取代 P14R 和 E205G。虽然这两种突变都不影响 tRNA 结合或 EPRS 与多合成酶复合物的关联，但 EPRS 谷氨酰-tRNA 合成酶 (ERS) 区域中的 E205G 在氨基酸激活和 tRNAGlu 充电方面存在缺陷。P14R 突变在体外诱导构象变化并改变 tRNA 充电动力学。我们认为，EPRS 变体中催化活性的改变和构象变化使患者细胞对应激敏感，引发综合应激反应 (ISR) 增加，从而降低细胞活力。事实上，表达复合杂合 EPRS 的患者来源的细胞显示出 ISR 的增强诱导，表明蛋白质稳态被破坏。这些结果对于了解 ARS 相关人类疾病机制和开发新疗法具有重要意义。