tRNA-sequestration as an underlying molecular mechanism of tyrosyl-tRNA synthetase-associated DI-CMTC pathology

氨基酰基-tRNA合成酶(AARs)是蛋白质翻译的关键酶，它使tRNA与同源氨基酸发生氨酰化反应。6个不同的AARs的杂合突变与毁灭性的显性遗传性Charcot-Marie-Tooth(CMT)周围神经病有关，该疾病的特征是周围运动和感觉轴突退化，导致进行性肌肉无力、消瘦和感觉功能障碍。不同CMT形式的潜在分子机制及其组织特异性效应仍然知之甚少。我们最近报道了一种新的CMT2D病理机制，与甘氨酰-tRNA合成酶(GARS)突变有关，GARS是一种II类AARs。GARS的CMT突变形式与同源tRNAs紧密结合并无法释放它们，从而耗尽甘氨酰tRNAGly进行翻译，从而导致核糖体在甘氨酸密码子上停滞不前。YARS杂合性突变是DI-CMTC的致病因素。通过分析果蝇和小鼠CMT模型(YarsE196K小鼠)中CMT突变体酪氨酰-tRNA合成酶(YARS)的tRNA结合和释放动力学，结合全细胞翻译速度和表达的分析，我们将确定另一类与CMT病理相关的I类AARs的分子机制。我们期望这种多层次的方法将揭示与CMT病理有因果联系的I类和II类AARS中突变的共同和不同的机制方面。

Aminoacyl-tRNA-synthetases (aaRS) are pivotal for protein translation; they aminoacylate tRNAs with cognate amino acid. Heterozygous mutations in six distinct AARSs are connected to devastating dominantly inherited Charcot-Marie-Tooth (CMT) peripheral neuropathies, which is characterized by degeneration of peripheral motor and sensory axons, leading to progressive muscle weakness and wasting and sensory dysfunction. The underlying molecular mechanisms of different CMT forms and their tissue-specific effect remain poorly understood. We recently reported a novel mechanism underlying the CMT2D pathology linked to mutations in the glycyl-tRNA synthetase (GARS), a class II aaRS. The CMT-mutant forms of GARS tightly bind the cognate tRNAs and fail to release them, thus, depleting glycyl-tRNAGly for translation and consequently causing ribosome stalling at Gly codons. Heterozygous mutations in YARS are causal to DI-CMTC pathology. By analysing the kinetics of tRNA binding and release of CMT-mutant tyrosyl-tRNA-synthetase (YARS) variants in Drosophila and mouse CMT models (YarsE196K mice), combined with cell-wide analysis of translation speed and expression, we will determine the molecular mechanism of another class I aaRS associated with CMT pathologies. We expect that this multilayered approach will reveal insights into common and distinct mechanistic facets of mutations in class I and class II aaRSs with a causal link to CMT pathologies.