The isolated carboxy-terminal domain of human mitochondrial leucyl-tRNA synthetase rescues the pathological phenotype of mitochondrial tRNA mutations in human cells

Authors


Abstract

Mitochondrial (mt) diseases are multisystem disorders due to mutations in nuclear or mtDNA genes. Among the latter, more than 50% are located in transfer RNA (tRNA) genes and are responsible for a wide range of syndromes, for which no effective treatment is available at present. We show that three human mt aminoacyl-tRNA syntethases, namely leucyl-, valyl-, and isoleucyl-tRNA synthetase are able to improve both viability and bioenergetic proficiency of human transmitochondrial cybrid cells carrying pathogenic mutations in the mt-tRNAIle gene. Importantly, we further demonstrate that the carboxy-terminal domain of human mt leucyl-tRNA synthetase is both necessary and sufficient to improve the pathologic phenotype associated either with these “mild” mutations or with the “severe” m.3243A>G mutation in the mt-tRNALeu(UUR) gene. Furthermore, we provide evidence that this small, non-catalytic domain is able to directly and specifically interact in vitro with human mt-tRNALeu(UUR) with high affinity and stability and, with lower affinity, with mt-tRNAIle. Taken together, our results sustain the hypothesis that the carboxy-terminal domain of human mt leucyl-tRNA synthetase can be used to correct mt dysfunctions caused by mt-tRNA mutations.

Synopsis

image

Non-cognate mitochondrial aminoacyl-tRNA syntethases improve viability and bionergetic proficiency of human cells with pathogenic mutations in the mt-tRNAIle gene. The isolated carboxy-terminal domain of human mt-leucyl tRNA synthetase improves the pathologic phenotype.

  • Mitochondrial aminoacyl-tRNA syntethases (mt-aaRSs) can rescue the pathologic phenotype of human cells carrying mutations, both in cognate and non-cognate mitochondrial tRNAs.
  • The carboxy-terminal domain of mt-leucyl syntethase (mt-LeuRS Cterm) is sufficient to exert the rescuing effect, even more efficiently than the whole enzyme.
  • In line with its rescuing effect, mt-LeuRS Cterm is imported within mitochondria, even in absence of a canonical mt import sequence.