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

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.

Emerging concepts in the therapy of mitochondrial disease

“…In addition, experiments in yeast and human cells have shown that the overexpression of either human mt-LeuRS or mt-ValRS was able of rescuing the pathological phenotype associated with mutations in both the cognate and the non-cognate mt-tRNA. A region in the carboxy-terminal domain of mt-LeuRS was found necessary and sufficient to determine this phenomenon, probably via a chaperone-like stabilizing effect [144,145].…”

Trends in Mitochondrial Therapeutics for Neurological Disease

“…Yeast tRNAs with artificially changed identity, from cytoplasmic lysine to mitochondrial leucine, partially rescued mitochondrial translation, steady-state levels of mtDNA-encoded respiratory chain subunits, and cellular respiration in human cells with the A3243G MELAS mutation in mttRNA Leu [74]. More recently, human mitochondrial leucyl tRNA synthetase, particularly a carboxy terminal fragment, was reported to rescue respiratory deficiency induced by pathogenic mt-tRNA mutations [69,75]. Mechanisms, particularly those involved in the suppression of non-cognate mutations, remain uncertain but unlikely to involve aminoacylation (domain absent from the carboxy terminal fragment), and are possibly related to stabilization of the mutant tRNAs.…”

The Role of Mitochondria in Oocyte and Early Embryo Health

“…Recently, much progress was made in developing curative treatments to several mitochondrial conditions. These treatments are based on discoveries such as mitochondria-specific nanocarrier molecules that allow mitochondria-specific drug delivery, medications that stabilize mitochondrial tRNA, as well as the resolving specific mitochondrial enzyme deficiencies [149][150][151].…”