Human Mitochondrial Leucyl-tRNA Synthetase Corrects Mitochondrial Dysfunctions Due to the tRNA^Leu(UUR) A3243G Mutation, Associated with Mitochondrial Encephalomyopathy, Lactic Acidosis, and Stroke-Like Symptoms and Diabetes

Abstract

Mutations in mitochondrial tRNA genes are associated with a wide spectrum of human diseases. In particular, the tRNA^Leu(UUR) A3243G mutation causes mitochondrial encephalomyopathy, lactic acidosis, and stroke-like symptoms (MELAS) and 2% of cases of type 2 diabetes. The primary defect in this mutation was an inefficient aminoacylation of the tRNA^Leu(UUR). In the present study, we have investigated the molecular mechanism of the A3243G mutation and whether the overexpression of human mitochondrial leucyl-tRNA synthetase (LARS2) in the cytoplasmic hybrid (cybrid) cells carrying the A3243G mutation corrects the mitochondrial dysfunctions. Human LARS2 localizes exclusively to mitochondria, and LARS2 is expressed ubiquitously but most abundantly in tissues with high metabolic rates. We showed that the alteration of aminoacylation tRNA^Leu(UUR) caused by the A3243G mutation led to mitochondrial translational defects and thereby reduced the aminoacylated efficiencies of tRNA^Leu(UUR) as well as tRNA^Ala and tRNA^Met. We demonstrated that the transfer of human mitochondrial leucyl-tRNA synthetase into the cybrid cells carrying the A3243G mutation improved the efficiency of aminoacylation and stability of mitochondrial tRNAs and then increased the rates of mitochondrial translation and respiration, consequently correcting the mitochondrial dysfunction. These findings provide new insights into the molecular mechanism of maternally inherited diseases and a step toward therapeutic interventions for these disorders.

View correction statement:

Correction for Li and Guan, “Human Mitochondrial Leucyl-tRNA Synthetase Corrects Mitochondrial Dysfunctions Due to the tRNALeu(UUR) A3243G Mutation, Associated with Mitochondrial Encephalomyopathy, Lactic Acidosis, and Stroke-Like Symptoms and Diabetes”

This paper is dedicated to the memory of Giuseppe Attardi, a pioneer in mitochondrial genetics and biomedicine.

We are grateful to Anne Chomyn (California Institute of Technology) for cell lines and Linda Spremulli (University of North Carolina) for the human LARS2 cDNA plasmid.

This work was supported by Public Health Service grants RO1NS44015 from the National Institute of Neurological Disorders and Stroke and RO1DC05230 and RO1DC07696 from the National Institute on Deafness and Other Communication Disorders to M.X.G.