Related Experiment Video
Updated: Oct 25, 2025
Structure-function Studies in Mouse Embryonic Stem Cells Using Recombinase-mediated Cassette Exchange
Published on: April 27, 2017
Exploring the Ability of LARS2 Carboxy-Terminal Domain in Rescuing the MELAS Phenotype
Francesco Capriglia1, Francesca Rizzo1, Giuseppe Petrosillo2
1Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari Aldo Moro, 70125 Bari, Italy.
Abstract:
The m.3243A>G mutation within the mitochondrial mt-tRNALeu(UUR) gene is the most prevalent variant linked to mitochondrial encephalopathy with lactic acidosis and stroke-like episodes (MELAS) syndrome. This pathogenic mutation causes severe impairment of mitochondrial protein synthesis due to alterations of the mutated tRNA, such as reduced aminoacylation and a lack of post-transcriptional modification. In transmitochondrial cybrids, overexpression of human mitochondrial leucyl-tRNA synthetase (LARS2) has proven effective in rescuing the phenotype associated with m.3243A>G substitution. The rescuing activity resides in the carboxy-terminal domain (Cterm) of the enzyme; however, the precise molecular mechanisms underlying this process have not been fully elucidated. To deepen our knowledge on the rescuing mechanisms, we demonstrated the interactions of the Cterm with mutated mt-tRNALeu(UUR) and its precursor in MELAS cybrids. Further, the effect of Cterm expression on mitochondrial functions was evaluated. We found that Cterm ameliorates de novo mitochondrial protein synthesis, whilst it has no effect on mt-tRNALeu(UUR) steady-state levels and aminoacylation. Despite the complete recovery of cell viability and the increase in mitochondrial translation, Cterm-overexpressing cybrids were not able to recover bioenergetic competence. These data suggest that, in our MELAS cell model, the beneficial effect of Cterm may be mediated by factors that are independent of the mitochondrial bioenergetics.
Insights
The carboxy-terminal domain of LARS2 partially rescues mitochondrial protein synthesis in MELAS syndrome models by interacting with mutated mitochondrial tRNA. However, it does not restore full mitochondrial bioenergetic function.
Area of Science:
- Mitochondrial genetics
- Molecular biology
- Cellular pathophysiology
Background:
- The m.3243A>G mutation in mitochondrial DNA is a primary cause of MELAS syndrome, severely impacting mitochondrial protein synthesis.
- Overexpression of leucyl-tRNA synthetase (LARS2) can rescue MELAS phenotypes, with the carboxy-terminal domain (Cterm) being crucial for this effect.
- The exact molecular mechanisms of Cterm-mediated rescue in MELAS remain unclear.
Purpose of the Study:
- To investigate the interaction between the LARS2 Cterm and mutated mitochondrial tRNA in MELAS cybrids.
- To evaluate the impact of Cterm expression on mitochondrial functions and cellular viability in a MELAS model.
- To elucidate the specific molecular pathways involved in Cterm's rescuing activity.
Main Methods:
- Utilized transmitochondrial cybrid models carrying the m.3243A>G MELAS mutation.
- Demonstrated interactions between the LARS2 Cterm and mutated mt-tRNALeu(UUR) and its precursor.
- Assessed mitochondrial protein synthesis, tRNA levels, aminoacylation, cell viability, and bioenergetic competence in Cterm-overexpressing cybrids.
Main Results:
- The LARS2 Cterm interacts with mutated mt-tRNALeu(UUR) and its precursor in MELAS cybrids.
- Cterm expression ameliorates de novo mitochondrial protein synthesis and fully recovers cell viability.
- Cterm does not affect mt-tRNALeu(UUR) steady-state levels or aminoacylation and fails to restore full bioenergetic competence.
Conclusions:
- The LARS2 Cterm exhibits a beneficial effect on mitochondrial protein synthesis and cell viability in MELAS models, independent of tRNA levels or aminoacylation.
- The rescuing mechanism of Cterm in MELAS cybrids involves factors not directly linked to restoring mitochondrial bioenergetic function.
- Further research is needed to fully understand the non-bioenergetic pathways mediating Cterm's therapeutic potential in MELAS syndrome.
