The imbalance of protein metabolism is the major cause of skeletal muscle atrophy, and the decrease of protein synthesis directly leads to the occurrence and development of age-related sarcopenia. The canonical role of leucyl-tRNA synthetase (LeuRS) is ligating leucine to the cognate tRNA, and thus it plays a central role in genetic coding. With the further studies of LeuRS in recent years, LeuRS has been found to control protein homeostasis in aging skeletal muscle via its non-canonical role. In this paper, we reviewed the structure and biological features of aminoacyl-tRNA synthetase and LeuRS, and summarized the recent advances in studies on the effects of LeuRS in regulating aging skeletal muscle protein synthesis as an intracellular leucine sensor. Moreover, we also analyzed the potential role of LeuRS in activation of mammalian target of rapamycin complex 1 (mTORC1) signaling transduction pathway in response to anabolic stimuli such as exercise and amino acids ingestion. This paper may provide some new ideas for the prevention, diagnosis and treatment of age-related sarcopenia.
Amino Acyl-tRNA Synthetases ; genetics ; Leucine-tRNA Ligase ; genetics ; Muscle, Skeletal ; Protein Biosynthesis

Infantile liver failure syndrome type 1 (ILFS1) is a Mendelian disease due to biallelic mutations in the cytoplasmic leucyl-tRNA synthetase gene (LARS). This study aimed to report the clinical and molecular features of the first non-caucasian ILFS1 patient, providing reliable evidences for the definite diagnosis of ILFS1. The 2 years and 9 months old male patient was referred to the hospital with hepatosplenomegaly over 1 year. At age 17 months, he was found to have hepatosplenomegaly and anemia. Since then, he had been managed in different hospitals. The laboratory tests showed liver dysfunction, hypoproteinemia, coagulopathy and anemia, along with histologically-confirmed cirrhosis and fatty liver; however, the etiology remained undetermined. The subsequent SLC25A13 mutation analysis by means of prevalent mutation screening and Sanger sequencing only revealed a paternally-inherited mutation c.1658G>A, and no aberrant SLC25A13 transcripts could be detected from the maternal allele on cDNA cloning analysis, ruling out the possibility of citrin deficiency. Further target exome high-throughout sequencing of genes relevant to genetic liver diseases detected a paternal c.2133_2135del (p.L712del) and a maternal c.1183G>A (p.D395N) mutation in LARS gene. This finding was then confirmed by Sanger sequencing, and ILFS1 was thus definitely diagnosed. The child has been followed up till age 4 years, and his condition became stabilized.
Child, Preschool ; High-Throughput Nucleotide Sequencing ; Humans ; Leucine-tRNA Ligase ; genetics ; Liver Failure ; diagnosis ; genetics ; Male ; Mitochondrial Membrane Transport Proteins ; genetics ; Mutation

Molecular mechanism of lung carcinogenesis and its aggressive nature is still largely elusive. To uncover the biomarkers related with tumorigenesis and behavior of lung cancer, we screened novel differentially expressed genes (DEG) in A549 lung cancer cell line by comparison with CCD-25Lu, normal pulmonary epithelial cell line, using annealing control primer(ACP)- based GeneFishing system. Of the DEGs, over-expression of leucyl-tRNA synthetase 1 (LARS1) was prominent and this up-regulation was confirmed by immunoblotting and real-time quantitative RT-PCR analysis. In addition to A549 cell line, primary lung cancer tissues also expressed higher level of LARS1 mRNA than their normal counter tissues. To explore the oncogenic potential of LARS1 over-expression in lung cancer, we knocked-down LARS1 by treating siRNA and observed the tumor behavior. LARS1 knock-down cells showed reduced ability to migrate through transwell membrane and to form colonies in both soft agar and culture plate. Taken together, these findings suggest that LARS1 may play roles in migration and growth of lung cancer cells, which suggest its potential implication in lung tumorigenesis.
Base Sequence ; Blotting, Western ; Cell Line, Tumor ; *Cell Movement ; DNA Primers ; Humans ; Leucine-tRNA Ligase/genetics/*metabolism ; Lung Neoplasms/*enzymology/pathology ; *RNA, Small Interfering ; Reverse Transcriptase Polymerase Chain Reaction