Leucyl-tRNA synthetase deficiency systemically induces excessive autophagy in zebrafish

Masanori Inoue,Kenji Ihara,Hiroshi Shiraishi,Nobuyuki Shimizu,Hiroaki Miyahara,Ryohei Umeda,Miwako Maeda,Reiko Hanada,Kyoko Kiyota,Mika Tsumori,Toshikatsu Hanada,Tohru Ishitani

doi:10.1038/s41598-021-87879-4

Masanori Inoue, Kenji Ihara + Show 10 more

Open Access

https://doi.org/10.1038/s41598-021-87879-4

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Abstract

Leucyl-tRNA synthetase (LARS) is an enzyme that catalyses the ligation of leucine with leucine tRNA. LARS is also essential to sensitize the intracellular leucine concentration to the mammalian target of rapamycin complex 1 (mTORC1) activation. Biallelic mutation in the LARS gene causes infantile liver failure syndrome type 1 (ILFS1), which is characterized by acute liver failure, anaemia, and neurological disorders, including microcephaly and seizures. However, the molecular mechanism underlying ILFS1 under LARS deficiency has been elusive. Here, we generated Lars deficient (larsb−/−) zebrafish that showed progressive liver failure and anaemia, resulting in early lethality within 12 days post fertilization. The atg5-morpholino knockdown and bafilomycin treatment partially improved the size of the liver and survival rate in larsb−/− zebrafish. These findings indicate the involvement of autophagy in the pathogenesis of larsb−/− zebrafish. Indeed, excessive autophagy activation was observed in larsb−/− zebrafish. Therefore, our data clarify a mechanistic link between LARS and autophagy in vivo. Furthermore, autophagy regulation by LARS could lead to development of new therapeutics for IFLS1.

Highlights

Leucyl-transfer RNAs (tRNAs) synthetase (LARS) is an enzyme that catalyses the ligation of leucine with leucine tRNA
LARS has a non-canonical role as a mammalian target of rapamycin complex 1-associated protein required for amino acid-induced mTORC1 activation, indicating that LARS is a tRNA synthetase, and an intracellular leucine sensor for mTORC1 s ignalling[5,6,7,8]
Biallelic mutation in the cytoplasmic LARS leads to an infantile hepatopathy called infantile liver failure syndrome type 1 (ILFS1), which is characterized by acute liver failure in the first few months and is associated with failure to thrive, anaemia, microcephaly, muscular hypotonia, and seizures[15,16]

Summary

Introduction

Leucyl-tRNA synthetase (LARS) is an enzyme that catalyses the ligation of leucine with leucine tRNA. Larsb+/+ larvae had no apparent autophagic structures in the liver, larsb−/− larvae displayed large vacuoles, including floating nuclei and various sized dots with Lc3b immunoreactivity, thereby indicating autophagic cell death (Fig. 3C). Autophagy caused by Larsb deficiency occurred in some tissues, including the skeletal muscle and spinal cord, the liver was the most damaged tissue in larsb−/− zebrafish.

Results

Conclusion