Novel and critical function of leucyl-tRNA synthetase in maintaining gastric carcinoma cell homeostasis

An ancient and classic family of enzymes called aminoacyl-tRNA synthetases (aaRSs) charge tRNAs with their cognate amino acids so that tRNAs are prepared for accurate translation of the genetic code, generating proteins essential for all living systems. As living organisms evolved to be more sophisticated systems, transitioning from unicellular to multicellular species, the demand for house-keeping proteins to develop a higher order of functional complexity has also emerged. Thus, aaRSs were repurposed throughout evolution to include non-aminoacylation functions. This included, as just one example, maintenance of homeostasis to accommodate more specialized activity to respond to new and changing environments. In recent years, increasing experimental evidence has shown that aaRSs are also involved in regulating metabolism, development, innate immunity, and inflammation. In one specific case, leucyl-tRNA synthetase (LARS) activates mammalian target of rapamycin complex in response to nutrients level to regulate metabolism of the cell. Because cancer profoundly alters the metabolism of the cell, it was hypothesized that aaRSs may play critical role in its regulation. Bioinformatic studies showed that gastric cancer patients have up-regulated mRNA and protein levels of LARS, suggesting that LARS could be involved in the progression of gastric carcinoma. A combination of approaches measuring the degree of aggressiveness of gastric carcinoma cells demonstrated that the knockdown of LARS decreases viability, proliferation, and migration of carcinoma cells without altering the global translation rate. This suggests that the role of LARS is independent of its house-keeping activity in translation. Immunoblotting analysis and qRT-PCR analysis uncovered up-regulation of tumor suppressor gene, p53, as well as other genes in the apoptosis pathway. In particular, RNA-sequencing identified genes that are significantly enriched in the p53 signaling pathway upon LARS knockdown. Conversely, overexpression of LARS in gastric carcinoma cells appeared to decrease the activity of p53. Interestingly, investigation of LARS mutants demonstrated that leucine substrate-binding and catalytic aminoacylation activity are indispensable for the downregulation of p53. Subsequent activation of p53 after LARS knockdown up-regulates p53 target tumor suppressor genes including p21 and p27. Subsequent to activation of tumor suppressor genes, carcinoma cells undergo cell cycle arrest, ultimately leading to apoptosis, which would explain the underlying mechanism of the attenuation of growth of gastric cancer cells.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Biochemistry

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2023

Author dc:creator

• Kim, Giyeong

Contributors dc:contributor

• Chen, Lin-Feng
• Martinis, Susan A
• Zhang, Kai
• Nelson, Erik R

• Leucyl-trna Synthetase
• P53
• P21
• Cancer

Statement dc:rights

• Copyright 2023 Giyeong Kim

Language dc:language

en, eng

Handle dc:identifier

https://hdl.handle.net/2142/120566

OAI record oai:identifier

https://www.ideals.illinois.edu/oai-pmh?verb=GetRecord&metadataPrefix=etdms&identifier=oai%3Awww.ideals.illinois.edu%3A2142%2F120566