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  • Tissue-specific alternative splicing separates the catalytic and cell signaling functions of human leucyl-tRNA synthetase.

Tissue-specific alternative splicing separates the catalytic and cell signaling functions of human leucyl-tRNA synthetase.

The Journal of biological chemistry (2022-02-25)
Max Baymiller, Benjamin Nordick, Connor M Forsyth, Susan A Martinis
ABSTRACT

The aminoacyl-tRNA synthetases are an ancient and ubiquitous component of all life. Many eukaryotic synthetases balance their essential function, preparing aminoacyl-tRNA for use in mRNA translation, with diverse roles in cell signaling. Herein, we use long-read sequencing to discover a leukocyte-specific exon skipping event in human leucyl-tRNA synthetase (LARS). We show that this highly expressed splice variant, LSV3, is regulated by serine-arginine-rich splicing factor 1 (SRSF1) in a cell-type-specific manner. LSV3 has a 71 amino acid deletion in the catalytic domain and lacks any tRNA leucylation activity in vitro. However, we demonstrate that this LARS splice variant retains its role as a leucine sensor and signal transducer for the proliferation-promoting mTOR kinase. This is despite the exon deletion in LSV3 including a portion of the previously mapped Vps34-binding domain used for one of two distinct pathways from LARS to mTOR. In conclusion, alternative splicing of LARS has separated the ancient catalytic activity of this housekeeping enzyme from its more recent evolutionary role in cell signaling, providing an opportunity for functional specificity in human immune cells.

MATERIALS
Product Number
Brand
Product Description

Millipore
ANTI-FLAG® M2 Affinity Gel, purified immunoglobulin, buffered aqueous glycerol solution
Roche
Phytohemagglutinin-L (PHA-L), from Phaseolus vulgaris
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cOmplete, Mini, EDTA-free Protease Inhibitor Cocktail, Protease Inhibitor Cocktail Tablets provided in a glass vial, Tablets provided in a glass vial
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Phorbol 12-myristate 13-acetate, ≥99% (TLC), film or powder
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Bovine Serum Albumin, heat shock fraction, pH 7, ≥98%