Calpain Cleaves Most Components in the Multiple Aminoacyl-tRNA Synthetase Complex and Affects Their Functions

Abstract

Background: The human multiple aminoacyl-tRNA synthetase complex (MSC) has an elongated and multiarmed structure, which might be sensitive to proteases such as calpain in vivo.Results: Partial calpain hydrolysis of MSC components generated specific fragments.Conclusion: Calpain hydrolysis could dissociate the MSC, thereby affecting its function.Significance: Calpain proteolytically degrades MSC components and might regulate the canonical and non-canonical functions of aaRS.

Structural control of caspase-generated glutamyl-tRNA synthetase by appended noncatalytic WHEP domains

“…Furthermore, our nonlinear Guinier point exclusion analysis clearly demonstrates that the minor aggregation observed in ERS 2.5W protein preparation had little effect on the SANS-derived structures. Interestingly, the overall SANS structure of ERS 2.5W is reminiscent of the small-angle X-ray scattering-derived structure of the MSC (53), which exhibited an elongated and multiarmed shape, with demonstrated in- WHEP-driven conformation of glutamyl-tRNA synthetase creased surface accessibility to proteases such as caspases (31) and calpains (30). One implication of this finding is that the WHEP domains of EPRS may contribute in part to the hydrodynamic shape of the MSC.…”

“…With the remarkable selectivity of caspases for the 926 DQVD 929 cleavage site in EPRS, and with the striking conservation of this sequence across more than 600 million years of evolution, it is likely that it is a functionally significant cleavage event. Fragments of EPRS can be generated by additional post-transcriptional and post-translational mechanisms, such as coding-region polyadenylation (EPRS-N1) (14) and calpain-mediated cleavage (30). EPRS-N1 is basally produced in several cell types and is a competitive inhibitor of GAIT complex assembly on target mRNA during translational repression (14).…”

“…EPRS-N1 is basally produced in several cell types and is a competitive inhibitor of GAIT complex assembly on target mRNA during translational repression (14). Calcium-activated calpains target EPRS at several undefined sites, including the WHEP linker, and it is unclear whether calpain-generated EPRS fragments are proteolytically stable in vivo (30). In contrast, caspase-3 and -7 are activated via regulated intrinsic and extrinsic pathways in apoptotic and nonapoptotic contexts and proteolytically process highly specific consensus sites, often generating bioactive fragments (47).…”

“…Proteolytic cleavage of MSC components has been previously demonstrated and proposed to regulate the canonical and noncanonical functions of MSC synthetases and scaffolding proteins (30,31). EPRS has been shown to be a proteolytic target of caspase and calpain activity in vitro; however, neither the cleavage event nor the resulting structural alteration has been characterized (30 -33).…”

Nitrosative stress inhibits aminoacylation and editing activities of mitochondrial threonyl-tRNA synthetase by S-nitrosation

“…The following antibodies were used: anti-β-Actin (KM9001) from Sungene Biotech and the preparation of anti-ThrRS and anti-GluProRS has been described in previous reports ( 11 , 39 ). Purified mature hmtThrRS and mitochondrial AlaRS (mtAlaRS) ( 40 , 41 ) were used as antigens to generate anti-mtThrRS or anti-mtAlaRS antibodies, respectively.…”