MARS2 encodes mitochondrial methionyl-tRNA synthetase, which canonically functions in mitochondrial protein synthesis by mediating the formation of fMet-tRNAifMet for translation initiation 1. Beyond its traditional role, MARS2 exhibits non-canonical functions through direct interaction with the mitochondrial calcium uniporter (MCU), stimulating mitochondrial Ca2+ influx in a methionine-dependent manner 1. This interaction serves as a molecular switch regulating cellular metabolism and calcium homeostasis. When MARS2 is depleted, mitochondrial Ca2+ influx decreases, leading to p53 upregulation through Ca2+-dependent CaMKII/CREB signaling, which triggers metabolic rewiring from glycolysis to the pentose phosphate pathway and reduces cellular reactive oxygen species levels 1. This metabolic switch inhibits epithelial-mesenchymal transition via cellular redox regulation, suggesting tumor suppressive functions 1. MARS2 expression is regulated by ZEB1 transcription factor in response to Wnt signaling 1. Clinically, MARS2 mutations are associated with combined oxidative phosphorylation deficiency 25 and spastic ataxia 3, reflecting its critical role in mitochondrial function. The dual role of MARS2 in both protein synthesis and calcium-mediated metabolic control positions it as a key regulator of mitochondrial homeostasis and cellular energetics.