Fig. 7: Schematic of MCARE function in fast-twitch skeletal muscles.

In WT muscle fibers, MCARE enhances SERCA1 activity by displacing its inhibitory micropeptide MRLN, thereby maintaining Ca²⁺ homeostasis. In contrast, Mcare-deficient fast-twitch fibers exhibit impaired Ca²⁺ reuptake, leading to Ca²⁺ homeostasis disruption. This dysfunction results in muscle atrophy, rippling contractions, and increased vulnerability to physical stress.