Protein arginine methyltransferases coordinate mitochondrial stress adaptation and neuromuscular function.

Sarcopenia and neuromuscular degeneration are key drivers of functional decline during ageing and arise not solely from muscle loss but also from failure of mitochondrial and metabolic stress adaptation across the neuromuscular system. Mitochondrial dysfunction, characterized by impaired oxidative phosphorylation, defective quality control and redox imbalance, contributes directly to muscle weakness, neuromuscular junction instability and motor unit degeneration. However, the upstream mechanisms governing the transition from adaptive remodelling to degenerative collapse remain incompletely defined. Protein arginine methyltransferases (PRMTs) have emerged as critical modulators of mitochondrial and metabolic stress signalling. Beyond epigenetic regulation, PRMTs influence signalling pathways that intersect with AMP-activated protein kinase (AMPK)-Forkhead box O (FOXO) and mechanistic target of rapamycin (mTOR), thereby regulating mitochondrial biogenesis, selective autophagy and mitophagy, proteostatic balance, and anabolic restraint. Distinct PRMT family members exert non-redundant functions across muscle fibres, satellite cells and motor neurons, collectively shaping neuromuscular stress resilience. We propose that PRMTs act as molecular rheostats that bias cellular responses to mitochondrial stress towards adaptive resolution or progression to neuromuscular degeneration, thereby positioning PRMT-regulated metabolic signalling as a unifying mechanism underlying sarcopenia and compromised healthspan.