PRMT1 (protein arginine methyltransferase 1) is essential for neuromuscular junction and mitochondrial homeostasis via mitophagy regulation

The neuromuscular junction (NMJ) is essential for transmitting neural stimulus to muscles, triggering muscle contraction. Mitochondria are enriched in NMJ to support the energy needs required for neuromuscular function and stability. Thus, maintaining mitochondrial homeostasis through the clearance of damaged mitochondria, a process known as mitophagy, is vital for preserving neuromuscular health. Here, we highlight the crucial role of muscle PRMT1 in maintaining NMJ and mitochondrial homeostasis via mitophagy regulation. PRMT1 is distinctively expressed in myofibers, accumulating in the postsynaptic area, with its levels upregulated in denervated muscles. PRMT1-ablated muscles displayed disrupted NMJs and an accumulation of abnormal mitochondria, accompanied by increased mitochondrial oxidative stress. Additionally, <i>prmt1</i> depletion in muscles specifically impaired TBK1 (TANK binding kinase 1)-OPTN (optineurin)-mediated mitophagy. Overall, our findings suggest that PRMT1 plays a critical role in maintaining NMJ and mitochondrial health by regulating selective mitophagy through TBK1-OPTN.<b>Abbreviations:</b> ADMA: asymmetric arginine dimethylation; BTX: α-bungarotoxin; EDL: extensor digitorum longus; FDB: flexor digitorum brevis; GAS: gastrocnemius; NMJ: Neuromuscular junction; Mko: mice with muscle-specific <i>prmt1</i> ablation; MTOR: mechanistic target of rapamycin kinase; OPTN: optineurin; PRMT1: protein arginine methyltransferase 1; SA: sodium arsenate; SNI: sciatic nerve crush injury; Sol: soleus; SQSTM1/p62: sequestosome 1; TBK1: TANK binding kinase 1; TOMM20: translocase of outer mitochondrial membrane 20; TA: tibialis anterior; VDAC1: voltage dependent anion channel 1.