Replating induces mTOR-dependent rescue of protein synthesis in Charcot-Marie-Tooth diseased neurons

Abstract

Charcot-Marie-Tooth disease (CMT) is an inherited peripheral neuropathy characterized by sensory dysfunction and muscle weakness, manifesting in the most distal limbs first and progressing more proximal. Over a hundred genes are currently linked to CMT with enrichment for activities in myelination, axon transport, and protein synthesis. Mutations in tRNA synthetases cause dominantly inherited forms of CMT and animal models with CMT-linked mutations in these enzymes display defects in neuronal protein synthesis. Rescuing protein synthesis in CMT mutant neurons could offer exciting therapeutic options beyond symptom management. To address this need, we expressed CMT-linked variants in tyrosyl tRNA synthetase (YARS-CMT) in primary sensory neurons and evaluated impacts on protein synthesis and cell viability. YARS-CMT expression reduced protein synthesis in these neurons prior to the onset of caspase-dependent axon degeneration and cell death. To determine how YARS-CMT expression affects axon outgrowth, we dissociated and replated these neurons to stimulate axon regeneration. To our surprise, axonal regrowth occurred normally in replated YARS-CMT neurons. Moreover, replating YARS-CMT neurons rescued protein synthesis. Inhibiting mTOR suppressed rescue of protein synthesis after replating, consistent with its significant role in protein synthesis during axon regeneration. These discoveries identify new avenues for augmenting protein synthesis in diseased neurons and restoring protein synthesis in CMT or other neurological disorders.