Nutrient-sensing and mTORC1 regulation in neuronal homeostasis: from metabolic signaling to neurodegeneration

Neurons rely on precise nutrient-sensing mechanisms to sustain proteostasis and stress resilience across a lifetime. Among these, mechanistic target of rapamycin complex 1 (mTORC1) functions as a central metabolic hub, integrating amino acid availability, growth factor signals, and energetic status to coordinate protein synthesis, autophagy, and neuronal survival. Neuronal mTORC1 regulation is highly specialised, reflecting unique metabolic demands, axonal compartmentalisation, and dependence on long-term homeostatic control that is not shared by non-neuronal cell types. Beyond canonical PI3K–Akt and AMPK signaling, emerging evidence highlights metabolic intermediates — most notably leucine-derived acetyl-coenzyme A (AcCoA) — as critical upstream regulators that couple nutrient flux to mTORC1 activity via EP300-mediated Raptor acetylation. Chronic dysregulation of these pathways drives persistent mTORC1 hyperactivation, progressive autophagy impairment, and accumulation of proteotoxic species, collectively contributing to neurodegeneration. In Alzheimer's disease, aberrant mTORC1 activity is linked to tau hyperphosphorylation and amyloid-β accumulation; in Parkinson's disease, to α-synuclein aggregation and mitophagy failure; in Huntington's disease, to impaired clearance of mutant huntingtin; and in ALS, to dysregulated proteostasis in motor neurons. This mini review synthesizes current understanding of neuronal mTORC1 regulation, with emphasis on the AcCoA–acetylation axis as an emerging metabolic control mechanism, its disease-specific implications across major neurodegenerative conditions, and the therapeutic opportunities these insights reveal upstream of mTORC1.