mTOR signaling networks: mechanistic insights and translational frontiers in disease therapeutics

The mammalian target of rapamycin (mTOR) pathway is a central regulator of cellular growth, metabolism, and homeostasis, integrating a wide array of intracellular and extracellular cues, including nutrient availability, growth factors, and cellular stress, to coordinate anabolic and catabolic processes such as protein, lipid, and nucleotide synthesis; autophagy; and proteasomal degradation. The dysregulation of this signaling hub has broad implications for health and disease. To commemorate the 50th anniversary of the discovery of rapamycin, we provide a comprehensive synthesis of five decades of mTOR research. This review traces the historical trajectory from the early characterization of the biological effects of rapamycin to the elucidation of its molecular target and downstream pathways. We integrate fundamental and emerging insights into the roles of mTOR across nearly all domains of cell biology and development, with a particular focus on the expanding landscape of therapeutic interventions targeting this pathway. Special emphasis is placed on the crosstalk between mTOR signaling and mitochondrial regulation, highlighting the mechanisms by which these two metabolic hubs co-regulate cellular adaptation, survival, and disease progression. The dynamic interplay between mTOR and mitochondrial networks governs key aspects of bioenergetics, redox balance, and cell fate decisions and is increasingly implicated in pathophysiological contexts ranging from cancer and aging to neurodegenerative and immune disorders.