Phosphatidylinositol 3-kinase/Akt/mammalian target of rapamycin signaling pathway (PI3K-Akt-mTOR pathway)

The **PI3K/Akt/mammalian target of rapamycin (mTOR) signaling pathway** is an intracellular signal transduction cascade that plays a central role in regulating cell growth, proliferation, metabolism, survival, apoptosis suppression, angiogenesis, autophagy control and other vital cellular processes. The core components include phosphatidylinositol 3‑kinase (**PI3K**), the serine/threonine kinase **Akt** (also known as protein kinase B), and the mechanistic target of rapamycin (**mTOR**) which forms two complexes—mTORC1 and mTORC2. Activation typically begins at the cell membrane via receptor tyrosine kinases or G protein-coupled receptors responding to extracellular signals such as growth factors or hormones. This leads to sequential activation/phosphorylation events culminating in increased protein synthesis via S6 kinase activation by mTORC1. Dysregulation—most commonly overactivation—of this axis is implicated in many cancers due to its roles in promoting proliferation while suppressing apoptosis. Loss-of-function mutations in negative regulators like PTEN further drive oncogenicity. The clinical relevance has led to development of targeted therapies including allosteric or catalytic inhibitors against various nodes within this network; for example rapamycin analogs inhibit mTOR activity directly. Because "Akt-mTOR" refers collectively to multiple proteins within an integrated network rather than one discrete molecular entity or receptor gene product—and because drugs generally do not bind both simultaneously—the term does not correspond precisely to standard therapeutic targets such as individual enzymes or receptors.

Other names

PI3K/Akt/mTOR pathwayPI3K-Akt signaling pathwayAkt/PKB signaling pathwaymTOR signaling axis

mTOR inhibition blocks protein synthesis and cell growth/proliferation by inhibiting mTORC1 activity. AKT inhibition promotes apoptosis and reduces cell survival signals. PI3K inhibition prevents activation of downstream AKT/mTOR signaling.