Phosphoinositide 3-kinase class I and mechanistic target of rapamycin complexes 1 and 2 (PI3K class I and mTORC1/mTORC2)

**Phosphoinositide 3-kinase class I (PI3K class I)** and the **mechanistic target of rapamycin complexes 1 and 2 (mTORC1 and mTORC2)** are critical components of the PI3K/AKT/mTOR signaling pathway, a central regulator of cellular metabolism, growth, proliferation, and survival[1][2][3][7]. - **PI3K class I** enzymes are heterodimeric lipid kinases activated by cell surface receptors (such as receptor tyrosine kinases and G protein-coupled receptors), leading to the production of phosphatidylinositol (3,4,5)-trisphosphate (PIP3) and activation of downstream signaling, including AKT and mTOR[2][4][6]. - **mTORC1** is a multisubunit protein complex (containing mTOR, Raptor, mLST8, and other components) that responds primarily to growth factor and nutrient stimuli to promote protein, lipid, and nucleotide synthesis and inhibit autophagy[1][9]. - **mTORC2** (contains mTOR, Rictor, SIN1, mLST8, Protor) is activated downstream of PI3K signaling in many contexts and regulates cell survival, cytoskeleton organization, and AKT activation[3][5]. These two nodal signaling hubs are **dysregulated in many diseases, notably cancer, and are prominent therapeutic targets**. Drugs inhibiting PI3K and/or mTOR enzymatic activity are in clinical use or development for various cancers and immune disorders, but toxicity and resistance remain significant therapeutic challenges[1][9]. *For rigorous database or structured entries, PI3K class I, mTORC1, and mTORC2 should ideally be listed as distinct entities. The above reflects their common co-targeting in research and therapy.*

Other names

PI3K/mTOR pathwayPI3K class IA and IB (for PI3K)mTOR (sometimes used broadly)mechanistic target of rapamycin complex 1 (mTORC1)mechanistic target of rapamycin complex 2 (mTORC2)PI3-kinase/mTOR

ATP-competitive inhibition of PI3K or mTOR kinase activity Allosteric inhibition (e.g., rapamycin binds FKBP12 and then mTORC1) Dual inhibition of both PI3K and mTOR (some compounds block both enzyme families)