Phosphoinositide 3-kinase class IA (PI3K class IA) (PI3K class IA)

Class IA Phosphoinositide 3-kinases (PI3Ks) are essential lipid kinases that function as critical nodes in the intracellular signaling pathways regulating cell growth, proliferation, and metabolism (Fruman et al., 2017, Cell). These enzymes exist as heterodimers, comprising one of three catalytic p110 subunits (alpha, beta, or delta) and a regulatory p85 subunit (Jean & Kiger, 2014, J Cell Sci). They are primarily activated by receptor tyrosine kinases (RTKs) and G protein-coupled receptors, leading to the production of the second messenger phosphatidylinositol 3,4,5-trisphosphate (PIP3) (Vanhaesebroeck et al., 2010, Nat Rev Drug Discov). PIP3 subsequently recruits and activates downstream effectors such as AKT and mTOR, which drive pro-survival and anabolic processes. Mutations in the genes encoding these subunits, particularly PIK3CA, or the loss of the negative regulator PTEN, are frequently observed in various cancers, leading to constitutive pathway activation (Thorpe et al., 2015, Nat Rev Cancer). Consequently, PI3K class IA has become a major therapeutic target, with several isoform-specific and pan-PI3K inhibitors approved for treating breast cancer and hematologic malignancies (FDA, 2019; 2023). Beyond oncology, the delta isoform is a key target for primary immunodeficiencies and inflammatory disorders due to its restricted expression in hematopoietic cells.

Other names

Class IA PI3KPhosphatidylinositol 3-kinase class IAPI3Kalpha/beta/deltap110-p85 complexPI3K class 1A

Competitive inhibition of the ATP-binding site of the p110 catalytic subunits (alpha, beta, or delta), preventing the phosphorylation of phosphatidylinositol 4,5-bisphosphate (PIP2) into phosphatidylinositol 3,4,5-trisphosphate (PIP3), thereby blocking the recruitment and activation of downstream AKT/mTOR signaling pathways.