Phosphatidylinositol signaling pathway (PI signaling pathway) (PI signaling pathway)

The phosphatidylinositol and phosphatidylinositol phosphate signaling pathways are essential regulatory networks that control diverse cellular functions including growth, proliferation, and metabolism [KEGG Pathway: map04070]. These pathways function through the reversible phosphorylation of phosphatidylinositol at the 3, 4, and 5 positions of the inositol ring, catalyzed by specific kinases and phosphatases [Cantley, Science, 2002]. Key second messengers such as phosphatidylinositol 3,4,5-trisphosphate (PIP3) are generated, which recruit pleckstrin homology (PH) domain-containing proteins like AKT to the plasma membrane [Manning & Toker, Cell, 2017]. This recruitment triggers downstream cascades, most notably the PI3K/AKT/mTOR axis, which is a central regulator of protein synthesis and cell cycle progression [Fruman et al., Cell, 2017]. Aberrant activation of these pathways is a common driver in oncology, often resulting from mutations in the PIK3CA gene or the loss of the PTEN phosphatase [Thorpe et al., Nat Rev Cancer, 2015]. Consequently, these pathways are major focal points for drug development, with numerous inhibitors targeting PI3K isoforms, AKT, and mTOR currently in clinical use or development [Janku et al., Nat Rev Clin Oncol, 2018].

Other names

Phosphoinositide signaling pathwayPI3K/AKT/mTOR pathwayPhosphatidylinositol phosphate signalingInositol phosphate metabolism

Drugs targeting this pathway primarily act as small molecule inhibitors of specific lipid kinases (e.g., PI3K) or protein kinases (e.g., AKT, mTOR), thereby blocking the production or downstream effects of phosphoinositide second messengers like PIP3 [Janku et al., 2018; Thorpe et al., 2015].