Phosphatidyl 3-kinases (PI3K) are a family of lipid kinases involved in many cellular processes, including cell growth, proliferation, differentiation, motility, and survival. PI3K is a heterodimer composed of 2 subunits—an 85 kDa regulatory subunit (p85) and a 110 kDa catalytic subunit. The PIK3CA gene encodes p110α, one of the catalytic subunits.
PI3K converts PI(4,5)P2 [Phosphatidylinositol 4,5-bisphosphate] to PI(3,4,5)P3 [Phosphatidylinositol (3,4,5)-trisphosphate] on the inner leaflet of the cell membrane. PI(3,4,5)P3 recruits important downstream signaling proteins, such as AKT, to the cell membrane resulting in increased activity of these proteins.
Mutant PIK3CA has been implicated in the pathogenesis of several cancers, including colon cancer, gliomas, gastric cancer, breast cancer, endometrial cancer, and lung cancer (COSMIC; Samuels et al. 2004)
Figure 1. Schematic of the MAPK and PI3K pathways. . Growth factor binding to receptor tyrosine kinase results in activation of the MAPK signaling pathway (RAS-RAF-MEK-ERK) and the PI3K pathway (PI3K-AKT-mTOR). The letter "K" within the schema denotes the tyrosine kinase domain.
Last Updated: June 1, 2012