Phosphatidylinositol 3-kinase beta isoform (PI3Kβ)

Phosphatidylinositol 3‑kinase beta isoform (PI3Kβ) is a member of the class IA phosphoinositide 3‑kinases. It functions as a heterodimer composed of a regulatory subunit (commonly p85) and a catalytic subunit known as p110β encoded by the PIK3CB gene. This enzyme catalyzes phosphorylation of phosphatidylinositol-(4,5)-bisphosphate [PI(4,5)P2] at the D‑3 position to generate phosphatidylinositol-(3,4,5)-trisphosphate [PI(3,4,5)P₃], which acts as a second messenger recruiting PH domain-containing proteins like AKT to cellular membranes. Activation occurs downstream of receptor tyrosine kinases and G protein-coupled receptors. The resulting signal transduction regulates diverse cellular processes including growth/proliferation, survival/apoptosis resistance mechanisms, metabolism, migration, and differentiation. Dysregulation—by mutation or overexpression—of class I PI 3‑kinases including β has been implicated in oncogenesis across multiple tumor types. As such it represents an important therapeutic target under investigation for cancer drug development. The enzyme’s structure includes several domains facilitating interactions with regulatory proteins and membrane lipids; its activity can be modulated by upstream kinases/phosphatases or direct small-molecule inhibition.

Other names

PI3K betaPhosphoinositide 3-kinase betap110β (refers to the catalytic subunit encoded by PIK3CB)PIK3CB (gene name)

Drugs targeting this molecule typically act as ATP competitive inhibitors of its lipid kinase activity, thereby blocking downstream signaling through pathways such as AKT/PKB.