Phosphatidylinositol 4,5-bisphosphate 3-kinase catalytic subunit beta isoform

PIK3CB encodes the catalytic beta isoform of phosphatidylinositol 3-kinase (PI3K), an enzyme that phosphorylates phosphatidylinositol 4,5-bisphosphate to generate PIP3 (UniProt: P42338). PIP3 recruits PH domain-containing proteins such as AKT1 and PDPK1 to cell membranes, activating signaling cascades involved in cell growth, survival, and proliferation. PIK3CB also participates in platelet activation, autophagosome formation, and clathrin-mediated endocytosis through both kinase-dependent and kinase-independent mechanisms (UniProt: P42338).

PIK3CB is broadly expressed across tissues and is involved in multiple signaling pathways downstream of G-protein coupled receptors and receptor tyrosine kinases. The protein plays roles in cell survival and migration, with dysregulation implicated in oncogenic transformation and tumor growth (UniProt: P42338).

PIK3CB is downregulated in Alzheimer's disease brain tissue (Chaparral AD proteomics). In a TMT-labeled proteomic analysis of post-mortem AD brain versus age-matched controls across four subcellular fractions, PIK3CB showed a mean log2 fold-change of −0.94, indicating reduced protein abundance in the disease state. This downregulation may reflect impaired phosphatidylinositol signaling and AKT pathway activity in AD neuropathology.