Phosphoinositide 3-kinase alpha catalytic subunit mutant (PI3Kα (mutant))

Mutant phosphoinositide 3-kinase alpha (PI3Kα) refers to oncogenic variants of the p110α catalytic subunit, encoded by the PIK3CA gene, which forms a dimer with the regulatory subunit p85α. These gain-of-function mutants, most commonly at positions E542K and E545K (helical domain) and H1047R (kinase domain), drive constitutive activation of PI3Kα, increasing membrane recruitment, abrogating normal regulation, and promoting downstream PI3K-AKT-mTOR signaling linked to cell proliferation, survival, and tumorigenesis. PI3Kα mutant proteins play a major role as oncogenic drivers in a large fraction of solid tumors, making them prime therapeutic targets. Crystal and cryo-EM studies reveal that helical domain mutations often disrupt inhibitory interactions with the nSH2 domain of p85α, while kinase domain mutations favor membrane association and ATP-binding modifications. Multiple selective inhibitors—including alpelisib (BYL-719)—are in clinical or preclinical development, though side effects and resistance remain a challenge. Biomarker strategies rely on detecting specific PIK3CA mutations to guide targeted therapy.

Other names

PI3Kα mutantPIK3CA mutantPIK3CA (mutant)p110α mutant

Inhibition of lipid kinase activity by direct binding to the ATP-binding site or allosteric sites, blocking phosphorylation of phosphatidylinositol substrates, thereby dampening downstream AKT/mTOR signaling. Some inhibitors are designed for wild-type versus mutant selectivity