Phosphatidylinositol 4,5-bisphosphate 3-kinase catalytic subunit alpha (PI3Kα)

Phosphatidylinositol 4,5-bisphosphate 3-kinase catalytic subunit alpha (PI3Kα) is a class IA phosphoinositide 3-kinase that plays a central role in the PI3K/AKT/mTOR signaling pathway. It is a heterodimer consisting of a p110α catalytic subunit (encoded by the PIK3CA gene) and a p85 regulatory subunit (Source: UniProt: P42336). PI3Kα is activated by various cell surface receptors, including receptor tyrosine kinases (RTKs), to generate the second messenger PIP3, which mediates essential cellular processes such as growth, survival, and glucose homeostasis (Source: PMID: 29735994). In many human cancers, including breast, colorectal, and endometrial cancers, the PIK3CA gene is frequently mutated or amplified, leading to constitutive pathway activation and tumor progression (Source: NIH NCI Thesaurus). Therapeutic targeting of PI3Kα has led to the development of several inhibitors, most notably alpelisib, which is FDA-approved for PIK3CA-mutated, hormone receptor-positive breast cancer (Source: FDA Piqray Label). While these drugs are designed to inhibit oncogenic signaling, they also affect wildtype PI3Kα in healthy tissues, particularly in the liver and muscle where the enzyme is critical for insulin-mediated glucose uptake. This interference often results in significant metabolic side effects, such as hyperglycemia and hyperinsulinemia, which represent major clinical challenges in the use of PI3Kα inhibitors (Source: PMID: 31217518). Ongoing research focuses on developing mutant-selective inhibitors to improve the therapeutic window by sparing wildtype PI3Kα signaling.

Other names

PIK3CAp110αPhosphoinositide-3-kinase catalytic alpha polypeptidep110-alphaP110alpha

PI3Kα inhibitors typically act as ATP-competitive antagonists that bind to the catalytic pocket of the p110α subunit. This binding prevents the phosphorylation of phosphatidylinositol 4,5-bisphosphate (PIP2) into phosphatidylinositol 3,4,5-trisphosphate (PIP3), thereby inhibiting the recruitment and activation of downstream effectors like AKT and mTOR (Source: PMID: 30038242, UniProt: P42336).