Phosphatidylinositol 4,5-bisphosphate 3-kinase catalytic subunit alpha (PI3Kα) RAS-binding domain – RAS–PI3Kα interface (PI3Kα RBD–RAS interface)

The PI3Kα RAS-binding domain (RBD) – RAS–PI3Kα interface is a critical regulatory site within the Phosphatidylinositol 4,5-bisphosphate 3-kinase catalytic subunit alpha (PI3Kα). PI3Kα is a lipid kinase that converts PIP2 to PIP3, a secondary messenger that triggers the AKT/mTOR signaling cascade to promote cell growth and survival (UniProt P42336). The RBD allows PI3Kα to function as a direct effector of RAS GTPases; upon growth factor stimulation, activated RAS-GTP binds to the RBD, facilitating the recruitment of PI3Kα to the plasma membrane and its subsequent activation (PubMed: 29033127). This interaction is frequently hyperactivated in human cancers through mutations in either the PIK3CA gene or RAS isoforms (KRAS, HRAS, NRAS), making the interface a high-priority therapeutic target (PubMed: 30249607). Unlike traditional ATP-competitive inhibitors, drugs targeting this interface aim to disrupt the physical protein-protein interaction, potentially reducing systemic toxicities like hyperglycemia associated with total PI3K inhibition. Experimental agents such as rigosertib have been studied for their ability to act as RAS mimetics that block these effector interactions (PubMed: 27156451). Targeting this specific interface offers a strategy to selectively inhibit RAS-driven PI3K signaling while sparing basal PI3K activity.

Other names

p110α RAS-binding domainPIK3CA RBDRAS-PI3Kα interaction sitePI3K-RAS interface

Inhibition of protein-protein interaction between RAS and PI3Kα, preventing RAS-mediated recruitment and activation of the PI3K pathway.