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

The RAS-binding domain (RBD) of Phosphatidylinositol 4,5-bisphosphate 3-kinase catalytic subunit alpha (PI3Kα) is a specialized structural motif within the p110α protein, encoded by the PIK3CA gene, that mediates essential protein-protein interactions with activated RAS GTPases (UniProt: P42336). This interaction serves as a critical regulatory mechanism, allowing RAS to recruit PI3Kα to the plasma membrane where it converts phosphatidylinositol 4,5-bisphosphate (PIP2) into phosphatidylinositol 3,4,5-trisphosphate (PIP3), thereby triggering the AKT/mTOR signaling cascade (PubMed: 27058662). PI3Kα is one of the most frequently mutated oncogenes in human cancers, particularly in breast, endometrial, and colorectal malignancies, where it drives uncontrolled cell growth and survival (PubMed: 30545854). While most clinical inhibitors like alpelisib target the ATP-binding pocket of the kinase domain, the RBD is a significant focal point for research into disrupting RAS-effector interactions, which is particularly relevant in RAS-mutant cancers. Therapeutic targeting of PI3Kα is highly effective but is frequently associated with metabolic side effects, most notably hyperglycemia, because PI3Kα is a primary mediator of the cellular response to insulin (PubMed: 31091374). Consequently, managing glucose levels is a primary clinical challenge when utilizing drugs that affect this target.

Other names

p110α RAS-binding domainPIK3CA RBDPhosphoinositide 3-kinase alpha RBDp110-alpha RBDPhosphatidylinositol 3-kinase catalytic subunit alpha RBD

Inhibition of the catalytic activity of the p110α subunit or disruption of the physical interaction between activated RAS GTPases and the PI3Kα RAS-binding domain to prevent the recruitment of PI3K to the plasma membrane and subsequent AKT pathway activation (PubMed: 27058662, PubMed: 30545854).