Phosphoinositide 3-kinase regulatory subunit alpha (p85α) (PIK3R1)

The Phosphoinositide 3-kinase regulatory subunit alpha (p85α), encoded by the PIK3R1 gene, is a critical adapter protein that regulates the activity and localization of the Class IA PI3K catalytic subunits, most notably p110α (UniProt: P27986). It functions by binding to phosphorylated tyrosine residues on activated growth factor receptors via its SH2 domains, thereby recruiting the PI3K complex to the plasma membrane to initiate signaling (PubMed: 24651010). Beyond its role as an adapter, p85α maintains the catalytic subunit in a low-activity state under basal conditions and protects it from degradation (NCBI Gene: 5295). Mutations in PIK3R1 are associated with various malignancies, including endometrial and colon cancers, where they often lead to overactivation of the AKT signaling pathway (PubMed: 21677173). Additionally, germline mutations in this gene cause SHORT syndrome, characterized by growth retardation and insulin resistance (PubMed: 23812750). While most clinical inhibitors like Alpelisib target the catalytic p110α subunit, the regulatory p85α subunit is a vital component of the therapeutic target complex and a key determinant of pathway sensitivity and resistance (DrugBank: DB11715). Therapeutic modulation of this pathway is a major strategy in oncology, though it is frequently complicated by metabolic side effects such as hyperglycemia due to the pathway's role in insulin signaling.

Other names

p85-alphaPI3-kinase regulatory subunit alphaP85AGRB1Phosphatidylinositol 3-kinase 85 kDa regulatory subunit alpha

Inhibition of the PI3K catalytic subunit (p110) activity within the PI3K complex, preventing the conversion of phosphatidylinositol 4,5-bisphosphate (PIP2) to phosphatidylinositol 3,4,5-trisphosphate (PIP3) (PubMed: 24651010, DrugBank: DB11715).