Phosphoinositide 3-kinase regulatory subunit 1 (PIK3R1)

Phosphoinositide 3-kinase regulatory subunit 1 (PIK3R1), widely known as p85-alpha, is a pivotal regulatory component of the Class IA phosphoinositide 3-kinase (PI3K) complex. It plays a dual role by stabilizing the catalytic p110 subunits and maintaining them in an inhibited state until activated by cell surface receptors (UniProt: P27306). Upon stimulation of receptor tyrosine kinases, PIK3R1 recruits the PI3K complex to the cell membrane, facilitating the production of PIP3 and the subsequent activation of the AKT/mTOR signaling pathway, which is essential for cell growth and insulin response (PubMed: 22869208). Genetic alterations in PIK3R1 are major contributors to human disease. Gain-of-function mutations are frequent in cancers such as endometrial and breast carcinoma, where they disrupt the inhibitory interface between the regulatory and catalytic subunits, driving oncogenic signaling (PubMed: 24634280). Furthermore, germline mutations can cause Activated PI3K Delta Syndrome 2 (APDS2), a severe immunodeficiency, or SHORT syndrome, a condition marked by insulin resistance and growth delays (NIH: GARD). Therapeutic strategies include the use of pathway inhibitors like leniolisib, specifically approved for APDS2, making PIK3R1 a critical focal point for precision medicine in both oncology and immunology (PubMed: 36803274).

Other names

Phosphatidylinositol 3-kinase regulatory subunit alphap85-alphaP85AGRB1Phosphoinositide 3-kinase 85 kDa regulatory subunit alpha

Stabilization and negative regulation of PI3K catalytic subunits (p110 alpha, beta, and delta); drugs typically inhibit the catalytic activity of the PI3K heterodimer or address signaling overactivation caused by regulatory subunit mutations.