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Description

Phosphatidylinositol 3-kinase regulatory subunit alpha (UniProt: P27986, also known as Phosphatidylinositol 3-kinase 85 kDa regulatory subunit alpha, PI3-kinase regulatory subunit alpha, PtdIns-3-kinase regulatory subunit p85-alpha, PI3-kinase subunit p85-alpha, PI3K regulatory subunit alpha, PtdIns-3-kinase regulatory subunit alpha) is encoded by the PIK3R1 (also known as GRB1) gene (Gene ID: 5295) in human. PI3K regulatory subunit alpha catalyzes the phosphorylation of PI(4,5)P2 inositol ring at the 3 position to generate PI(3,4,5)P3, a potent second messenger that mediates survival signaling and insulin action. PI3 Kinase is a heterodimeric complex composed of an 85 kDa regulatory subunit and a 110 kDa catalytic subunit. Following ligand binding, tyrosine phosphorylation of growth factor receptors creates docking sites for p85 binding (through its SH2 domains), and acts as an adapter, mediating the association of the p110 catalytic unit to the plasma membrane. PI3 kinase alpha plays a role in insulin-stimulated increase in glucose uptake and glycogen synthesis in insulin-sensitive tissues. Mutations in PIK3R1 gene are known to be associated with insulin resistance.