Inter-Src homology 2 (iSH2) helical domain of Class IA Phosphoinositide 3-kinase Regulatory subunit 2, PIK3R2, also called p85beta
PI3Ks catalyze the transfer of the gamma-phosphoryl group from ATP to the 3-hydroxyl of the inositol ring of D-myo-phosphatidylinositol (PtdIns) or its derivatives. They play an important role in a variety of fundamental cellular processes, including cell motility, the Ras pathway, vesicle trafficking and secretion, immune cell activation, and apoptosis. They are classified according to their substrate specificity, regulation, and domain structure. Class IA PI3Ks are heterodimers of a p110 catalytic (C) subunit and a p85-related regulatory (R) subunit. The R subunit down-regulates PI3K basal activity, stabilizes the C subunit, and plays a role in the activation downstream of tyrosine kinases. All R subunits contain two SH2 domains that flank an intervening helical domain (iSH2), which binds to the N-terminal adaptor-binding domain (ABD) of the catalytic subunit. p85beta, also called PIK3R2, contains N-terminal SH3 and GAP domains. It is expressed ubiquitously but at lower levels than p85alpha. Its expression is increased in breast and colon cancer, correlates with tumor progression, and enhanced invasion. During viral infection, the viral nonstructural (NS1) protein binds p85beta specifically, which leads to PI3K activation and the promotion of viral replication. Mice deficient with PIK3R2 develop normally and exhibit moderate metabolic and immunological defects.
Comment:Class IA PI3Ks consist of heterodimers of a p110 catalytic (C) subunit and a p85-related regulatory (R) subunit. The C and R subunits interact mainly through the iSH2 domain of R subunits and the N-terminal ABD of C subunits.
Structure:2Y3A: Mus musculus p85beta iSH2 domain interacts with p110beta; contacts at 4A. - View structure with Cn3D