UNASSIGNED: Class IB @entity7425 3-kinases y (PI3Ky) are second-messenger-generating enzymes downstream of signalling cascades triggered by G-protein-coupled receptors (GPCRs). PI3Ky variants have one catalytic p110y subunit that can form two different heterodimers by binding to one of a pair of non-catalytic subunits, @entity31771 or @entity70185 . Growing experimental data argue for a different regulation of @entity31771 -p110y and @entity70185 -p110y allowing integration into distinct signalling pathways. Pharmacological tools enabling distinct modulation of the two variants are missing. The ability of an anti-p110y monoclonal antibody [mAb(A)p110y] to block PI3Ky enzymatic activity attracted us to characterize this tool in detail using purified proteins. In order to get insight into the antibody-p110y interface, @entity3884 - @entity6189 exchange coupled to @entity15 ( @entity15 ) measurements were performed demonstrating binding of the monoclonal antibody to the C2 domain in p110y, which was accompanied by conformational changes in the helical domain harbouring the Gby-binding site. We then studied the modulation of phospholipid vesicles association of PI3Ky by the antibody. @entity31771 -p110y showed a significantly reduced Gby-mediated phospholipid recruitment as compared with @entity70185 -p110y. Concomitantly, in the presence of mAb(A)p110y, Gby did not bind to @entity31771 -p110y. These data correlated with the ability of the antibody to block Gby-stimulated lipid kinase activity of @entity31771 -p110y 30-fold more potently than @entity70185 -p110y. Our data argue for differential regulatory functions of the non-catalytic subunits and a specific Gby-dependent regulation of @entity70185  in PI3Ky activation. In this scenario, we consider the antibody as a valuable tool to dissect the distinct roles of the two PI3Ky variants downstream of GPCRs.

Different inhibition of Gby-stimulated class IB phosphoinositide 3-kinase (PI3K) variants by a monoclonal antibody. Specific function of XXXX as a Gby-dependent regulator of PI3Ky enzymatic activity.

@entity3884 :: ('MESH:D006859', 'Chemical') :: ['hydrogen'] @entity7425 :: ('CHEBI:18179', 'Chemical') :: ['phosphoinositide'] @entity70185 :: ('23533', 'Gene') :: ['p101'] @entity31771 :: ('10989', 'Gene') :: ['p87'] @entity6189 :: ('MESH:D003903', 'Chemical') :: ['deuterium'] @entity15 :: ('MESH:D009103', 'Disease') :: ['MS', 'HDX-MS']
@entity70185 :: (23533,Gene) :: ['p101']
