Kinases are one of the most intensively pursued drug targets investigated for the treatment of cancer. Kinase inhibitors usually target the ATP binding site; however, the similarity of this site across many kinases often results to non-selectivity. Allosteric modulators of protein function offer a novel approach of inhibition that target less conserved binding sites found on the inactive enzymes; thus higher selectivity can be obtained. PI3Ka is the most frequently mutated kinase in human cancers with one of its most common mutations being a histidine changed to arginine in exon 20 (H1047R). Molecular dynamics (MD) simulations in aqueous solution were carried out totaling one microsecond for both wild type (WT) and mutant PI3Ka proteins. Binding site analysis in the kinase domain identified cavities in the vicinity of the H1047R mutation and the membrane binding regions. Virtual screening and subsequent biochemical assays in these sites identified several micromolar PI3Ka inhibitors. The effect of the inhibitors on WT and mutant PI3Ka-membrane association was subsequently studied by SPR experiments. These experiments showed that these small molecules significantly alter protein-membrane affinity, unlike other known PI3Ka inhibitors like wortmannin. Further description of these newly-identified binding sites and modeling of the PI3Ka interactions with the cell membrane may facilitate the development of novel mutant-specific PI3Ka inhibitors that target the protein-membrane interface and exploit the altered conformation of the mutant with respect to the wild type protein.

Modulation of PI3Ka protein-membrane interactions by small molecules investigated with a combined experimental and theoretical approach

248th National Meeting (2014)

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