B199
Targeting the plekstrin homology domain
Tom Elliott1, Joseph Nemeth1, Alexander Gray2, Pete Downes2, Stuart Conway1
1University of St Andrews, Fife, UK, 2University of Dundee, Dundee, UK
Phosphatidylinositol (3,4,5)-trisphosphate (PtdIns(3,4,5)P3) is an important intracellular signalling molecule that is up regulated following activation of insulin receptors, certain G-protein coupled receptors and tyrosine kinase receptors. PtdIns(3,4,5)P3 exerts its biological action through binding to effector proteins that contain specific phosphate-binding motifs. The majority of these binding sites are plekstrin homology (PH) domain containing-proteins such as protein kinase B (PKB), general receptor for phosphoinositides 1 (GRP1) and tandem-PH-domain-containing protein 1 and 2 (TAPP1 and 2). Selective inhibitors of phosphate binding will aid the biological investigation of these proteins and provide detailed insight into their role and those of PtdIns(3,4,5)P3. Importantly, up regulation of PKB is known to occur in numerous human malignancies, and therefore PKB inhibition may provide useful route to cancer chemotherapeutics. Our research is directed towards the chemical synthesis of PtdIns(3,4,5)P3 analogues designed to act as selective PH domain inhibitors.
Herein we detail a chemical synthetic approach towards derivatives of PtdIns(3,4,5)P3, commencing the meso compound myo-inositol. Using a series of protecting group manipulations a synthetically useful enantiopure intermediate can be obtained. From this intermediate, a bio-isosteric phosphate mimic can be incorporated selectively for each phosphate group of PtdIns(3,4,5)P3. Biological analysis of these analogues will elucidate the importance of each phosphate group in PH domain binding, which will direct the synthesis of inhibitors of improved selectivity and potency. The initial biological investigations indicate that the O-1 analogues bind to the PH domain of GRP1 and could potentially show inhibitory activity while the O-4 position modified derivatives showed no binding affinity for this protein.
