Modulation of PDZ domain-mediated protein-protein interactions

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PDZ (PSD-95, Dlg, ZO-1) domains play important roles in cellular signalling pathways by mediating protein-protein interactions. The native peptide ligands bind into a ridge between a ß-strand and the C-terminal helix which has properties of a small-molecule binding site. Inhibitors with low to medium affinity for several PDZ domains were identified in the first funding period and members of the respective substance classes were collected in a PDZ-library . Improvements of the AF6 PDZ domain Inhibitors by modelling-chemistry cycles resulted in compounds with ten to twenty micromolar dissociation constants, disrupting the AF6-Bcr interaction in cell lysates. In the second funding period we want to exploit our results and focus on three PDZ domains (AF6, DVL, Shank3), aiming at an understanding of the biology of the respective proteins. The AF6 PDZ domain inhibitors will be investigated further in cell biological and in vivo experiments using a zebra fish model (collaboration with Ted Allison, Alberta). Inhibitors of Dishevelled (DVL9) will be investigated with respect their effects on the Wnt signalling pathway in collaboration with TP 9 (Birchmeier, von Kries). The role of the Shank3 in the postsynaptic density will be investigated together with Dietmar Schmitz, of the Berlin Neurocure program. The identification of selectivity patterns of PDZ domains by computational methods will help to further develop even more specific inhibitors. Specific ligands will be generated by cycles of NMR-spectroscopic investigations, Computer assisted ligand design, and medicinal chemistry. As a model case we will develop specific ligands binding to CAL but not to NHERF, two proteins playing crucial roles in cystic fibrosis.