Research in our lab focuses primarily on molecular recognition between small to medium size ligands (usually peptides) and their macromolecular targets (usually membrane-associated, G protein-coupled receptors, GPCRs) and spans structure-based drug design and synthesis, combinatorial synthesis, protein structure modeling, and biochemical characterization.
1. Development of mixed efficacy opioid ligands
Several reports have suggested that simultaneous administration of mu opioid receptor (MOR) agonists with delta opioid receptor (DOR) antagonists results in analgesia with greatly reduced dependence and tolerance liabilities, features which limit opioid use clinically. Using our validated models for the active (agonist binding) and inactive (antagonist binding) states of MOR and DOR we are developing ligands that act as agonists at MOR and, simultaneously, as antagonists at DOR. Such compounds could have significant clinical value.
2. Design and synthesis of biologically active opioid peptides and peptidomimetics
A main interest in our opioid ligand studies is to be able to use our opioid receptor models to design ligands, sharing a common (or similar) structural scaffold, that are selective for the individual opioid receptors, MOR, DOR, KOR, and the related orphan receptor, ORL1. Many literature reports suggest potential clinical value for agents selective for each of these targets. However, peptides often have properties (too large; too polar; too enzymatically labile) that adversely affect their bioavailability and thus limit their potential as drugs. Consequently we have a strong interest in transferring the key elements of our peptide based structural templates to non-peptide structures (peptidomimetics) and, as in our peptide series, have as the ultimate goal the development of a single central scaffold (or closely related scaffolds) whose differential modification would result in selectivity for different receptors.
3. Investigations of MOR and DOR trafficking and crosstalk
To complement our development of MOR/DOR mixed efficacy ligands, we are also exploring the mechanism by which DOR antagonists, and the DOR receptor itself, affect the development of tolerance and dependence at MOR. To this end we have designed selective fluorescent ligands for MOR and DOR and plan to monitor the trafficking and crosstalk of MOR and DOR in live cell systems using confocal microscopy.
4. Homology modeling of GPCRs, important drug targets
A combination of bioinformatics, molecular modeling and experimental techniques is used to obtain structural models of different G protein-coupled receptors, including opioid, melanocortin, PAR, adrenergic, glycoprotein and gonadotropin-releasing hormone receptors. These protein models are invaluable for guiding our design of opioid receptor-specific ligands with desired properties and, more generally, for examining ligand-protein interactions, mechanisms of signaling and transport, to analyze protein polymorphisms, to design site-directed mutagenesis studies, and to develop pharmaco-chaperones and other receptor-specific ligands.
5. Peptides and proteins in membranes
A comprehensive quantitative model of folding, insertion and association of a-helical peptides and proteins in membranes is under development. It combines thermodynamic theory of helix-coil transition in membranes, empirical energy functions derived from protein engineering data, and the new anisotropic solvent model of the lipid bilayer (PPM 2.0). As a part of this project, we have developed the OPM database which provides 3D structures of transmembrane, monotopic and peripheral proteins whose spatial positions are optimized with respect to the lipid bilayer.
For more information on specific projects please browse our web site!