My research group is a computational chemistry group. We are involved in large scale simulations of transmembrane proteins (G protein-coupled receptors) embedded in lipid bilayers, as well in studies of the interactions of drugs with these proteins. Our calculations are carried out on a new Linux cluster here at UNCG and on a Blue Gene main frame computer at the IBM Thomas J. Watson Research Center . These calculations focus primarily on the cannabinoids (CBs), but also include the opioid and dopamine systems. We have established collaborations with medicinal chemists and pharmacologists such that compounds we design can be synthesized and evaluated. We also have established collaborations with molecular biologists so that mutations that we design to test hypotheses concerning the importance of individual amino acid residues can also be generated and evaluated. We use the resultant experimental information to improve our models, with the goal that at any given time, these models represent the current state of knowledge in the field. A few examples of projects in progress in the lab are given below:
Endocannabinoid Project: How Do Endocannabinoids Enter the CB1 and CB2 Receptors? Supported by National Institutes of Health Grants (DA03934 and DA021358)
One area of interest in the cannabinoid field at present is the field of endogenous cannabinoids. These are the ligands that are made in our bodies for specific interaction with cannabinoid receptors. Emerging knowledge about the endocannbinoid system in the brain has indicated that this system was designed to suppress overactive neurotransmitter release from vesicle stores in the brain, thereby exerting a “calming” effect on neurotransmission. In this way, the cannabinoid system has an important effect on mood and on memory.
In the past few years, we have undertaken a study aimed at elucidating how endocannabInoids enter the CB1 and CB2 receptors and how they bind after entering. In collaboration with Dr. Mike Pitman (Project Leader, Blue Gene Membrane Protein Science Biomolecular Dynamics and Scalable Modeling Computational Biology Center, IBM Thomas J. Watson Research Center), we have recently undertaken microsecond scale molecular dynamics (MD) studies of the interaction of 2-AG, the CB2 endogenous agonist with the CB2 receptor in a POPC bilayer (NVT ensemble, T=310K, with velocity resampling occuring every nanosecond). In one of these simulations (now near 2 microseconds), a 2-AG molecule approaches CB2 in the TMH6/TMH7 area and enters CB2 by passing between these two helices. This simulation exhibits many of the elements associated with receptor activation. The figure above illustrates the position of 2-AG at 288ns poised to enter CB2 between TMH6 and TMH7. Additional simulations are currently underway to ascertain if the full binding/activation event can be simulated.
Supported by National Institutes of Health Grant (DA023204)
We have recently received a new grant award. The overall goal of this project is to characterize two putative cannabinoid receptor sub-types: GPR55 and GPR35 and to develop high affinity antagonists for each. Receptor cloning, receptor mutation, radioligand binding and functional characterizations will be performed in the laboratory of Dr. Mary E. Abood at California Pacific Medical Research Institute. We are presently refining computer models of GPR35 and GPR55. Our predictions will be tested experimentally through mutation studies performed in Dr. Abood's lab. Illustrated above are preliminary computer models of GPR55 and GPR35.
REPRESENTATIVE PUBLICATIONS
1. R. M. Whitnell, D. P. Hurst, P. H. Reggio, F. Guarnieri. “Conformational Memories with Variable Bond Angles”, J. Comput. Chem. 29, 741-752 (2008).
2. S. Anavi- Goffer , D. Fleischer, D. P. Hurst, D. L. Lynch, J. Barnett-Norris, S. Shi, D. L. Lewis, S. Mukhopadhyay, A. C. Howlett, P. H. Reggio, M. E. Abood. “Helix 8 Leu in the CB1 Cannabinoid Receptor Contributes to Selective Signal Transduction.” J. Biol. Chem., 282, 25100-25113 (2007).
3. A. Kapur, D.P. Hurst, D. Fleischer, R. Whitnell, A. Makriyannis, P.H. Reggio, M.E. Abood. “Mutation Studies of S7.39 and S2.60 in the Human CB1 Cannabinoid Receptor: Evidence for a Serine Induced Bend in CB1 Transmembrane Helix 7.” Mol. Pharmacol. 71, 1512-1524 (2007).
4. D. P. Hurst, U. Umijiego, D.L. Lynch , H. H. Seltzman, S. Hyatt, M. Roche, S. D. McAllister, D. Fleischer, A. Kapur, M. E. Abood, S. Shi, J. Jones, D. L. Lewis and P. H. Reggio .” Biarylpyrazole Inverse Agonists at the Cannabinoid CB1 Receptor: Importance of the C-3 Carboxamide Oxygen/Lysine3.28(192) Interaction.” J. Med. Chem. 49, 5969-5987 (2006).
5. D.L.Lynch and P.H. Reggio. “Cannabinoid CB1 Receptor Recognition of Endocannabinoids via the Lipid Bilayer: Molecular Dynamics Simulations of CB1 Transmembrane Helix 6 and Anandamide in a Phospholipid Bilayer.” J. Comp. Aided Mol. Design 20, 495-509 (2006).