The discovery of the endogenous cannabinoid (CB) system, i.e. the CB receptors (the subtypes CB1 and CB2), endogenous ligands and enzymes for CB ligand metabolism, has triggered intensive pharmacological research into the CB receptors and the therapeutic potential of cannabinergic ligands. The CB2 receptor is known to be involved in the signal transduction cascades in the immune system, and has a great therapeutic potential for developing CB2 drugs without CB1-related psychotropic side effects for treatment of chronic neuro-pain, neuronal disorders, autoimmune diseases, and gliomas and other tumors of immune origin, thereby benefiting the millions of patients who suffer from the autoimmune/immune-related diseases for which we have no cure. Over the years, however, structural and functional studies of CB receptors have focused on predicting structures by computer modeling, identification of the specific sites for ligand binding and G-protein coupling whereas studies on experiment 3D CB structures are limited, in particular for the CB2 receptor. To understand the molecular mechanism behind these pharmacological and biochemical events, it is important to characterize the contacting points and binding domains and then elucidate the specific CB2/ligand recognition and CB2/G-protein coupling mechanisms at molecular structural level. In our published and pilot studies, we have successfully investigated the structural and conformational features of several CB2 protein functional domains;CB ligand structures and active pharmacophoric features;and agonist/antagonist recognition sites in the CB2 receptor. However, many questions still remain about CB2 receptor structure-function relationship as well as CB2 ligands and G-protein recognition mechanisms. The objective of this proposal is to identify/characterize the key residues/functional domains and elucidate their 3D structures of recognition pockets important to agonist and antagonist binding as well as G-protein coupling recognitions in the CB2 receptor by the combined biophysical and biochemical approaches. Our long term goal is to understand, in structural and functional terms, the molecular mechanisms of human CB2 activation and G-protein cell signaling process in order to facilitate the structure-based design for novel CB2 ligands. Having completed the "proof-of-concept" research work, we propose the specific goals and in-depth research to three aims.
Aim 1 : Characterize the functional domains and key residues important to the CB2 ligand recognition and derive the structural determinants of the agonist/antagonist binding domains in the transmembrane and extra-cellular segments.
Aim 2 : Investigate and define the structural and functional features of the important CB2 intracellular segments and key residues involving G-protein coupling and intracellular cell signaling by the biophysical approaches developed and validated in Aim 1.
Aim 3 : Explore full-length CB2 receptor and confirm the key residues determined in Aims 1 and 2 and verify their importance to CB2 ligand recognition and G-protein coupling by functional binding assays and site-directed mutations of the native CB2 receptor. The elucidated CB2 agonist/antagonist recognition pockets and G-protein coupling domains will be further examined by our established computer modeling and receptor docking algorithms. Our proposed research and the outcomes will shed light onto a better understanding of CB2 structure/function and its mechanism of actions, and provide the structural bases for CB2-specific drug design in future. The techniques and methods developed from the proposed CB2 receptor research will also have a significant impact to other GPCRs.

Public Health Relevance

This proposal is to identify and elucidate their 3D structures of recognition pockets important to agonist and antagonist binding as well as G-protein coupling recognitions in the cannabinoid CB2 receptor. The long-term benefits will allow us to better understand, in structural and functional terms, the molecular mechanisms of human CB2 activation and G-protein cell signaling process in order to facilitate structure-based design for novel CB2 chemical probes.

National Institute of Health (NIH)
National Institute on Drug Abuse (NIDA)
Research Project (R01)
Project #
Application #
Study Section
Macromolecular Structure and Function D Study Section (MSFD)
Program Officer
Hillery, Paul
Project Start
Project End
Budget Start
Budget End
Support Year
Fiscal Year
Total Cost
Indirect Cost
University of Pittsburgh
Schools of Pharmacy
United States
Zip Code
Wang, Lirong; Xie, Xiang-Qun (2014) Computational target fishing: what should chemogenomics researchers expect for the future of in silico drug design and discovery? Future Med Chem 6:247-9
Cai, Zhengxin; Ouyang, Qin; Zeng, Dexing et al. (2014) 64Cu-labeled somatostatin analogues conjugated with cross-bridged phosphonate-based chelators via strain-promoted click chemistry for PET imaging: in silico through in vivo studies. J Med Chem 57:6019-29
Feng, Zhiwei; Alqarni, Mohammed Hamed; Yang, Peng et al. (2014) Modeling, molecular dynamics simulation, and mutation validation for structure of cannabinoid receptor 2 based on known crystal structures of GPCRs. J Chem Inf Model 54:2483-99
Wang, Nuozhou; Bartlow, Patrick; Ouyang, Qin et al. (2014) Recent advances in antimultiple myeloma drug development. Pharm Pat Anal 3:261-77
Liu, Haibin; Wang, Lirong; Lv, Mingliang et al. (2014) AlzPlatform: an Alzheimer's disease domain-specific chemogenomics knowledgebase for polypharmacology and target identification research. J Chem Inf Model 54:1050-60
Feng, Rentian; Milcarek, Christine A; Xie, Xiang-Qun (2014) Antagonism of cannabinoid receptor 2 pathway suppresses IL-6-induced immunoglobulin IgM secretion. BMC Pharmacol Toxicol 15:30
Zhang, Shaojuan; Jia, Ningyang; Shao, Pin et al. (2014) Target-selective phototherapy using a ligand-based photosensitizer for type 2 cannabinoid receptor. Chem Biol 21:338-44
Chen, Xiaofei; Cao, Yan; Zhang, Hai et al. (2014) Comparative normal/failing rat myocardium cell membrane chromatographic analysis system for screening specific components that counteract doxorubicin-induced heart failure from Acontium carmichaeli. Anal Chem 86:4748-57
Alqarni, Mohammed; Myint, Kyaw Zeyar; Tong, Qin et al. (2014) Examining the critical roles of human CB2 receptor residues Valine 3.32 (113) and Leucine 5.41 (192) in ligand recognition and downstream signaling activities. Biochem Biophys Res Commun 452:334-9
Liu, Haibin; Wang, Lirong; Su, Weiwei et al. (2014) Advances in recent patent and clinical trial drug development for Alzheimer's disease. Pharm Pat Anal 3:429-47

Showing the most recent 10 out of 24 publications