The Conformational Properties of the Highly Selective Cannabinoid Receptor Ligand CP-55,940

Abstract

During a search for novel drugs possessing analgesic properties but devoid of the psychotropic effects of marijuana, a group of molecules designated as nonclassical cannabinoids was synthesized by Pfizer. Of these nonclassical cannabinoids CP-55,940 has received the most attention principally because it was used as the high affinity radioligand during the discovery and characterization of the G-protein-coupled cannabinoid receptor. In an effort to obtain information on the stereoelectronic requirements at the cannabinoid receptor active site, we have studied the conformational properties of CP-55,940 using a combination of solution NMR and computer modeling methods. Our data show that for the most energetically favored conformation, (i) the aromatic phenol ring is perpendicular to the cyclohexane ring, and the phenolic O-H bond is coplanar with the aromatic ring and points away from the cyclohexyl ring; ii) the dimethylheptyl chain adopts one of four preferred conformations in all of which the chain is almost perpendicular to the phenol ring; and iii) an intramolecular H-bond between the phenolic and hydroxypropyl groups allows all three hydroxyl groups of CP-55,940 to be oriented toward the upper face of the molecule. Such an orientation by the OH groups may be a characteristic requirement for cannabimimetic activity.The psychoactive effects of cannabinoids, particularly ⌬ 9 -tetrahydrocannabinol (⌬ 9 -THC), 1 are well documented and offer a vexing target for new therapeutic drug discovery. Potential therapeutic applications include analgesia, sedation, attenuation of the nausea and vomiting due to cancer chemotherapy, appetite stimulation, decreasing intraocular pressure in glaucoma, certain motor or convulsant disorders, and concentration-time deficits (1, 2). A most probable site at which many of the pharmacological effects of cannabimimetics are induced is now thought to be the cannabinoid receptor (CB). This receptor type (CB1 and CB2 subtypes are described) is a subgroup of the G i -protein-coupled seven transmembrane spanning receptor superfamily (3). The CB1 receptor subtype is found predominately in brain (4, 5), whereas the CB2 receptor subtype is reported only in peripheral tissue (6).A series of compounds was designed, synthesized, and designated as nonclassical cannabinoids (NCCs), e.g. CP-55,940 in Fig. 1, which differ from classical cannabinoids by the absence of a tetrahydropyran ring, e.g. ⌬ 9 -THC and (Ϫ)9␤-OH-hexahydrocannabinol (7,8). Although the NCCs possess significant analgesic activity, there was sufficient data to indicate that these NCC molecules still exhibit the behavioral effects of the classical analogs (9, 10). Key pharmacophores for the NCC analogs include a phenolic hydroxyl (Ph-OH), an aliphatic side chain attached to the phenyl ring, and a cyclohexyl ring (Cring), all of which are also present in the natural cannabinoid ⌬ 9 -THC. Two additional pharmacophores, the northern and southern aliphatic hydroxyl groups, are not found in the natural cannabinoids but are present in mos...

Mutation Studies of Ser7.39 and Ser2.60 in the Human CB1Cannabinoid Receptor: Evidence for a Serine-Induced Bend in CB1Transmembrane Helix 7

“…At the CB 1 WT binding site identified by modeling studies, CP55,940 is oriented with all three hydroxyls on the same face of the molecule. This orientation of the hydroxyls is consistent with the binding site model for CP55,940 proposed by Xie et al (1996) based upon NMR solution spectra. Each of these hydroxyls finds a hydrogen bonding interaction in the CB 1 WT R* bundle model.…”

The Conformation, Location, and Dynamic Properties of the Endocannabinoid Ligand Anandamide in a Membrane Bilayer

“…Based on substantial experimental evidence, it has been proposed that lipophilic ligands interact with their respective target proteins by first partitioning into the membrane bilayer where they assume a preferred location and orientation (5). We can thus postulate that the lipophilic anandamide resides predominantly within the membrane bilayer either following its release within a neural synapse or after its enzymatic synthesis within the cell membrane by membrane-bound enzymes (7).…”

“…Accumulated evidence indicates that many fatty acid-derived lipophilic neurotransmitters are synthesized, stored, and degraded and also exert their functions within the lipid membrane (1,2). Therefore, it has been suggested that the conformation, location, and orientation of the ligand in the membrane are critical in determining its ability to reach and interact productively with its site of action (3)(4)(5). Exploring the conformational and dynamic properties of these ligands in the membrane can lead to a better understanding of the molecular features involved in their interactions with the target proteins (6).…”

The molecular logic of endocannabinoid signalling

“…This response is accompanied by an elevation in tissue anandamide content, indicating that it might be due to a net increase in anandamide formation rather than to extracellular release of preformed anandamide 27 by the role of an intramembranous amino-acid residue (lysine-192) in the binding of anandamide to CB 1 (REF. 39), as well as by the finding that certain cannabinoid agonists can approach the receptor by lateral membrane diffusion 40 . Nevertheless, it does not account for two pieces of evidence.…”