High-resolution crystal structure of the human CB1 cannabinoid receptor

Abstract

The human cannabinoid G protein-coupled receptors (GPCRs) CB1 and CB2 mediate the functional responses to the endocannabinoids anandamide and 2-arachidonyl glycerol (2-AG), as well as the widely consumed plant (phyto)cannabinoid Δ9-tetrahydrocannabinol (THC)1. The cannabinoid receptors have been the targets of intensive drug discovery efforts due to the therapeutic potential of modulators for controlling pain2, epilepsy3, obesity4, and other maladies. While much progress has recently been made in understanding the biophysical properties of GPCRs, investigations of the molecular mechanisms of the cannabinoids and their receptors have lacked high-resolution structural data. We used GPCR engineering and lipidic cubic phase (LCP) crystallization to determine the structure of the human CB1 receptor bound to the inhibitor taranabant at 2.6 Å resolution. CB1's extracellular surface, including the highly conserved membrane-proximal amino-terminal (N-terminal) region, is distinct from other lipid-activated GPCRs and forms a critical part of the ligand binding pocket. Docking studies further demonstrate how this same pocket may accommodate the cannabinoid agonist THC. Our CB1 structure provides an atomic framework for studying cannabinoid receptor function, and will aid the design and optimization of cannabinoid system modulators for therapeutic ends.

Hydrogen/Deuterium Exchange Mass Spectrometry of Human Green Opsin Reveals a Conserved Pro-Pro Motif in Extracellular Loop 2 of Monostable Visual G Protein-Coupled Receptors

“…The melting temperature difference of 24 °C indicates a reduced stability of green opsin, which is in agreement with other class A GPCRs such as the human CB1 cannabinoid receptor. 74 Unlike rhodopsin, most GPCRs are inherently unstable and express multiple ligandspecific active states. 9,10,75 Successful crystallization of rhodopsin in its active and inactive states without stabilizing agents, signaling partners, or antibodies suggests that both states are discrete and do not suffer from inherent instability and multiple heterogeneous states.…”

Methods for the Development of In Silico GPCR Models

“…S1PR1 (Hanson et al, 2012), LPAR1 (Chrencik et al, 2015), and CB1 (Hua et al, 2016; Shao et al, 2016) are the only lipid-sensing receptors from this set of class A GPCRs that have been crystallized. The widely studied receptors Rho (Li, Edwards, Burghammer, Villa, & Schertler, 2004), β2-AR (Rasmussen et al, 2011), μ-OR (Manglik, Kruse, Kobilka, Thian, Jesper, et al, 2012) and the cannabinoid-related orphan receptors GPR55 (Ross, 2009) and GPR18 (Pertwee et al, 2010) were also included for comparison.…”

Crystal structures of agonist-bound human cannabinoid receptor CB1

“…The principal Cannabis constituent, Δ 9 -THC, exerts its psychotropic effects by activating CB 1 , which is also the primary target of the endocannabinoids, anandamide (AEA) and 2-arachidonoyl glycerol (2-AG) 1,6 . Structural examination of CB 1 in complex with the antagonist AM6538 2 and taranabant 7 provides molecular insights into the inactive state of the receptor, yet does not inform us as to how CB 1 elicits its diverse physiological effects.…”