Molecular determinants of tetrahydrocannabinol binding to the glycine receptor

Abstract

The recognition of Cannabis as a source of new compounds suitable for medical use has attracted strong interest from the scientific community in its research, and substantial progress has accumulated regarding cannabinoids' activity; however, a thorough description of their molecular mechanisms of action remains a task to complete. Highlighting their complex pharmacology, the list of cannabinoids' interactors has vastly expanded beyond the canonical cannabinoid receptors. Among those, we have focused our study on the glycine receptor (GlyR), an ion channel involved in the modulation of nervous system responses, including, to our interest, sensitivity to peripheral pain. Here, we report the use of computational methods to investigate possible binding modes between the GlyR and Δ9‐tetrahydrocannabinol (THC). After obtaining a first pose for the THC binding from a biased molecular docking simulation and subsequently evaluating it by molecular dynamic simulations, we found a dynamic system with an identifiable representative binding mode characterized by the specific interaction with two transmembrane residues (Phe293 and Ser296). Complementarily, we assessed the role of membrane cholesterol in this interaction and positively established its relevance for THC binding to GlyR. Lastly, the use of restrained molecular dynamics simulations allowed us to refine the description of the binding mode and of the cholesterol effect. Altogether, our findings contribute to the current knowledge about the GlyR‐THC mode of binding and propose a new starting point for future research on how cannabinoids in general, and THC in particular, modulate pain perception in view of its possible clinical applications.

Structural Basis for Molecular Recognition of Cannabinoids by Inhibitory Cys-Loop Channels

“…Further, the analysis of the ligand–receptor interaction appears somewhat limited, mentioning only the formation of a single hydrogen bond between THC and Ser296. Finally, it is worth noting that the orientation of THC proposed in this study differs from that observed in subsequent cryo-EM structures or more rigorous MD simulations …”

“…Auspiciously, a combination of docking and MD simulations from the hGlyR-α3 crystal structure could accurately predict the global orientation of THC in the Ser296 binding site, 33 in a similar position to that observed in the cryo-EM structures. Only slight differences from the cryo-EM model are observed, especially concerning various Phe residues interacting with the THC aromatic ring, which opens new research directions.…”

“…Finally, it is worth noting that the orientation of THC proposed in this study differs from that observed in subsequent cryo-EM structures 32 or more rigorous MD simulations. 33 In the same year, the authors explored the action of CBD and various of its synthetic analogues on GlyR-α3. 42 They found that the potentiation caused by DH-CBD in receptors expressed in HEK293 cells was higher than the potentiation observed for CBD and, oppositely, that DD-CBD inhibited cannabinoid-induced I Gly .…”

“…Concurrently with Kumar's paper, a combined docking and MD simulation study to explore how THC binds to the crystal structure of human GlyR-α3 was reported by us. 33 The initial positions were first attempted to be constructed by Autodock with grids centered on the Cα atom of Ser296 (TM3 17 ); however, this procedure did not provide solutions with acceptable energies and frequencies. It is worth noting that the use of GOLD docking package also failed to correctly predict the binding mode of THC at the GlyR site: the solution obtained by Koniuszewski et al placed THC in the opposite orientation to that observed in the CryoEM structures.…”

“…31 Here, we review the advances made toward understanding the molecular determinants of cannabinoid action, starting with the first reports of phytocannabinoids' effects on inhibitory Cys-loop channels, the establishment of their significance in THC-induced analgesia, followed by a critical revision of the different molecular models proposed over the years. To conclude, we examine recent findings obtained from both the resolution of cryo-EM structures 32 and thorough computational studies on the cannabinoid binding mode, 33 comparing results, strengths, and limitations of each method. Disclosing a proper methodology to decipher the mechanism of action of cannabinoids on inhibitory channels may enable the elucidation of the precise pharmacological actions of cannabinoids on the CNS.…”