Prediction of Essential Binding Domains for the Endocannabinoid N-Arachidonoylethanolamine (AEA) in the Brain Cannabinoid CB1 receptor

Abstract

{triangleup}9-tetrahydrocannabinol ({triangleup}9-THC), the main active ingredient of Cannabis sativa (marijuana), interacts with the human brain cannabinoid (CB1) receptor and mimics pharmacological effects of endocannabinoids (eCBs) N-arachidonylethanolamide (AEA) and 2-arachidonoylglycerol (2-AG). Given recent intriguing findings that some allosteric modulators can enhance selectively the AEA-activated CB1 receptor, it is imperative to determine the structure of the AEA-bound CB1 receptor. However, due to its highly flexible nature of AEA, establishing its binding mode to the CB1 receptor is elusive. The aim of the present study was to explore many possible binding conformations of AEA within the binding pocket of the CB1 receptor that is confirmed in the recently available X-ray crystal structures of the agonist-bound CB1 receptors and predict essential AEA binding domains. We performed long time molecular dynamics stimulations of plausible AEA docking poses until its receptor binding interactions became optimally established. Our simulation results revealed that AEA favors to bind to the hydrophobic channel of the CB1 receptor, suggesting that the hydrophobic channel holds essential significance in AEA binding to the CB1 receptor. Our results also suggest that the H2/H3 region of the CB1 receptor is an AEA binding subsite privileged possibly over the H7 region. The results of the present study contribute to identifying the (hidden) allosteric site(s) of the CB1 receptor in our immediate future study.