In silico strategy for isoform-selective 5-HT2AR and 5-HT2CR inhibitors

5-HT2AR and 5-HT2CR are widely expressed throughout the brain and have been drawing significant clinical interest due to their involvement in mediating mental disorders. Indeed, 5-HT2AR acts as a biological target for atypical antipsychotics and addiction, and 5-HT2CR also serves as a therapeutic target for depression and addiction. Given that 5-HT2AR and 5-HT2CR provide opposing influences upon DA mesocorticoaccumbens output, plus 5-HT2CR is thought to be involved in appetite that might result in the side effect of weight gain, it makes great sense for drug design to provide the selective mechanisms of 5-HT2AR and 5-HT2CR in order to meet the increasing need for more effective medications. Toward this end, the structure and chemical properties of crucial residues between 5-HT2AR and 5-HT2CR were analyzed based on their individual crystal structures. Moreover, pruvanserin and RS102221, the highly selective antagonists of 5-HT2AR and 5-HT2CR, respectively, were employed to illuminate the selective binding modes through a comprehensive application of in silico methods, including molecular docking, molecular dynamic simulations, MM-GBSA, alanine scanning mutagenesis, DFT technologies, and structure-based pharmacophore modeling. It was found that although 5-HT2A/CR isoforms share high sequence homology in active pockets, they do possess distinctive physiological functions. The key residues that contributed to the selectivity between 5-HT2A/CR are ASP155, LEU229, TRP336, and PHE340 of 5-HT2AR, as well as ASP134, LEU209, and PHE328 of 5-HT2CR. Moreover, in view of the much smaller hydrophobic region of the 5-HT2AR, a ligand with reduced side chain volume would increase its selectivity to 5-HT2AR, and vice versa. In addition, considering that RS102221/5-HT2CR formed more water bridges compared to that of pruvanserin/5-HT2AR, hydrogen bonding interactions should be emphasized in the design of 5-HT2CR selective inhibitors. Collectively, this study provided novel insights into the rational selectivity mechanisms of 5-HT2AR/5-HT2CR inhibitors, which laid important foundations for designing selective inhibitors towards 5-HT2AR and 5-HT2CR.