Abstract
G protein-coupled receptors (GPCRs) are major therapeutic targets, yet the orphan receptor GPR88 remains relatively underexplored. GPR88 is highly expressed in the striatum and has been implicated in neurological and neuropsychiatric disorders. The synthetic agonists 2-PCCA and RTI-13951-33 are important tools for studying GPR88, but their residue-level recognition at the receptor’s allosteric site remains unclear. Here, we used computational mutagenesis in Schrödinger Maestro to compare how 2-PCCA and RTI-13951-33 respond to substitutions at Ser282 and Gly283. Using the GPR88 cryo-EM structure (PDB 7EJX), Gly283 was mutated to Ala or Trp and Ser282 to Asp or Arg. Ligand stereoisomers were evaluated using Glide XP docking, and top-ranked poses were rescored with Prime MM-GBSA. Most mutations produced less favorable predicted binding, while Ser282 to Asp produced more favorable binding for both ligands, with a larger effect for RTI-13951-33. Paired analysis with Bonferroni correction identified significant effects of Ala283 and Asp282 for RTI-13951-33, whereas 2-PCCA showed significance only for Arg282. Energy decomposition further indicated altered electrostatic, hydrogen-bonding, and solvation contributions in the RTI/Asp282 model. Together, these findings support ligand-specific sensitivity within the GPR88 allosteric pocket and suggest partially distinct recognition mechanisms.