Interaction analyses of hTAAR1 and mTAAR1 with antagonist EPPTB

Area of Science:

• Pharmacology
• Computational Chemistry
• Structural Biology

Background:

• Trace amine-associated receptor 1 (TAAR1) is crucial for regulating monoaminergic neurotransmission.
• EPPTB is a potent antagonist for mouse TAAR1 but shows weak activity against human TAAR1, necessitating structural investigation.
• Understanding TAAR1-ligand interactions is vital for developing targeted therapeutics.

Purpose of the Study:

• To elucidate the molecular mechanisms behind the differential binding affinity of EPPTB to mouse (m) and human (h) TAAR1.
• To identify key amino acid residues contributing to the observed differences in antagonist activity.
• To provide a structural basis for future drug design targeting TAAR1.

Main Methods:

• Homology modeling was employed to generate structural models of hTAAR1.
• Molecular docking and molecular dynamics (MD) simulations were performed to analyze ligand-receptor interactions.
• Molecular mechanics-generalized Born surface area (MM-GBSA) calculations were used to predict binding energies.

Main Results:

• MD simulations revealed eight populated conformers for the hTAAR1-EPPTB complex, useful for virtual screening.
• MM-GBSA calculations indicated a stronger binding energy for EPPTB with mTAAR1 (-106.7 kcal/mol) compared to hTAAR1 (-96.5 kcal/mol).
• Specific amino acid differences in the binding sites of mTAAR1 (Y153, A193, Y287) and hTAAR1 (F154, T194, I290) were identified as potential contributors to the affinity variation.

Conclusions:

• The study successfully explains the lower binding affinity of EPPTB to hTAAR1 compared to mTAAR1 through computational analysis.
• Identified structural differences in TAAR1 binding pockets provide insights into antagonist selectivity.
• The findings support structure-based drug design for developing selective TAAR1 modulators.