Structural Insight into the Inactive/Active States of 5-HT1AR and Molecular Mechanisms of Electric Fields in...

Probing the differences between inactive/active states of the serotonin 1A receptor (5-HT1AR) and the dynamic receptor conformations is vital for understanding signaling transduction pathways and diverse physiological responses. Here, we compared the conformational features between the inactive and active states of 5-HT1AR and explored the role of serotonin in the activation process of 5-HT1AR by using molecular dynamics (MD) simulations. The results show that the position of TM6 and the arrangements of key motifs exhibit distinctions in the inactive and active states of 5-HT1AR. The binding of serotonin to 5-HT1AR is mostly driven by hydrophobic, aromatic stacking, anion-π, and H-bonding interactions. We also performed additional MD simulations with electric fields (EFs) of 0.01 and 0.03 V/nm to investigate the effects of EFs on the conformation of the 5-HT1AR-serotonin complex. The conformational change of 5-HT1AR and the inward movement of TM6 are increased with the field strength, indicative of a dependence on the strength of the EF. The EF of 0.03 V/nm affects the binding behaviors of serotonin with 5-HT1AR and further disturbs the activation of 5-HT1AR by serotonin. This study first reveals atomic-level information about the distinct features between inactive and active states of 5-HT1AR and demonstrates the pivotal role of EF in modulating the 5-HT1AR-ligand complex.