Residues remote from the binding pocket control the antagonist selectivity towards the corticotropin-releasing factor receptor-1

The corticotropin releasing factors receptor-1 and receptor-2 (CRF(1)R and CRF(2)R) are therapeutic targets for treating neurological diseases. Antagonists targeting CRF(1)R have been developed for the potential treatment of anxiety disorders and alcohol addiction. It has been found that antagonists targeting CRF(1)R always show high selectivity, although CRF(1)R and CRF(2)R share a very high rate of sequence identity. This has inspired us to study the origin of the selectivity of the antagonists. We have therefore built a homology model for CRF(2)R and carried out unbiased molecular dynamics and well-tempered metadynamics simulations for systems with the antagonist CP-376395 in CRF(1)R or CRF(2)R to address this issue. We found that the side chain of Tyr(6.63) forms a hydrogen bond with the residue remote from the binding pocket, which allows Tyr(6.63) to adopt different conformations in the two receptors and results in the presence or absence of a bottleneck controlling the antagonist binding to or dissociation from the receptors. The rotameric switch of the side chain of Tyr356(6.63) allows the breaking down of the bottleneck and is a perquisite for the dissociation of CP-376395 from CRF(1)R.