Identification of a Crucial Amino Acid in the Helix Position 6.51 of Human Tachykinin Neurokinin 1 and 3 Receptors Contributing to the Insurmountable Mode of Antagonism by Dual NK₁/NK₃ Antagonists

Abstract

The neurokinins are neuropeptides that elicit their effect through three GPCRs called NK(1), NK(2), and NK(3). Compounds 5 and 6 are dual hNK(1) (K(i) of 0.7 and 0.3 nM) and hNK(3) (K(i) of 2.9 and 1.7 nM) antagonists. Both compounds exhibit an insurmountable mode of antagonism at hNK(1), whereas at hNK(3), they differ in that 5 is an insurmountable but 6 a surmountable antagonist. Using homology modeling and site-directed mutagenesis, hNK(1)-Phe264 and hNK(3)-Tyr315 were found to be the molecular determinants of hNK(1) and hNK(3) antagonism by 5 and 6. In [(3)H]IP studies, the mutation hNK(1)-F264Y converted the mode of action of 5 from insurmountable to partial insurmountable antagonism while it had no effect on that of 6. Conversely, the mutation hNK(3)-Y315F enhanced the insurmountable behavior of 5 and converted 6's surmountable to an insurmountable antagonism. This finding was further confirmed by characterizing additional derivatives of 5 and 6, most notably with a hybrid structure.

Human substance P receptor binding mode of the antagonist drug aprepitant by NMR and crystallography

“…Overall, 15 residues are involved in the binding of aprepitant, of which 10 are highly conserved across the neurokinin receptor subfamily (Supplementary Figure 6). However, the key residue F264 6.51 , which, to our knowledge, is not known to be involved in the ligand binding of NK1R, is presented as tyrosine in NK2R and NK3R 33 . In the NK1R structure, the residue F264 6.51 forms a strong edge–π interaction with the bis-trifluomethyl-phenyl ring of aprepitant, and the substitution of the phenyl group with the phenolic group may disrupt the interaction and cause a spatial clash with the ligand.…”

Pharmacophore Modeling, Virtual Screening, and in Vitro Testing Reveal Haloperidol, Eprazinone, and Fenbutrazate as Neurokinin Receptors Ligands

“…While selective NKR antagonists in clinical trials had rather disappointing outcomes, new hopes are now given to dual and/or triple NKR ligands for the treatment of diverse pathologies. , We therefore aimed to develop a set of models combining NK 1 R, NK 2 R, and NK 3 R activity, which was able to identify the majority of NKR-active compounds from our literature data set and at the same time finds as few decoys as possible. A way to achieve this goal is the generation of various models, the hit lists of which are complementary to each other .…”

“…The unsatisfactory results of subtype receptor-selective compounds in clinical trials shifted the research efforts toward nonselective NKR antagonists favoring the antagonism of more than one NKR in accordance with the activity profiles of the endogenous ligands SP, NKA, and NKB. For example, targeting the treatment of schizophrenia, Hoffmann–La Roche proceeded to investigate dual NK 1 R-/NK 3 R-antagonists, while Novartis 2011 concentrated on the development of compounds binding to all three receptors …”