Open AccessAffinity, potency, efficacy, and selectivity of neurokinin A analogs at human recombinant NK2 and NK1 receptors
Author(s) -
N. M. J. Rupniak,
Elisabetta Perdonà,
Cristiana Griffante,
Palmina Cavallini,
Anna Sava,
Daniel J. Ricca,
Karl B. Thor,
Edward C. Burgard,
Mauro Corsi
Publication year - 2018
Publication title -
plos one
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.99
H-Index - 332
ISSN - 1932-6203
DOI - 10.1371/journal.pone.0205894
Subject(s) - agonist , receptor , potency , chemistry , neurokinin a , ec50 , biochemistry , substance p , in vitro , neuropeptide
A series of peptide NK2 receptor agonists was evaluated for affinity, potency, efficacy, and selectivity at human recombinant NK2 and NK1 receptors expressed in CHO cells to identify compounds with the greatest separation between NK2 and NK1 receptor agonist activity. Binding studies were performed using displacement of [ 125 I]-NKA binding to NK2 receptors and displacement of [ 3 H]-Septide binding to NK1 receptors expressed in CHO cells. Functional studies examining the increase in intracellular calcium levels and cyclic AMP stimulation were performed using the same cell lines. A correlation was demonstrated between binding affinities (Ki) and potency to increase intracellular calcium (EC 50 ) for NK2 and NK1 receptors. Ranking compounds by their relative affinity (Ki) or potency (EC 50 ) at NK2 or NK1 receptors indicated that the most selective NK2 agonists tested were [Lys 5 ,MeLeu 9 ,Nle 10 ]-NKA(4-10) (NK1/NK2 Ki ratio = 674; NK1/NK2 EC 50 ratio = 105) and [Arg 5 ,MeLeu 9 ,Nle 10 ]-NKA(4-10) (NK1/NK2 Ki ratio = 561; NK1/NK2 EC 50 ratio = 70). The endogenous peptide, NKA, lacked selectivity with an NK1/NK2 Ki ratio = 20 and NK1/NK2 EC 50 ratio = 1. Of the compounds selected for evaluation in cyclic AMP stimulation assays, [β-Ala 8 ]-NKA(4–10) had the greatest selectivity for activation of NK2 over NK1 receptors (NK1/NK2 EC 50 ratio = 244), followed by [Lys 5 ,MeLeu 9 ,Nle 10 ]-NKA(4-10) (ratio = 74), and NKA exhibited marginal selectivity (ratio = 2.8).