Affinity, potency, efficacy, and selectivity of neurokinin A analogs at human recombinant NK2 and NK1 receptors

PLoS One. 2018 Oct 25;13(10):e0205894. doi: 10.1371/journal.pone.0205894. eCollection 2018.

Abstract

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 [125I]-NKA binding to NK2 receptors and displacement of [3H]-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 (EC50) for NK2 and NK1 receptors. Ranking compounds by their relative affinity (Ki) or potency (EC50) at NK2 or NK1 receptors indicated that the most selective NK2 agonists tested were [Lys5,MeLeu9,Nle10]-NKA(4-10) (NK1/NK2 Ki ratio = 674; NK1/NK2 EC50 ratio = 105) and [Arg5,MeLeu9,Nle10]-NKA(4-10) (NK1/NK2 Ki ratio = 561; NK1/NK2 EC50 ratio = 70). The endogenous peptide, NKA, lacked selectivity with an NK1/NK2 Ki ratio = 20 and NK1/NK2 EC50 ratio = 1. Of the compounds selected for evaluation in cyclic AMP stimulation assays, [β-Ala8]-NKA(4-10) had the greatest selectivity for activation of NK2 over NK1 receptors (NK1/NK2 EC50 ratio = 244), followed by [Lys5,MeLeu9,Nle10]-NKA(4-10) (ratio = 74), and NKA exhibited marginal selectivity (ratio = 2.8).

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Animals
  • CHO Cells
  • Calcium / metabolism
  • Cell Membrane / metabolism
  • Cricetinae
  • Cricetulus
  • Cyclic AMP / metabolism
  • Dose-Response Relationship, Drug
  • Drug Evaluation, Preclinical
  • Humans
  • Neurokinin A / analogs & derivatives*
  • Neurokinin A / chemistry*
  • Peptides / chemistry
  • Receptors, Neurokinin-1 / chemistry*
  • Receptors, Neurokinin-2 / chemistry*
  • Recombinant Proteins / chemistry*
  • Reproducibility of Results

Substances

  • Peptides
  • Receptors, Neurokinin-1
  • Receptors, Neurokinin-2
  • Recombinant Proteins
  • TACR1 protein, human
  • Neurokinin A
  • Cyclic AMP
  • Calcium

Grants and funding

NMJR, KBT, DJR and ECB are partners of Dignify Therapeutics LLC. MC, CG, PC, AS and EP are employees of Aptuit. Research reported in this publication was supported in part by the National Institute on Aging of the National Institutes of Health under award number R43AG055169. The funder provided support in the form of salaries for KBT, DJR and ECB and research funding, but did not have any additional role in the study design, data collection and analysis, decision to publish, or preparation of the manuscript. The specific roles of these authors are articulated in the ‘author contributions’ section.