Peptide and nonpeptide antagonist interaction with constitutively active human AT1 receptors

Minh Tam Le, Patrick M.L. Vanderheyden, M. árta Szaszák, L. ászló Hunyady, Veerle Kersemans, Georges Vauquelin

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28 Citations (Scopus)

Abstract

Wild type human AT1 receptors (WT-AT1) and mutant receptors, in which Asn111 was replaced by glycine (N111G), alanine (N111A) and serine (N111S), or in which Asp281 was replaced by alanine (D281A) or in which N111G and D281A replacements were combined, were transiently expressed in CHO-K1 cells. While the biphenyltetrazole compound candesartan dissociated slowly and behaved as an insurmountable antagonist for WT-AT1, it dissociated swiftly and only produced a rightward shift of the angiotensin Ang II- and -IV dose-response curves for inositol phosphate (IP) accumulation in cells expressing N111G. [3H]candesartan competition binding yielded the same potency order of the related biphenyltetrazoles for WT-AT1 and mutated receptors, i.e. candesartan>EXP3174>irbesartan>losartan. Affinities were equal for WT-AT1 and D281A and 40- to 400-fold lower for all Asn111 mutants. Mutations did not affect the affinity of the peptide antagonist [Sar1Ile8]Ang II (SARILE). Basal IP accumulation in cells with WT-AT1 was not affected by any biphenyltetrazole antagonists and was increased by SARILE to 19% of the maximal Ang II stimulation. Basal IP accumulation was higher for cells expressing the Asn111-mutated receptors. For N111G, this accumulation was partially inhibited by all the biphenyltetrazoles upon long-term (18hr) exposure. In these cells SARILE produced the same maximal stimulation as Ang II. Asn111-mutated AT1 receptors are thought to mimic the pre-activated state of the wild type receptor and comparing the efficacy and affinity of ligands for such mutated receptors facilitate the distinction of partial (SARILE) and inverse (biphenyltetrazoles) agonists from true antagonists.

Original languageEnglish
Pages (from-to)1329-1338
Number of pages10
JournalBiochemical Pharmacology
Volume65
Issue number8
DOIs
Publication statusPublished - Apr 15 2003

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Keywords

  • AT receptor
  • CHO cells
  • Constitutive mutant
  • Insurmountable
  • Nonpeptide antagonist
  • Surmountable

ASJC Scopus subject areas

  • Biochemistry
  • Pharmacology

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