Occurrence and pharmacological characterization of four human tachykinin NK sub(2) receptor variants

• Published in: Biochemical pharmacology 2008-08, Vol.76 (4), p.476-481
• Main Authors: Ahlstedt, Ingela, Engberg, Susanna, Smith, John, Perrey, Chris, Moody, Adrian, Morten, John, Lagerstroem-Fermer, Maria, Drmota, Tomas, Von Mentzer, Bengt, Paahlman, Ingrid, Lindstroem, Erik
• Format: Article
• Language: English
• ISSN: 0006-2952
• DOI: 10.1016/j.bcp.2008.06.003

Tachykinin NK sub(2) receptor antagonists are potentially beneficial in treating various disorders including irritable bowel syndrome, urinary incontinence, depression and anxiety. The current study evaluates the frequency of single nucleotide polymorphisms (SNPs) in the human NK sub(2) receptor gene (TACR2). In addition, the potency of the endogenous peptide agonist neurokinin A (NKA), and the small molecule antagonists saredutant (NK sub(2)-selective) and ZD6021 (pan-NK antagonist) at the various NK sub(2) receptor protein variants were determined. The TACR2 gene was sequenced from 37 individuals. Two amino acid changing SNPs encoding the NK sub(2) receptor variants Ile23Thr and Arg375His were found. The frequency of the four possible protein variants differed between populations. Site-directed mutagenesis was performed introducing either SNP or both SNPs into the TACR2 gene and the constructs were transfected into CHO cells. NKA-evoked increases in intracellular Ca super(2+) were monitored by FLIPR. The potency of saredutant and ZD6021 was evaluated by their ability to inhibit NKA-induced increases in intracellular Ca super(2+). NKA evoked increases in intracellular Ca super(2+) with a potency ranging between 1 and 5 nM in CHO cells expressing the different constructs. Saredutant and ZD6021 blocked NKA-evoked increases in intracellular Ca super(2+) with pK sub(b) values ranging between 8.8-9.3 and 7.9-8.7, respectively. The current study demonstrates that polymorphisms leading to the Ile23Thr and Arg375His amino acid exchanges are highly prevalent in the human TACR2 gene. These polymorphisms however do not appear to affect the potency of the endogenous agonist NKA or the small molecule antagonists saredutant and ZD6021 with respect to intracellular Ca super(2+) signalling.