Biochemical and Biophysical Research Communications
cDNA Sequence and heterologous expression of the human neurokinin-3 receptor☆
Abstract
Functional cDNA clones encoding the human neurokinin-3 receptor were isolated from human brain mRNA. The cloned human neurokinin-3 receptor was expressed in COS cells and Xenopus oocytes, where peptide binding affinity and intracellular effector activation were determined. Neurokinin B is the most potent agonist, followed by eledoisin, substance K and substance P. The binding affinities of these peptides at the human neurokinin-3 receptor differ quantitatively from the rat receptor, implying a functional consequence of the sequence divergence between the two species. Heterologous expression in oocytes revealed that, unlike the neurokinin-1 receptor, the efficacy of ion channel activation mediated by the neurokinin-3 receptor does not approximate the binding affinity. The heterologous expression of the human neurokinin-3 receptor will facilitate further investigation into its biochemical functions.
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Synthesis and biological evaluation of novel fluoro and iodo quinoline carboxamides as potential ligands of NK-3 receptors for in vivo imaging studies
2004, Bioorganic and Medicinal ChemistryIn order to develop radioligands of human NK-3 receptor (hNK-3r) for imaging studies by positron emission tomography (PET) or single photon emission computed tomography (SPECT), a new series of fluoro- and iodo-quinoline carboxamides were synthesized and evaluated in a target receptor binding assay. Compared to the unsubstituted parent compound SB 223 412 (Ki=27 nM ± 9), affinity was not altered for the analogues 1c and 2c bearing a fluorine in position 8 (Ki ∼ 24–27 nM), and was only slightly reduced for compounds 1b, 2b, 1e and 2e fluorinated or iodinated at the position 7 (Ki ∼ 49–67 nM). A drastic reduction in binding (Ki > 115 nM) was observed for all other halogenated compounds 1a, 2a, 1d, 2d, 1f and 2f.
Molecular and pharmacological characterization of the murine tachykinin NK<inf>3</inf> receptor
2001, European Journal of PharmacologyStarting with a partial sequence from Genbank, polymerase chain reaction (PCR) was utilized to isolate the full-length cDNA for NK3 receptor from mouse brain. The murine NK3 receptor has a predicted sequence of 452 amino acids, sharing 96% and 86% identity to the rat and human NK3 receptors, respectively. Binding affinities and functional potencies of tachykinin receptor agonists were similar in HEK (human embryonic kidney) 293 cells expressing murine NK3 receptor and human NK3 receptor, although substance P and neurokinin A were more potent stimulators of Ca2+ mobilization in murine NK3 receptor cells. NK3 receptor-selective antagonists from two structural classes, had 10- to 100-fold lower binding affinities for murine NK3 receptor compared to human NK3 receptor, and about 5- to 10-fold reduced potency in the murine NK3 receptor functional assay. The results demonstrate species differences in the potencies of tachykinin receptor antagonists in murine and human NK3 receptors, and the lower potencies in the former should be taken into consideration when using murine disease models.
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Tachykinins increase [<sup>3</sup>H]acetylcholine release in mouse striatum through multiple receptor subtypes
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These findings indicate that tachykinins modulate the activity of mouse striatal cholinergic interneurons. Furthermore, neurokinin-2 receptors are shown to perform a role in mouse that has not been identified previously in other species.
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Sequence data from this article have been deposited with the EMBL/GenBank Data Libraries under Accession No. M89473.