Evidence That the Proposed Novel Human “Neurokinin-4” Receptor Is Pharmacologically Similar to the Human Neurokinin-3 Receptor but Is Not of Human Origin
- Henry M. Sarau1,
- Jeffrey L. Mooney3,
- Dulcie B. Schmidt1,
- James J. Foley1,
- Peter T. Buckley1,
- Giuseppe A. M. Giardina4,
- Da Y. Wang2,
- Jonathan A. Lee1,2 and
- Douglas W. P. Hay1
- Departments of 1Pulmonary Biology (H.M.S., D.B.S., J.J.F., P.T.B., D.W.P.H.), 2Gene Expression Sciences (D.Y.W., J.A.L.), and 3Molecular Biology (J.L.M.), SmithKline Beecham Pharmaceuticals, King of Prussia, Pennsylvania; and 4Department of Medicinal Chemistry, Via Zambeletti, Milan, Italy (G.A.M.G.)
Abstract
There have been proposals that the tachykinin receptor classification should be extended to include a novel receptor, the “neurokinin-4” receptor (NK-4R), which has a close homology with the human NK-3 receptor (hNK-3R). We compared the pharmacological and molecular biological characteristics of the hNK-3R and NK-4R. Binding experiments, with 125I-[MePhe7]-NKB binding to HEK 293 cell membranes transiently expressing the hNK-3R (HEK 293-hNK-3R) or NK-4R (HEK 293-NK-4R), and functional studies (Ca2+ mobilization in the same cells) revealed a similar profile of sensitivity to tachykinin agonists and antagonists for both receptors; i.e., in binding studies with the hNK-3R, MePhe7-NKB > NKB > senktide ≫ NKA = Substance P; with the NK-4R, MePhe7-NKB > NKB = senktide ≫ Substance P = NKA; and with antagonists, SB 223412 = SR 142801 > SB 222200 ≫ SR 48968 ≫ CP 99994 for both hNK-3R and NK-4R. Thus, the pharmacology of the two receptors was nearly identical. However, attempts to isolate or identify the NK-4R gene by using various molecular biological techniques were unsuccessful. Procedures, including nested polymerase chain reaction studies, that used products with restriction endonuclease sites specific for either hNK-3R or NK-4R, failed to demonstrate the presence of NK-4R in genomic DNA from human, monkey, mouse, rat, hamster, or guinea pig, and in cDNA libraries from human lung, brain, or heart, whereas the hNK-3R was detectable in the latter libraries. In view of the failure to demonstrate the presence of the putative NK-4R it is thought to be premature to extend the current tachykinin receptor classification.
Footnotes
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Send reprint requests to: Douglas W. P. Hay, Ph.D., Department of Pulmonary Biology, UW2532, SmithKline Beecham Pharmaceuticals, 709 Swedeland Rd., King of Prussia, PA 19406. E-mail:douglas_w_hay{at}sbphrd.com
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↵1 Current address: Eli Lilly and Company, Research Technologies and Proteins, Lilly Corporation Center, Indianapolis, IN.
- Abbreviations:
- NK
- neurokinin
- TM
- transmembrane
- hNK-3R
- human neurokinin-3 receptor
- NK-4R
- putative human NK-4 receptor
- SB 222200
- (S)-(−)-N-(α-ethylbenzyl)-3-methyl-2-phenylquinoline-4-carboxamide
- SB 223412
- (S)-(−)-N-(α-ethylbenzyl)-3-hydroxy-2-phenylquino line-4-carboxamide
- SR 142801, (S)-(+)-N-{{3-[1-benzoyl-3-(3,4-dichlorophenyl)piperidine-3-yl]prop-1-yl}-4-phenylpiperidin-4-yl}-N- methylacetamide
- SR 48964, (S)-N-methyl-N[4-(4-acetylamino-4-phenyl piperidino)-2-(3,4-dichlorophenyl)butyl]benzamide
- CP 99994
- (+)-(2S,3S)-cis-(2-methoxybenzylamino)-2-phenylpiperidine dihydrochloride
- PCR
- polymerase chain reaction
- HEK
- human embryonic kidney
- HEK 293-hNK-3R
- HEK 293 cells transiently expressing the human NK-3 receptor
- HEK 293-NK-4R
- HEK 293 cells transiently expressing the human NK-4 receptor
- UTR
- untranslated region
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- Received February 29, 2000.
- Accepted May 26, 2000.
- The American Society for Pharmacology and Experimental Therapeutics
