Y4 Receptors Mediate the Inhibitory Responses of Pancreatic Polypeptide in Human and Mouse Colon Mucosa
- Address correspondence to:
Dr. Helen M. Cox, Wolfson Centre for Age-Related Diseases, King's College London, Guy's Campus, London SE1 1UL, UK. E-mail: helen.m.cox{at}kcl.ac.uk
Abstract
The antisecretory effects of several Y agonists, including pancreatic polypeptide (PP), indicate the presence of Y1, Y2, and Y4 receptors in mouse and human (h) colon mucosae. Here, we used preparations from human and from wild-type (WT), Y4, and Y1 receptor knockout (-/-) mice, alongside Y4 receptor-transfected cells to define the relative functional contribution of the Y4 receptor. First, rat (r) PP antisecretory responses were lost in murine Y4-/- preparations, but hPP and Pro34 peptide YY (PYY) costimulated Y4 and Y1 receptors in WT mucosa. The Y1 antagonist/Y4 agonist GR231118 [(Ile,Glu,Pro,Dpr,Tyr,Arg,Leu,Arg,Try-NH2)-2-cyclic(2,4′),(2′,4)-diamide] elicited small Y4-mediated antisecretory responses in human tissues pretreated with the Y1 antagonist, BIBO3304 [(R)-N-[[4-(aminocarbonylaminomethyl)-phenyl]methyl]-N2-(diphenylacetyl)-argininamide trifluoroacetate)], and attenuated Y4-mediated hPP responses in mouse and human mucosa. GR231118 and rPP were also antisecretory in hY4-transfected epithelial monolayers but were partial agonists compared with hPP at this receptor. In Y4-transfected human embryonic kidney (HEK) 293 cells, Y4 ligands displaced [125I]hPP binding with orders of affinity (pKi) at human (hPP = rPP > GR231118 > Pro34PYY = PYY) and mouse (rPP = hPP > GR231118 > Pro34PYY > PYY) Y4 receptors. GR231118- and rPP-stimulated guanosine 5′-3-O-(thio)triphosphate binding through hY4 receptors with significantly lower efficacy than hPP. GR231118 marginally increased basal but abolished further PP-induced hY4 internalization to recycling (transferrin-labeled) pathways in HEK293 cells. Taken together, these findings show that Y4 receptors play a definitive role in attenuating colonic anion transport and may be useful targets for novel antidiarrheal agents due to their limited peripheral expression.
Footnotes
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This work was supported by a combination of Wellcome Trust and Biotechnology and Biological Sciences Research Council awards (to H.M.C.) and by a Wellcome Trust VIP Award (to N.D.H.).
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Article, publication date, and citation information can be found at http://jpet.aspetjournals.org.
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doi:10.1124/jpet.106.106500.
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ABBREVIATIONS: PP, pancreatic polypeptide; NPY, neuropeptide Y; PYY, peptide YY; VIP, vasoactive intestinal polypeptide; BIBO3304, (R)-N-[[4-(aminocarbonylaminomethyl)-phenyl]methyl]-N2-(diphenylacetyl)-argininamide trifluoroacetate); BIIE0246, (S)-N2-[[1-[2-[4-[(R,S)-5,11-dihydro-6(6h)-oxodibenz[b,e]azepin-11-yl]-1-piperazinyl]-2-oxoethyl]cyclopentyl]acetyl]-N-[2-[1,2-dihydro-3,5(4H)-dioxo-1,2-diphenyl-3H-1,2,4-triazol-4-yl]ethyl]-argininamide; GR231118 (GR), (Ile,Glu,Pro,Dpr,Tyr,Arg,Leu,Arg,Try-NH2)-2-cyclic(2,4′),(2′,4)-diamide; WT, wild type; m, mouse; r, rat; h, human; SRIF, somatrophin release inhibitory factor (somatostatin-14); GTPγ[35S], guanosine 5′-O-(3-[35S]thio)triphosphate; DMEM, Dulbecco's modified Eagle's medium; HA, hemagglutinin; KH, Krebs-Henseleit; HEK, human embryonic kidney; Isc, short circuit current; UK14,304, 5-bromo-N-(4,5-dihydro-1H-imidazol-2-yl)-6-quinoxalinamine; BSA, bovine serum albumin; ANOVA, analysis of variance; BIBP3226, ((R)-N2-diphenylacetyl)-N-[4-hydroxyphenyl)methyl]-argininamide; BIBP3435, ((S)-N2-diphenylacetyl)-N-[(4-hydroxyphenyl)methyl]-argininamide.
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The online version of this article (available at http://jpet.aspetjournals.org) contains supplemental material.
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- Received April 19, 2006.
- Accepted June 27, 2006.
- The American Society for Pharmacology and Experimental Therapeutics
