Constitutive neuropeptide Y Y₄ receptor expression in human colonic adenocarcinoma cell lines

Abstract

1 Three human adenocarcinoma cell lines, , Col-6 and Col-1 have been studied as con¯uent epithelial layers able to transport ions vectorially in response to basolateral vasoactive intestinal polypeptide (VIP) and pancreatic polypeptides (PP). 4 GR231118 (1 mM) had no PP-like e ects. In Col-24 and Col-1, GR231118 signi®cantly attenuated bPP (30 nM) or hPP (100 nM) responses, but it did not alter bPP responses in Col-6. BIBP3226 and GR231118 both inhibited Y 1 -mediated responses which were only present in Col-6. 5 RT ± PCR analysis con®rmed the presence of hY 4 receptor mRNA in Col-24 and Col-1 epithelia but a barely visible hY 4 product was observed in Col-6 and we suggest that an atypical Y 4 receptor is expressed in this cell line.

Y4 Receptors Mediate the Inhibitory Responses of Pancreatic Polypeptide in Human and Mouse Colon Mucosa

“…The inhibitory Y 4 responses to a maximal GR231118 concentration were slower, smaller, and less transient than hPP responses in these cells. The more transient character of high-concentration hPP responses (also seen in Y 4 constitutively expressing epithelia; Cox et al, 2001b) indicate that hY 4 receptors will desensitize following agonist exposure (as do epithelial Y 1 receptors; Holliday et al, 2005). These findings contrast with the apparent lack of hY 4 desensitization reported previously, perhaps because of the long-term (24-h) PP pretreatment used as a conditioning stimulus in that study (Voisin et al, 2000).…”

“…(Gerald et al, 1996;Cox et al, 2001b); however, hPP stimulation of mY 1 receptors is noteworthy given that we have previously shown hPP to be inactive at human Y 1 receptors (Cox and Tough, 2002) and rat colon mucosa (that expresses Y 1 but not Y 4 receptors) (Tough and Cox, 1996).…”

“…35 S] binding [hPP Ͼ Ͼ rPP (low efficacy) Ͼ PYY (low potency)] more accurately predicts the relative capacity of these peptides to produce functional responses mediated by endogenous hY 4 receptors (Cox et al, 2001b). GR231118 has also been reported to activate Y 4 receptors, inhibiting forskolin-induced cAMP accumulation as a full agonist, but with reduced potency compared with hPP (Parker et al, 1998;Schober et al, 1998).…”

“…In addition, endogenous stimulation of epithelial Y 1 receptors by PYY or neuronal Y 2 receptors by NPY provides antisecretory tone in these two tissues, as revealed by competitive antagonists [i.e., BIBO3304 (Y 1 ) or BIIE0246 (Y 2 )] (Cox and Tough, 2002;Hyland and Cox, 2005). Notably, human colon adenocarcinoma cell lines express Y 4 receptors either alone (Cox et al, 2001b) or alongside Y 1 receptors (Tough and Cox, 1996) but not Y 2 receptors.…”

“…To date, however, detailed characterization of Y 4 -mediated responses has been hampered by the lack of selective ligands. The Y 1 -preferring agonist Pro 34 PYY has efficacy at the Y 4 receptor but only at high concentrations (Cox et al, 2001b). In addition GR231118, a homodimeric peptide based on the C-terminal sequence of NPY [(Ile, Glu,Pro,Dpr,Tyr,Arg,Leu,Arg,Try-NH 2 )-2-cyclic(2,4Ј),(2Ј,4)-diamide, also known as 1229U91] was originally identified as a competitive Y 1 receptor antagonist with low Y 2 affinity (Daniels et al, 1995;Hegde et al, 1995), but this dimeric nonapeptide also has Y 4 affinity and efficacy (Matthews et al, 1997;Parker et al, 1998;Schober et al, 1998Schober et al, , 2000.…”