Constitutive neuropeptide YY4 receptor expression in human colonic adenocarcinoma cell lines

1 Three human adenocarcinoma cell lines, Colony-24 (Col-24), Col-6 and Col-l have been studied as confluent epithelial layers able to transport ions vectorially in response to basolateral vasoactive intestinal polypeptide (VIP) and pancreatic polypeptides (PP). 2 Different species PP stimulated responses in Col-24 with Y-4-like pharmacology. Bovine (b)PP, human (h)PP and porcine (p)PP were equipotent (EC50 values 3.0-5.0 nM) while rat (r)PP, avian (a)PP and [Leu(31), Pro(34)]PYY (Pro(34)PYY) were significantly less potent. PYY was inactive. The PP pharmacology in Col-1 was comparable with Col-24. However, Col-6 cells were different; pPP had an EC50 intermediate (22.0 nM) between that of bPP (3.0 nM) and hPP (173.2 nM), with aPP and rPP being at least a further fold less potent. 3 Deamidation of Tyr(36) in bPP (by O-methylation or hydroxylation) or removal of the residue resulted in significant loss of activity in Col-24. 4 GR231118 (1 muM) had no PP-like effects. In Col-24 and Col-1, GR231118 significantly 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 confirmed the presence of hY(4) receptor mRNA in Col-24 and Col-1 epithelia but a barely visible hY4 product was observed in Col-6 and we suggest that an atypical Yq receptor is expressed in this cell line.