Calcitonin gene‐related peptide receptors in human gastrointestinal epithelia

Abstract

Rat a-CGRP (0.2 nM) responses in HCA-7 epithelia were inhibited by the C-terminal fragment CGRP(8-37) (1 g.M). Pretreatment of Col-29 cells with CGRP(8-37) did not, however, alter the size or profile of responses to ra-CGRP (1 nM). 6 We conclude that high-affinity CGRP receptors exist on the basolateral surface of both cell lines, however they differ in their sensitivity to CGRP(8-37) and agonist orders of potency. Thus different CGRP receptor subtypes appear to predominate in these two epithelial cell types.

Functional characterization of receptors with affinity for PYY, NPY, [Leu31, Pro34]NPY and PP in a human colonic epithelial cell line

“…The predominance of peptide receptors in the basolateral membranes of Col-6 monolayers was similar to, not only the sidedness seen for other agonists (MacVinish et al, 1993;Cox & Tough, 1994) in epithelial lines derived from the same parent cell line (Marsh et al, 1993) but also to the sidedness of NPY and PYY responses in jejunal and colonic mucosal preparations . Thus these cells can provide a useful model system for the study of peptide receptors in polarized epithelia in the absence of other mucosal cell types.…”

“…Once confluent in culture flasks (25 cmn) epithelia were trypsinized (0.5% tryp~sin in versene, w/v) and seeded onto collagen-coated millipore filters as described previously (Cox & Tough, 1994). Cells covered the 0.2 cm2 area of filter within 10 days and once confluent, filters were used within 3 days.…”

Comparison of the expression of calcitonin receptor‐like receptor (CRLR) and receptor activity modifying proteins (RAMPs) with CGRP and adrenomedullin binding in cell lines

“…The behaviour of the Col-29 cells in this study stands in contrast to the CGRP 2 -like phenotype that we and others have previously found (Poyner et al, 1998;Cox & Tough, 1994). Perhaps signi®cantly there were dierences between the behaviour of the cells in the hands of Cox and Tough, who found that 3 mM CGRP 8-37 had no eect on the response to CGRP and ourselves, who found that this concentration was able to antagonize CGRP.…”

“…Since we would expect the pK b value for CGRP in Col-29 cells to be at least one log unit lower than in SK-N-MC cells (Poyner et al, 1998), in this circumstance the CGRP receptor in these Col-29 cells could not be con®rmed as CGRP 2 . This result is contrary to published data (Cox & Tough, 1994) and indeed our own data (Poyner et al, 1998) ]a-CGRP was a more potent agonist in both cell types but there was only a 2 fold dierence between the two cell lines with an EC 50 of 67 nM in SK-N-MC cells and 152 nM in Col-29 cells ( Figure 1d). The similarity of responses with these agonists also suggests that the Col-29 cells used in this study have a CGRP 1 rather than CGRP 2 phenotype.…”

WHAT MAKES A CGRP2 RECEPTOR?

“…Several hypotheses have been put forward. Species differences (rat atria vs guinea‐pig vas deferens) were proposed as an explanation for initial observations of heterogeneity; however, a spread of pA 2 values for CGRP 8–37 has since been observed in tissues from the same species and in discrete cell lines 33,43,45,46 . A range of other possibilities for the heterogeneity has also been suggested, including experimental artefacts, differential metabolism of antagonists, the use of non‐equilibrium conditions, problems of tissue accessibility and proteolysis.…”