CGRP and adrenomedullin binding correlates with transcript levels for Calcitonin Receptor‐Like Receptor (CRLR) and Receptor Activity Modifying Proteins (RAMPs) in rat tissues

Abstract

1 Putative receptors for CGRP and adrenomedullin have been investigated in the rat. Calcitonin Receptor-Like Receptor (CRLR), in combination with Receptor Activity Modifying Proteins (RAMPs) is hypothesized to bind either CGRP or adrenomedullin. The receptors known as RDC1 and L1 have also been shown to bind CGRP and adrenomedullin respectively. 2 In this study it is shown that rat CRLR cDNA speci®es a CGRP receptor when co-transfected with RAMP-1 cDNA and an adrenomedullin receptor when co-transfected with either RAMP-2 or RAMP-3 cDNA in human embryonic kidney 293 cells. 3 CRLR, RAMP, RCD1 and L1 mRNA levels and CGRP and adrenomedullin receptor densities have been measured and correlated with each other in eight rat tissues selected for their distinctive patterns of CGRP and adrenomedullin binding. 4 The data are consistent with the predictions of the CRLR/RAMP model. CGRP binding correlates well with RAMP-1 mRNA levels (R=1.0, P=0.007), adrenomedullin binding shows a tendency to vary with RAMP-2 mRNA levels (R=0.85, P=0.14) and total binding is correlated with CRLR mRNA levels (R=0.94, P=0.03). The data do not support the hypothesis that RDC1 and L1 account for the majority of CGRP and adrenomedullin binding respectively.

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

“…CRLR functions as a CGRP 1 receptor when co-expressed with RAMP1 but as an adrenomedullinpreferring receptor in the presence of either RAMP2 or RAMP3 in transfection studies using HEK 293T cells (McLatchie et al, 1998). This basic hypothesis has been supported by further transfection studies from a number of groups (Mu et al, 1998;Kamitani et al, 1999;Chakravarty et al, 2000), however more information is required concerning the relevance of these receptor combinations to the physiological actions of CGRP and adrenomedullin. Whether CGRP 2 receptors are also formed by CRLR and RAMP combinations is not yet known.…”

“…We found a signi®cant correlation between CGRP binding and RAMP1 mRNA expression but the correlation between adrenomedullin binding and RAMP2 expression was not signi®cant (Chakravarty et al, 2000). As an extension to this study we have evaluated the relationship between CGRP and adrenomedullin binding and CRLR/RAMP transcript levels in immortalized cell lines.…”

The action of CGRP and SP on cultured skin fibroblasts

“…The simultaneous expression of CLR and RAMP is essential for the expression of functional receptors. Studies on transfection of different cell types have confirmed this hypothesis [63][64][65].…”

RAMP et récepteurs couplés aux protéines G

“…L'antagoniste CGRP a permis de définir deux types de R-CGRP [3,4]: le R-CGRP 1 sensible aux propriétés antagonistes du CGRP , mais peu sensible aux effets agonistes d'un analogue linéaire, le [Cys(ACM) 2,7] hCGRPα [4] et le R-CGRP 2 , beaucoup moins sensible au CGRP , alors que l'analogue linéaire est agoniste à la concentration de 10 -8 ou 10 -7 M. Les récepteurs de l'ADM (R-ADM) sont, quant à eux, présents dans de nombreux tissus [5]. En dehors de la moelle épinière, la liaison de l'ADM au niveau du système nerveux est faible, contrairement au CGRP [6].…”

“…Le foie est un organe pour lequel une expression équivalente des trois RAMP a été observée [17]. Les études de liaison par radioligands ont montré une corrélation entre le phéno-type du récepteur endogène et l'expression tissulaire d'un RAMP donné en présence de CRLR [5]. En d'autres termes, une corrélation élevée existe entre l'expression de RAMP1 et la liaison au CGRP et entre RAMP2 et la liaison à l'ADM.…”