CL/RAMP2 and CL/RAMP3 produce pharmacologically distinct adrenomedullin receptors: a comparison of effects of adrenomedullin22-52, CGRP8-37 and BIBN4096BS.
Adrenomedullin (AM) has two known receptors formed by the calcitonin receptor-like receptor (CL) and receptor activity-modifying protein (RAMP) 2 or 3: we report the effects of the antagonist fragments of human AM and CGRP (AM22-52 and CGRP8-37) in inhibiting AM at human (h), rat (r) and mixed species CL/RAMP2 and CL/RAMP3 receptors transiently expressed in Cos 7 cells or endogenously expressed as rCL/rRAMP2 complexes by Rat 2 and L6 cells. AM22-52 (10 microM) antagonised AM at all CL/RAMP2 complexes (apparent pA2 values: 7.34+/-0.14 (hCL/hRAMP2), 7.28+/-0.06 (Rat 2), 7.00+/-0.05 (L6), 6.25+/-0.17 (rCL/hRAMP2)). CGRP8-37 (10 microM) resembled AM22-52 except on the rCL/hRAMP2 complex, where it did not antagonise AM (apparent pA2 values: 7.04+/-0.13 (hCL/hRAMP2), 6.72+/-0.06 (Rat2), 7.03+/-0.12 (L6)). On CL/RAMP3 receptors, 10 microM CGRP8-37 was an effective antagonist at all combinations (apparent pA2 values: 6.96+/-0.08 (hCL/hRAMP3), 6.18+/-0.18 (rCL/rRAMP3), 6.48+/-0.20 (rCL/hRAMP3)). However, 10 microM AM22-52 only antagonised AM at the hCL/hRAMP3 receptor (apparent pA2 6.73+/-0.14). BIBN4096BS (10 microM) did not antagonise AM at any of the receptors. Where investigated (all-rat and rat/human combinations), the agonist potency order on the CL/RAMP3 receptor was AM approximately betaCGRP>alphaCGRP. rRAMP3 showed three apparent polymorphisms, none of which altered its coding sequence. This study shows that on CL/RAMP complexes, AM22-52 has significant selectivity for the CL/RAMP2 combination over the CL/RAMP3 combination. On the mixed species receptor, CGRP8-37 showed the opposite selectivity. Thus, depending on the species, it is possible to discriminate pharmacologically between CL/RAMP2 and CL/RAMP3 AM receptors.
Hay
D L
DL
Pharmaceutical Sciences Research Institute, Aston University, Birmingham B4 7ET, UK.
Howitt
S G
SG
Conner
A C
AC
Schindler
M
M
Smith
D M
DM
Poyner
D R
DR
D053607:Adrenomedullin; D000818:Animals; D019556:COS Cells; D015740:Calcitonin Gene-Related Peptide / Q000494:pharmacology; D058286:Calcitonin Receptor-Like Protein; D002522:Chlorocebus aethiops; D000242:Cyclic AMP / Q000037:antagonists & inhibitors / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D008565:Membrane Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism*; D010446:Peptide Fragments / Q000494:pharmacology; D010455:Peptides / Q000378:metabolism*; D010879:Piperazines / Q000494:pharmacology; D011799:Quinazolines / Q000494:pharmacology; D051381:Rats; D058263:Receptor Activity-Modifying Protein 2; D058264:Receptor Activity-Modifying Protein 3; D058261:Receptor Activity-Modifying Proteins; D058265:Receptors, Adrenomedullin; D018003:Receptors, Calcitonin / Q000037:antagonists & inhibitors / Q000378:metabolism*; D018000:Receptors, Peptide / Q000037:antagonists & inhibitors / Q000378:metabolism*
C545578:CALCRL protein, human; D058286:Calcitonin Receptor-Like Protein; C545580:Calcrl protein, rat; D047908:Intracellular Signaling Peptides and Proteins; D008565:Membrane Proteins; D010446:Peptide Fragments; D010455:Peptides; D010879:Piperazines; D011799:Quinazolines; C545503:RAMP2 protein, human; C545504:RAMP3 protein, human; C545509:Ramp2 protein, rat; C545510:Ramp3 protein, rat; D058263:Receptor Activity-Modifying Protein 2; D058264:Receptor Activity-Modifying Protein 3; D058261:Receptor Activity-Modifying Proteins; D058265:Receptors, Adrenomedullin; D018003:Receptors, Calcitonin; D018000:Receptors, Peptide; C104782:adrenomedullin (22-52); C058636:calcitonin gene-related peptide (8-37); D053607:Adrenomedullin; D000242:Cyclic AMP; D015740:Calcitonin Gene-Related Peptide; C406305:olcegepant