title: Non-peptidic antagonists of the CGRP receptor, BIBN4096BS and MK-0974, interact with the calcitonin receptor-like receptor via methionine-42 and RAMP1 via tryptophan-74.
abstract: The receptor for calcitonin gene-related peptide (CGRP) has been the target for the development of novel small molecule antagonists for the treatment of migraine. Two such antagonists, BIBN4096BS and MK-0974, have shown great promise in clinical trials and hence a deeper understanding of the mechanism of their interaction with the receptor is now required. The structure of the CGRP receptor is unusual since it is comprised of a hetero-oligomeric complex between the calcitonin receptor-like receptor (CRL) and an accessory protein (RAMP1). Both the CLR and RAMP1 components have extracellular domains which interact with each other and together form part of the peptide-binding site. It seems likely that the antagonist binding site will also be located on the extracellular domains and indeed Trp-74 of RAMP1 has been shown to form part of the binding site for BIBN4096BS. However, despite a chimeric study demonstrating the role of the N-terminal domain of CLR in antagonist binding, no specific residues have been identified. Here we carry out a mutagenic screen of the extreme N-terminal domain of CLR (residues 23-63) and identify a mutant, Met-42-Ala, which displays 48-fold lower affinity for BIBN4096BS and almost 900-fold lower affinity for MK-0974. In addition, we confirm that the Trp-74-Lys mutation at human RAMP1 reduces BIBN4096BS affinity by over 300-fold and show for the first time a similar effect for MK-0974 affinity. The data suggest that the non-peptide antagonists occupy a binding site close to the interface of the N-terminal domains of CLR and RAMP1.
authors.affiliation: Institute of Membrane & Systems Biology, LIGHT Laboratories, Faculty of Biological Sciences, University of Leeds, Leeds LS2 9JT, UK.
authors.forename: Philip S
authors.initials: PS
authors.lastname: Miller
authors.forename: James
authors.initials: J
authors.lastname: Barwell
authors.forename: David R
authors.initials: DR
authors.lastname: Poyner
authors.forename: Mark J
authors.initials: MJ
authors.lastname: Wigglesworth
authors.forename: Stephen L
authors.initials: SL
authors.lastname: Garland
authors.forename: Dan
authors.initials: D
authors.lastname: Donnelly
mesh_terms: D001381:Azepines / Q000737:chemistry / Q000378:metabolism* / Q000494:pharmacology; D000077221:Calcitonin Gene-Related Peptide Receptor Antagonists; D058286:Calcitonin Receptor-Like Protein; D006801:Humans; D007093:Imidazoles / Q000737:chemistry / Q000378:metabolism* / Q000494:pharmacology; D047908:Intracellular Signaling Peptides and Proteins / Q000235:genetics / Q000378:metabolism*; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D008715:Methionine / Q000235:genetics / Q000378:metabolism; D010879:Piperazines / Q000737:chemistry / Q000378:metabolism* / Q000494:pharmacology; D017434:Protein Structure, Tertiary; D011799:Quinazolines / Q000737:chemistry / Q000378:metabolism* / Q000494:pharmacology; D058262:Receptor Activity-Modifying Protein 1; D058261:Receptor Activity-Modifying Proteins; D018003:Receptors, Calcitonin / Q000235:genetics / Q000378:metabolism*; D014364:Tryptophan / Q000235:genetics / Q000378:metabolism
chemical_list: D001381:Azepines; C545578:CALCRL protein, human; D000077221:Calcitonin Gene-Related Peptide Receptor Antagonists; D058286:Calcitonin Receptor-Like Protein; D007093:Imidazoles; D047908:Intracellular Signaling Peptides and Proteins; D008565:Membrane Proteins; D010879:Piperazines; D011799:Quinazolines; C545502:RAMP1 protein, human; D058262:Receptor Activity-Modifying Protein 1; D058261:Receptor Activity-Modifying Proteins; D018003:Receptors, Calcitonin; D014364:Tryptophan; D008715:Methionine; C525458:telcagepant; C406305:olcegepant