title: The role of the extracellular loops of the CGRP receptor, a family B GPCR.
abstract: The CGRP (calcitonin gene-related peptide) receptor is a family B GPCR (G-protein-coupled receptor). It consists of a GPCR, CLR (calcitonin receptor-like receptor) and an accessory protein, RAMP1 (receptor activity-modifying protein 1). RAMP1 is needed for CGRP binding and also cell-surface expression of CLR. There have been few systematic studies of the ECLs (extracellular loops) of family B GPCRs. However, they are likely to be especially important for the interaction of the N-termini of the peptide agonists that are the natural agonists for these receptors. We have carried out alanine scans on all three ECLs of CLR, as well as their associated juxtamembrane regions. Residues within all three loops influence CGRP binding and receptor activation. Mutation of Ala203 and Ala206 on ECL1 to leucine increased the affinity of CGRP. Residues at the top of TM (transmembrane) helices 2 and 3 influenced CGRP binding and receptor activation. L351A and E357A in TM6/ECL3 reduced receptor expression and may be needed for CLR association with RAMP1. ECL2 seems especially important for CLR function; of the 16 residues so far examined in this loop, eight residues reduce the potency of CGRP at stimulating cAMP production when mutated to alanine.
authors.affiliation: School of Life and Health Sciences, Aston University, Birmingham, B4 7ET, U.K.
authors.forename: James
authors.initials: J
authors.lastname: Barwell
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Woolley
authors.forename: Mark
authors.initials: M
authors.lastname: Wheatley
authors.forename: Alex C
authors.initials: AC
authors.lastname: Conner
authors.forename: David R
authors.initials: DR
authors.lastname: Poyner
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D005110:Extracellular Space / Q000737:chemistry*; D006801:Humans; D008969:Molecular Sequence Data; D011485:Protein Binding; D017433:Protein Structure, Secondary; D018015:Receptors, Calcitonin Gene-Related Peptide / Q000737:chemistry* / Q000378:metabolism*; D013329:Structure-Activity Relationship
chemical_list: D018015:Receptors, Calcitonin Gene-Related Peptide