Extracellular loops 1 and 3 and their associated transmembrane regions of the calcitonin receptor-like receptor are needed for CGRP receptor function

Biochim Biophys Acta. 2011 Oct;1813(10):1906-16. doi: 10.1016/j.bbamcr.2011.06.005. Epub 2011 Jun 16.


The first and third extracellular loops (ECL) of G protein-coupled receptors (GPCRs) have been implicated in ligand binding and receptor function. This study describes the results of an alanine/leucine scan of ECLs 1 and 3 and loop-associated transmembrane (TM) domains of the secretin-like GPCR calcitonin receptor-like receptor which associates with receptor activity modifying protein 1 to form the CGRP receptor. Leu195Ala, Val198Ala and Ala199Leu at the top of TM2 all reduced αCGRP-mediated cAMP production and internalization; Leu195Ala and Ala199Leu also reduced αCGRP binding. These residues form a hydrophobic cluster within an area defined as the "minor groove" of rhodopsin-like GPCRs. Within ECL1, Ala203Leu and Ala206Leu influenced the ability of αCGRP to stimulate adenylate cyclase. In TM3, His219Ala, Leu220Ala and Leu222Ala have influences on αCGRP binding and cAMP production; they are likely to indirectly influence the binding site for αCGRP as well as having an involvement in signal transduction. On the exofacial surfaces of TMs 6 and 7, a number of residues were identified that reduced cell surface receptor expression, most noticeably Leu351Ala and Glu357Ala in TM6. The residues may contribute to the RAMP1 binding interface. Ile360Ala impaired αCGRP-mediated cAMP production. Ile360 is predicted to be located close to ECL2 and may facilitate receptor activation. Identification of several crucial functional loci gives further insight into the activation mechanism of this complex receptor system and may aid rational drug design.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Amino Acid Substitution
  • Animals
  • COS Cells
  • Calcitonin Gene-Related Peptide / chemistry*
  • Calcitonin Gene-Related Peptide / genetics
  • Calcitonin Gene-Related Peptide / metabolism
  • Calcitonin Gene-Related Peptide / physiology*
  • Calcitonin Receptor-Like Protein / chemistry*
  • Calcitonin Receptor-Like Protein / genetics
  • Calcitonin Receptor-Like Protein / metabolism
  • Calcitonin Receptor-Like Protein / physiology*
  • Cattle
  • Cell Membrane / metabolism
  • Chlorocebus aethiops
  • Cyclic AMP / metabolism
  • Humans
  • Models, Biological
  • Models, Molecular
  • Molecular Sequence Data
  • Mutagenesis, Site-Directed
  • Mutant Proteins / chemistry
  • Mutant Proteins / metabolism
  • Mutant Proteins / physiology
  • Protein Binding
  • Protein Interaction Domains and Motifs / genetics
  • Protein Interaction Domains and Motifs / physiology*
  • Protein Structure, Secondary / genetics
  • Protein Structure, Secondary / physiology*
  • Receptor Activity-Modifying Protein 1 / chemistry
  • Receptor Activity-Modifying Protein 1 / metabolism


  • CALCRL protein, human
  • Calcitonin Receptor-Like Protein
  • Mutant Proteins
  • RAMP1 protein, human
  • Receptor Activity-Modifying Protein 1
  • Cyclic AMP
  • Calcitonin Gene-Related Peptide