scholarly journals Similarity between class A and class B G-protein-coupled receptors exemplified through calcitonin gene-related peptide receptor modelling and mutagenesis studies

2013 ◽  
Vol 10 (79) ◽  
pp. 20120846 ◽  
Author(s):  
Shabana Vohra ◽  
Bruck Taddese ◽  
Alex C. Conner ◽  
David R. Poyner ◽  
Debbie L. Hay ◽  
...  
Keyword(s):  
G Protein ◽  
Calcitonin Gene Related Peptide ◽  
G Protein Coupled Receptors ◽  
Cgrp Receptor ◽  
Conserved Residues ◽  
Related Peptide ◽  
Class A ◽  
Calcitonin Gene ◽  
Class B ◽  
G Protein Coupled

Modelling class B G-protein-coupled receptors (GPCRs) using class A GPCR structural templates is difficult due to lack of homology. The plant GPCR, GCR1, has homology to both class A and class B GPCRs. We have used this to generate a class A–class B alignment, and by incorporating maximum lagged correlation of entropy and hydrophobicity into a consensus score, we have been able to align receptor transmembrane regions. We have applied this analysis to generate active and inactive homology models of the class B calcitonin gene-related peptide (CGRP) receptor, and have supported it with site-directed mutagenesis data using 122 CGRP receptor residues and 144 published mutagenesis results on other class B GPCRs. The variation of sequence variability with structure, the analysis of polarity violations, the alignment of group-conserved residues and the mutagenesis results at 27 key positions were particularly informative in distinguishing between the proposed and plausible alternative alignments. Furthermore, we have been able to associate the key molecular features of the class B GPCR signalling machinery with their class A counterparts for the first time. These include the [K/R]KLH motif in intracellular loop 1, [I/L]xxxL and KxxK at the intracellular end of TM5 and TM6, the NPXXY/VAVLY motif on TM7 and small group-conserved residues in TM1, TM2, TM3 and TM7. The equivalent of the class A DRY motif is proposed to involve Arg 2.39 , His 2.43 and Glu 3.46 , which makes a polar lock with T 6.37 . These alignments and models provide useful tools for understanding class B GPCR function.

Multiple affinity and guanine nucleotide sensitive forms of the calcitonin gene related peptide (CGRP) receptor

1995 ◽  
Vol 73 (7) ◽  
pp. 968-973 ◽  
Author(s):  
Tapan K. Chatterjee ◽  
Rory A. Fisher
Keyword(s):  
G Protein ◽  
Conformational Changes ◽  
Ternary Complex ◽  
Protein S ◽  
Calcitonin Gene Related Peptide ◽  
Cgrp Receptor ◽  
Peripheral Tissues ◽  
Related Peptide ◽  
Calcitonin Gene ◽  
G Protein Coupled

Calcitonin gene related peptide (CGRP) is a novel neuropeptide with an impressive array of biological actions consistent with its diverse tissue distribution and suggested role as neurotransmitter or neuromodulator. Binding sites for CGRP with properties consistent with those of receptors are present in both central and peripheral tissues. Radioligand binding studies were performed to investigate the fundamental processes underlying CGRP receptor activation and signaling following agonist occupancy of the receptor. These studies documented the existence of a selective, high affinity, and homogeneous population of binding sites for CGRP in membranes prepared from central and various peripheral tissues. The affinity of [125I]CGRP for these sites was regulated by GTP or its stable analog GTPγS, indicating coupling of CGRP receptors to G-protein(s). Kinetic studies documented the existence of the CGRP receptor in multiple affinity states when both coupled to and uncoupled from G-proteins(s). These findings suggest that CGRP occupancy of its receptor induces conformational changes in the receptor that may be involved in its coupling to G-proteins and that the resulting ligand–receptor–G-protein ternary complex exists in multiple affinity conformational states. It seems likely that the multiple affinity states of the CGRP receptor ternary complex are involved differentially in signaling by and desensitization of the receptor. This evidence for agonist-induced conformational changes in a G-protein-coupled receptor prior to its coupling with G-protein(s) and for the existence of the ligand–receptor–G-protein ternary complex in multiple affinity conformational states is novel and extends our current understanding of the nature of the processes involved in agonist-dependent activation of G-protein-coupled receptors.Key words: calcitonin gene related peptide receptor, G-protein, multiple affinity.

scholarly journals An allosteric role for receptor activity-modifying proteins in defining GPCR pharmacology

2016 ◽  
Vol 2 (1) ◽  
Author(s):  
Joseph J Gingell ◽  
John Simms ◽  
James Barwell ◽  
David R Poyner ◽  
Harriet A Watkins ◽  
...  
Keyword(s):  
G Protein ◽  
Protein Interaction ◽  
G Protein Coupled Receptors ◽  
Receptor Activity ◽  
Calcitonin Receptor ◽  
Related Peptide ◽  
Calcitonin Gene ◽  
Receptor Activity Modifying Proteins ◽  
G Protein Coupled ◽  
Insight Into

Abstract G protein-coupled receptors are allosteric proteins that control transmission of external signals to regulate cellular response. Although agonist binding promotes canonical G protein signalling transmitted through conformational changes, G protein-coupled receptors also interact with other proteins. These include other G protein-coupled receptors, other receptors and channels, regulatory proteins and receptor-modifying proteins, notably receptor activity-modifying proteins (RAMPs). RAMPs have at least 11 G protein-coupled receptor partners, including many class B G protein-coupled receptors. Prototypic is the calcitonin receptor, with altered ligand specificity when co-expressed with RAMPs. To gain molecular insight into the consequences of this protein–protein interaction, we combined molecular modelling with mutagenesis of the calcitonin receptor extracellular domain, assessed in ligand binding and functional assays. Although some calcitonin receptor residues are universally important for peptide interactions (calcitonin, amylin and calcitonin gene-related peptide) in calcitonin receptor alone or with receptor activity-modifying protein, others have RAMP-dependent effects, whereby mutations decreased amylin/calcitonin gene-related peptide potency substantially only when RAMP was present. Remarkably, the key residues were completely conserved between calcitonin receptor and AMY receptors, and between subtypes of AMY receptor that have different ligand preferences. Mutations at the interface between calcitonin receptor and RAMP affected ligand pharmacology in a RAMP-dependent manner, suggesting that RAMP may allosterically influence the calcitonin receptor conformation. Supporting this, molecular dynamics simulations suggested that the calcitonin receptor extracellular N-terminal domain is more flexible in the presence of receptor activity-modifying protein 1. Thus, RAMPs may act in an allosteric manner to generate a spectrum of unique calcitonin receptor conformational states, explaining the pharmacological preferences of calcitonin receptor-RAMP complexes. This provides novel insight into our understanding of G protein-coupled receptor-protein interaction that is likely broadly applicable for this receptor class.

Calcitonin, calcitonin gene-related peptide, adrenomedullin and amylin: homologous peptides, separate receptors and overlapping biological actions

1995 ◽  
Vol 133 (1) ◽  
pp. 17-20 ◽  
Author(s):  
Roman Muff ◽  
Walter Born ◽  
Jan A Fischer
Keyword(s):  
Bioactive Peptides ◽  
Disulfide Bridge ◽  
Calcitonin Gene Related Peptide ◽  
G Protein Coupled Receptors ◽  
Calcitonin Receptor ◽  
Related Peptide ◽  
Calcitonin Gene ◽  
Ring Structures ◽  
G Protein Coupled ◽  
Biological Actions

Muff R, Born W, Fischer JA. Calcitonin, calcitonin gene-related peptide, adrenomedullin and amylin: homologous peptides, separate receptors and overlapping biological actions. Eur J Endocrinol 1995;133:17–20. ISSN 0804–4643 Calcitonin, calcitonin gene-related peptide, adrenomedullin and amylin are structurally related peptides with N-terminal 6–7 amino acid ring structures linked by a disulfide bridge and with amidated C-termini. Among the related bioactive peptides, the structures of the calcitonin receptor and subtypes thereof have been identified so far through molecular cloning. Cross-reaction between receptors of calcitonin, calcitonin gene-related peptide, adrenomedullin and amylin, as well as overlapping biological actions, anticipate that the respective receptors belong to a family of G-protein-coupled receptors that include those of parathyroid hormone, secretin and vasointestinal peptide. Jan A Fischer, Klinik Balgrist, Forchstrasse 340, CH-8008 Zurich, Switzerland

Calcitonin gene-related peptide receptors in rat trigeminal ganglion do not control spinal trigeminal activity

2012 ◽  
Vol 108 (2) ◽  
pp. 431-440 ◽  
Author(s):  
Oana Covasala ◽  
Sören L. Stirn ◽  
Stephanie Albrecht ◽  
Roberto De Col ◽  
Karl Messlinger
Keyword(s):  
Trigeminal Ganglion ◽  
Dura Mater ◽  
Calcitonin Gene Related Peptide ◽  
Afferent Input ◽  
Nitric Oxide Donor ◽  
Cgrp Receptor ◽  
Related Peptide ◽  
Trigeminal Neurons ◽  
Calcitonin Gene ◽  
Evoked Activity

Calcitonin gene-related peptide (CGRP) is regarded as a key mediator in the generation of primary headaches. CGRP receptor antagonists reduce migraine pain in clinical trials and spinal trigeminal activity in animal experiments. The site of CGRP receptor inhibition causing these effects is debated. Activation and inhibition of CGRP receptors in the trigeminal ganglion may influence the activity of trigeminal afferents and hence of spinal trigeminal neurons. In anesthetized rats extracellular activity was recorded from neurons with meningeal afferent input in the spinal trigeminal nucleus caudalis. Mechanical stimuli were applied at regular intervals to receptive fields located in the exposed cranial dura mater. α-CGRP (10−5 M), the CGRP receptor antagonist olcegepant (10−3 M), or vehicle was injected through the infraorbital canal into the trigeminal ganglion. The injection of volumes caused transient discharges, but vehicle, CGRP, or olcegepant injection was not followed by significant changes in ongoing or mechanically evoked activity. In animals pretreated intravenously with the nitric oxide donor glyceryl trinitrate (GTN, 250 μg/kg) the mechanically evoked activity decreased after injection of CGRP and increased after injection of olcegepant. In conclusion, the activity of spinal trigeminal neurons with meningeal afferent input is normally not controlled by CGRP receptor activation or inhibition in the trigeminal ganglion. CGRP receptors in the trigeminal ganglion may influence neuronal activity evoked by mechanical stimulation of meningeal afferents only after pretreatment with GTN. Since it has previously been shown that olcegepant applied to the cranial dura mater is ineffective, trigeminal activity driven by meningeal afferent input is more likely to be controlled by CGRP receptors located centrally to the trigeminal ganglion.

scholarly journals Constitutive Activity among Orphan Class-A G Protein Coupled Receptors

PLoS ONE ◽  
2015 ◽  
Vol 10 (9) ◽  
pp. e0138463 ◽  
Author(s):  
Adam L. Martin ◽  
Michael A. Steurer ◽  
Robert S. Aronstam
Keyword(s):  
G Protein ◽  
G Protein Coupled Receptors ◽  
Constitutive Activity ◽  
Class A ◽  
G Protein Coupled
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