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Garelja M, Au M, Brimble MA, Gingell JJ, Hendrikse ER, Lovell A, Prodan N, Sexton PM, Siow A, Walker CS, Watkins HA, Williams GM, Wootten D, Yang SH, Harris PWR, Hay DL. Molecular Mechanisms of Class B GPCR Activation: Insights from Adrenomedullin Receptors. ACS Pharmacol Transl Sci 2020; 3:246-262. [PMID: 32296766 PMCID: PMC7155197 DOI: 10.1021/acsptsci.9b00083] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2019] [Indexed: 02/07/2023]
Abstract
Adrenomedullin (AM) is a 52 amino acid peptide that plays a regulatory role in the vasculature. Receptors for AM comprise the class B G protein-coupled receptor, the calcitonin-like receptor (CLR), in complex with one of three receptor activity-modifying proteins (RAMPs). The C-terminus of AM is involved in binding to the extracellular domain of the receptor, while the N-terminus is proposed to interact with the juxtamembranous portion of the receptor to activate signaling. There is currently limited information on the molecular determinants involved in AM signaling, thus we set out to define the importance of the AM N-terminus through five signaling pathways (cAMP production, ERK phosphorylation, CREB phosphorylation, Akt phosphorylation, and IP1 production). We characterized the three CLR:RAMP complexes through the five pathways, finding that each had a distinct repertoire of intracellular signaling pathways that it is able to regulate. We then performed an alanine scan of AM from residues 15-31 and found that most residues could be substituted with only small effects on signaling, and that most substitutions affected signaling through all receptors and pathways in a similar manner. We identify F18, T20, L26, and I30 as being critical for AM function, while also identifying an analogue (AM15-52 G19A) which has unique signaling properties relative to the unmodified AM. We interpret our findings in the context of new structural information, highlighting the complementary nature of structural biology and functional assays.
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Affiliation(s)
- Michael
L. Garelja
- School
of Biological Sciences, University of Auckland, Auckland, 1010, New Zealand
| | - Maggie Au
- School
of Biological Sciences, University of Auckland, Auckland, 1010, New Zealand
- Maurice
Wilkins Centre for Molecular Biodiscovery, University of Auckland, Auckland, 1010, New Zealand
| | - Margaret A. Brimble
- School
of Biological Sciences, University of Auckland, Auckland, 1010, New Zealand
- Maurice
Wilkins Centre for Molecular Biodiscovery, University of Auckland, Auckland, 1010, New Zealand
- School
of Chemical Sciences, University of Auckland, Auckland, 1010, New Zealand
| | - Joseph J. Gingell
- School
of Biological Sciences, University of Auckland, Auckland, 1010, New Zealand
- Maurice
Wilkins Centre for Molecular Biodiscovery, University of Auckland, Auckland, 1010, New Zealand
| | - Erica R. Hendrikse
- School
of Biological Sciences, University of Auckland, Auckland, 1010, New Zealand
| | - Annie Lovell
- School
of Biological Sciences, University of Auckland, Auckland, 1010, New Zealand
| | - Nicole Prodan
- School
of Biological Sciences, University of Auckland, Auckland, 1010, New Zealand
| | - Patrick M. Sexton
- Drug
Discovery Biology and Department of Pharmacology, Monash Institute
of Pharmaceutical Sciences, Monash University, Parkville, Victoria 3052, Australia
| | - Andrew Siow
- School
of Biological Sciences, University of Auckland, Auckland, 1010, New Zealand
- School
of Chemical Sciences, University of Auckland, Auckland, 1010, New Zealand
| | - Christopher S. Walker
- School
of Biological Sciences, University of Auckland, Auckland, 1010, New Zealand
- Maurice
Wilkins Centre for Molecular Biodiscovery, University of Auckland, Auckland, 1010, New Zealand
| | - Harriet A. Watkins
- School
of Biological Sciences, University of Auckland, Auckland, 1010, New Zealand
- Maurice
Wilkins Centre for Molecular Biodiscovery, University of Auckland, Auckland, 1010, New Zealand
| | - Geoffrey M. Williams
- Maurice
Wilkins Centre for Molecular Biodiscovery, University of Auckland, Auckland, 1010, New Zealand
- School
of Chemical Sciences, University of Auckland, Auckland, 1010, New Zealand
| | - Denise Wootten
- Drug
Discovery Biology and Department of Pharmacology, Monash Institute
of Pharmaceutical Sciences, Monash University, Parkville, Victoria 3052, Australia
| | - Sung H. Yang
- School
of Biological Sciences, University of Auckland, Auckland, 1010, New Zealand
- Maurice
Wilkins Centre for Molecular Biodiscovery, University of Auckland, Auckland, 1010, New Zealand
| | - Paul W. R. Harris
- School
of Biological Sciences, University of Auckland, Auckland, 1010, New Zealand
- Maurice
Wilkins Centre for Molecular Biodiscovery, University of Auckland, Auckland, 1010, New Zealand
- School
of Chemical Sciences, University of Auckland, Auckland, 1010, New Zealand
| | - Debbie L. Hay
- School
of Biological Sciences, University of Auckland, Auckland, 1010, New Zealand
- Maurice
Wilkins Centre for Molecular Biodiscovery, University of Auckland, Auckland, 1010, New Zealand
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Hay DL, Harris PWR, Kowalczyk R, Brimble MA, Rathbone DL, Barwell J, Conner AC, Poyner DR. Structure-activity relationships of the N-terminus of calcitonin gene-related peptide: key roles of alanine-5 and threonine-6 in receptor activation. Br J Pharmacol 2014; 171:415-26. [PMID: 24125506 PMCID: PMC3904261 DOI: 10.1111/bph.12464] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2013] [Revised: 09/10/2013] [Accepted: 10/07/2013] [Indexed: 01/02/2023] Open
Abstract
BACKGROUND AND PURPOSE The N-terminus of calcitonin gene-related peptide (CGRP) is important for receptor activation, especially the disulphide-bonded ring (residues 1-7). However, the roles of individual amino acids within this region have not been examined and so the molecular determinants of agonism are unknown. This study has examined the role of residues 1, 3-6 and 8-9, excluding Cys-2 and Cys-7. EXPERIMENTAL APPROACH CGRP derivatives were substituted with either cysteine or alanine; further residues were introduced at position 6. Their affinity was measured by radioligand binding and their efficacy by measuring cAMP production in SK-N-MC cells and β-arrestin 2 translocation in CHO-K1 cells at the CGRP receptor. KEY RESULTS Substitution of Ala-5 by cysteine reduced affinity 270-fold and reduced efficacy for production of cAMP in SK-N-MCs. Potency at β-arrestin translocation was reduced by ninefold. Substitution of Thr-6 by cysteine destroyed all measurable efficacy of both cAMP and β-arrestin responses; substitution with either alanine or serine impaired potency. Substitutions at positions 1, 4, 8 and 9 resulted in approximately 10-fold reductions in potency at both responses. Similar observations were made at a second CGRP-activated receptor, the AMY(1(a)) receptor. CONCLUSIONS AND IMPLICATIONS Ala-5 and Thr-6 are key determinants of agonist activity for CGRP. Ala-5 is also very important for receptor binding. Residues outside of the 1-7 ring also contribute to agonist activity.
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Affiliation(s)
- Debbie L Hay
- School of Biological Sciences and Maurice Wilkins Centre for Molecular Biodiscovery, The University of Auckland, Auckland, New Zealand
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Watkins HA, Rathbone DL, Barwell J, Hay DL, Poyner DR. Structure-activity relationships for α-calcitonin gene-related peptide. Br J Pharmacol 2013; 170:1308-22. [PMID: 23186257 PMCID: PMC3838678 DOI: 10.1111/bph.12072] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2012] [Revised: 10/11/2012] [Accepted: 11/15/2012] [Indexed: 12/30/2022] Open
Abstract
UNLABELLED Calcitonin gene-related peptide (CGRP) is a member of the calcitonin (CT) family of peptides. It is a widely distributed neuropeptide implicated in conditions such as neurogenic inflammation. With other members of the CT family, it shares an N-terminal disulphide-bonded ring which is essential for biological activity, an area of potential α-helix, and a C-terminal amide. CGRP binds to the calcitonin receptor-like receptor (CLR) in complex with receptor activity-modifying protein 1 (RAMP1), a member of the family B (or secretin-like) GPCRs. It can also activate other CLR or calcitonin-receptor/RAMP complexes. This 37 amino acid peptide comprises the N-terminal ring that is required for receptor activation (residues 1-7); an α-helix (residues 8-18), a region incorporating a β-bend (residues 19-26) and the C-terminal portion (residues 27-37), that is characterized by bends between residues 28-30 and 33-34. A few residues have been identified that seem to make major contributions to receptor binding and activation, with a larger number contributing either to minor interactions (which collectively may be significant), or to maintaining the conformation of the bound peptide. It is not clear if CGRP follows the pattern of other family B GPCRs in binding largely as an α-helix. LINKED ARTICLES This article is part of a themed section on Neuropeptides. To view the other articles in this section visit http://dx.doi.org/10.1111/bph.2013.170.issue-7.
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Affiliation(s)
- Harriet A Watkins
- School of Biological Sciences, University of AucklandAuckland, New Zealand
- Maurice Wilkins Centre for Molecular Biodiscovery, University of AucklandAuckland, New Zealand
| | - Dan L Rathbone
- School of Life and Health Sciences, Aston UniversityBirmingham, UK
| | - James Barwell
- School of Life and Health Sciences, Aston UniversityBirmingham, UK
| | - Debbie L Hay
- School of Biological Sciences, University of AucklandAuckland, New Zealand
- Maurice Wilkins Centre for Molecular Biodiscovery, University of AucklandAuckland, New Zealand
| | - David R Poyner
- School of Life and Health Sciences, Aston UniversityBirmingham, UK
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Peptidergic nerves in the eye, their source and potential pathophysiological relevance. ACTA ACUST UNITED AC 2006; 53:39-62. [PMID: 16872680 DOI: 10.1016/j.brainresrev.2006.06.002] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2005] [Revised: 06/09/2006] [Accepted: 06/13/2006] [Indexed: 12/17/2022]
Abstract
Over the last five decades, several neuropeptides have been discovered which subsequently have been found to be highly conserved during evolution, to be widely distributed both in the central and peripheral nervous system and which act as neurotransmitters and/or neuromodulators. In the eye, the first peptide to be explored was substance P which was reported to be present in the retina but also in peripherally innervated tissues of the eye. Substance P is certainly the best characterized peptide which has been found in sensory neurons innervating the eye. Functionally, it has been shown to act trophically on corneal wound healing and to participate in the irritative response in lower mammals, a model for neurogenic inflammation, where it mediates the noncholinergic nonadrenergic contraction of the sphincter muscle. Over the last three decades, the interest has extended to investigate the presence and distribution of other neuropeptides including calcitonin gene-related peptide, vasoactive intestinal polypeptide, neuropeptide Y, pituitary adenylate cyclase-activating polypeptides, cholecystokinin, somatostatin, neuronal nitric oxide, galanin, neurokinin A or secretoneurin and important functional results have been obtained for these peptides. This review focuses on summarizing the current knowledge about neuropeptides in the eye excluding the retina and retinal pigment epithelium and to elucidate their potential functional significance.
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Alajuuma P, Oksala O, Uusitalo H. Amylin Competes for Binding Sites of CGRP in the Chamber Angle and Uvea of Monkey, Cat, and Pig Eye. J Ocul Pharmacol Ther 2003; 19:555-67. [PMID: 14733713 DOI: 10.1089/108076803322660477] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Calcitonin gene-related peptide (CGRP) binding sites have been identified previously in the eyes of monkey, cat, pig, and guinea pig. In this study, the ability of cat, human, and rat amylins to displace the binding of CGRP in the anterior part of the eye of monkey, cat, and pig was studied. The location and displacement of 125I-hCGRPalpha by amylins as concentrations of 1-1000 nM were studied in cryosections by autoradiography. In the monkey eye, cat and rat amylins were able to compete for the binding sites of CGRP in ciliary muscle and ciliary processes. In the cat eye, cat and human amylins clearly displaced CGRP binding from ciliary muscle, ciliary processes, iris, and chamber angle. Furthermore, rat amylin clearly displaced CGRP binding from ciliary muscle and ciliary processes. In the pig eye, cat, human, and rat amylins competed for the binding sites of CGRP in ciliary muscle, ciliary processes, iris, and limbal conjunctiva. Specific amylin receptors or the possible physiological role of amylin in the eye have not hitherto been reported. It seems, however, that amylin can bind to ocular CGRP receptors and thus probably plays a role in the regulation of the same functions as CGRP, (e.g., aqueous humor outflow).
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Affiliation(s)
- Päivi Alajuuma
- Santen Oy, Tampere, Finland, and Department of Ophthalmology, Kuopio University Hospital, Kuopio, Finland.
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Clementi G, Floriddia ML, Prato A, Marino A, Drago F. Adrenomedullin and ocular inflammation in the rabbit. Eur J Pharmacol 2000; 400:321-6. [PMID: 10988350 DOI: 10.1016/s0014-2999(00)00376-9] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Adrenomedullin administered peripherally in the rabbit (at doses of 1.25, 2.5 and 5 microg/kg ) caused a dose-dependent conjunctival hyperemia accompanied by an increase of inflammatory cell number and prostaglandin E(2) concentration in the aqueous humor, and of uveal vascular response and myeloperoxidase activity. The inflammatory effect of the peptide, injected at the dose of 5 microg/kg, was abolished by pretreatment with the inhibitor of nitric oxide synthase, N(G)-nitro-L-arginine methylester (50 mg/kg, i.v.). Moreover, the i.v. pretreatment with the calcitonin gene-related peptide 8-37 fragment (calcitonin gene-related peptide, CGRP-(8-37), 2.5 microg/kg), receptor antagonist of CGRP, did not inhibit the conjunctival hyperemia. In contrast, the i.v. pretreatment with the adrenomedullin receptor antagonist, adrenomedullin-(22-52) fragment (2.5 microg/kg), abolished adrenomedullin-induced ocular inflammation. These results suggest that adrenomedullin causes conjunctival hyperemia, and this effect involves the nitric oxide system acting through specific adrenomedullin receptors.
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Affiliation(s)
- G Clementi
- Department of Experimental and Clinical Pharmacology, School of Medicine, University of Catania, Viale A. Doria 6, 95125, Catania, Italy
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