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Winfield I, Barkan K, Routledge S, Robertson NJ, Harris M, Jazayeri A, Simms J, Reynolds CA, Poyner DR, Ladds G. The Role of ICL1 and H8 in Class B1 GPCRs; Implications for Receptor Activation. Front Endocrinol (Lausanne) 2021; 12:792912. [PMID: 35095763 PMCID: PMC8796428 DOI: 10.3389/fendo.2021.792912] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/11/2021] [Accepted: 12/15/2021] [Indexed: 11/13/2022] Open
Abstract
The first intracellular loop (ICL1) of G protein-coupled receptors (GPCRs) has received little attention, although there is evidence that, with the 8th helix (H8), it is involved in early conformational changes following receptor activation as well as contacting the G protein β subunit. In class B1 GPCRs, the distal part of ICL1 contains a conserved R12.48KLRCxR2.46b motif that extends into the base of the second transmembrane helix; this is weakly conserved as a [R/H]12.48KL[R/H] motif in class A GPCRs. In the current study, the role of ICL1 and H8 in signaling through cAMP, iCa2+ and ERK1/2 has been examined in two class B1 GPCRs, using mutagenesis and molecular dynamics. Mutations throughout ICL1 can either enhance or disrupt cAMP production by CGRP at the CGRP receptor. Alanine mutagenesis identified subtle differences with regard elevation of iCa2+, with the distal end of the loop being particularly sensitive. ERK1/2 activation displayed little sensitivity to ICL1 mutation. A broadly similar pattern was observed with the glucagon receptor, although there were differences in significance of individual residues. Extending the study revealed that at the CRF1 receptor, an insertion in ICL1 switched signaling bias between iCa2+ and cAMP. Molecular dynamics suggested that changes in ICL1 altered the conformation of ICL2 and the H8/TM7 junction (ICL4). For H8, alanine mutagenesis showed the importance of E3908.49b for all three signal transduction pathways, for the CGRP receptor, but mutations of other residues largely just altered ERK1/2 activation. Thus, ICL1 may modulate GPCR bias via interactions with ICL2, ICL4 and the Gβ subunit.
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MESH Headings
- Amino Acid Motifs/physiology
- Calcitonin Receptor-Like Protein/metabolism
- Calcitonin Receptor-Like Protein/physiology
- Calcitonin Receptor-Like Protein/ultrastructure
- Calcium Signaling
- Cyclic AMP/metabolism
- HEK293 Cells
- Humans
- MAP Kinase Signaling System
- Molecular Dynamics Simulation
- Protein Domains
- Protein Structure, Tertiary
- Receptor Activity-Modifying Protein 1/metabolism
- Receptor Activity-Modifying Protein 1/physiology
- Receptor Activity-Modifying Protein 1/ultrastructure
- Receptors, Calcitonin Gene-Related Peptide/metabolism
- Receptors, Calcitonin Gene-Related Peptide/physiology
- Receptors, Calcitonin Gene-Related Peptide/ultrastructure
- Receptors, Corticotropin-Releasing Hormone/metabolism
- Receptors, Corticotropin-Releasing Hormone/physiology
- Receptors, Corticotropin-Releasing Hormone/ultrastructure
- Receptors, G-Protein-Coupled
- Receptors, Glucagon/metabolism
- Receptors, Glucagon/physiology
- Receptors, Glucagon/ultrastructure
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Affiliation(s)
- Ian Winfield
- Department of Pharmacology, University of Cambridge, Cambridge, United Kingdom
| | - Kerry Barkan
- Department of Pharmacology, University of Cambridge, Cambridge, United Kingdom
| | - Sarah Routledge
- Department of Pharmacology, University of Cambridge, Cambridge, United Kingdom
- School of Life and Health Sciences, Aston University, Birmingham, United Kingdom
| | | | - Matthew Harris
- Department of Pharmacology, University of Cambridge, Cambridge, United Kingdom
| | | | - John Simms
- School of Life and Health Sciences, Aston University, Birmingham, United Kingdom
| | | | - David R. Poyner
- School of Life and Health Sciences, Aston University, Birmingham, United Kingdom
- *Correspondence: Graham Ladds, ; David R. Poyner,
| | - Graham Ladds
- Department of Pharmacology, University of Cambridge, Cambridge, United Kingdom
- *Correspondence: Graham Ladds, ; David R. Poyner,
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Liang YL, Khoshouei M, Deganutti G, Glukhova A, Koole C, Peat TS, Radjainia M, Plitzko JM, Baumeister W, Miller LJ, Hay DL, Christopoulos A, Reynolds CA, Wootten D, Sexton PM. Cryo-EM structure of the active, G s-protein complexed, human CGRP receptor. Nature 2018; 561:492-497. [PMID: 30209400 PMCID: PMC6166790 DOI: 10.1038/s41586-018-0535-y] [Citation(s) in RCA: 165] [Impact Index Per Article: 27.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2018] [Accepted: 06/26/2018] [Indexed: 12/29/2022]
Abstract
Calcitonin gene-related peptide (CGRP) is a widely expressed neuropeptide that has a major role in sensory neurotransmission. The CGRP receptor is a heterodimer of the calcitonin receptor-like receptor (CLR) class B G-protein-coupled receptor and a type 1 transmembrane domain protein, receptor activity-modifying protein 1 (RAMP1). Here we report the structure of the human CGRP receptor in complex with CGRP and the Gs-protein heterotrimer at 3.3 Å global resolution, determined by Volta phase-plate cryo-electron microscopy. The receptor activity-modifying protein transmembrane domain sits at the interface between transmembrane domains 3, 4 and 5 of CLR, and stabilizes CLR extracellular loop 2. RAMP1 makes only limited direct contact with CGRP, consistent with its function in allosteric modulation of CLR. Molecular dynamics simulations indicate that RAMP1 provides stability to the receptor complex, particularly in the positioning of the extracellular domain of CLR. This work provides insights into the control of G-protein-coupled receptor function.
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Affiliation(s)
- Yi-Lynn Liang
- Drug Discovery Biology and Department of Pharmacology, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, Victoria, Australia
| | - Maryam Khoshouei
- Department of Molecular Structural Biology, Max Planck Institute of Biochemistry, Martinsried, Germany
- Novartis Institutes for Biomedical Research, Novartis Pharma, Basel, Switzerland
| | | | - Alisa Glukhova
- Drug Discovery Biology and Department of Pharmacology, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, Victoria, Australia
| | - Cassandra Koole
- Drug Discovery Biology and Department of Pharmacology, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, Victoria, Australia
| | - Thomas S Peat
- CSIRO Biomedical Manufacturing, Melbourne, Victoria, Australia
| | - Mazdak Radjainia
- Drug Discovery Biology and Department of Pharmacology, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, Victoria, Australia
- Thermo Fisher Scientific, Eindhoven, The Netherlands
| | - Jürgen M Plitzko
- Department of Molecular Structural Biology, Max Planck Institute of Biochemistry, Martinsried, Germany
| | - Wolfgang Baumeister
- Department of Molecular Structural Biology, Max Planck Institute of Biochemistry, Martinsried, Germany
| | - Laurence J Miller
- Drug Discovery Biology and Department of Pharmacology, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, Victoria, Australia
- Department of Molecular Pharmacology and Experimental Therapeutics, Mayo Clinic, Scottsdale, AZ, USA
| | - Deborah L Hay
- School of Biological Sciences, University of Auckland, Auckland, New Zealand
- Maurice Wilkins Centre for Molecular Biodiscovery, University of Auckland, Auckland, New Zealand
| | - Arthur Christopoulos
- Drug Discovery Biology and Department of Pharmacology, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, Victoria, Australia
| | | | - Denise Wootten
- Drug Discovery Biology and Department of Pharmacology, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, Victoria, Australia.
- School of Pharmacy, Fudan University, Shanghai, China.
| | - Patrick M Sexton
- Drug Discovery Biology and Department of Pharmacology, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, Victoria, Australia.
- School of Pharmacy, Fudan University, Shanghai, China.
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