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Kuwasako K, Hay DL, Nagata S, Hikosaka T, Kitamura K, Kato J. The third extracellular loop of the human calcitonin receptor-like receptor is crucial for the activation of adrenomedullin signalling. Br J Pharmacol 2012; 166:137-50. [PMID: 22142144 DOI: 10.1111/j.1476-5381.2011.01803.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
BACKGROUND AND PURPOSE The extracellular loops (ECLs) in Family A GPCRs are important for ligand binding and receptor activation, but little is known about the function of Family B GPCR ECLs, especially ECL3. Calcitonin receptor-like receptor (CLR), a Family B GPCR, functions as a calcitonin gene-related peptide (CGRP) and an adrenomedullin (AM) receptor in association with three receptor activity-modifying proteins (RAMPs). Here, we examined the function of the ECL3 of human CLR within the CGRP and AM receptors. EXPERIMENTAL APPROACH A CLR ECL3 chimera, in which the ECL3 of CLR was substituted with that of VPAC2 (a Family B GPCR that is unable to interact with RAMPs), and CLR ECL3 point mutants were constructed and transiently transfected into HEK-293 cells along with each RAMP. Cell-surface expression of each receptor complex was then measured by flow cytometry; [(125) I]-CGRP and [(125) I]-AM binding and intracellular cAMP accumulation were also measured. KEY RESULTS Co-expression of the CLR ECL3 chimera with RAMP2 or RAMP3 led to significant reductions in the induction of cAMP signalling by AM, but CGRP signalling was barely affected, despite normal cell-surface expression of the receptors and normal [(125) I]-AM binding. The chimera had significantly decreased AM, but not CGRP, responses in the presence of RAMP1. Not all CLR ECL3 mutants supported these findings. CONCLUSIONS AND IMPLICATIONS The human CLR ECL3 is crucial for AM-induced cAMP responses via three CLR/RAMP heterodimers, and activation of these heterodimers probably relies on AM-induced conformational changes. This study provides a clue to the molecular basis of the activation of RAMP-based Family B GPCRs.
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Affiliation(s)
- Kenji Kuwasako
- Frontier Science Research Center, University of Miyazaki, Miyazaki, Japan.
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Kusano S, Kukimoto-Niino M, Hino N, Ohsawa N, Okuda KI, Sakamoto K, Shirouzu M, Shindo T, Yokoyama S. Structural basis for extracellular interactions between calcitonin receptor-like receptor and receptor activity-modifying protein 2 for adrenomedullin-specific binding. Protein Sci 2012; 21:199-210. [PMID: 22102369 PMCID: PMC3324764 DOI: 10.1002/pro.2003] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2011] [Accepted: 11/10/2011] [Indexed: 11/06/2022]
Abstract
The calcitonin receptor-like receptor (CRLR), a class B GPCR, forms a heterodimer with receptor activity-modifying protein 2 (RAMP2), and serves as the adrenomedullin (AM) receptor to control neovascularization, while CRLR and RAMP1 form the calcitonin gene-related peptide (CGRP) receptor. Here, we report the crystal structures of the RAMP2 extracellular domain alone and in the complex with the CRLR extracellular domain. The CRLR-RAMP2 complex exhibits several intermolecular interactions that were not observed in the previously reported CRLR-RAMP1 complex, and thus the shape of the putative ligand-binding pocket of CRLR-RAMP2 is distinct from that of CRLR-RAMP1. The CRLR-RAMP2 interactions were confirmed for the full-length proteins on the cell surface by site-specific photo-crosslinking. Mutagenesis revealed that AM binding requires RAMP2 residues that are not conserved in RAMP1. Therefore, the differences in both the shapes and the key residues of the binding pocket are essential for the ligand specificity.
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Affiliation(s)
- Seisuke Kusano
- RIKEN Systems and Structural Biology Center1-7-22 Suehiro-cho, Tsurumi-ku, Yokohama 230-0045, Japan
| | - Mutsuko Kukimoto-Niino
- RIKEN Systems and Structural Biology Center1-7-22 Suehiro-cho, Tsurumi-ku, Yokohama 230-0045, Japan
| | - Nobumasa Hino
- RIKEN Systems and Structural Biology Center1-7-22 Suehiro-cho, Tsurumi-ku, Yokohama 230-0045, Japan
| | - Noboru Ohsawa
- RIKEN Systems and Structural Biology Center1-7-22 Suehiro-cho, Tsurumi-ku, Yokohama 230-0045, Japan
| | - Ken-ichi Okuda
- RIKEN Systems and Structural Biology Center1-7-22 Suehiro-cho, Tsurumi-ku, Yokohama 230-0045, Japan
| | - Kensaku Sakamoto
- RIKEN Systems and Structural Biology Center1-7-22 Suehiro-cho, Tsurumi-ku, Yokohama 230-0045, Japan
| | - Mikako Shirouzu
- RIKEN Systems and Structural Biology Center1-7-22 Suehiro-cho, Tsurumi-ku, Yokohama 230-0045, Japan
| | - Takayuki Shindo
- Department of Organ Regeneration, Graduate School of Medicine, Shinshu UniversityMatsumoto, Nagano 390-8621, Japan
| | - Shigeyuki Yokoyama
- RIKEN Systems and Structural Biology Center1-7-22 Suehiro-cho, Tsurumi-ku, Yokohama 230-0045, Japan
- Laboratory of Structural Biology, Department of Biophysics and Biochemistry, Graduate School of Science, The University of TokyoBunkyo-ku, Tokyo 113-0033, Japan
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Kuwasako K, Kitamura K, Nagata S, Hikosaka T, Takei Y, Kato J. Shared and separate functions of the RAMP-based adrenomedullin receptors. Peptides 2011; 32:1540-50. [PMID: 21645567 DOI: 10.1016/j.peptides.2011.05.022] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/11/2011] [Revised: 05/20/2011] [Accepted: 05/20/2011] [Indexed: 11/25/2022]
Abstract
Adrenomedullin (AM) is a novel hypotensive peptide that exerts a variety of strongly protective effects against multiorgan damage. AM-specific receptors were first identified as heterodimers composed of calcitonin-receptor-like receptor (CLR), a G protein coupled receptor, and one of two receptor activity-modifying proteins (RAMP2 or RAMP3), which are accessory proteins containing a single transmembrane domain. RAMPs are required for the surface delivery of CLR and the determination of its phenotype. CLR/RAMP2 (AM₁ receptor) is more highly AM-specific than CLR/RAMP3 (AM₂ receptor). Although there have been no reports showing differences in intracellular signaling via the two AM receptors, in vitro studies have shed light on their distinct trafficking and functionality. In addition, the tissue distributions of RAMP2 and RAMP3 differ, and their gene expression is differentially altered under pathophysiological conditions, which is suggestive of the separate roles played by AM₁ and AM₂ receptors in vivo. Both AM and the AM₁ receptor, but not the AM₂ receptor, are crucial for the development of the fetal cardiovascular system and are able to effectively protect against various vascular diseases. However, AM₂ receptors reportedly play an important role in maintaining a normal body weight in old age and may be involved in immune function. In this review article, we focus on the shared and separate functions of the AM receptor subtypes and also discuss the potential for related drug discovery. In addition, we mention their possible function as receptors for AM2 (or intermedin), an AM-related peptide whose biological functions are similar to those of AM.
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Affiliation(s)
- Kenji Kuwasako
- Frontier Science Research Center, University of Miyazaki, 5200 Kihara, Kiyotake, Miyazaki, Miyazaki 889-1692, Japan.
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Bailey RJ, Bradley JWI, Poyner DR, Rathbone DL, Hay DL. Functional characterization of two human receptor activity-modifying protein 3 variants. Peptides 2010; 31:579-84. [PMID: 20034525 DOI: 10.1016/j.peptides.2009.12.016] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/21/2009] [Revised: 12/10/2009] [Accepted: 12/11/2009] [Indexed: 11/21/2022]
Abstract
Adrenomedullin (AM) and amylin are involved in angiogenesis/lymphangiogenesis and glucose homeostasis/food intake, respectively. They activate receptor activity-modifying protein (RAMP)/G protein-coupled receptor (GPCR) complexes. RAMP3 with the calcitonin receptor-like receptor (CLR) forms the AM(2) receptor, whereas when paired with the calcitonin receptor AMY(3) receptors are formed. RAMP3 interacts with other GPCRs although the consequences of these interactions are poorly understood. Therefore, variations in the RAMP3 sequence, such as single nucleotide polymorphisms or mutations could be relevant to human health. Variants of RAMP3 have been identified. In particular, analysis of AK222469 (Homo sapiens mRNA for receptor (calcitonin) activity-modifying protein 3 precursor variant) revealed several nucleotide differences, three of which encoded amino acid changes (Cys40Trp, Phe100Ser, Leu147Pro). Trp56Arg RAMP3 is a polymorphic variant of human RAMP3 at a conserved amino acid position. To determine their function we used wild-type (WT) human RAMP3 as a template for introducing amino acid mutations. Mutant or WT RAMP3 function was determined in Cos-7 cells with CLR or the calcitonin receptor (CT((a))). Cys40Trp/Phe100Ser/Leu147Pro RAMP3 was functionally compromised, with reduced AM and amylin potency at the respective AM(2) and AMY(3(a)) receptor complexes. Cys40Trp and Phe100Ser mutations contributed to this phenotype, unlike Leu147Pro. Reduced cell-surface expression of mutant receptor complexes probably explains the functional data. In contrast, Trp56Arg RAMP3 was WT in phenotype. This study provides insight into the role of these residues in RAMP3. The existence of AK222469 in the human population has implications for the function of RAMP3/GPCR complexes, particularly AM and amylin receptors.
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Affiliation(s)
- Richard J Bailey
- School of Biological Sciences, University of Auckland, Symonds Street, Auckland, New Zealand.
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Harikumar KG, Simms J, Christopoulos G, Sexton PM, Miller LJ. Molecular basis of association of receptor activity-modifying protein 3 with the family B G protein-coupled secretin receptor. Biochemistry 2010; 48:11773-85. [PMID: 19886671 DOI: 10.1021/bi901326k] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The three receptor activity-modifying proteins (RAMPs) have been recognized as being important for the trafficking and function of a subset of family B G protein-coupled receptors, although the structural basis for this has not been well established. In the current work, we use morphological fluorescence techniques, bioluminescence resonance energy transfer, and bimolecular fluorescence complementation to demonstrate that the secretin receptor associates specifically with RAMP3, but not with RAMP1 or RAMP2. We use truncation constructs, peptide competition experiments, and chimeric secretin-GLP1 receptor constructs to establish that this association is structurally specific, dependent on the intramembranous region of the RAMP and TM6 and TM7 of this receptor. There were no observed changes in secretin-stimulated cAMP, intracellular calcium, ERK1/2 phosphorylation, or receptor internalization in receptor-bearing COS or CHO-K1 cells in the presence or absence of exogenous RAMP transfection, although the secretin receptor trafficks normally to the cell surface in these cells in a RAMP-independent manner, resulting in both free and RAMP-associated receptor on the cell surface. RAMP3 association with this receptor was shown to be capable of rescuing a receptor mutant (G241C) that is normally trapped intracellularly in the biosynthetic machinery. Similarly, secretin receptor expression had functional effects on adrenomedullin activity, with increasing secretin receptor expression competing for RAMP3 association with the calcitonin receptor-like receptor to yield a functional adrenomedullin receptor. These data provide important new insights into the structural basis for RAMP3 interaction with a family B G protein-coupled receptor, potentially providing a highly selective target for drug action. This may be representative of similar interactions between other members of this receptor family and RAMP proteins.
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Affiliation(s)
- Kaleeckal G Harikumar
- Department of Molecular Pharmacology and Experimental Therapeutics, Mayo Clinic, Scottsdale, Arizona 85259, USA
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Qi T, Simms J, Bailey RJ, Wheatley M, Rathbone DL, Hay DL, Poyner DR. Structure−Function Analysis of RAMP1−RAMP3 Chimeras. Biochemistry 2009; 49:522-31. [DOI: 10.1021/bi9019093] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Tao Qi
- School of Biological Sciences, University of Auckland, Auckland, New Zealand
| | - John Simms
- School of Life and Health Sciences, Aston University, Birmingham B4 7ET, U.K
- Department of Pharmacology, University of Monash, Clayton 3800, Australia
| | - Richard J. Bailey
- School of Biological Sciences, University of Auckland, Auckland, New Zealand
| | - Mark Wheatley
- School of Biosciences, University of Birmingham, Birmingham B15 2TT, U.K
| | - Dan L. Rathbone
- School of Life and Health Sciences, Aston University, Birmingham B4 7ET, U.K
| | - Debbie L. Hay
- School of Biological Sciences, University of Auckland, Auckland, New Zealand
| | - David R. Poyner
- School of Life and Health Sciences, Aston University, Birmingham B4 7ET, U.K
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Qi T, Hay DL. Structure-function relationships of the N-terminus of receptor activity-modifying proteins. Br J Pharmacol 2009; 159:1059-68. [PMID: 20015292 DOI: 10.1111/j.1476-5381.2009.00541.x] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
The receptor activity-modifying proteins (RAMPs) are a family of three single transmembrane proteins that have been identified as accessory proteins to some G-protein-coupled receptors (GPCRs). They can regulate their pharmacology, forward trafficking and recycling, depending on the GPCR. The best characterized receptor complexes formed by RAMPs and GPCRs are the calcitonin peptide family receptors. The association of RAMP1 with the calcitonin receptor-like receptor (CL) constitutes the calcitonin gene-related peptide receptor, whereas RAMP2 or 3 with CL generates adrenomedullin receptors. In this case, the RAMPs substantially alter the pharmacology and trafficking properties of this GPCR. Amylin receptor subtypes are formed from calcitonin receptor (CTR) interactions with RAMPs. Although the RAMPs themselves are not responsive to calcitonin peptide family ligands, there is clear evidence that they participate in ligand binding, although it is still unclear whether this is by directly participating in binding or through allosteric modulation of CL or CTR. A considerable amount of mutagenesis data have now been generated on RAMPs to try and identify the residues that play a role in ligand interactions, and to also identify which residues in RAMPs interact with CL and CTR. This review will focus on RAMP mutagenesis studies with CL, summarizing and discussing the available data in association with current RAMP models and structures. The data reveal key regions in RAMPs that are important for ligand binding and receptor interactions.
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Affiliation(s)
- Tao Qi
- University of Auckland, New Zealand
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Kuwasako K, Kitamura K, Nagata S, Kato J. Flow cytometric analysis of the calcitonin receptor-like receptor domains responsible for cell-surface translocation of receptor activity-modifying proteins. Biochem Biophys Res Commun 2009; 384:249-54. [PMID: 19394311 DOI: 10.1016/j.bbrc.2009.04.097] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2009] [Accepted: 04/21/2009] [Indexed: 12/18/2022]
Abstract
The three receptor activity-modifying proteins (RAMPs1, -2, and -3) associate with a wide variety of G protein-coupled receptors (GPCRs), including calcitonin receptor-like receptor (CRLR). In this study, we used flow cytometry to measure RAMP translocation to the cell surface as a marker of RAMP-receptor interaction. Because VPAC2 does not interact with RAMPs, although, like CRLR, it is a Family B peptide hormone receptor, we constructed a set of chimeric CRLR/VPAC2 receptors to evaluate the trafficking interactions between CRLR domains and each RAMP. We found that CRLR regions extending from transmembrane domain 1 (TM1) through TM5 are necessary and sufficient for the transport of RAMPs to the plasma membrane. In addition, the extracellular N-terminal domain of CRLR, its 3rd intracellular loop and/or TM6 were also important for the cell-surface translocation of RAMP2, but not RAMP1 or RAMP3. Other regions within CRLR were not involved in trafficking interactions with RAMPs. These findings provide new insight into the trafficking interactions between accessory proteins such as RAMPs and their receptor partners.
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Affiliation(s)
- Kenji Kuwasako
- Frontier Science Research Center, University of Miyazaki, 5200 Kihara, Kiyotake, Miyazaki 889-1692, Japan.
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