RAMPs: the past, present and future

doi:10.1016/j.tibs.2006.09.006

Trends in Biochemical Sciences

Volume 31, Issue 11, November 2006, Pages 631-638

https://doi.org/10.1016/j.tibs.2006.09.006 Get rights and content

The discovery of receptor-activity-modifying proteins (RAMPs) as accessory proteins required for the appropriate localization and function of certain G-protein coupled receptors (GPCRs) produced a paradigm shift in our understanding of GPCR regulation. Three RAMPs have now been demonstrated to be crucial for various aspects of the life cycle of calcitonin-like receptor (CLR) including endoplasmic reticulum-to-Golgi translocation, internalization and recycling. Although the RAMP–CLR interaction was the first to be identified, other GPCRs belonging to both the class B and C families of GPCRs also seem to be regulated by RAMPs. The recent advances in our knowledge of the cellular and biochemical regulation of RAMPs and how they in turn regulate the life cycle of GPCRs could lead to therapeutic advances in several diseases.

Section snippets

The discovery of RAMPs

The reception and transmission of information between cells is one of the most fundamental of all physiological processes. The seven-transmembrane (7-TM) G-protein coupled receptors (GPCRs) constitute the largest family of cell-surface receptors and, notably, ∼40% of therapeutic drug targets are directed towards these receptors. At present, ∼950 genes that encode for GPCRs have been identified in the human genome. Therefore, it is not surprising that understanding the cellular expression and

Expression and distribution of RAMPs

RAMPs are ubiquitous, although the abundance of each individual isoform depends on the tissue type (Table 1). In addition, RAMP isoform expression usually correlates with the response of a given cell type to CGRP, AM or both. For example, in aortic endothelial cells, expression of RAMP2 but not RAMP1 has been reported. These cells selectively respond to AM and not to CGRP [18]. In some cells such as SKNMC, although both RAMP1 and RAMP2 are present, the cells respond to only CGRP [19]. It is not

Molecular mechanisms of RAMP–receptor interactions

From a variety of biochemical and confocal microscopy approaches, it is now clear that RAMPs and the CLR interact at the endoplasmic reticulum (ER) or Golgi and remain partners throughout the life cycle of the receptor 35, 36, 37. Recent studies have also suggested that structural elements in the N terminus of CLR (amino acids 23–60) are required for CLR–RAMP1 transport to the cell surface [38]. In addition, the amino acid sequence The-Arg-Asn-Lys-Ile-Met-Thr in the N terminus of mouse CLR was

Role of extracellular and transmembrane domains of RAMPs

In an effort to identify the domains responsible for agonist-binding specificity in RAMP1, the behavior of various deletion mutants of the extracellular domain have been examined [42]. Deletion of amino acid residues 91–94, 96–100 or 101–103 abolishes binding to, and the cAMP stimulation by, CGRP or AM. Deletion of residues 78–80 or 88–90 decreases only the AM-induced cAMP response. Using chimeras of the extracellular domains of RAMP1, and transmembrane and intracellular domains of

Role of the RAMP C terminus

The roles of the intracellular tails of the RAMPs have traditionally received less attention than those of the extracellular and intramembrane domains. However, new data indicate that these short domains are important determinants of function: deletion of the C-terminal tail of RAMP3 significantly enhances AM-induced internalization of the receptor complex without affecting the cell-surface targeting of the receptor, AM binding or AM signaling [53]. The cytoplasmic tails of the RAMPs contain

Interaction of RAMPs with class B GPCRs

Although initially thought to be important only in the case of CLR, subsequent studies have shown that CTR could also dimerize with RAMPs. However, this interaction changed the ligand selectivity of CTR from CT to AMY [65]. The binding of CT to the CTR and signaling does not require RAMPs, whereas AMY binding and signaling requires dimerization with RAMPs. Recent studies have shown that, in addition to CLR and CTR, other receptors in the class B of GPCRs (Box 1) can also interact with RAMPs. In

Interaction of RAMPs with class C GPCRs

Until now, RAMPs were primarily associated with the regulation of class B GPCRs. However, a recent study has demonstrated that GPCRs belonging to the class C family can also be regulated by RAMPs: a recombinant calcium-sensing receptor (CaSR) expressed in COS7 cells does not translocate to the membrane unless RAMP1 or RAMP3, but not RAMP2, is co-expressed [67] – a paradigm that is similar to that of CLR. RAMPs also facilitate the trafficking of CaSR from the ER to the Golgi in addition to

Concluding remarks and future perspectives

Although heterodimerization of GPCRs is now a well-accepted phenomenon, the regulation of receptor signaling has become more complicated because of the diversity in ligand binding and signaling pathways that the various combinations of heterodimers can evoke. This is especially true for CGRP and AM binding to CLR. Because AM and CGRP receptors are potential therapeutic targets for several diseases such as migraine, hypertension, pulmonary hypertension and sepsis, understanding how ligand

Acknowledgements

We acknowledge the American Heart Association (Grant # 0255636N) for support.

References (70)

K. Kuwasako
Adrenomedullin receptors: pharmacological features and possible pathophysiological roles
Peptides
(2004)
Y. Takei
Identification of novel adrenomedullin in mammals: a potent cardiovascular and renal regulator
FEBS Lett.
(2004)
J. Roh
Intermedin is a calcitonin/calcitonin gene-related peptide family peptide acting through the calcitonin receptor-like receptor/receptor activity-modifying protein receptor complexes
J. Biol. Chem.
(2004)
N. Aiyar
A cDNA encoding the calcitonin gene-related peptide type 1 receptor
J. Biol. Chem.
(1996)
M. Ogoshi
Identification of a novel adrenomedullin gene family in teleost fish
Biochem. Biophys. Res. Commun.
(2003)
M. Udawela
The receptor activity modifying protein family of G protein coupled receptor accessory proteins
Semin. Cell Dev. Biol.
(2004)
M.A. Prado
The role of the CGRP-receptor component protein (RCP) in adrenomedullin receptor signal transduction
Peptides
(2001)
B.N. Evans
CGRP-RCP, a novel protein required for signal transduction at calcitonin gene-related peptide and adrenomedullin receptors
J. Biol. Chem.
(2000)
M. Flahaut
Respective roles of calcitonin receptor-like receptor (CRLR) and receptor activity-modifying proteins (RAMP) in cell surface expression of CRLR/RAMP heterodimeric receptors
J. Biol. Chem.
(2002)
J.M. Bomberger
Novel function for receptor activity-modifying proteins (RAMPs) in post-endocytic receptor trafficking
J. Biol. Chem.
(2005)

J.M. Bomberger

Receptor activity-modifying protein (RAMP) isoform-specific regulation of adrenomedullin receptor trafficking by NHERF-1

J. Biol. Chem.

(2005)

R. Muff

Receptor activity modifying proteins regulate the activity of a calcitonin gene-related peptide receptor in rabbit aortic endothelial cells

FEBS Lett.

(1998)

M.S. Moodbidri et al.

Induction of BAALC and down regulation of RAMP3 in astrocytes treated with differentiation inducers

Cell Biol. Int.

(2006)

I. Marquez-Rodas

Aldosterone increases RAMP1 expression in mesenteric arteries from spontaneously hypertensive rats

Regul. Pept.

(2006)

E. Oie

RAMP2 and RAMP3 mRNA levels are increased in failing rat cardiomyocytes and associated with increased responsiveness to adrenomedullin

J. Mol. Cell. Cardiol.

(2005)

B. Uzan

RAMPs and CRLR expressions in osteoblastic cells after dexamethasone treatment

Biochem. Biophys. Res. Commun.

(2004)

H. Onitsuka

Differential gene expression of adrenomedullin receptors in pressure- and volume-overloaded heart–role of angiotensin II

Peptides

(2004)

K. Tadokoro

Altered gene expression of adrenomedullin and its receptor system and molecular forms of tissue adrenomedullin in left ventricular hypertrophy induced by malignant hypertension

Regul. Pept.

(2003)

K. Kuwasako

Visualization of the calcitonin receptor-like receptor and its receptor activity-modifying proteins during internalization and recycling

J. Biol. Chem.

(2000)

S. Hilairet

Protein-protein interaction and not glycosylation determines the binding selectivity of heterodimers between the calcitonin receptor-like receptor and the receptor activity-modifying proteins

J. Biol. Chem.

(2001)

S. Hilairet

Agonist-promoted internalization of a ternary complex between calcitonin receptor-like receptor, receptor activity-modifying protein 1 (RAMP1), and β-arrestin

J. Biol. Chem.

(2001)

S. Steiner

The function of conserved cysteine residues in the extracellular domain of human receptor-activity-modifying protein

FEBS Lett.

(2003)

A. Aldecoa

Mammalian calcitonin receptor-like receptor/receptor activity modifying protein complexes define calcitonin gene-related peptide and adrenomedullin receptors in Drosophila Schneider 2 cells

FEBS Lett.

(2000)

K. Kuwasako

Identification of the human receptor activity-modifying protein 1 domains responsible for agonist binding specificity

J. Biol. Chem.

(2003)

T.J. Fitzsimmons

The extracellular domain of receptor activity-modifying protein 1 is sufficient for calcitonin receptor-like receptor function

J. Biol. Chem.

(2003)

K. Kuwasako

The seven amino acids of human RAMP2 (86) and RAMP3 (59) are critical for agonist binding to human adrenomedullin receptors

J. Biol. Chem.

(2001)

J. Simms

Characterization of the structure of RAMP1 by mutagenesis and molecular modeling

Biophys. J

(2006)

R.J. Bailey et al.

Pharmacology of the human CGRP1 receptor in Cos 7 cells

Peptides

(2006)

J.J. Mallee

Receptor activity-modifying protein 1 determines the species selectivity of non-peptide CGRP receptor antagonists

J. Biol. Chem.

(2002)

K. Kuwasako

Functions of the cytoplasmic tails of the human receptor activity-modifying protein components of calcitonin gene-related peptide and adrenomedullin receptors

J. Biol. Chem.

(2006)

S.W. Whiteheart et al.

Multiple binding proteins suggest diverse functions for the N-ethylmaleimide sensitive factor

J. Struct. Biol.

(2004)

I. Song

Interaction of the N-ethylmaleimide-sensitive factor with AMPA receptors

Neuron

(1998)

M. Cong

Binding of the β2 adrenergic receptor to N-ethylmaleimide-sensitive factor regulates receptor recycling

J. Biol. Chem.

(2001)

N. Parameswaran

Desensitization and resensitization of adrenomedullin-sensitive receptor in rat mesangial cells

Eur. J. Pharmacol.

(2000)

W.B. Sneddon

Activation-independent parathyroid hormone receptor internalization is regulated by NHERF1 (EBP50)

J. Biol. Chem.

(2003)

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Receptor activity-modulating proteins (RAMPs) are accessory molecules that form complexes with specific G protein-coupled receptors (GPCRs) and modulate their functions. It is established that RAMP interacts with the glucagon receptor family of GPCRs but the underlying mechanism is poorly understood. In this study, we used a bioluminescence resonance energy transfer (BRET) approach to comprehensively investigate such interactions. In conjunction with cAMP accumulation, Gα_q activation and β-arrestin1/2 recruitment assays, we not only verified the GPCR–RAMP pairs previously reported, but also identified new patterns of GPCR–RAMP interaction. While RAMP1 was able to modify the three signaling events elicited by both glucagon receptor (GCGR) and glucagon-like peptide-1 receptor (GLP-1R), and RAMP2 mainly affected β-arrestin1/2 recruitment by GCGR, GLP-1R and glucagon-like peptide-2 receptor, RAMP3 showed a widespread negative impact on all the family members except for growth hormone-releasing hormone receptor covering the three pathways. Our results suggest that RAMP modulates both G protein dependent and independent signal transduction among the glucagon receptor family members in a receptor-specific manner. Mapping such interactions provides new insights into the role of RAMP in ligand recognition and receptor activation.
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Receptor activity-modifying proteins (RAMPs) interact with G-protein-coupled receptors (GPCRs) to modify their functions, imparting significant implications upon their physiological and therapeutic potentials. Resurging interest in identifying RAMP–GPCR interactions has recently been fueled by coevolution studies and orthogonal technological screening platforms. These new studies reveal previously unrecognized RAMP-interacting GPCRs, many of which expand beyond Class B GPCRs. The consequences of these interactions on GPCR function and physiology lays the foundation for new molecular therapeutic targets, as evidenced by the recent success of erenumab. Here, we highlight recent papers that uncovered novel RAMP–GPCR interactions, human RAMP–GPCR disease-causing mutations, and RAMP-related human pathologies, paving the way for a new era of RAMP-targeted drug development.
Development of a Novel Model of Central Retinal Vascular Occlusion and the Therapeutic Potential of the Adrenomedullin–Receptor Activity–Modifying Protein 2 System
2019, American Journal of Pathology
Central retinal vein occlusion (CRVO) is an intractable disease that causes visual acuity loss with retinal ischemia, hemorrhage, and edema. In this study, we developed an experimental CRVO model in mice and evaluated the therapeutic potential of the pleiotropic peptide adrenomedullin (ADM) and its receptor activity–modifying protein 2 (RAMP2). The CRVO model, which had phenotypes resembling those seen in the clinic, was produced by combining i.p. injection of Rose bengal, a photoactivator dye enhancing thrombus formation, with laser photocoagulation. Retinal vascular area, analyzed using fluorescein angiography and fluorescein isothiocyanate–perfused retinal flat mounts, was decreased after induction of CRVO but gradually recovered from day 1 to 7. Measurements of retinal thickness using optical coherence tomography and histology revealed prominent edema early after CRVO, followed by gradual atrophy. Reperfusion after CRVO was diminished in Adm and Ramp2 knockout (KO) mice but was increased by exogenous ADM administration. CRVO also increased expression of a coagulation factor, oxidative stress markers, and a leukocyte adhesion molecule in both wild-type and Adm KO mice, and the effect was more pronounced in Adm KO mice. Using retinal capillary endothelial cells, ADM was found to directly suppress retinal endothelial injury. The retinoprotective effects of the Adm-Ramp2 system make it a novel therapeutic target for the treatment of CRVO.
Detection of Concordance between Transcriptional Levels of GPCRs and Receptor-Activity-Modifying Proteins
2019, iScience
Citation Excerpt :
G protein-coupled receptors (GPCRs) participate in a wide range of basic molecular processes and are highly druggable therapeutic targets (Venkatakrishnan et al., 2013). Receptor-activity-modifying proteins (RAMPs) have been shown to interact with several GPCRs and affect their ligand specificity, cellular trafficking, and post-translational modification (McLatchie et al., 1998; Parameswaran and Spielman, 2006; Weston et al., 2015). For example, the calcitonin receptor-like receptor (CALCRL), arguably the most studied GPCR in this context, interacts with RAMP1 in a way that facilitates the receptor's transport to the plasma membrane (Parameswaran and Spielman, 2006) and determines its ligand specificity (Hay and Pioszak, 2016; Hay et al., 2006).
A recent phylogenetic analysis showed global co-evolution of G protein-coupled receptors (GPCRs) and receptor-activity-modifying proteins (RAMPs) suggesting global interactions between these two protein families. Experimental validation of these findings is challenging because in humans whereas there are only three genes encoding RAMPs, there are about 800 genes encoding GPCRs. Here, we report an experimental approach to evaluate GPCR-RAMP interactions. As a proof-of-concept experiment, we over-expressed RAMP2 in HEK293T cells and evaluated the effect on the transcriptional levels of 14 representative GPCRs that were selected based on the earlier phylogenetic analysis. We utilized a multiplexed error-correcting fluorescence in situ hybridization (MERFISH) method to detect message levels for individual GPCRs in single cells. The MERFISH results showed changes in GPCR message levels with RAMP2 over-expression in a concordant pattern that was predicted by the earlier phylogenetic analysis. These results provide additional evidence that GPCR-RAMP interactions are more widespread than previously appreciated and that these interactions have functional consequences.
Is the activity of CGRP and Adrenomedullin regulated by RAMP (−2) and (−3) in Trypanosomatidae? An in-silico approach
2018, Infection, Genetics and Evolution
The Calcitonin-Like Receptor (CLR) belongs to the classical seven-transmembrane segment molecules coupled to heterotrimeric G proteins. Its pharmacology depends on the simultaneous expression of the so-called Receptor Activity Modifier Proteins (RAMP-) −1, −2 and −3. RAMP-associated proteins modulate glycosylation and cellular traffic of CLR, therefore determining its pharmacodynamics. In higher eukaryotes, the complex formed by CLR and RAMP-1 is more akin to bind Calcitonin Gene-Related Peptide (CGRP), whereas those formed by CLR and RAMP-2 or RAMP-3, bind preferentially Adrenomedullin (AM). In lower eukaryotes, RAMPs, or any homologous protein, have not been identified until now. Herein we demonstrated a negative chemotactic response elicited by CGRP (10⁻⁹ and 10⁻⁸ M) and AM (10⁻⁹ to 10⁻⁵ M). Whether or not this response is receptor mediated should be verified, as well as the expression of a 24 kDa band in Leishmania, recognized by western blot analysis by the use of (human-)-RAMP-2 antibodies as detection probes. Queries with human RAMP-2 and RAMP-3 protein sequences in blastp against Leishmania (Viannia) braziliensis predicted proteome, allowed us to detect two sequence alignments in the parasite: A RAMP-2-aligned sequence corresponding to Leishmania folylpolyglutamate synthase (FPGS), and a RAMP-3 aligned protein, a hypothetical Leishmania protein with yet unknown function. The presence of homologous of these proteins was described in-silico in other members of the Trypanosomatidae. These preliminary and not yet complete data suggest the feasibility that both CGRP and Adrenomedullin activities may be regulated by homologs of RAMP- (−2) and (−3) in these parasites.
Neuroendocrine Peptides
2016, Encyclopedia of Immunobiology
The peripheral nervous system is connected with primary and secondary lymphoid organs through sensory nerves that may regulate immune responses through release of the neuropeptide calcitonin gene-related peptide (CGRP). Local and systemic levels of CGRP rapidly increase during inflammation caused by pathogens or tissue damage. The CGRP receptor in immune cells is coupled to heterotrimeric Gα_S proteins and initiates an increase in cellular cAMP levels leading to the activation of protein kinase A (PKA). CGRP modulates both innate and adaptive immune responses. Exposure of macrophages to CGRP during TLR4-driven stimulation impairs production of inflammatory cytokines such as TNF and IL-12, enhances production of the immunosuppressive cytokine IL-10, and promotes the generation of a regulatory macrophage phenotype. During adaptive immune responses, CGRP inhibits Th1 cell activity, but enhances effector functions of Th9 and Th17 cells. Consequently, CGRP plays an important role for the development and outcome of inflammatory disorders including sepsis, autoimmunity, and allergies.

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Trends in Biochemical Sciences

ReviewRAMPs: the past, present and future

Section snippets

The discovery of RAMPs

Expression and distribution of RAMPs

Molecular mechanisms of RAMP–receptor interactions

Role of extracellular and transmembrane domains of RAMPs

Role of the RAMP C terminus

Interaction of RAMPs with class B GPCRs

Interaction of RAMPs with class C GPCRs

Concluding remarks and future perspectives

Acknowledgements

Peptides

FEBS Lett.

J. Biol. Chem.

J. Biol. Chem.

Biochem. Biophys. Res. Commun.

Semin. Cell Dev. Biol.

Peptides

J. Biol. Chem.

J. Biol. Chem.

J. Biol. Chem.

J. Biol. Chem.

FEBS Lett.

Cell Biol. Int.

Regul. Pept.

J. Mol. Cell. Cardiol.

Biochem. Biophys. Res. Commun.

Peptides

Regul. Pept.

J. Biol. Chem.

J. Biol. Chem.

J. Biol. Chem.

FEBS Lett.

FEBS Lett.

J. Biol. Chem.

J. Biol. Chem.

J. Biol. Chem.

Biophys. J

Peptides

J. Biol. Chem.

J. Biol. Chem.

J. Struct. Biol.

Neuron

J. Biol. Chem.

Eur. J. Pharmacol.

J. Biol. Chem.

Review
RAMPs: the past, present and future