Complexing Receptor Pharmacology

Sexton, Patrick M.; Morfis, Maria; Tilakaratne, Nanda; Hay, Debbie L.; Udawela, Madhara; Christopoulos, George; Christopoulos, Arthur

doi:10.1196/annals.1317.076

Cited by 75 publications

(65 citation statements)

References 44 publications

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“…Peptides of this family also share a unique mechanism of G-protein coupled receptor signaling by a novel class of single transmembrane proteins called receptor activity modifying proteins (RAMPs). RAMPs were first identified through their association with the calcitonin receptor-like receptor (CLR) and can interact with many other class II GPCRs to determine receptor ligand binding specificity [27]. In the case of CLR, association with RAMP1 produces a CGRP receptor, while association with RAMP2 or RAMP3 produces a receptor specific for AM.…”

Section: Introductionmentioning

confidence: 99%

Mice heterozygous for adrenomedullin exhibit a more extreme inflammatory response to endotoxin-induced septic shock

Dackor

Caron

2007

Peptides

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Adrenomedullin (AM) is a highly conserved peptide that can act as a potent vasodilator, antimicrobial factor and anti-inflammatory factor. Several studies have implicated diverse roles for AM in regulating the inflammatory and hemodynamic responses to septic shock. Moreover, during sepsis the receptors that mediate AM signaling [calcitonin receptor-like receptor (calcrl) and receptor activity modifying proteins (RAMP) 2 and 3] undergo dynamic and robust changes in their expression. Although numerous studies have used animal models to study the role of administered or increased AM in septic animals, genetic studies to determine the consequences of reduced AM during septic shock have not yet been performed. Here, we used a murine model of lipopolysaccharide (LPS)-induced septic shock to assess the inflammatory response in mice heterozygous for the AM gene. Following LPS challenge, AM +/− mice had higher expression of TNF-α and IL-1β than LPS-treated wild-type (WT) controls. Consequently, serum TNF-α was also significantly elevated in LPS-treated AM +/− mice compared to WT LPS-treated mice. We also observed higher serum levels of liver enzymes, suggesting more advanced end-organ damage in mice with genetically reduced AM. Finally, we found that RAMP2 and calcrl expression levels were markedly reduced in LPS-treated mice, whereas RAMP3 expression was significantly elevated. Importantly, these changes in receptor gene expression were conserved in AM +/− mice, demonstrating that AM peptide itself does not impact directly on the expression of the genes encoding its receptors. We therefore conclude that during septic shock the dynamic modulation of AM and its receptors primarily functions to dampen the inflammatory response.

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Section: Introductionmentioning

confidence: 99%

Mice heterozygous for adrenomedullin exhibit a more extreme inflammatory response to endotoxin-induced septic shock

Dackor

Caron

2007

Peptides

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“…The GABA B1 receptor contains an endoplasmic reticulum retention signal in its cytoplasmic tail and must form a heterodimer with a GABA B2 receptor before the GABA B receptor can move to the cell surface (4). Receptor activity modifying proteins (RAMPs) facilitate trafficking and alter the ligand specificity of several class B GPCRs (5). MRAP is expressed in the adrenal cortex but is not found in commonly used model cells such as HEK293, COS, and CHO, and the MC2 receptor is not active when it is expressed in cells lacking MRAP.…”

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confidence: 99%

“…RAMP1 or MRAP. RAMP1 served as a negative control; it is a single transmembrane domain accessory protein for the calcitonin receptor-like receptor (5). When MC2 receptor was expressed with RAMP1 ( Fig.…”

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confidence: 99%

Melanocortin-2 receptor accessory protein MRAP forms antiparallel homodimers

Sebag

Hinkle

2007

Proc. Natl. Acad. Sci. U.S.A.

155

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The melanocortin-2 (MC2) receptor accessory protein (MRAP) is required for trafficking of the G protein-coupled MC2 receptor to the plasma membrane. The mechanism of action and structure of MRAP, which has a single transmembrane domain, are unknown. Here, we show that MRAP displays a previously uncharacterized topology. Epitopes on both the N-and C-terminal ends of MRAP were localized on the external face of CHO cells at comparable levels. Using antibodies raised against N-and C-terminal MRAP peptides, we demonstrated that both ends of endogenous MRAP face the outside in adrenal cells. Nearly half of MRAP was glycosylated at the single endogenous N-terminal glycosylation site, and over half was glycosylated when the natural glycosylation site was replaced by one in the C-terminal domain. A mutant MRAP with potential glycosylation sites on both sides of the membrane was singly but not doubly glycosylated, suggesting that MRAP is not monotopic. Coimmunoprecipitation of differentially tagged MRAPs established that MRAP is a dimer. By selectively immunoprecipitating cell surface MRAP in one or the other orientation, we showed that MRAP homodimers are antiparallel and form a stable complex with MC2 receptor. In the absence of MRAP, MC2 receptor was trapped in the endoplasmic reticulum, but with MRAP, the MC2 receptor was glycosylated and localized on the plasma membrane, where it signaled in response to ACTH. MRAP acted specifically, because it did not increase surface expression of other melanocortin, ␤2-adrenergic, or TSH-releasing hormone receptors. MRAP is the first eukaryotic membrane protein identified with an antiparallel homodimeric structure.ACTH ͉ G protein-coupled receptor ͉ membrane ͉ orientation T he G protein-coupled receptor (GPCR) family is the largest group of membrane proteins in the human genome. GPCRs respond to a wide array of signals and regulate numerous intracellular signaling pathways. They are characterized by an extracellular amino terminus that is usually glycosylated, seven transmembrane domains, and a cytoplasmic carboxyl terminus. After synthesis in the endoplasmic reticulum, GPCRs must move to the plasma membrane before they can signal in response to extracellular ligands.In the adrenal gland, the melanocortin-2 (MC2) receptor, also referred to as the corticotropin (ACTH) receptor, is activated by the pituitary hormone ACTH and promotes glucocorticoid biosynthesis. The MC2 receptor is expressed primarily in the adrenal cortex and is positively coupled to adenylyl cyclase. The MC2 receptor is a member of the class A rhodopsin-like family and the smallest known GPCR. Individuals harboring inactivating mutations in the MC2 receptor suffer from familial glucocorticoid deficiency, or hereditary unresponsiveness to ACTH (1). Recently, it was discovered that familial glucocorticoid deficiency can also arise from mutations in an accessory protein required for ACTH signaling, the MC2 receptor accessory protein (MRAP) (2). Lack of functional MRAP, like the lack of an MC2 receptor, causes ACTH re...

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“…In particular, RAMP heterodimerization with calcitonin receptors is required for the formation of amylin receptors [58] [59] . More recent work has revealed that the RAMPs may modulate other functions such as receptor internalization and recycling and also the strength of activation of downstream signaling pathways [60] . Further studies, including conditional gene targeting models, which enable the spatial and temporal modulation of RAMP gene expression, are needed to elucidate the more detailed pathophysiological roles of the RAMP system.…”

Section: Discussionmentioning

confidence: 99%

Regulation of Adrenomedullin and its Family Peptide by RAMP System – Lessons from Genetically Engineered Mice

Shindo¹,

Sakurai²,

Kamiyoshi³

et al. 2013

CPPS

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Adrenomedullin (ADM), originally identified as a vasodilating peptide, is now recognized to be a pleiotropic molecule involved in both the pathogenesis of cardiovascular diseases and circulatory homeostasis.Homozygotes of ADM knockout mice (ADM-/-) were lethal at mid-gestation with abnormalities of vascular development and this finding clarified the angiogenic potency of ADM. Calcitonin gene-related peptide (CGRP), which has a structure and function similar to that of ADM, has been identified as a family peptide of ADM. Unlike ADM-/-, CGRP-/-were apparently normal. Therefore, the study of knockout mice first clarified the distinctly different physiological roles between ADM and CGRP.In contrast, heterozygotes of ADM knockout mice (ADM+/-) were alive but showed blood pressure elevation, reduced neovascularization, and enhanced neointimal formation by arterial injury.Based on these observations, there was hope ADM would have a therapeutic use.However, ADM has a short half-life in the blood stream and its application in chronic disease has limitations. Therefore, we focused on the ADM receptor system. The calcitonin-receptor-like receptor (CLR), which is the ADM receptor, associates with one of the accessory proteins, called receptor activity-modifying proteins (RAMPs). By interacting with RAMP1, CLR exhibits a high affinity for CGRP, whereas by interacting with either RAMP2 or -3, CLR exhibits a high affinity for ADM.We generated RAMP knockout mice and found that vascular phenotypes similar to ADM-/-were reproduced only in RAMP2-/-. This shows that RAMP2 is the key

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Complexing Receptor Pharmacology

Cited by 75 publications

References 44 publications

Mice heterozygous for adrenomedullin exhibit a more extreme inflammatory response to endotoxin-induced septic shock

Mice heterozygous for adrenomedullin exhibit a more extreme inflammatory response to endotoxin-induced septic shock

Melanocortin-2 receptor accessory protein MRAP forms antiparallel homodimers

Regulation of Adrenomedullin and its Family Peptide by RAMP System – Lessons from Genetically Engineered Mice

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