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Lu J, Piper SJ, Zhao P, Miller LJ, Wootten D, Sexton PM. Targeting VIP and PACAP Receptor Signaling: New Insights into Designing Drugs for the PACAP Subfamily of Receptors. Int J Mol Sci 2022; 23:8069. [PMID: 35897648 PMCID: PMC9331257 DOI: 10.3390/ijms23158069] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2022] [Revised: 07/18/2022] [Accepted: 07/20/2022] [Indexed: 12/16/2022] Open
Abstract
Pituitary Adenylate Cyclase-Activating Peptide (PACAP) and Vasoactive Intestinal Peptide (VIP) are neuropeptides involved in a diverse array of physiological and pathological processes through activating the PACAP subfamily of class B1 G protein-coupled receptors (GPCRs): VIP receptor 1 (VPAC1R), VIP receptor 2 (VPAC2R), and PACAP type I receptor (PAC1R). VIP and PACAP share nearly 70% amino acid sequence identity, while their receptors PAC1R, VPAC1R, and VPAC2R share 60% homology in the transmembrane regions of the receptor. PACAP binds with high affinity to all three receptors, while VIP binds with high affinity to VPAC1R and VPAC2R, and has a thousand-fold lower affinity for PAC1R compared to PACAP. Due to the wide distribution of VIP and PACAP receptors in the body, potential therapeutic applications of drugs targeting these receptors, as well as expected undesired side effects, are numerous. Designing selective therapeutics targeting these receptors remains challenging due to their structural similarities. This review discusses recent discoveries on the molecular mechanisms involved in the selectivity and signaling of the PACAP subfamily of receptors, and future considerations for therapeutic targeting.
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Affiliation(s)
- Jessica Lu
- Drug Discovery Biology, Australian Research Council Centre for Cryo-Electron Microscopy of Membrane Proteins, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, VIC 3052, Australia
| | - Sarah J Piper
- Drug Discovery Biology, Australian Research Council Centre for Cryo-Electron Microscopy of Membrane Proteins, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, VIC 3052, Australia
| | - Peishen Zhao
- Drug Discovery Biology, Australian Research Council Centre for Cryo-Electron Microscopy of Membrane Proteins, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, VIC 3052, Australia
| | - Laurence J Miller
- Department of Molecular Pharmacology and Experimental Therapeutics, Mayo Clinic, Scottsdale, AZ 85259, USA
| | - Denise Wootten
- Drug Discovery Biology, Australian Research Council Centre for Cryo-Electron Microscopy of Membrane Proteins, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, VIC 3052, Australia
| | - Patrick M Sexton
- Drug Discovery Biology, Australian Research Council Centre for Cryo-Electron Microscopy of Membrane Proteins, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, VIC 3052, Australia
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2
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Dickson L, Finlayson K. VPAC and PAC receptors: From ligands to function. Pharmacol Ther 2008; 121:294-316. [PMID: 19109992 DOI: 10.1016/j.pharmthera.2008.11.006] [Citation(s) in RCA: 273] [Impact Index Per Article: 17.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2008] [Accepted: 11/18/2008] [Indexed: 02/03/2023]
Abstract
Vasoactive intestinal peptide (VIP) and the pituitary adenylate cyclase activating polypeptides (PACAPs) share 68% identity at the amino acid level and belong to the secretin peptide family. Following the initial discovery of VIP almost four decades ago a substantial amount of knowledge has been presented describing the mechanisms of action, distribution and pleiotropic functions of these related peptides. It is now known that the physiological actions of these widely distributed peptides are produced through activation of three common G-protein coupled receptors (VPAC(1), VPAC(2) and PAC(1)R) which preferentially stimulate adenylate cyclase and increase intracellular cAMP, although stimulation of other intracellular messengers, including calcium and phospholipase D, has been reported. Using a range of in vitro and in vivo approaches, including cell-based functional assays, transgenic animals and rodent models of disease, VPAC/PAC receptor activation has been associated with numerous physiological processes (e.g. control of circadian rhythms) and clinical conditions (e.g. pulmonary hypertension), which underlies on-going research efforts and makes these peptides and their cognate receptors attractive targets for the pharmaceutical industry. However, despite the considerable interest in VPAC/PAC receptors and the processes which they mediate, there is still a paucity of selective and available, non-peptide ligands, which has hindered further advances in this field both at the basic research and clinical level. This review summarises the current knowledge of VIP/PACAP and the VPAC/PAC receptors with regard to their distribution, pharmacology, signalling pathways, splice variants and finally, the utility of animal models in exploring their physiological roles.
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Affiliation(s)
- Louise Dickson
- Centre for Integrative Physiology, University of Edinburgh, EH8 9XD, UK
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3
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Kim SH, Youm JH, Lee DK, Park SY, Shin CY, Ryu JS, La HO, Song HJ, Min YS, Sohn UD. Effect of hydrogen peroxide on VIP-induced relaxation of the cat lower esophageal sphincter. Arch Pharm Res 2008; 30:1419-25. [PMID: 18087810 DOI: 10.1007/bf02977366] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
We investigated the effects of hydrogen peroxide (H2O2) on relaxation of the cat lower esophageal sphincter (LES). Vasoactive intestinal peptide (VIP) caused dose-dependent relaxation of LES, and H2O2 reduced VIP-induced relaxation. Relaxation was also attenuated by pertussis toxin (PTX), indicating a Gi/o component. VIP treatment increased [35S]GTPgammaS binding to Gs and Gi3 protein, but not to Go, Gq, Gil or Gi2. This increase in Gs or Gi3 binding was reduced by H2O2. However, the relaxation induced by sodium nitroprusside (SNP), 3-morpholino sydnomine (SIN-1), 8-br cGMP (cGMP analog), forskolin (adenylate cyclase activator), and dibutyryl-cAMP (a stable cAMP analog) was not reduced by H2O2. These data suggest that H202 inhibits VIP-induced relaxation via a Gi-dependent pathway, perhaps by inhibiting the activation of G(i3) or Gs downstream of the VIP receptor and independent of cAMP or NO-cGMP signaling.
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Affiliation(s)
- Sung Hyo Kim
- Department of Pharmacology, College of Pharmacy, Chung Ang University, Seoul 156-756, Korea
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4
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Peres CM, Aronoff DM, Serezani CH, Flamand N, Faccioli LH, Peters-Golden M. Specific leukotriene receptors couple to distinct G proteins to effect stimulation of alveolar macrophage host defense functions. THE JOURNAL OF IMMUNOLOGY 2007; 179:5454-61. [PMID: 17911632 DOI: 10.4049/jimmunol.179.8.5454] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Leukotrienes (LTs) are lipid mediators implicated in asthma and other inflammatory diseases. LTB(4) and LTD(4) also participate in antimicrobial defense by stimulating phagocyte functions via ligation of B leukotriene type 1 (BLT1) receptor and cysteinyl LT type 1 (cysLT1) receptor, respectively. Although both Galpha(i) and Galpha(q) proteins have been shown to be coupled to both BLT1 and cysLT1 receptors in transfected cell systems, there is little known about specific G protein subunit coupling to LT receptors, or to other G protein-coupled receptors, in primary cells. In this study we sought to define the role of specific G proteins in pulmonary alveolar macrophage (AM) innate immune responses to LTB(4) and LTD(4). LTB(4) but not LTD(4) reduced cAMP levels in rat AM by a pertussis toxin (PTX)-sensitive mechanism. Enhancement of FcgammaR-mediated phagocytosis and bacterial killing by LTB(4) was also PTX-sensitive, whereas that induced by LTD(4) was not. LTD(4) and LTB(4) induced Ca(2+) and intracellular inositol monophosphate accumulation, respectively, highlighting the role of Galpha(q) protein in mediating PTX-insensitive LTD(4) enhancement of phagocytosis and microbicidal activity. Studies with liposome-delivered G protein blocking Abs indicated a dependency on specific Galpha(q/11) and Galpha(i3) subunits, but not Galpha(i2) or G(beta)gamma, in LTB(4)-enhanced phagocytosis. The selective importance of Galpha(q/11) protein was also demonstrated in LTD(4)-enhanced phagocytosis. The present investigation identifies differences in specific G protein subunit coupling to LT receptors in antimicrobial responses and highlights the importance of defining the specific G proteins coupled to heptahelical receptors in primary cells, rather than simply using heterologous expression systems.
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MESH Headings
- Animals
- Cells, Cultured
- Cyclic AMP/antagonists & inhibitors
- Cyclic AMP/metabolism
- Down-Regulation/immunology
- Female
- GTP-Binding Protein alpha Subunit, Gi2/biosynthesis
- GTP-Binding Protein alpha Subunit, Gi2/genetics
- GTP-Binding Protein alpha Subunits, Gq-G11/biosynthesis
- GTP-Binding Protein alpha Subunits, Gq-G11/genetics
- GTP-Binding Proteins/biosynthesis
- GTP-Binding Proteins/metabolism
- GTP-Binding Proteins/physiology
- Intracellular Fluid/metabolism
- Leukotriene B4/antagonists & inhibitors
- Leukotriene B4/physiology
- Leukotriene D4/antagonists & inhibitors
- Leukotriene D4/physiology
- Macrophage Activation/immunology
- Macrophages, Alveolar/immunology
- Macrophages, Alveolar/metabolism
- Rats
- Rats, Wistar
- Receptors, Leukotriene/metabolism
- Receptors, Leukotriene/physiology
- Toxoids/pharmacology
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Affiliation(s)
- Camila M Peres
- Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine, University of Michigan Health System, Ann Arbor, MI 48109, USA
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Goursaud S, Pineau N, Becq-Giraudon L, Gressens P, Muller JM, Janet T. Human H9 cells proliferation is differently controlled by vasoactive intestinal peptide or peptide histidine methionine: implication of a GTP-insensitive form of VPAC1 receptor. J Neuroimmunol 2005; 158:94-105. [PMID: 15589042 DOI: 10.1016/j.jneuroim.2004.08.018] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2004] [Revised: 07/09/2004] [Accepted: 08/16/2004] [Indexed: 11/29/2022]
Abstract
The proliferation of human lymphoblastoma cell line (H9) was differently stimulated by Peptide Histidine Methionine (PHM) and Vasoactive Intestinal Peptide (VIP). PHM induced a cyclic AMP (cAMP) accumulation, abolished by Adenylate Cyclase (AC) inhibitors leading to a loss of proliferative effect. VIP mitogenic activity was Pertussis toxin (PTX) sensitive and AC inhibitors insensitive. Pharmacological experiments performed on H9 membranes with or without a GTP analogue indicated expression of both GTP-insensitive and -sensitive PHM/VIP high-affinity binding sites (HA). H9 cells expressed only the VPAC1 receptor. VIP(10-28), known as a VPAC1 antagonist, bond to all GTP-insensitive PHM sites and inhibited evenly the PHM and VIP mitogenic actions. These data strongly suggested different mechanisms initiated by VIP and PHM and highlighted the key role of GTP-insensitive binding sites in the control of cell proliferation.
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MESH Headings
- Adenine/analogs & derivatives
- Adenine/pharmacology
- Adenylyl Cyclase Inhibitors
- Analysis of Variance
- Blotting, Southern
- Bromodeoxyuridine/metabolism
- Cell Line, Tumor
- Cell Proliferation/drug effects
- Cyclic AMP/metabolism
- Dose-Response Relationship, Drug
- Drug Interactions
- Gene Expression/drug effects
- Guanosine Triphosphate/pharmacology
- Guanylyl Imidodiphosphate/pharmacology
- Humans
- Imines/pharmacology
- Iodine Isotopes/pharmacokinetics
- Lymphoma
- Peptide Fragments/pharmacology
- Peptide PHI/pharmacology
- Pertussis Toxin/pharmacology
- Protein Binding/drug effects
- RNA, Messenger/biosynthesis
- Radioligand Assay/methods
- Receptors, Cell Surface/genetics
- Receptors, Cell Surface/metabolism
- Receptors, Pituitary Adenylate Cyclase-Activating Polypeptide
- Receptors, Vasoactive Intestinal Peptide/genetics
- Receptors, Vasoactive Intestinal Peptide/metabolism
- Receptors, Vasoactive Intestinal Peptide, Type II
- Receptors, Vasoactive Intestinal Polypeptide, Type I
- Reverse Transcriptase Polymerase Chain Reaction/methods
- Time Factors
- Vasoactive Intestinal Peptide/antagonists & inhibitors
- Vasoactive Intestinal Peptide/pharmacology
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Affiliation(s)
- Stephanie Goursaud
- IPBC CNRS-UMR 6187 Pôle Biologie Santé, 40 avenue du Recteur Pineau, 86022 Poitiers, France
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6
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Delgado M, Pozo D, Ganea D. The significance of vasoactive intestinal peptide in immunomodulation. Pharmacol Rev 2004; 56:249-90. [PMID: 15169929 DOI: 10.1124/pr.56.2.7] [Citation(s) in RCA: 295] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
First identified by Said and Mutt some 30 years ago, the vasoactive intestinal peptide (VIP) was originally isolated as a vasodilator peptide. Subsequently, its biochemistry was elucidated, and within the 1st decade, their signature features as a neuropeptide became consolidated. It did not take long for these insights to permeate the field of immunology, out of which surprising new attributes for VIP were found in the last years. VIP is rapidly transforming into something more than a mere hormone. In evolving scientifically from a hormone to a novel agent for modifying immune function and possibly a cytokine-like molecule, VIP research has engaged many physiologists, molecular biologists, biochemists, endocrinologists, and pharmacologists and it is a paradigm to explore mutual interactions between neural and neuroendocrine links in health and disease. The aim of this review is firstly to update our knowledge of the cellular and molecular events relevant to VIP function on the immune system and secondly to gather together recent data that support its role as a type 2 cytokine. Recognition of the central functions VIP plays in cellular processes is focusing our attention on this "very important peptide" as exciting new candidates for therapeutic intervention and drug development.
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Affiliation(s)
- Mario Delgado
- Instituto de Parasitologia y Biomedicina "Lopez Neyra," Calle Ventanilla 11, Granada 18001, Spain.
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7
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Hermans E. Biochemical and pharmacological control of the multiplicity of coupling at G-protein-coupled receptors. Pharmacol Ther 2003; 99:25-44. [PMID: 12804697 DOI: 10.1016/s0163-7258(03)00051-2] [Citation(s) in RCA: 221] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
For decades, it has been generally proposed that a given receptor always interacts with a particular GTP-binding protein (G-protein) or with multiple G-proteins within one family. However, for several G-protein-coupled receptors (GPCR), it now becomes generally accepted that simultaneous functional coupling with distinct unrelated G-proteins can be observed, leading to the activation of multiple intracellular effectors with distinct efficacies and/or potencies. Multiplicity in G-protein coupling is frequently observed in artificial expression systems where high densities of receptors are obtained, raising the question of whether such complex signalling reveals artefactual promiscuous coupling or is a genuine property of GPCRs. Multiple biochemical and pharmacological evidence in favour of an intrinsic property of GPCRs were obtained in recent studies. Thus, there are now many examples showing that the coupling to multiple signalling pathways is dependent on the agonist used (agonist trafficking of receptor signals). In addition, the different couplings were demonstrated to involve distinct molecular determinants of the receptor and to show distinct desensitisation kinetics. Such multiplicity of signalling at the level of G-protein coupling leads to a further complexity in the functional response to agonist stimulation of one of the most elaborate cellular transmission systems. Indeed, the physiological relevance of such versatility in signalling associated with a single receptor requires the existence of critical mechanisms of dynamic regulation of the expression, the compartmentalisation, and the activity of the signalling partners. This review aims at summarising the different studies that support the concept of multiplicity of G-protein coupling. The physiological and pharmacological relevance of this coupling promiscuity will be discussed.
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Affiliation(s)
- Emmanuel Hermans
- Laboratoire de Pharmacologie Expérimentale, Université Catholique de Louvain, FARL 54.10, Avenue Hippocrate 54, B-1200 Brussels, Belgium.
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8
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Laburthe M, Couvineau A. Molecular pharmacology and structure of VPAC Receptors for VIP and PACAP. REGULATORY PEPTIDES 2002; 108:165-73. [PMID: 12220741 DOI: 10.1016/s0167-0115(02)00099-x] [Citation(s) in RCA: 122] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
VIP and PACAP are two prominent neuropeptides which share two common G protein-coupled receptors VPAC1 and VPAC2 while PACAP has an additional specific receptor PAC1. This paper reviews the present knowledge regarding three aspects of VPAC receptors including: (i). receptor specificity towards natural VIP-related peptides and pharmacology of synthetic agonists or antagonists; (ii). receptor signaling; (iii). molecular basis of ligand-receptor interaction as determined by site-directed mutagenesis, construction of receptor chimeras and structural modeling.
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MESH Headings
- Amino Acid Sequence
- Animals
- Humans
- Ligands
- Models, Molecular
- Neuropeptides/physiology
- Pituitary Adenylate Cyclase-Activating Polypeptide
- Protein Conformation
- Receptors, Pituitary Adenylate Cyclase-Activating Polypeptide
- Receptors, Pituitary Adenylate Cyclase-Activating Polypeptide, Type I
- Receptors, Pituitary Hormone/physiology
- Receptors, Vasoactive Intestinal Peptide/chemistry
- Receptors, Vasoactive Intestinal Peptide/physiology
- Receptors, Vasoactive Intestinal Peptide, Type II
- Receptors, Vasoactive Intestinal Polypeptide, Type I
- Substrate Specificity
- Vasoactive Intestinal Peptide/chemistry
- Vasoactive Intestinal Peptide/metabolism
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Affiliation(s)
- M Laburthe
- Neuroendocrinology and Cell Biology, INSERM U41O, Faculté de Médecine Xavier Bichat, 75018, Paris, France.
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9
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Martin Shreeve S. Identification of G-proteins coupling to the vasoactive intestinal peptide receptor VPAC(1) using immunoaffinity chromatography: evidence for precoupling. Biochem Biophys Res Commun 2002; 290:1300-7. [PMID: 11812005 DOI: 10.1006/bbrc.2002.6342] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
VPAC(1) receptor subtype-specific G-protein interactions were identified using a strategy that exploits an essential initial signaling event, namely the functional and physical association of the receptor with G-protein. An immunoaffinity purification column was constructed using a previously characterized antibody that had been raised against the first extracellular loop of the VPAC(1) receptor. VPAC(1)/G-protein complexes were solubilized from membranes and copurified. Receptor and Galpha-proteins were detected in eluates using (125)I-VIP labeling and immunoblotting, respectively. Human VPAC(1) transfected in HEK293 cells couples to Gs but not Gi3, Gi1/2, or Gq. Rat VPAC(1) in brain membranes is coupled to Gs and Gi3. Rat VPAC(1) in lung membranes couples to Gs, Gi3, and Gq. Pretreatment of membranes with VIP increased the level of all G-proteins copurifying with VPAC(1). Immunoaffinity chromatography also revealed VPAC(1) receptor precoupling to G-protein in the absence of VIP pretreatment. This was confirmed using a cross-linking procedure to capture VIP receptor/G-protein complexes in the native membrane milieu prior to solubilization. Precoupling suggests that there is a significant basal level of VPAC(1) receptor activity especially in cells, such as some human malignant tumor cells, that express high levels of receptor.
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Affiliation(s)
- S Martin Shreeve
- Department of Pharmacology, University of Vermont, Burlington 05405, USA.
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10
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Roumy M, Zajac JM. Neuropeptide FF receptors couple to a cholera toxin-sensitive G-protein in rat dorsal raphe neurones. Eur J Pharmacol 2001; 417:45-9. [PMID: 11301058 DOI: 10.1016/s0014-2999(01)00896-2] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
In rat dorsal raphe neurones, nociceptin (300 nM) reduced the peak [Ca(2+)](i) transient, triggered by depolarization, by 36.7+/-1.8% (n=46). This effect of nociceptin decreased to 16.7+/-2.9% (n=18) after pre-treatment of the neurones with pertussis toxin (5 microg/ml, 2-6 h) but was unchanged (37.4+/-2.1%, n=44) after pre-incubation with cholera toxin (5 microg/ml, 2-6 h). This suggests that, in dorsal raphe neurones, the ORL1 receptor couples to inhibitory (G(i/o)) G-proteins. The neuropeptide FF analogue, [D-Tyr1, (N-Me)Phe(3)]neuropeptide FF (10, 100, 1000 nM), acted as an anti-opioid and reduced the effect of nociceptin (300 nM, 30 s) by 62.0+/-3.3% (n=28). Following pre-incubation with cholera toxin (5 microg/ml, 2-6 h) [D-Tyr1, (N-Me)Phe3] neuropeptide FF was unable, at the three concentrations tested, to block nociceptin activity. We conclude that, in rat dorsal raphe neurones, neuropeptide FF receptors couple to stimulatory G-proteins (Gs).
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Affiliation(s)
- M Roumy
- Institut de Pharmacologie et de Biologie Structurale, C.N.R.S. UMR 5089, 205 Route de Narbonne, 31077 Cedex, Toulouse, France.
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11
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Di Salvo J, Koch GE, Johnson KE, Blake AD, Daugherty BL, DeMartino JA, Sirotina-Meisher A, Liu Y, Springer MS, Cascieri MA, Sullivan KA. The CXCR4 agonist ligand stromal derived factor-1 maintains high affinity for receptors in both Galpha(i)-coupled and uncoupled states. Eur J Pharmacol 2000; 409:143-54. [PMID: 11104827 DOI: 10.1016/s0014-2999(00)00846-3] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The alpha chemokine receptor CXCR4 and its only characterized chemokine ligand, stromal cell-derived factor-1 (SDF-1), are postulated to be important in the development of the B-cell arm of the immune system. In addition, CXCR4 is a critical coreceptor in support of viral entry by T-cell line tropic strains (X4) of the Human Immunodeficiency Virus Type 1 (HIV-1), viral variants which predominate in some infected individuals in end stage disease. SDF-1 can block X4-tropic HIV-1 infection of CD4+ target cells in vitro, and allelic variants of the human gene encoding SDF-1 in vivo correlate with delayed disease progression. Therefore, CXCR4 may be an appropriate target for therapeutic intervention in acquired immunodeficiency syndrome (AIDS), and knowledge of the pharmacology of SDF-1 binding to its cognate receptor will be important in the interpretation of these experiments. We report here a Kd derived using a competition binding assay of 4.5 nM for CXCR4 endogenously expressed on peripheral blood monocytes and T-cells. This affinity is similar to that which SDF-1 exhibits when binding to endogenous CXCR4 on an established immortal Jurkat T-cell line as well as recombinant CXCR4 transfected into Chinese Hamster Ovary (CHO) cells. We also demonstrate that the determined affinity of SDF-1 for CXCR4 is reflective of its ability to induce a CXCR4-mediated signal transduction in these different cell types. Furthermore, using Bordetella pertussis toxin, we observe that high affinity binding of SDF-1 to CXCR4 is independent of the G-protein coupled state of the receptor, as uncoupling of G-protein did not lead to the appearance of measurable low affinity SDF-1 binding sites. Moreover, binding affinity and receptor number were unaffected by uncoupling for both recombinant and endogenously expressed CXCR4. Thus, SDF-1 is novel among agonist ligands of G protein-coupled receptors in that it appears to have equal affinity for both the G protein-coupled and uncoupled states of CXCR4.
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MESH Headings
- Animals
- Binding, Competitive/drug effects
- CHO Cells
- Chemokine CXCL12
- Chemokines, CXC/metabolism
- Chemokines, CXC/pharmacology
- Colforsin/pharmacology
- Cricetinae
- Cyclic AMP/metabolism
- Dose-Response Relationship, Drug
- GTP-Binding Protein alpha Subunits, Gi-Go/metabolism
- Gene Expression
- Guanosine 5'-O-(3-Thiotriphosphate)/pharmacology
- Humans
- Jurkat Cells
- Leukocytes, Mononuclear/cytology
- Leukocytes, Mononuclear/drug effects
- Leukocytes, Mononuclear/metabolism
- Pertussis Toxin
- Receptors, CXCR4/agonists
- Receptors, CXCR4/genetics
- Receptors, CXCR4/metabolism
- Signal Transduction/drug effects
- T-Lymphocytes/cytology
- T-Lymphocytes/drug effects
- T-Lymphocytes/metabolism
- Virulence Factors, Bordetella/pharmacology
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Affiliation(s)
- J Di Salvo
- Department of Immunology and Rheumatology, Merck Research Laboratories, RY80M-213, P.O. Box 2000, Rahway, NJ 07065, USA.
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