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Poll BG, Chen L, Chou CL, Raghuram V, Knepper MA. Landscape of GPCR expression along the mouse nephron. Am J Physiol Renal Physiol 2021; 321:F50-F68. [PMID: 34029142 PMCID: PMC8321805 DOI: 10.1152/ajprenal.00077.2021] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2021] [Revised: 05/20/2021] [Accepted: 05/20/2021] [Indexed: 12/11/2022] Open
Abstract
Kidney transport and other renal functions are regulated by multiple G protein-coupled receptors (GPCRs) expressed along the renal tubule. The rapid, recent appearance of comprehensive unbiased gene expression data in the various renal tubule segments, chiefly RNA sequencing and protein mass spectrometry data, has provided a means of identifying patterns of GPCR expression along the renal tubule. To allow for comprehensive mapping, we first curated a comprehensive list of GPCRs in the genomes of mice, rats, and humans (https://hpcwebapps.cit.nih.gov/ESBL/Database/GPCRs/) using multiple online data sources. We used this list to mine segment-specific and cell type-specific expression data from RNA-sequencing studies in microdissected mouse tubule segments to identify GPCRs that are selectively expressed in discrete tubule segments. Comparisons of these mapped mouse GPCRs with other omics datasets as well as functional data from isolated perfused tubule and micropuncture studies confirmed patterns of expression for well-known receptors and identified poorly studied GPCRs that are likely to play roles in the regulation of renal tubule function. Thus, we provide data resources for GPCR expression across the renal tubule, highlighting both well-known GPCRs and understudied receptors to provide guidance for future studies.
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Affiliation(s)
- Brian G Poll
- Epithelial Systems Biology Laboratory, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland
| | - Lihe Chen
- Epithelial Systems Biology Laboratory, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland
| | - Chung-Lin Chou
- Epithelial Systems Biology Laboratory, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland
| | - Viswanathan Raghuram
- Epithelial Systems Biology Laboratory, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland
| | - Mark A Knepper
- Epithelial Systems Biology Laboratory, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland
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2
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The Role of Adrenoceptors in the Retina. Cells 2020; 9:cells9122594. [PMID: 33287335 PMCID: PMC7761662 DOI: 10.3390/cells9122594] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2020] [Revised: 11/29/2020] [Accepted: 12/01/2020] [Indexed: 01/16/2023] Open
Abstract
The retina is a part of the central nervous system, a thin multilayer with neuronal lamination, responsible for detecting, preprocessing, and sending visual information to the brain. Many retinal diseases are characterized by hemodynamic perturbations and neurodegeneration leading to vision loss and reduced quality of life. Since catecholamines and respective bindings sites have been characterized in the retina, we systematically reviewed the literature with regard to retinal expression, distribution and function of alpha1 (α1)-, alpha2 (α2)-, and beta (β)-adrenoceptors (ARs). Moreover, we discuss the role of the individual adrenoceptors as targets for the treatment of retinal diseases.
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Alpha-1 Adrenergic Receptors Modulate Glutamate and GABA Neurotransmission onto Ventral Tegmental Dopamine Neurons during Cocaine Sensitization. Int J Mol Sci 2020; 21:ijms21030790. [PMID: 31991781 PMCID: PMC7036981 DOI: 10.3390/ijms21030790] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2019] [Revised: 01/16/2020] [Accepted: 01/20/2020] [Indexed: 12/25/2022] Open
Abstract
The ventral tegmental area (VTA) plays an important role in the reward and motivational processes that facilitate the development of drug addiction. Presynaptic α1-AR activation modulates glutamate and Gamma-aminobutyric acid (GABA) release. This work elucidates the role of VTA presynaptic α1-ARs and their modulation on glutamatergic and GABAergic neurotransmission during cocaine sensitization. Excitatory and inhibitory currents (EPSCs and IPSCs) measured by a whole cell voltage clamp show that α1-ARs activation increases EPSCs amplitude after 1 day of cocaine treatment but not after 5 days of cocaine injections. The absence of a pharmacological response to an α1-ARs agonist highlights the desensitization of the receptor after repeated cocaine administration. The desensitization of α1-ARs persists after a 7-day withdrawal period. In contrast, the modulation of α1-ARs on GABA neurotransmission, shown by decreases in IPSCs' amplitude, is not affected by acute or chronic cocaine injections. Taken together, these data suggest that α1-ARs may enhance DA neuronal excitability after repeated cocaine administration through the reduction of GABA inhibition onto VTA dopamine (DA) neurons even in the absence of α1-ARs' function on glutamate release and protein kinase C (PKC) activation. α1-AR modulatory changes in cocaine sensitization increase our knowledge of the role of the noradrenergic system in cocaine addiction and may provide possible avenues for therapeutics.
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Odagaki Y, Kinoshita M, Ota T. Functional activation of Gα q/11 protein via α 1 -adrenoceptor in rat cerebral cortical membranes. Clin Exp Pharmacol Physiol 2019; 46:567-574. [PMID: 30869808 DOI: 10.1111/1440-1681.13084] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2019] [Revised: 02/21/2019] [Accepted: 03/09/2019] [Indexed: 11/26/2022]
Abstract
Although it is recognized that α1 -adrenoceptors are coupled to diverse intracellular signalling pathways, its primary transduction mechanisms are evoked by activating phospholipase C in the cell membrane through Gαq/11 , resulting in production of inositol 1,4,5-trisphosphate and diacylglycerol. However, there have been few studies that indicate directly the involvement of Gαq/11 proteins in this signalling pathway in the central nervous system. In the current study, we tried to pharmacologically characterize (-)-adrenaline-stimulated [35 S]GTPγS binding to Gαq/11 in rat brain membranes. Functional activation of Gαq/11 coupled to α1 -adrenoceptor was investigated by using [35 S]GTPγS binding/immunoprecipitation assay in the membranes prepared from rat cerebral cortex, hippocampus, and striatum. The specific [35 S]GTPγS binding to Gαq/11 was stimulated by (-)-adrenaline in a concentration-dependent and saturable manner in rat cerebral cortical membranes. In hippocampal or striatal membranes, the stimulatory effects of (-)-adrenaline were scarce. The effect of (-)-adrenaline was potently inhibited by prazosin, a potent and selective α1 -adrenoceptor antagonist, but not by yohimbine, a selective α2 -adrenoceptor antagonist. The response was mimicked by cirazoline, but not by R(-)-phenylephrine. Although oxymetazoline also stimulated the specific [35 S]GTPγS binding to Gαq/11 as an apparent "super-agonist", detailed pharmacological characterization revealed that its agonistic properties in this experimental system were derived from off-target effects on 5-HT2A receptors, but not via α1 -adrenoceptors. In conclusion, functional coupling of α1 -adrenoceptors to Gαq/11 proteins are detectable in rat brain membranes by means of [35 S]GTPγS binding/immunoprecipitation assay. It is necessary to interpret the experimental data with caution when oxymetazoline is included as an agonist at α1 -adrenoceptors.
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Affiliation(s)
- Yuji Odagaki
- Department of Psychiatry, Faculty of Medicine, Saitama Medical University, Moroyama-machi, Iruma-gun, Saitama 350-0495, Japan
| | - Masakazu Kinoshita
- Department of Psychiatry, Faculty of Medicine, Saitama Medical University, Moroyama-machi, Iruma-gun, Saitama 350-0495, Japan
| | - Toshio Ota
- Department of Psychiatry, Faculty of Medicine, Saitama Medical University, Moroyama-machi, Iruma-gun, Saitama 350-0495, Japan
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Synthesis and Pharmacological Evaluation of Novel Silodosin-Based Arylsulfonamide Derivatives as α 1A/α 1D-Adrenergic Receptor Antagonist with Potential Uroselective Profile. Molecules 2018; 23:molecules23092175. [PMID: 30158432 PMCID: PMC6225212 DOI: 10.3390/molecules23092175] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2018] [Revised: 08/03/2018] [Accepted: 08/13/2018] [Indexed: 11/16/2022] Open
Abstract
Benign prostatic hyperplasia (BPH) is the most common male clinical problem impacting the quality of life of older men. Clinical studies have indicated that the inhibition of α1A-/α1D adrenoceptors might offer effective therapy in lower urinary tract symptoms. Herein, a limited series of arylsulfonamide derivatives of (aryloxy)ethyl alicyclic amines was designed, synthesized, and biologically evaluated as potent α1-adrenoceptor antagonists with uroselective profile. Among them, compound 9 (3-chloro-2-fluoro-N-([1-(2-(2-(2,2,2-trifluoroethoxy)phenoxy]ethyl)piperidin-4-yl)methyl)benzenesulfonamide) behaved as an α1A-/α1D-adrenoceptor antagonist (Ki(α1) = 50 nM, EC50(α1A) = 0.8 nM, EC50(α1D) = 1.1 nM), displayed selectivity over α2-adrenoceptors (Ki(α2) = 858 nM), and a 5-fold functional preference over the α1B subtype. Compound 9 showed adequate metabolic stability in rat-liver microsome assay similar to the reference drug tamsulosin (Clint = 67 and 41 µL/min/mg, respectively). Compound 9 did not decrease systolic and diastolic blood pressure in normotensive anesthetized rats in the dose of 2 mg/kg, i.v. These data support development of uroselective agents in the group of arylsulfonamides of alicyclic amines with potential efficacy in the treatment of lower urinary tract symptoms associated to benign prostatic hyperplasia.
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McGrath JC. Localization of α-adrenoceptors: JR Vane Medal Lecture. Br J Pharmacol 2015; 172:1179-94. [PMID: 25377869 PMCID: PMC4337695 DOI: 10.1111/bph.13008] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2014] [Revised: 10/06/2014] [Accepted: 10/27/2014] [Indexed: 01/08/2023] Open
Abstract
UNLABELLED This review is based on the JR Vane Medal Lecture presented at the BPS Winter Meeting in December 2011 by J.C. McGrath. A recording of the lecture is included as supporting information. It covers his laboratory's work from 1990 to 2010 on the localization of vascular α1 -adrenoceptors in native tissues, mainly arteries. MAIN POINTS (i) α1 -adrenoceptors are present on several cell types in arteries, not only on medial smooth muscle, but also on adventitial, endothelial and nerve cells; (ii) all three receptor subtypes (α1 A , α1 B , α1 D ) are capable of binding ligands at the cell surface, strongly indicating that they are capable of function and not merely expressed. (iii) all of these cell types can take up an antagonist ligand into the intracellular compartments to which endocytosing receptors move; (iv) each individual subtype can exist at the cell surface and intracellularly in the absence of the other subtypes. As functional pharmacological experiments show variations in the involvement of the different subtypes in contractions of different arteries, it is concluded that the presence and disposition of α1 -adrenoceptors in arteries is not a simple guide to their involvement in function. Similar locations of the subtypes, even in different cell types, suggest that differences between the distribution of subtypes in model systems do not directly correlate with those in native tissues. This review includes a historical summary of the alternative terms used for adrenoceptors (adrenergic receptors, adrenoreceptors) and the author's views on the use of colours to illustrate different items, given his partial colour-blindness.
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Affiliation(s)
- John C McGrath
- School of Life Sciences, University of GlasgowGlasgow, UK
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Velásquez-Martínez MC, Vázquez-Torres R, Rojas LV, Sanabria P, Jiménez-Rivera CA. Alpha-1 adrenoreceptors modulate GABA release onto ventral tegmental area dopamine neurons. Neuropharmacology 2014; 88:110-21. [PMID: 25261018 DOI: 10.1016/j.neuropharm.2014.09.002] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2014] [Revised: 08/29/2014] [Accepted: 09/01/2014] [Indexed: 01/08/2023]
Abstract
The ventral tegmental area (VTA) plays an important role in reward and motivational processes involved in drug addiction. Previous studies have shown that alpha1-adrenoreceptors (α1-AR) are primarily found pre-synaptically at this area. We hypothesized that GABA released onto VTA-dopamine (DA) cells is modulated by pre-synaptic α1-AR. Recordings were obtained from putative VTA-DA cells of male Sprague-Dawley rats (28-50 days postnatal) using whole-cell voltage clamp technique. Phenylephrine (10 μM; α1-AR agonist) decreased the amplitude of GABAA receptor-mediated inhibitory postsynaptic currents (IPSCs) evoked by electrical stimulation of afferent fibers (n = 7; p < 0.05). Prazosin (1 μM, α1-AR antagonist), blocked this effect. Paired-pulse ratios were increased by phenylephrine application (n = 13; p < 0.05) indicating a presynaptic site of action. Spontaneous IPSCs frequency but not amplitude, were decreased in the presence of phenylephrine (n = 7; p < 0.05). However, frequency or amplitude of miniature IPSCs were not changed (n = 9; p > 0.05). Phenylephrine in low Ca(2+) (1 mM) medium decreased IPSC amplitude (n = 7; p < 0.05). Chelerythrine (a protein kinase C inhibitor) blocked the α1-AR action on IPSC amplitude (n = 6; p < 0.05). Phenylephrine failed to decrease IPSCs amplitude in the presence of paxilline, a BK channel blocker (n = 7; p < 0.05). Taken together, these results demonstrate that α1-ARs at presynaptic terminals can modulate GABA release onto VTA-DA cells. Drug-induced changes in α1-AR could contribute to the modifications occurring in the VTA during the addiction process.
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Affiliation(s)
- Maria C Velásquez-Martínez
- Department of Physiology, Medical Sciences Campus, University of Puerto Rico, San Juan, PR, USA; Laboratorio de Neurociencias y Comportamiento, Departamento de Ciencias Básicas, Facultad de Salud, Universidad Industrial de Santander, Bucaramanga, Colombia
| | - Rafael Vázquez-Torres
- Department of Physiology, Medical Sciences Campus, University of Puerto Rico, San Juan, PR, USA
| | - Legier V Rojas
- Department of Physiology, Universidad Central del Caribe, Bayamón, PR, USA
| | - Priscila Sanabria
- Department of Physiology, Universidad Central del Caribe, Bayamón, PR, USA
| | - Carlos A Jiménez-Rivera
- Department of Physiology, Medical Sciences Campus, University of Puerto Rico, San Juan, PR, USA.
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Bhat HF, Adams ME, Khanday FA. Syntrophin proteins as Santa Claus: role(s) in cell signal transduction. Cell Mol Life Sci 2013; 70:2533-54. [PMID: 23263165 PMCID: PMC11113789 DOI: 10.1007/s00018-012-1233-9] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2012] [Revised: 11/21/2012] [Accepted: 12/03/2012] [Indexed: 11/30/2022]
Abstract
Syntrophins are a family of cytoplasmic membrane-associated adaptor proteins, characterized by the presence of a unique domain organization comprised of a C-terminal syntrophin unique (SU) domain and an N-terminal pleckstrin homology (PH) domain that is split by insertion of a PDZ domain. Syntrophins have been recognized as an important component of many signaling events, and they seem to function more like the cell's own personal 'Santa Claus' that serves to 'gift' various signaling complexes with precise proteins that they 'wish for', and at the same time care enough for the spatial, temporal control of these signaling events, maintaining overall smooth functioning and general happiness of the cell. Syntrophins not only associate various ion channels and signaling proteins to the dystrophin-associated protein complex (DAPC), via a direct interaction with dystrophin protein but also serve as a link between the extracellular matrix and the intracellular downstream targets and cell cytoskeleton by interacting with F-actin. They play an important role in regulating the postsynaptic signal transduction, sarcolemmal localization of nNOS, EphA4 signaling at the neuromuscular junction, and G-protein mediated signaling. In our previous work, we reported a differential expression pattern of alpha-1-syntrophin (SNTA1) protein in esophageal and breast carcinomas. Implicated in several other pathologies, like cardiac dys-functioning, muscular dystrophies, diabetes, etc., these proteins provide a lot of scope for further studies. The present review focuses on the role of syntrophins in membrane targeting and regulation of cellular proteins, while highlighting their relevance in possible development and/or progression of pathologies including cancer which we have recently demonstrated.
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Affiliation(s)
- Hina F Bhat
- Department of Biotechnology, University of Kashmir, Srinagar, Jammu and Kashmir, India.
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Baker KD, Edwards TM, Rickard NS. The role of intracellular calcium stores in synaptic plasticity and memory consolidation. Neurosci Biobehav Rev 2013; 37:1211-39. [PMID: 23639769 DOI: 10.1016/j.neubiorev.2013.04.011] [Citation(s) in RCA: 74] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2013] [Revised: 04/18/2013] [Accepted: 04/22/2013] [Indexed: 12/20/2022]
Abstract
Memory processing requires tightly controlled signalling cascades, many of which are dependent upon intracellular calcium (Ca(2+)). Despite this, most work investigating calcium signalling in memory formation has focused on plasma membrane channels and extracellular sources of Ca(2+). The intracellular Ca(2+) release channels, ryanodine receptors (RyRs) and inositol (1,4,5)-trisphosphate receptors (IP3Rs) have a significant capacity to regulate intracellular Ca(2+) signalling. Evidence at both cellular and behavioural levels implicates both RyRs and IP3Rs in synaptic plasticity and memory formation. Pharmacobehavioural experiments using young chicks trained on a single-trial discrimination avoidance task have been particularly useful by demonstrating that RyRs and IP3Rs have distinct roles in memory formation. RyR-dependent Ca(2+) release appears to aid the consolidation of labile memory into a persistent long-term memory trace. In contrast, IP3Rs are required during long-term memory. This review discusses various functions for RyRs and IP3Rs in memory processing, including neuro- and glio-transmitter release, dendritic spine remodelling, facilitating vasodilation, and the regulation of gene transcription and dendritic excitability. Altered Ca(2+) release from intracellular stores also has significant implications for neurodegenerative conditions.
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Affiliation(s)
- Kathryn D Baker
- School of Psychology and Psychiatry, Monash University, Clayton 3800, Victoria, Australia.
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Velásquez-Martinez MC, Vázquez-Torres R, Jiménez-Rivera CA. Activation of alpha1-adrenoceptors enhances glutamate release onto ventral tegmental area dopamine cells. Neuroscience 2012; 216:18-30. [PMID: 22542873 DOI: 10.1016/j.neuroscience.2012.03.056] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2011] [Revised: 03/09/2012] [Accepted: 03/16/2012] [Indexed: 01/23/2023]
Abstract
The ventral tegmental area (VTA) plays an important role in reward and motivational processes that facilitate the development of drug addiction. Glutamatergic inputs into the VTA contribute to dopamine (DA) neuronal activation related to reward and response-initiating effects in drug abuse. Previous investigations indicate that alpha1-adrenoreceptors (α1-ARs) are primarily localized at presynaptic elements in the ventral midbrain. Studies from several brain regions have shown that presynaptic α1-AR activation enhances glutamate release. Therefore, we hypothesized that glutamate released onto VTA-DA neurons is modulated by pre-synaptic α1-AR. Recordings were obtained from putative VTA-DA cells of male Sprague-Dawley rats (28-50 days postnatal) using voltage clamp techniques. Phenylephrine (10 μM) and methoxamine (80μM), both α1-AR agonists, increased AMPA receptor-mediated excitatory postsynaptic currents' (EPSCs) amplitude evoked by electrical stimulation of afferent fibers (p<0.05). This effect was blocked by the α1-AR antagonist prazosin (1 μM). Phenylephrine decreased the paired-pulse ratio (PPR) and increased spontaneous EPSCs' frequencies but not their amplitudes suggesting a presynaptic locus of action. No changes in miniature EPSCs (0.5μM, tetrodotoxin [TTX]) were observed after phenylephrine's application which suggests that α1-AR effect was action potential dependent. Normal extra- and intracellular Ca(2+) concentration seems necessary for the α1-AR effect since phenylephrine in low Ca(2+) artificial cerebrospinal fluid (ACSF) and depletion of intracellular Ca(2+) stores with thapsigargin (10 μM) failed to increase the AMPA EPSCs' amplitude. Chelerythrine (1μM, protein kinase C (PKC) inhibitor) but not Rp-cAMPS (11 μM, PKA inhibitor) blocked the α1-AR activation effect on AMPA EPSCs, indicating that a PKC intracellular pathway is required. These results demonstrated that presynaptic α1-AR activation modulates glutamatergic inputs that affect VTA-DA neuronal excitability. α1-AR action might be heterosynaptically localized at glutamatergic fibers terminating onto VTA-DA neurons. It is suggested that drug-induced changes in α1-AR could be part of the neuroadaptations occurring in the mesocorticolimbic circuitry during the addiction process.
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Affiliation(s)
- M C Velásquez-Martinez
- Department of Physiology, University of Puerto Rico, Medical Sciences Campus, San Juan, Puerto Rico, USA
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11
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García-Sáinz JA, Romero-Ávila MT, Alcántara-Hernández R. Mechanisms involved in α1B-adrenoceptor desensitization. IUBMB Life 2011; 63:811-5. [PMID: 21815242 DOI: 10.1002/iub.519] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2011] [Accepted: 05/22/2011] [Indexed: 12/12/2022]
Abstract
α(1B)-Adrenergic receptors mediate many of the actions of the natural catecholamines, adrenaline and noradrenaline. They belong to the seven transmembrane domains G protein-coupled receptor superfamily and exert their actions mainly through activation of Gq proteins and phosphoinositide turnover/calcium signaling. Many hormones and neurotransmitters are capable of inducing α(1B)-adrenergic receptor phosphorylation and desensitization; among them: adrenaline and noradrenaline, phorbol esters, endothelin-I, bradykinin, lysophosphatidic acid, insulin, EGF, PDGF, IGF-I, TGF-β, and estrogens. Key protein kinases for these effects are G protein coupled receptor kinases and protein kinase C. The lipid/protein kinase, phosphoinositide-3 kinase also appears to play a key role, acting upstream of protein kinase C. In addition to the agents employed for cells stimulation, we observed that paracrine/autocrine mediators also participate; these processes include EGF transactivation and sphingosine-1-phosphate production and action. The complex regulation of these receptors unlocks opportunities for therapeutic intervention.
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Affiliation(s)
- J Adolfo García-Sáinz
- Departamento de Biología Celular y Desarrollo, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México. Ap. Postal 70-248, México, Distrito Federal.
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12
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Functional characterization of heterotrimeric G-proteins in rat diaphragm muscle. Respir Physiol Neurobiol 2010; 175:212-9. [PMID: 21084061 DOI: 10.1016/j.resp.2010.11.005] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2010] [Revised: 10/06/2010] [Accepted: 11/09/2010] [Indexed: 01/05/2023]
Abstract
Seven-transmembrane receptors mediate diverse skeletal muscle responses for a wide variety of stimuli, via activation of heterotrimeric G-proteins. Herein we evaluate the expression and activation of rat diaphragm or cultured skeletal muscle G-proteins using [(35)S]GTPγS. Total membrane Gα subunit content was 4-7 times higher in rat primary cultured myotubes and L6 cell line than in diaphragm (32.6±1.2fmol/mg protein) and 7-27% of them were in the active conformational state. Immunoprecipitation assay showed equal expression of diaphragm Gαs, Gαq and Gαi/o. Addition of GDP allowed the measurement of G-protein activation by different GPCR, including adrenoceptor, adenosine, melatonin and muscarinic receptors. Diaphragm denervation resulted in a marked increase in both total and active state G-protein levels. Together, the results show that [(35)S]GTPγS binding assay is a sensitive and valuable method to evaluate GPCR activity in skeletal muscle cells, which is of particular interest for pharmacological analysis of drugs with potential use in the management of respiratory muscle failure.
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Song Z, Gomes DA, Stevens W, Sladek CD. Multiple alpha1-adrenergic receptor subtypes support synergistic stimulation of vasopressin and oxytocin release by ATP and phenylephrine. Am J Physiol Regul Integr Comp Physiol 2010; 299:R1529-37. [PMID: 20881098 DOI: 10.1152/ajpregu.00532.2010] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Simultaneous exposure of explants of the hypothalamo-neurohypophyseal system (HNS) to ATP and the α(1)-adrenergic receptor (α(1)-R) agonist, phenylephrine (ATP+PE) induces a synergistic stimulation of vasopressin and oxytocin (VP/OT) release that is sustained for hours. The current studies confirm that the synergism is dependent upon activation of α(1)-R by demonstrating that an α(1)-R antagonist prevents the response. The role of the α(1)A, B, and D-adrenergic receptor subtypes in the synergistic effect of ATP+PE on intracellular calcium ([Ca(2+)](i)) in supraoptic nucleus (SON) neurons and VP/OT release from neural lobe was evaluated. The increase in [Ca(2+)](i) induced by PE in SON predominantly reflects release from intracellular stores and is mediated by activation of the α(1)A adrenergic receptor subtype. The α(1)A subtype is also required for the sustained elevation in [Ca(2+)](i) induced by ATP+PE. In contrast, although synergistic stimulation of VP/OT release was eliminated by removal of PE and was blunted by benoxathian, an α(1)-R antagonist that is not subtype selective, no single α(1)-R subtype selective antagonist prevented sustained stimulation of VP/OT release by ATP+PE. Thus, sustained activation of α(1)-R is essential for the synergistic VP and OT response to ATP+PE, but multiple α(1)-R subtypes can support the response. Redundancy amongst the α(1)-R subunits in supporting this response is consistent with the predicted importance of the response for sustaining the elevated VP release required to prevent cardiovascular collapse during hemorrhage and sepsis.
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Affiliation(s)
- Zhilin Song
- Dept. of Physiology and Biophysics, Univ. of Colorado, School of Medicine, 12800 E. 19 Ave, Aurora, CO 80045, USA
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Gassner M, Ruscheweyh R, Sandkühler J. Direct excitation of spinal GABAergic interneurons by noradrenaline. Pain 2009; 145:204-10. [DOI: 10.1016/j.pain.2009.06.021] [Citation(s) in RCA: 65] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2009] [Revised: 06/02/2009] [Accepted: 06/16/2009] [Indexed: 11/26/2022]
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15
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Buccioni M, Kandhavelu M, Angeli P, Cristalli G, Dal Ben D, Giardinà D, Lambertucci C, Lammi C, Volpini R, Marucci G. Identification of α1-adrenoceptor subtypes involved in contraction of young CD rat epididymal vas deferens. Eur J Pharmacol 2009; 602:388-94. [DOI: 10.1016/j.ejphar.2008.10.067] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2008] [Revised: 10/14/2008] [Accepted: 10/31/2008] [Indexed: 11/29/2022]
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16
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Coactivation of M(1) muscarinic and alpha1 adrenergic receptors stimulates extracellular signal-regulated protein kinase and induces long-term depression at CA3-CA1 synapses in rat hippocampus. J Neurosci 2008; 28:5350-8. [PMID: 18480291 DOI: 10.1523/jneurosci.5058-06.2008] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Intact cholinergic innervation from the medial septum and noradrenergic innervation from the locus ceruleus are required for hippocampal-dependent learning and memory. However, much remains unclear about the precise roles of acetylcholine (ACh) and norepinephrine (NE) in hippocampal function, particularly in terms of how interactions between these two transmitter systems might play an important role in synaptic plasticity. Previously, we reported that activation of either muscarinic M(1) or adrenergic alpha1 receptors induces activity- and NMDA receptor-dependent long-term depression (LTD) at CA3-CA1 synapses in acute hippocampal slices, referred to as muscarinic LTD (mLTD) and norepinephrine LTD (NE LTD), respectively. In this study, we tested the hypothesis that mLTD and NE LTD are independent forms of LTD, yet require activation of a common Galphaq-coupled signaling pathway for their induction, and investigated the net effect of coactivation of M(1) and alpha1 receptors on the magnitude of LTD induced. We find that neither mLTD nor NE LTD requires phospholipase C activation, but both plasticities are prevented by inhibiting the Src kinase family and extracellular signal-regulated protein kinase (ERK) activation. Interestingly, LTD can be induced when M(1) and alpha1 agonists are coapplied at concentrations too low to induce LTD when applied separately, via a summed increase in ERK activation. Thus, because ACh and NE levels in vivo covary, especially during periods of memory encoding and consolidation, cooperative signaling through M(1) and alpha1 receptors could function to induce long-term changes in synaptic function important for cognition.
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Role of alpha1-adrenoceptor subtypes in the effects of methylenedioxy methamphetamine (MDMA) on body temperature in the mouse. Br J Pharmacol 2007; 153:591-7. [PMID: 18037913 DOI: 10.1038/sj.bjp.0707590] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
BACKGROUND AND PURPOSE We have investigated the ability of alpha(1)-adrenoceptor antagonists to affect the hyperthermia produced by methylenedioxy methamphetamine (MDMA) in conscious mice. EXPERIMENTAL APPROACH Mice were implanted with temperature probes under ether anaesthesia and allowed 2 weeks recovery. MDMA (20 mg kg(-1)) was administered subcutaneously 30 min after vehicle or test antagonist or combination of antagonists and effects on body temperature monitored. KEY RESULTS Following vehicle, MDMA produced a hyperthermia, reaching a maximum increase of 1.8 degrees C at 140 min. Prazosin (0.1 mg kg(-1)) revealed an early significant hypothermia to MDMA of -1.94 degrees C. The alpha(1A)-adrenoceptor antagonist RS 100329 (0.1 mg kg(-1)), or the alpha(1D)-adrenoceptor antagonist BMY 7378 (0.5 mg kg(-1)) given alone, did not reveal a hypothermia to MDMA, but the combination of the two antagonists revealed a significant hypothermia to MDMA. The putative alpha(1B)-adrenoceptor antagonist cyclazosin (1 mg kg(-1)) also revealed a significant hypothermia to MDMA, but actions of cyclazosin at the other alpha(1)-adrenoceptor subtypes cannot be excluded. CONCLUSIONS AND IMPLICATIONS More than one subtype of alpha(1)-adrenoceptor is involved in a component of the hyperthermic response to MDMA in mouse, probably both alpha(1A)- and alpha(1D)-adrenoceptors, and removal of this alpha(1)-adrenoceptor-mediated component reveals an initial hypothermia.
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18
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Lewis SJ, Hoque A, Sandock K, Robertson TP, Bates JN, Kooy NW. Differential effects of peroxynitrite on the function of arginine vasopressin V1a receptors and alpha1-adrenoceptors in vivo. Vascul Pharmacol 2007; 46:24-34. [PMID: 16861049 DOI: 10.1016/j.vph.2006.06.004] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2006] [Revised: 06/08/2006] [Accepted: 06/09/2006] [Indexed: 11/24/2022]
Abstract
OBJECTIVE The aim of this study was to provide evidence that peroxynitrite may differentially affect the function of arginine vasopressin (AVP) V(1a) receptors and alpha(1)-adrenoceptors in vascular smooth muscle of the rat METHODS The vasoconstrictor responses elicited by AVP, or the alpha(1)-adrenoceptor agonist, phenylephrine, were determined in anesthetized rats before and after injections of (i) peroxynitrite, the thiol chelator, para-hydroxymercurobenzoic acid (PHMBA), or the electron acceptor, nitroblue tetrazolium (NBT). The ability of the reducing agent, glutathione, to reverse the loss of response to phenylephrine and AVP in peroxynitrite-treated rats was also examined. RESULTS The AVP-induced responses were suppressed 10-20 min but not 60-70 min after the administration of peroxynitrite. Glutathione reversed the above loss of response to AVP at 10-20 min. The responses elicited by phenylephrine were suppressed 10-20 min and 60-70 min after administration of peroxynitrite. Glutathione did not reverse the above losses of response to phenylephrine. In addition, the vasoconstrictor actions of AVP and phenylephrine were markedly suppressed after administration of PHMBA or nitroblue tetrazolium. CONCLUSIONS The above findings provide evidence that exogenously administered peroxynitrite may differentially affect the function of AVP V(1a) receptors and alpha(1)-adrenoceptors in vascular smooth muscle of the rat. The possibility that peroxynitrite impairs AVP V(1a) receptor function by transient oxidation events whereas peroxynitrite impairs alpha(1)-adrenoceptor function by transient oxidation and permanent nitration events will be discussed.
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MESH Headings
- Animals
- Aorta, Abdominal/drug effects
- Arginine Vasopressin/pharmacology
- Blood Pressure/drug effects
- Glutathione/pharmacology
- Hydroxymercuribenzoates/pharmacology
- Male
- Mesenteric Artery, Superior/drug effects
- Muscle, Smooth, Vascular/drug effects
- Muscle, Smooth, Vascular/metabolism
- Nitrates/metabolism
- Nitroblue Tetrazolium/pharmacology
- Oxidation-Reduction/drug effects
- Peroxynitrous Acid/metabolism
- Peroxynitrous Acid/pharmacology
- Phenylephrine/pharmacology
- Rats
- Rats, Sprague-Dawley
- Receptors, Adrenergic, alpha-1/drug effects
- Receptors, Adrenergic, alpha-1/metabolism
- Receptors, Vasopressin/drug effects
- Receptors, Vasopressin/metabolism
- Renal Artery/drug effects
- Time Factors
- Vascular Resistance/drug effects
- Vasoconstriction/drug effects
- Vasoconstrictor Agents/pharmacology
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Affiliation(s)
- Stephen J Lewis
- Department of Physiology and Pharmacology, College of Veterinary Medicine, University of Georgia, Athens, GA 30602-7389, USA.
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19
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Koshimizu TA, Tanoue A, Tsujimoto G. Clinical implications from studies of alpha1 adrenergic receptor knockout mice. Biochem Pharmacol 2006; 73:1107-12. [PMID: 17141736 DOI: 10.1016/j.bcp.2006.11.002] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2006] [Revised: 10/27/2006] [Accepted: 11/02/2006] [Indexed: 11/18/2022]
Abstract
alpha1-Adrenergic receptors (alpha1-ARs) modulate a large number of physiological functions in cardiovascular and noncardiovascular tissues. Because individual members of the alpha1-AR family (alpha1A-, alpha1B-, and alpha1D-ARs) have overlapping expression profiles in most tissues, elucidation of the precise physiological roles of individual alpha1-AR subtypes remains a challenging task. To alleviate this constraint, a gene targeting approach has been employed to generate mutant mice lacking one or two alpha1-AR genes. Recent studies on these mutant mouse strains are discussed in this article, with an emphasis on the role of alpha1-AR in the central nervous system and lower urinary tracts. These are two major tissues of particular interest for the development of new therapeutic strategies targeted to the alpha1-ARs. By combining gene targeting techniques with pharmacological tools, the specific roles of alpha1-AR subtypes could be delineated.
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Affiliation(s)
- Taka-aki Koshimizu
- Department of Genomic Drug Discovery Science, Graduate School of Pharmaceutical Sciences, Kyoto University, Yoshida Shimoadachi-cho, Sakyo-ku, Kyoto 606-8501, Japan
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20
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Chen L, Hodges RR, Funaki C, Zoukhri D, Gaivin RJ, Perez DM, Dartt DA. Effects of alpha1D-adrenergic receptors on shedding of biologically active EGF in freshly isolated lacrimal gland epithelial cells. Am J Physiol Cell Physiol 2006; 291:C946-56. [PMID: 16760267 PMCID: PMC2151204 DOI: 10.1152/ajpcell.00014.2006] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Transactivation of EGF receptors by G protein-coupled receptors is a well-known phenomenon. This process involves the ectodomain shedding of growth factors in the EGF family by matrix metalloproteinases. However, many of these studies employ transformed and/or cultured cells that overexpress labeled growth factors. In addition, few studies have shown that EGF itself is the growth factor that is shed and is responsible for transactivation of the EGF receptor. In this study, we show that freshly isolated, nontransformed lacrimal gland acini express two of the three known alpha(1)-adrenergic receptors (ARs), namely, alpha(1B)- and alpha(1D)-ARs. Alpha(1D)-ARs mediate phenylephrine (an alpha(1)-adrenergic agonist)-induced protein secretion and activation of p42/p44 MAPK, because the alpha(1D)-AR inhibitor BMY-7378, but not the alpha(1A)-AR inhibitor 5-methylurapidil, inhibits these processes. Activation of p42/p44 MAPK occurs through transactivation of the EGF receptor, which is inhibited by the matrix metalloproteinase ADAM17 inhibitor TAPI-1. In addition, phenylephrine caused the shedding of EGF from freshly isolated acini into the buffer. Incubation of freshly isolated cells with conditioned buffer from cells treated with phenylephrine resulted in activation of the EGF receptor and p42/p44 MAPK. The EGF receptor inhibitor AG1478 and an EGF-neutralizing antibody blocked this activation of p42/p44 MAPK. We conclude that in freshly isolated lacrimal gland acini, alpha(1)-adrenergic agonists activate the alpha(1D)-AR to stimulate protein secretion and the ectodomain shedding of EGF to transactivate the EGF receptor, potentially via ADAM17, which activates p42/p44 MAPK to negatively modulate protein secretion.
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Affiliation(s)
- LiLi Chen
- Schepens Eye Research Institute and Department of Ophthalmology, Harvard Medical School, Boston, MA
| | - Robin R. Hodges
- Schepens Eye Research Institute and Department of Ophthalmology, Harvard Medical School, Boston, MA
- * Address correspondence to: Robin R. Hodges, Schepens Eye Research Institute, 20 Staniford Street, Boston, MA 02114. Tel: 617-912-7424; FAX: 617-912-0104;
| | - Chika Funaki
- Schepens Eye Research Institute and Department of Ophthalmology, Harvard Medical School, Boston, MA
| | - Driss Zoukhri
- Tufts University School of Dental Medicine, Boston, MA
| | | | - Dianne M. Perez
- Lerner Research Institute, The Cleveland Clinic, Cleveland, OH
| | - Darlene A. Dartt
- Schepens Eye Research Institute and Department of Ophthalmology, Harvard Medical School, Boston, MA
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21
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Scarparo AC, Visconti MA, Castrucci AMDL. Signalling pathways evoked by alpha1-adrenoceptors in human melanoma cells. Cell Biochem Funct 2006; 24:119-29. [PMID: 16444773 DOI: 10.1002/cbf.1309] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The biological effects of catecholamines in mammalian pigment cells are poorly understood, but in poikilothermic vertebrates they regulate the translocation of pigment granules. We have previously demonstrated in SK-Mel 23-human melanoma cells the presence of low affinity alpha(1)-adrenoceptors, which mediate a decrease in cell proliferation and increase in tyrosinase activity, with no change of tyrosinase expression. In this report, we investigated the signalling pathways involved in these responses. Calcium mobilization in response to phenylephrine (PHE), an alpha(1)-adrenergic agonist, was investigated by confocal microscopy, and no change of fluorescence during the treatment was observed, suggesting that calcium is not involved in the signalling pathway activated by alpha(1)-adrenoceptors in SK-Mel 23 cells. cAMP levels, determined by enzyme-immunoassay, were significantly increased by PHE (10(-5)-10(-4)M), that could be blocked by the alpha(1)-adrenergic antagonist benoxathian (10(-5)-10(-4)M). Several biological assays were then performed with PHE, for 72 h, in the absence or presence of various signalling pathway inhibitors, in an attempt to determine the intracellular messengers involved in the responses of proliferation and tyrosinase activity. Our results suggest the participation of p38 and ERKs in PHE-induced decrease of proliferation, and possibly also of cAMP and protein kinase A. Regarding PHE-induced increase of tyrosinase activity, it is suggested that the following signalling components are involved: cAMP/PKA, PKC, PI3K, p38 and ERKs.
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Affiliation(s)
- Ana Cristina Scarparo
- Departamento de Fisiologia, Instituto de Biociências, Universidade de São Paulo, Brasil
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22
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Chen Z, Hague C, Hall RA, Minneman KP. Syntrophins regulate alpha1D-adrenergic receptors through a PDZ domain-mediated interaction. J Biol Chem 2006; 281:12414-20. [PMID: 16533813 DOI: 10.1074/jbc.m508651200] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
To find novel cytoplasmic binding partners of the alpha1D-adrenergic receptor (AR), a yeast two-hybrid screen using the alpha1D-AR C terminus as bait was performed on a human brain cDNA library. Alpha-syntrophin, a protein containing one PDZ domain and two pleckstrin homology domains, was isolated in this screen as an alpha1D-AR-interacting protein. Alpha-syntrophin specifically recognized the C terminus of alpha1D- but not alpha1A- or alpha1B-ARs. In blot overlay assays, the PDZ domains of syntrophin isoforms alpha, beta1, and beta2 but not gamma1 or gamma2 showed strong selective interactions with the alpha1D-AR C-tail fusion protein. In transfected human embryonic kidney 293 cells, full-length alpha1D- but not alpha1A- or alpha1B-ARs co-immunoprecipitated with syntrophins, and the importance of the receptor C terminus for the alpha1D-AR/syntrophin interaction was confirmed using chimeric receptors. Mutation of the PDZ-interacting motif at the alpha1D-AR C terminus markedly decreased inositol phosphate formation stimulated by norepinephrine but not carbachol in transfected HEK293 cells. This mutation also dramatically decreased alpha1D-AR binding and protein expression. In addition, stable overexpression of alpha-syntrophin significantly increased alpha1D-AR protein expression and binding but did not affect those with a mutated PDZ-interacting motif, suggesting that syntrophin plays an important role in maintaining receptor stability by directly interacting with the receptor PDZ-interacting motif. This direct interaction may provide new information about the regulation of alpha1D-AR signaling and the role of syntrophins in modulating G protein-coupled receptor function.
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Affiliation(s)
- Zhongjian Chen
- Department of Pharmacology, Emory University School of Medicine, Atlanta, Georgia 30322, USA
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23
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Abstract
Alpha1-Adrenergic receptors (AR) play an important role in the regulation of physiological responses mediated by norepinephrine and epinephrine, particularly in the cardiovascular system. The three cloned alpha1-AR subtypes (alpha1A, alpha1B, and alpha1D) are G protein-coupled receptors that signal through the Gq/11 signaling pathway, each showing distinct pharmacological properties and tissue distributions. However, due to the lack of highly subtype-selective drugs, the functional roles of individual subtypes are still not clear. Development of new subtype-specific drugs will greatly facilitate the identification of the functions of each subtype. Conopeptide rho-TIA has been found to be a new alpha1B-AR selective antagonist with different modes of inhibition at alpha1-AR subtypes. In addition, recent studies using genetically engineered mice have shed some light on alpha1-AR functions in vivo, especially in the cardiovascular system and brain. Several proteins have been shown to interact directly with particular alpha1-AR, and may be important in regulating receptor function. Receptor heterodimerization has been shown to be important for cell surface expression, signaling and internalization. These new observations are likely to help elucidate the functional roles of individual alpha1-AR subtypes.
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Affiliation(s)
- Zhong-jian Chen
- Department of Pharmacology, School of Medicine, Emory University, Atlanta, GA 30322, USA
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24
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Petrovska R, Kapa I, Klovins J, Schiöth HB, Uhlén S. Addition of a signal peptide sequence to the alpha1D-adrenoceptor gene increases the density of receptors, as determined by [3H]-prazosin binding in the membranes. Br J Pharmacol 2005; 144:651-9. [PMID: 15678090 PMCID: PMC1576044 DOI: 10.1038/sj.bjp.0706087] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
1. Both in mammalian tissues and in transfected cells, only low levels of alpha1D-adrenoceptors are detected in radioligand binding studies. It has been implicated that the comparatively long N-terminal tail of the alpha1D-adrenoceptor is responsible for the inefficient surface expression of the receptor. 2. In the present study, we created gene constructs for six N-terminally truncated variants of the human alpha1D-adrenoceptor. These constructs were used to transfect Neuro2A cells. We show that the density of alpha1D-adrenoceptors, observed by [3H]-prazosin binding, gradually increased with longer truncations of the N-terminus. This seems to indicate that the long N-terminal tail nonspecifically interferes with receptor translocation to the plasma membrane. 3. The addition of a 16 amino acids long signal peptide to the N-terminus of the wild-type alpha1D-adrenoceptor increased the density of receptor binding sites 10-fold in Neuro2A and COS-7 cells. This indicates that, after the addition of a signal peptide, the long N-terminal tail of the alpha1D-adrenoceptor does not interfere with proper translocation of the receptor to the plasma membrane. This, in turn, indicates that the N-terminal tail of the wild-type alpha1D-adrenoceptor, merely by its long length, hinders the first transmembrane helix of the receptor from being a signal anchor. 4. Neither the wild-type alpha1D-adrenoceptor (for which the expression level of [3H]-prazosin binding sites is low) nor the truncated alpha1D-adrenoceptor variant (for which the expression level of [3H]-prazosin binding sites is high) showed any constitutive activity in stimulating inositol phosphate accumulation. This indicates that the low expression level of [3H]-prazosin binding sites, after transfection with the wild-type alpha1D-adrenoceptor, is not caused by constitutive activity of the receptor and subsequent receptor downregulation.
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Affiliation(s)
- Ramona Petrovska
- Department of Pharmaceutical Biosciences, Unit of Pharmacology, Uppsala University, Box 591, BMC, Uppsala SE-751 24, Sweden
| | - Ivo Kapa
- Department of Neuroscience, Division of Pharmacology, Uppsala University, Uppsala, Sweden
- Biomedical Research and Study Centre, University of Latvia, Riga LV1069, Latvia
| | - Janis Klovins
- Department of Neuroscience, Division of Pharmacology, Uppsala University, Uppsala, Sweden
- Biomedical Research and Study Centre, University of Latvia, Riga LV1069, Latvia
| | - Helgi B Schiöth
- Department of Neuroscience, Division of Pharmacology, Uppsala University, Uppsala, Sweden
| | - Staffan Uhlén
- Department of Pharmaceutical Biosciences, Unit of Pharmacology, Uppsala University, Box 591, BMC, Uppsala SE-751 24, Sweden
- Author for correspondence:
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25
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García-Sáinz JA, Villalobos-Molina R. The elusive alpha(1D)-adrenoceptor: molecular and cellular characteristics and integrative roles. Eur J Pharmacol 2005; 500:113-20. [PMID: 15464025 DOI: 10.1016/j.ejphar.2004.07.016] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/01/2004] [Indexed: 11/16/2022]
Abstract
alpha(1)-Adrenoceptors seem to play key roles in cardiovascular, genitourinary, and central nervous system functions. This review will be focused on alpha(1D)-adrenoceptors. These receptors have intrinsic activity, and many of the more commonly used antagonists are in reality inverse agonists. alpha(1D)-Adrenoceptors are phosphorylated in the basal state, and the natural agonists, adrenaline and noradrenaline, increase their phosphorylation; similar effects are induced by direct activation of protein kinase C and through activation of nonadrenergic receptors. Interestingly, a large proportion of alpha(1D)-adrenoceptors are located in intracellular vesicles. Such intracellular location can be changed to surface expression through the use of inverse agonists and coexpression of alpha(1B)-adrenoceptors, which seem to act as pharmacological chaperons for proper plasma membrane insertion. The alpha(1D)-adrenoceptor amino terminus seems to contain a signal that keeps the receptor intracellularly, but interaction with other proteins may also contribute. The precise relationship between the intrinsic activity, phosphorylation, and intracellular location is currently unknown. alpha(1D)-Adrenoceptor activation induces contraction in a variety of vessels, and a role in the control of blood pressure has been suggested. Studies using young prehypertensive and adult spontaneously hypertensive rats as well as knockout mice suggest that vascular alpha(1D)-adrenoceptors are involved in the genesis/maintenance of hypertension.
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Affiliation(s)
- J Adolfo García-Sáinz
- Departamento de Biología Celular, Universidad Nacional Autónoma de México, Apartado Postal 70-248, 04510, México D. F., México.
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26
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Hague C, Bernstein LS, Ramineni S, Chen Z, Minneman KP, Hepler JR. Selective inhibition of alpha1A-adrenergic receptor signaling by RGS2 association with the receptor third intracellular loop. J Biol Chem 2005; 280:27289-95. [PMID: 15917235 DOI: 10.1074/jbc.m502365200] [Citation(s) in RCA: 85] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Regulators of G-protein signaling (RGS) proteins act directly on Galpha subunits to increase the rate of GTP hydrolysis and to terminate signaling. However, the mechanisms involved in determining their specificities of action in cells remain unclear. Recent evidence has raised the possibility that RGS proteins may interact directly with G-protein-coupled receptors to modulate their activity. By using biochemical, fluorescent imaging, and functional approaches, we found that RGS2 binds directly and selectively to the third intracellular loop of the alpha1A-adrenergic receptor (AR) in vitro, and is recruited by the unstimulated alpha1A-AR to the plasma membrane in cells to inhibit receptor and Gq/11 signaling. This interaction was specific, because RGS2 did not interact with the highly homologous alpha1B- or alpha1D-ARs, and the closely related RGS16 did not interact with any alpha1-ARs. The N terminus of RGS2 was required for association with alpha1A-ARs and inhibition of signaling, and amino acids Lys219, Ser220, and Arg238 within the alpha1A-AR i3 loop were found to be essential for this interaction. These findings demonstrate that certain RGS proteins can directly interact with preferred G-protein-coupled receptors to modulate their signaling with a high degree of specificity.
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Affiliation(s)
- Chris Hague
- Department of Pharmacology, Emory University School of Medicine, Atlanta, Georgia 30322, USA.
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27
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Milligan G, Pediani J, Fidock M, López-Giménez JF. Dimerization of alpha1-adrenoceptors. Biochem Soc Trans 2005; 32:847-50. [PMID: 15494031 DOI: 10.1042/bst0320847] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Three distinct genes encode alpha(1)-adrenoceptors. Although homodimers of each subtype have been reported, certain but not all combinations of heterodimers of the alpha(1)-adrenoceptors appear to form. Key studies in this field are reviewed and the approaches that have been applied to monitoring the selectivity and the basis of alpha(1)-adrenoceptor dimerization are discussed.
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Affiliation(s)
- G Milligan
- Molecular Pharmacology Group, Division of Biochemistry and Molecular Biology, Institute of Biomedical and Life Sciences, University of Glasgow, Glasgow G12 8QQ, Scotland, UK.
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28
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Guthrie CR, Murray AT, Franklin AA, Hamblin MW. Differential agonist-mediated internalization of the human 5-hydroxytryptamine 7 receptor isoforms. J Pharmacol Exp Ther 2005; 313:1003-10. [PMID: 15716386 DOI: 10.1124/jpet.104.081919] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
The human 5-hydroxytryptamine 7 (5-HT(7)) serotonin receptor is a class A G-protein coupled receptor that has three isoforms, 5-HT(7(a)), 5-HT(7(b)), and 5-HT(7(d)), which are produced by alternative splicing. The 5-HT(7) receptors are expressed in discrete areas of the brain and in both vascular and gastrointestinal smooth muscle. Central nervous system 5-HT(7) receptors may play a role in mood and sleep disorders. 5-HT(7) receptors show high affinity for a number of antidepressants and typical and atypical antipsychotics. We report here that the human 5-HT(7(d)) isoform expressed in human embryonic kidney (HEK) 293 cells exhibits a pattern of receptor trafficking in response to agonist that differ from 5-HT(7(a)) or 5-HT(7(b)) isoforms. We employed a modification of a live cell-labeling technique to demonstrate that surface 5-HT(7(d)) receptors are constitutively internalized in the absence of agonist. This is in contrast to 5-HT(7(a)) and 5-HT(7(b)) isoforms, which do not show this profound agonist-independent internalization. Indeed, the 5-HT(7(d)) isoform displays this internalization in the presence of a 5-HT(7) -specific antagonist. In addition, the human 5-HT(7) isoform shows a diminished efficacy in stimulation of cAMP-responsive reporter gene activity in transfected cells compared with 5-HT(7(a)) or 5-HT(7(b)) receptors expressed at comparable levels. Thus, the carboxy-terminal tail of 5-HT(7(d)), which is the longest among known human 5-HT(7) isoforms, may contain a motif that interacts with cellular transport mechanisms that is distinct from 5-HT(7(a)) and 5-HT(7(b)).
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Affiliation(s)
- Chris R Guthrie
- Veterans Affairs Puget Sound Health Care System, Seattle, WA 98108, USA.
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29
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Chen Z, Rogge G, Hague C, Alewood D, Colless B, Lewis RJ, Minneman KP. Subtype-selective Noncompetitive or Competitive Inhibition of Human α1-Adrenergic Receptors by ρ-TIA. J Biol Chem 2004; 279:35326-33. [PMID: 15194691 DOI: 10.1074/jbc.m403703200] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The 19-amino acid conopeptide (rho-TIA) was shown previously to antagonize noncompetitively alpha(1B)-adrenergic receptors (ARs). Because this is the first peptide ligand for these receptors, we compared its interactions with the three recombinant human alpha(1)-AR subtypes (alpha(1A), alpha(1B), and alpha(1D)). Radioligand binding assays showed that rho-TIA was 10-fold selective for human alpha(1B)-over alpha(1A)- and alpha(1D)-ARs. As observed with hamster alpha(1B)-ARs, rho-TIA decreased the number of binding sites (B(max)) for human alpha(1B)-ARs without changing affinity (K(D)), and this inhibition was unaffected by the length of incubation but was reversed by washing. However, rho-TIA had opposite effects at human alpha(1A)-ARs and alpha(1D)-ARs, decreasing K(D) without changing B(max), suggesting it acts competitively at these subtypes. rho-TIA reduced maximal NE-stimulated [(3)H]inositol phosphate formation in HEK293 cells expressing human alpha(1B)-ARs but competitively inhibited responses in cells expressing alpha(1A)- or alpha(1D)-ARs. Truncation mutants showed that the amino-terminal domains of alpha(1B)- or alpha(1D)-ARs are not involved in interaction with rho-TIA. Alanine-scanning mutagenesis of rho-TIA showed F18A had an increased selectivity for alpha(1B)-ARs, and F18N also increased subtype selectivity. I8A had a slightly reduced potency at alpha(1B)-ARs and was found to be a competitive, rather than noncompetitive, inhibitor in both radioligand and functional assays. Thus rho-TIA noncompetitively inhibits alpha(1B)-ARs but competitively inhibits the other two subtypes, and this selectivity can be increased by mutation. These differential interactions do not involve the receptor amino termini and are not because of the charged nature of the peptide, and isoleucine 8 is critical for its noncompetitive inhibition at alpha(1B)-ARs.
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Affiliation(s)
- Zhongjian Chen
- Department of Pharmacology, Emory University School of Medicine, Atlanta, Georgia 30322, USA
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Hieble JP. Alpha1-adrenoceptor subtype substitution in knockout mice. Br J Pharmacol 2004; 142:919. [PMID: 15210582 PMCID: PMC1575117 DOI: 10.1038/sj.bjp.0705871] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Affiliation(s)
- J Paul Hieble
- Department of Urology Research, GlaxoSmithKline, King of Prussia, PA, USA.
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Hague C, Uberti MA, Chen Z, Hall RA, Minneman KP. Cell surface expression of alpha1D-adrenergic receptors is controlled by heterodimerization with alpha1B-adrenergic receptors. J Biol Chem 2004; 279:15541-9. [PMID: 14736874 DOI: 10.1074/jbc.m314014200] [Citation(s) in RCA: 135] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
alpha(1)-Adrenergic receptors (ARs) belong to the large Class I G protein-coupled receptor superfamily and comprise three subtypes (alpha(1A), alpha(1B), and alpha(1D)). Previous work with heterologously expressed C-terminal green fluorescent protein (GFP)-tagged alpha(1)-ARs showed that alpha(1A)- and alpha(1B)-ARs localize to the plasma membrane, whereas alpha(1D)-ARs accumulate intracellularly. We recently showed that alpha(1D)- and alpha(1B)-ARs form heterodimers, whereas alpha(1D)- and alpha(1A)-ARs do not. Here, we examined the role of heterodimerization in regulating alpha(1D)-AR localization using both confocal imaging of GFP- or CFP-tagged alpha(1)-ARs and a luminometer-based surface expression assay in HEK293 cells. Co-expression with alpha(1B)-ARs caused alpha(1D)-ARs to quantitatively translocate to the cell surface, but co-expression with alpha(1A)-ARs did not. Truncation of the alpha(1B)-AR extracellular N terminus or intracellular C terminus had no effect on surface expression of alpha(1D)-ARs, suggesting primary involvement of the hydrophobic core. Co-transfection with an uncoupled mutant alpha(1B)-AR (Delta12alpha(1B)) increased both alpha(1D)-AR surface expression and coupling to norepinephrine-stimulated Ca(2+) mobilization. Finally, GFP-tagged alpha(1D)-ARs were not detected on the cell surface when expressed in rat aortic smooth muscle cells that express no endogenous ARs, but were almost exclusively localized on the surface when expressed in DDT(1)MF-2 cells, which express endogenous alpha(1B)-ARs. These studies demonstrate that alpha(1B)/alpha(1D)-AR heterodimerization controls surface expression and functional coupling of alpha(1D)-ARs, the N- and C-terminal domains are not involved in this interaction, and that alpha(1B)-AR G protein coupling is not required. These observations may be relevant to many other Class I G protein-coupled receptors, where the functional consequences of heterodimerization are still poorly understood.
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Affiliation(s)
- Chris Hague
- Department of Pharmacology, Emory University, Atlanta, Georgia 30322, USA
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