1
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Fragola NR, Brems BM, Mukherjee M, Cui M, Booth RG. Conformationally Selective 2-Aminotetralin Ligands Targeting the alpha2A- and alpha2C-Adrenergic Receptors. ACS Chem Neurosci 2023; 14:1884-1895. [PMID: 37104867 PMCID: PMC10628895 DOI: 10.1021/acschemneuro.3c00148] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2023] [Accepted: 04/11/2023] [Indexed: 04/29/2023] Open
Abstract
Many important physiological processes are mediated by alpha2A- and alpha2C-adrenergic receptors (α2Rs), a subtype of class A G protein-coupled receptors (GPCRs). However, α2R signaling is poorly understood, and there are few approved medications targeting these receptors. Drug discovery aimed at α2Rs is complicated by the high degree of binding pocket homology between α2AR and α2CR, which confounds ligand-mediated selective activation or inactivation of signaling associated with a particular subtype. Meanwhile, α2R signaling is complex and it is reported that activating α2AR is beneficial in many clinical contexts, while activating α2CR signaling may be detrimental to these positive effects. Here, we report on a novel 5-substituted-2-aminotetralin (5-SAT) chemotype that, depending on substitution, has diverse pharmacological activities at α2Rs. Certain lead 5-SAT analogues act as partial agonists at α2ARs, while functioning as inverse agonists at α2CRs, a novel pharmacological profile. Leads demonstrate high potency (e.g., EC50 < 2 nM) at the α2AR and α2CRs regarding Gαi-mediated inhibition of adenylyl cyclase and production of cyclic adenosine monophosphate (cAMP). To help understand the molecular basis of 5-SAT α2R multifaceted functional activity, α2AR and α2CR molecular models were built from the crystal structures and 1 μs molecular dynamics (MD) simulations and molecular docking experiments were performed for a lead 5-SAT with α2AR agonist and α2CR inverse agonist activity, i.e., (2S)-5-(2'-fluorophenyl)-N,N-dimethyl-1,2,3,4-tetrahydronaphthalen-2-amine (FPT), in comparison to the FDA-approved (for opioid withdrawal symptoms) α2AR/α2CR agonist lofexidine. Results reveal several interactions between FPT and α2AR and α2CR amino acids that may impact the functional activity. The computational data in conjunction with experimental in vitro affinity and function results provide information to understand ligand stabilization of functionally distinct GPCR conformations regarding α2AR and α2CRs.
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Affiliation(s)
- Nicholas R. Fragola
- Center
for Drug Discovery, Department of Pharmaceutical Sciences, Department of Chemistry
& Chemical Biology, Northeastern University, 208, Mugar Life Sciences Building, 360 Huntington Avenue, Boston, Massachusetts 02115, United States
| | - Brittany M. Brems
- Center
for Drug Discovery, Department of Pharmaceutical Sciences, Department of Chemistry
& Chemical Biology, Northeastern University, 208, Mugar Life Sciences Building, 360 Huntington Avenue, Boston, Massachusetts 02115, United States
| | - Munmun Mukherjee
- Center
for Drug Discovery, Department of Pharmaceutical Sciences, Department of Chemistry
& Chemical Biology, Northeastern University, 208, Mugar Life Sciences Building, 360 Huntington Avenue, Boston, Massachusetts 02115, United States
| | - Meng Cui
- Center
for Drug Discovery, Department of Pharmaceutical Sciences, Department of Chemistry
& Chemical Biology, Northeastern University, 208, Mugar Life Sciences Building, 360 Huntington Avenue, Boston, Massachusetts 02115, United States
| | - Raymond G. Booth
- Center
for Drug Discovery, Department of Pharmaceutical Sciences, Department of Chemistry
& Chemical Biology, Northeastern University, 208, Mugar Life Sciences Building, 360 Huntington Avenue, Boston, Massachusetts 02115, United States
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2
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Gaidin SG, Turovskaya MV, Mal’tseva VN, Zinchenko VP, Blinova EV, Turovsky EA. A Complex Neuroprotective Effect of Alpha-2-Adrenergic Receptor Agonists in a Model of Cerebral Ischemia–Reoxygenation In Vitro. BIOCHEMISTRY MOSCOW SUPPLEMENT SERIES A-MEMBRANE AND CELL BIOLOGY 2020. [DOI: 10.1134/s1990747819040068] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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3
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Chikuda M, Sato K. Effects of dexmedetomidine on porcine pulmonary artery vascular smooth muscle. BMC Anesthesiol 2019; 19:176. [PMID: 31510933 PMCID: PMC6740015 DOI: 10.1186/s12871-019-0843-2] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2019] [Accepted: 08/26/2019] [Indexed: 11/23/2022] Open
Abstract
Background The α2-receptor agonist dexmedetomidine (Dex) has been shown to produce sedative and analgesic effects not only with systemic administration but also when administered in the extradural space and around peripheral nerves. The effects and mechanism of action of Dex on pulmonary arteries, however, have not been determined. This study therefore aimed to investigate the effect of Dex on pulmonary arterial vascular smooth muscle by evaluating changes in isometric contraction tension. We then attempted to determine the effects of Dex on depolarization stimulation and receptor stimulation. Methods Endothelium-denuded porcine pulmonary arteries were sliced into 2- to 3-mm rings. We then exposed them to certain substances at various concentrations under different conditions of baseline stimulation (with KCl, adrenaline, caffeine, or histamine) and to α2-receptor stimulants or antagonists, or α1-receptor antagonists (imidazoline, yohimbine, rauwolscine, prazosin), and different conditions of Ca2+ depletion of the intracellular reservoir or extracellular stores. We measured the changes in isometric contraction tension with each addition or change in conditions. Results Dex enhanced the contraction induced by high-concentration KCl stimulation. Dex-induced enhancement of contraction induced by high-concentration KCl was completely suppressed by yohimbine and rauwolscine, which are α2-receptor antagonists, but not by prazosin. Dex, imidazoline, yohimbine, and rauwolscine reduced the increases in contraction tension induced by the receptor stimulant adrenaline. Dex suppressed the adrenaline-induced increases in contraction tension after depletion of the Ca2+ reservoir. In the absence of extracellular Ca2+, Dex suppressed the adrenaline- and histamine-induced increases in contraction tension but did not affect caffeine-induced increases. Conclusions Dex-enhanced, high-concentration KCl-induced contraction was mediated by α2-receptors. Adrenaline-induced contraction was suppressed by the α2-receptor stimulant Dex and α2-receptor antagonists yohimbine and rauwolscine, suggesting that the effect of Dex on adrenaline-induced contraction is attributable to its α2-receptor-blocking action. Dex inhibited receptor-activated Ca2+ channels and phosphatidylinositol-1,4,5-triphosphate-induced Ca2+ release but not Ca2+-induced Ca2+ release.
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Affiliation(s)
- Mami Chikuda
- Division of Dental Anesthesiology, Department of Reconstructive Oral and Maxillofacial Surgery, School of Dentistry, Iwate Medical University, 1-3-27 Chuo-dori, Morioka, Iwate, 020-8505, Japan
| | - Kenichi Sato
- Division of Dental Anesthesiology, Department of Reconstructive Oral and Maxillofacial Surgery, School of Dentistry, Iwate Medical University, 1-3-27 Chuo-dori, Morioka, Iwate, 020-8505, Japan.
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4
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Okada M, Fukuyama K, Kawano Y, Shiroyama T, Suzuki D, Ueda Y. Effects of acute and sub-chronic administrations of guanfacine on catecholaminergic transmissions in the orbitofrontal cortex. Neuropharmacology 2019; 156:107547. [PMID: 30802458 DOI: 10.1016/j.neuropharm.2019.02.029] [Citation(s) in RCA: 34] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2018] [Revised: 02/15/2019] [Accepted: 02/21/2019] [Indexed: 12/20/2022]
Abstract
The selective α2A adrenoceptor agonist guanfacine reduces hyperactivity and improves cognitive impairment in patients with attention-deficit/hyperactivity disorder (ADHD). The major mechanisms of guanfacine have been considered to involve activation of postsynaptic α2A adrenoceptor in frontal pyramidal neurons. However, the effects of chronic guanfacine administration on catecholaminergic transmissions associated with the orbitofrontal cortex (OFC) remain unclear. To explore the mechanisms of action of guanfacine on catecholaminergic transmission, the effects of its acute local or sub-chronic systemic administration on catecholamine release within pathways from locus coeruleus (LC) to OFC and reticular thalamic nucleus (RTN), from RTN to mediodorsal thalamic nucleus (MDTN), and from MDTN to OFC were determined using multi-probe microdialysis with ultra-high performance liquid chromatography. Acute OFC local administration of guanfacine did not affect catecholamine release in OFC. Acute LC local and sub-chronic systemic administrations of guanfacine reduced norepinephrine release in LC, OFC and RTN, and also reduced GABA release in MDTN, whereas AMPA-induced (perfusion with AMPA into NDTN) releases of l-glutamate, norepinephrine and dopamine in OFC were enhanced by sub-chronic systemic guanfacine administration. This study identified that catecholaminergic transmission is composed of three pathways: direct noradrenergic and co-releasing catecholaminergic LC-OFC pathways and intermediate LC-OFC (LC-RTN-MDTN-OFC) pathway. We demonstrated the dual actions of guanfacine on catecholaminergic transmission: attenuation of direct noradrenergic LC-OFC transmission at the resting stage and enhancement of direct co-releasing catecholaminergic LC-OFC transmission via GABAergic disinhibition in the intermediate LC-OFC pathway. These dual actions of guanfacine probably contribute to clinical actions of guanfacine against ADHD and its comorbid symptoms. This article is part of the Special Issue entitled 'Current status of the neurobiology of aggression and impulsivity'.
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Affiliation(s)
- Motohiro Okada
- Department of Neuropsychiatry, Division of Neuroscience, Graduate School of Medicine, Mie University, 2-174 Edobashi, Tsu, Mie, 514-8507, Japan.
| | - Kouji Fukuyama
- Department of Neuropsychiatry, Division of Neuroscience, Graduate School of Medicine, Mie University, 2-174 Edobashi, Tsu, Mie, 514-8507, Japan
| | - Yasuhiro Kawano
- Department of Neuropsychiatry, Division of Neuroscience, Graduate School of Medicine, Mie University, 2-174 Edobashi, Tsu, Mie, 514-8507, Japan
| | - Takashi Shiroyama
- Department of Neuropsychiatry, Division of Neuroscience, Graduate School of Medicine, Mie University, 2-174 Edobashi, Tsu, Mie, 514-8507, Japan
| | - Dai Suzuki
- Department of Neuropsychiatry, Division of Neuroscience, Graduate School of Medicine, Mie University, 2-174 Edobashi, Tsu, Mie, 514-8507, Japan
| | - Yuto Ueda
- Department of Neuropsychiatry, Division of Neuroscience, Graduate School of Medicine, Mie University, 2-174 Edobashi, Tsu, Mie, 514-8507, Japan
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5
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Hernández-Hernández E, Miralles A, Esteban S, García-Fuster MJ. Repeated treatment with the α2-adrenoceptor agonist UK-14304 improves cognitive performance in middle-age rats: Role of hippocampal Fas-associated death domain. J Psychopharmacol 2018; 32:248-255. [PMID: 29207901 DOI: 10.1177/0269881117742667] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The cell fate regulator Fas-associated death domain (FADD) balances cell death with non-apoptotic actions via its phosphorylated form. A recent study associated loss of cortical FADD with cognitive decline and increased risk of clinical dementia. Since the activation of cortical α2A-adrenoceptors improved memory deficits in various animal models of working memory loss, the present study evaluated whether UK-14304, an α2-adrenoceptor agonist known to acutely regulate brain FADD forms, would improve cognitive function in middle-aged rats. Sprague-Dawley rats were treated with UK-14304 (0.3 or 1 mg/kg) or saline (1 mL/kg) for seven days. Cognitive performance was evaluated in the eight-arm radial maze. FADD protein content was measured in the prefrontal cortex and hippocampus by Western blot analysis. The results showed that UK-14304 (1 mg/kg) improved cognitive performance (less time: -310±45 s, p=0.025 and fewer errors: -2.75±1.06, p=0.043 to complete the maze) and increased FADD selectively in the hippocampus (+35±11%, p=0.029). Interestingly, hippocampal FADD content negatively correlated with the time ( r=-0.651, p<0.01) needed to complete the maze. Thus, better cognitive scores were associated with higher FADD hippocampal content. These results support a role for α2-adrenoceptors in ameliorating cognition and suggest FADD protein content as a possible correlate for cognitive performance.
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Affiliation(s)
- Elena Hernández-Hernández
- 1 University Research Institute on Health Sciences (IUNICS), University of the Balearic Islands, and Balearic Islands Health Research Intitute (IdISBa), Palma, Spain.,2 Neurophysiology Research Group, University of the Balearic Islands, Palma, Spain
| | - Antonio Miralles
- 2 Neurophysiology Research Group, University of the Balearic Islands, Palma, Spain
| | - Susana Esteban
- 2 Neurophysiology Research Group, University of the Balearic Islands, Palma, Spain
| | - M Julia García-Fuster
- 1 University Research Institute on Health Sciences (IUNICS), University of the Balearic Islands, and Balearic Islands Health Research Intitute (IdISBa), Palma, Spain
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6
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Schopf K, Huber A. Membrane protein trafficking in Drosophila photoreceptor cells. Eur J Cell Biol 2016; 96:391-401. [PMID: 27964885 DOI: 10.1016/j.ejcb.2016.11.002] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2016] [Revised: 11/21/2016] [Accepted: 11/28/2016] [Indexed: 10/20/2022] Open
Abstract
Membrane protein trafficking occurs throughout the lifetime of neurons and includes the initial protein synthesis and anterograde transport to the plasma membrane as well as internalization, degradation, and recycling of plasma membrane proteins. Defects in protein trafficking can result in neuronal degeneration and underlie blinding diseases such as retinitis pigmentosa as well as other neuronal disorders. Drosophila photoreceptor cells have emerged as a model system for identifying the components and mechanisms involved in membrane protein trafficking in neurons. Here we summarize the current knowledge about trafficking of three Drosophila phototransduction proteins, the visual pigment rhodopsin and the two light-activated ion channels TRP (transient receptor potential) and TRPL (TRP-like). Despite some common requirements shared by rhodopsin and TRP, details in the trafficking of these proteins differ considerably, suggesting the existence of several trafficking pathways for these photoreceptor proteins.
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Affiliation(s)
- Krystina Schopf
- University of Hohenheim, Institute of Physiology, Department of Biosensorics, Stuttgart, Germany
| | - Armin Huber
- University of Hohenheim, Institute of Physiology, Department of Biosensorics, Stuttgart, Germany.
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7
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Hains AB, Yabe Y, Arnsten AF. Chronic Stimulation of Alpha-2A-Adrenoceptors With Guanfacine Protects Rodent Prefrontal Cortex Dendritic Spines and Cognition From the Effects of Chronic Stress. Neurobiol Stress 2015; 2:1-9. [PMID: 25664335 PMCID: PMC4316374 DOI: 10.1016/j.ynstr.2015.01.001] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2014] [Revised: 12/18/2014] [Accepted: 01/07/2015] [Indexed: 01/01/2023] Open
Abstract
The prefrontal cortex (PFC) provides top-down regulation of behavior, cognition, and emotion, including spatial working memory. However, these PFC abilities are greatly impaired by exposure to acute or chronic stress. Chronic stress exposure in rats induces atrophy of PFC dendrites and spines that correlates with working memory impairment. As similar PFC grey matter loss appears to occur in mental illness, the mechanisms underlying these changes need to be better understood. Acute stress exposure impairs PFC cognition by activating feedforward cAMP-calcium-K+ channel signaling, which weakens synaptic inputs and reduces PFC neuronal firing. Spine loss with chronic stress has been shown to involve calcium-protein kinase C signaling, but it is not known if inhibiting cAMP signaling would similarly prevent the atrophy induced by repeated stress. The current study examined whether inhibiting cAMP signaling through alpha-2A-adrenoceptor stimulation with chronic guanfacine treatment would protect PFC spines and working memory performance during chronic stress exposure. Guanfacine was selected due to 1) its established effects on cAMP signaling at post-synaptic alpha-2A receptors on spines in PFC, and 2) its increasing clinical use for the treatment of pediatric stress disorders. Daily guanfacine treatment compared to vehicle control was found to prevent dendritic spine loss in layer II/III pyramidal neurons of prelimbic PFC in rats exposed to chronic restraint stress. Guanfacine also protected working memory performance; cognitive performance correlated with dendritic spine density. These findings suggest that chronic guanfacine use may have clinical utility by protecting PFC gray matter from the detrimental effects of stress.
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Affiliation(s)
| | | | - Amy F.T. Arnsten
- Department of Neurobiology, Yale University School of Medicine, 333 Cedar St., New Haven, CT 06510, USA
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8
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Long KM, Kirby R. An update on cardiovascular adrenergic receptor physiology and potential pharmacological applications in veterinary critical care. J Vet Emerg Crit Care (San Antonio) 2008. [DOI: 10.1111/j.1476-4431.2007.00266.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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9
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Morishima M, Harada N, Hara S, Sano A, Seno H, Takahashi A, Morita Y, Nakaya Y. Monoamine oxidase A activity and norepinephrine level in hippocampus determine hyperwheel running in SPORTS rats. Neuropsychopharmacology 2006; 31:2627-38. [PMID: 16421512 DOI: 10.1038/sj.npp.1301028] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
An understanding of neurological mechanisms for wheel running by rodents, especially with high exercise activity, would be applicable to a strategy for promotion of exercise motivation in humans. One of several brain regions that are candidates for the regulation of physical exercise is the hippocampus. Here we examined the running activity of Spontaneously-Running-Tokushima-Shikoku (SPORTS) rat, a new animal model for high levels of wheel-running activity, and its relation with the hippocampal norepinephrine (NE) system including the levels of NE, adrenergic receptors, and degradation enzymes for monoamines. In the hippocampus of SPORTS rats, the level of NE in extracellular fluid was augmented, whereas the level in the homogenate of the whole tissue was decreased even for sedentary conditions. Elevated extracellular NE caused downregulation of alpha(2)-adrenergic receptors in the hippocampus of SPORTS rats. Local administration of alpha(2)-adrenergic receptor antagonist yohimbine, but not of alpha(2)-agonist clonidine, into the hippocampus suppressed high running activity in SPORTS rats. The protein expression and the activity levels of monoamine oxidase A (MAOA), a critical enzyme for the degradation of NE, were decreased in the hippocampus of SPORTS rats to increase extracellular NE level. Thus, inhibition of oxidase activity in normal Wistar rats markedly increased wheel-running activity. These results indicate that decreased MAOA activity, elevation of extracellular NE, and alpha(2)-adrenergic receptors in the hippocampus determine the neural basis of the psychological regulation of exercise behavior in SPORTS rats.
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Affiliation(s)
- Masaki Morishima
- Department of Nutrition and Metabolism, Institute of Health Biosciences, The University of Tokushima Graduate School, Kuramoto-cho, Tokushima City, Japan
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10
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Bernard V, Décossas M, Liste I, Bloch B. Intraneuronal trafficking of G-protein-coupled receptors in vivo. Trends Neurosci 2006; 29:140-7. [PMID: 16443287 DOI: 10.1016/j.tins.2006.01.006] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2005] [Revised: 11/09/2005] [Accepted: 01/12/2006] [Indexed: 02/01/2023]
Abstract
In vitro studies have widely demonstrated that the abundance and availability of G-protein-coupled receptors (GPCRs) at the cell surface is regulated by the neuronal environment and is the result of complex intraneuronal trafficking. However, this regulation is still poorly understood in vivo. Modulation of receptor availability at the neuronal membrane is a key event in the regulation of neuronal functions (e.g. neurotransmitter release or neuronal excitability in physiological, pathological or therapeutic conditions). We discuss the effects of duration of receptor stimulation (acute versus chronic) on the intraneuronal trafficking of GPCRs in vivo, and we show that this trafficking might differ according to subcellular compartment (soma, dendrites or axon terminals).
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Affiliation(s)
- Véronique Bernard
- Centre National de la Recherche Scientifique, Unité Mixte de Recherche 5541, Laboratoire d'Histologie-Embryologie, Université Victor Ségalen-Bordeaux 2, 146 Rue Léo-Saignat, 33076 Bordeaux Cedex, France.
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11
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Lemon G, Brockhausen J, Li GH, Gibson WG, Bennett MR. Calcium mobilization and spontaneous transient outward current characteristics upon agonist activation of P2Y2 receptors in smooth muscle cells. Biophys J 2005; 88:1507-23. [PMID: 15556987 PMCID: PMC1305209 DOI: 10.1529/biophysj.104.043976] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2004] [Accepted: 08/12/2004] [Indexed: 11/18/2022] Open
Abstract
A quantitative model is provided that links the process of metabotropic receptor activation and sequestration to the generation of inositol 1,4,5-trisphosphate, the subsequent release of calcium from the central sarcoplasmic reticulum, and the consequent release of calcium from subsarcolemma sarcoplasmic reticulum that acts on large-conductance potassium channels to generate spontaneous transient outward currents (STOCs). This model is applied to the case of STOC generation in vascular A7r5 smooth muscle cells that have been transfected with a chimera of the P2Y(2) metabotropic receptor and green fluorescent protein (P2Y(2)-GFP) and exposed to the P2Y(2) receptor agonist uridine 5'-triphosphate. The extent of P2Y(2)-GFP sequestration from the membrane on exposure to uridine 5'-triphosphate, the ensuing changes in cytosolic calcium concentration, as well as the interval between STOCs that are subsequently generated, are used to determine parameter values in the model. With these values, the model gives a good quantitative prediction of the dynamic changes in STOC amplitude observed upon activation of metabotropic P2Y(2) receptors in the vascular smooth muscle cell line.
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MESH Headings
- Animals
- Biological Transport, Active/drug effects
- Biological Transport, Active/physiology
- Calcium/metabolism
- Calcium Signaling/drug effects
- Calcium Signaling/physiology
- Cell Line
- Computer Simulation
- Membrane Potentials/drug effects
- Membrane Potentials/physiology
- Models, Biological
- Muscle, Smooth, Vascular/cytology
- Muscle, Smooth, Vascular/drug effects
- Muscle, Smooth, Vascular/physiology
- Myocytes, Smooth Muscle/drug effects
- Myocytes, Smooth Muscle/physiology
- Purinergic P2 Receptor Agonists
- Receptors, Purinergic P2/metabolism
- Receptors, Purinergic P2Y2
- Uridine Triphosphate/pharmacology
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Affiliation(s)
- G Lemon
- The School of Mathematics and Statistics, University of Sydney, New South Wales, Australia
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12
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Douglas AJ. Central noradrenergic mechanisms underlying acute stress responses of the Hypothalamo-pituitary-adrenal axis: adaptations through pregnancy and lactation. Stress 2005; 8:5-18. [PMID: 16019594 DOI: 10.1080/10253890500044380] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/25/2022] Open
Abstract
Hypothalamo-pituitary-adrenal axis responses to stress are attenuated perinatally, and may contribute towards conservation of energy stores and/or prevention of overexposure to glucocorticoid and its adverse effects in the developing fetus/neonate. Previous work has shown that reduced central drive to the hypothalamo-pituitary-adrenal axis is responsible, since parvocellular paraventricular nucleus neurone responses are reduced. One of the main input pathways to the paraventricular nucleus that is activated by the majority of stressors is the brainstem noradrenergic system. This review outlines key noradrenergic mechanisms that mediate hypothalamo-pituitary-adrenal axis responses to acute stress, and addresses aspects of their adaptation in pregnancy and lactation that can explain the stress hyporesponsiveness at that time. In summary, reduced noradrenaline release and adrenergic receptor expression in the paraventricular nucleus may lead to reduced sensitivity of the hypothalamo-pituitary-adrenal axis to adrenergic antagonists and agonists and its responses to stress. While there are subtle differences in these changes between pregnancy and lactation, it would appear that reduced effectiveness of the noradrenergic input can at least partly account for the reduced hypothalamo-pituitary-adrenal axis responses both pre- and post-natally.
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Affiliation(s)
- Alison J Douglas
- Laboratory of Neuroendocrinology, Centre for Integrative Physiology, SBCLS, College of Medicine and Veterinary Medicine, University of Edinburgh, Hugh Robson Building, George Square, UK.
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13
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Briest W, Rassler B, Deten A, Zimmer HG. Norepinephrine-induced cardiac hypertrophy and fibrosis are not due to mast cell degranulation. Mol Cell Biochem 2004; 252:229-37. [PMID: 14577597 DOI: 10.1023/a:1025596404975] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
The norepinephrine (NE)-induced hypertrophy of the left ventricle (LV) in the rat is preceded by increased interleukin (IL)-6 expression and associated with LV fibrosis. We have examined whether the elevated level of IL-6 may be due to mast cell degranulation. Therefore we tested the effect of cromoglycate sodium salt (cromolyn), an inhibitor of mast cell degranulation with anti-inflammatory and membrane-stabilizing activity, on the increased expression of IL-6 mRNA and of mRNAs of proteins involved in the remodelling of the extracellular matrix (ECM) which is induced by NE (0.1 mg/kg x h). After 4 h, the NE-induced increase in IL-6 mRNA expression was not influenced by cromolyn (20 mg/kg x h). Cromolyn-infusion for 3 days did not affect the extent of LV hypertrophy induced by NE, as measured by the LV weight/body weight (LVW/BW) ratio and by atrial natriuretic peptide (ANP) expression. Cromolyn induced a slight depression of the NE-induced elevation of the matrix metalloproteinase (MMP)-2. However, it did not affect the NE-induced elevated levels of mRNAs of collagen I and III and the tissue inhibitor of matrix metalloproteinase (TIMP)-2. Since cromolyn did not reduce the NE-effects in rat hearts in vivo we conclude that mast cell degranulation seems not to be involved in them.
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Affiliation(s)
- Wilfried Briest
- Carl-Ludwig-Institute of Physiology, University of Leipzig, Leipzig, Germany.
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14
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Tham CS, Lin FF, Rao TS, Yu N, Webb M. Microglial activation state and lysophospholipid acid receptor expression. Int J Dev Neurosci 2003; 21:431-43. [PMID: 14659994 DOI: 10.1016/j.ijdevneu.2003.09.003] [Citation(s) in RCA: 92] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022] Open
Abstract
We used a simple commercial magnetic immunobead method for the preparation of acutely isolated microglial cells from postnatal days 1-3 rat brain. With the exception of a 15 min enzyme incubation, all stages are carried out at 4 degrees C, minimizing the opportunity for changes in gene expression during the isolation to be reflected in changes in accumulated mRNA. The composition of the isolated cells was compared with that of microglial cultures prepared by conventional tissue culture methods, and the purity of microglia was comparable between the two preparations. RT-PCR analysis of several genes related to inflammatory products indicated that the acutely prepared cells were in a less activated condition than the conventionally tissue cultured cells. We examined the pattern of expression of receptors for lysophosphatidic acid (lpa) and sphingosine-1-phosphate (S1P) using quantitative real-time PCR (TaqMan PCR) techniques. mRNA for LPA1, S1P1, S1P2, S1P3 and S1P5 was detected in these preparations, but the levels of the different receptor mRNAs varied according to the state of activation of the cells. mRNA for LPA3 was only detected significantly in cultured cell after lipopolysaccharide (LPS) stimulation, being almost absent in cultured microglia and undetectable in the acutely isolated preparations. The levels of mRNA of LPA1 and S1P receptors was reduced by overnight exposure to S1P, while the same treatment significantly up-regulated the level of LPA3 mRNA.
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MESH Headings
- Animals
- Animals, Newborn
- Astrocytes/metabolism
- Base Sequence
- Blotting, Northern
- CD11b Antigen/genetics
- CD11b Antigen/metabolism
- Carrier Proteins/genetics
- Carrier Proteins/metabolism
- Cells, Cultured
- Cyclooxygenase 2
- Dose-Response Relationship, Drug
- Drug Interactions
- Enzyme Inhibitors/pharmacology
- Enzyme-Linked Immunosorbent Assay
- Fluorescent Antibody Technique/methods
- Gene Expression/drug effects
- Glial Fibrillary Acidic Protein/metabolism
- Imidazoles/pharmacology
- Indoles/metabolism
- Interleukin-6/genetics
- Interleukin-6/metabolism
- Isoenzymes/genetics
- Isoenzymes/metabolism
- Lectins/metabolism
- Lysophospholipids/pharmacology
- Microglia/metabolism
- Myelin Basic Protein/metabolism
- Nitric Oxide Synthase/genetics
- Nitric Oxide Synthase/metabolism
- Nitric Oxide Synthase Type II
- Oligodendroglia/metabolism
- Osteopontin
- Prostaglandin-Endoperoxide Synthases/genetics
- Prostaglandin-Endoperoxide Synthases/metabolism
- Pyridines/pharmacology
- RNA, Messenger/biosynthesis
- Rats
- Rats, Sprague-Dawley
- Receptors, G-Protein-Coupled/biosynthesis
- Receptors, G-Protein-Coupled/genetics
- Receptors, Lipoprotein/biosynthesis
- Receptors, Lipoprotein/drug effects
- Receptors, Lipoprotein/genetics
- Receptors, Lysophospholipid
- Reverse Transcriptase Polymerase Chain Reaction/methods
- Sialoglycoproteins/genetics
- Sialoglycoproteins/metabolism
- Tumor Necrosis Factor-alpha/metabolism
- p38 Mitogen-Activated Protein Kinases
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Affiliation(s)
- Chui-Se Tham
- Molecular Neuroscience Laboratory, Merck Research Laboratories, 3535 General Atomics Court, San Diego, CA 92121, USA
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15
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Abstract
The endothelium is more than just a passive vessel lining. New advances have revealed and expanded the multifactorial role of the endothelium in the homeostatic regulation of the microvasculature, including control of primary hemostasis, blood coagulation and fibrinolysis, platelet and leukocyte interactions with the vessel wall, lipoprotein metabolism, presentation of histocompatibility antigens, regulation of vascular tone and growth, and regulation of blood pressure. It possesses numerous receptors and releases compounds that affect the regulation of vascular tone and contribute to vascular permeability. Many crucial vasoactive endogenous compounds are formed in the endothelial cells to control the functions of vascular smooth muscle cells and circulating blood cells. Gap junctions facilitate the exchange of metabolites, ions, and other messenger molecules among endothelial cells and smooth muscle cells, and regulate cell growth. Among the numerous regulatory systems affecting microvascular function are the cholinergic and adrenergic (α1, α2, and β) systems. Flow-metabolism coupling is affected by a variety of signaling systems, including adenosine, oxygen, carbon dioxide, lactate, nitric oxide, and others. Agents such as the angiotensin system and endothelin, as well as others, play a role in autoregulation (maintenance of constant flow in the face of changing pressure). All of these are discussed in detail.
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Affiliation(s)
- Danja Striimper
- University of Münster, University Hospital Maastrich, The Netherlands
| | - Marcel Durieux
- University of Münster; Department of Anesthesiology, University Hospital Maastrich, The Netherlands
| | - Paul Roekaerts
- Department of Anesthesiology, University Hospital Maastrich, The Netherlands
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16
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Bernard V, Brana C, Liste I, Lockridge O, Bloch B. Dramatic depletion of cell surface m2 muscarinic receptor due to limited delivery from intracytoplasmic stores in neurons of acetylcholinesterase-deficient mice. Mol Cell Neurosci 2003; 23:121-33. [PMID: 12799142 DOI: 10.1016/s1044-7431(03)00034-4] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
We have studied the consequences of the constitutive acetylcholinesterase (AChE) deficiency in knockout mice for the AChE gene on the subcellular localization of the m2 receptor (m2R) and the regulation of its intraneuronal compartmentalization by the cholinergic environment, using immunohistochemistry at light and electron microscopic levels. (1) In AChE +/+ mice in vivo, m2R is mainly located at the neuronal membrane in striatum, hippocampus, and cortex. In AChE -/- mice, m2R is almost absent at the membrane but is accumulated in the endoplasmic reticulum and Golgi complex. (2) In vivo and in vitro (organotypic culture) dynamic studies demonstrate that the balance between membrane and intracytoplasmic m2R can be regulated by the cholinergic influence: In AChE -/- mice, m2R is translocated from the cytoplasm to the cell surface after (1) blockade of muscarinic receptors by atropine, (2) supplementation of AChE -/- neurons with AChE in vitro, and (3) disruption of the cortical and hippocampal cholinergic afferents in vitro. Our results suggest that the neurochemical environment may contribute to the control of the abundance and availability of cell surface receptors, and consequently to the control of neuronal sensitivity to neurotransmitters or drugs, by regulating their delivery from the endoplasmic reticulum and Golgi complex.
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Affiliation(s)
- Véronique Bernard
- Centre National de la Recherche Scientifique, Unité Mixte de Recherche 5541, Laboratoire d'Histologie-Embryologie, Université Victor Ségalen-Bordeaux 2, 146 rue Léo-Saignat, France.
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17
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Hamasaki J, Tsuneyoshi I, Katai R, Hidaka T, Boyle WA, Kanmura Y. Dual α2-Adrenergic Agonist and α1-Adrenergic Antagonist Actions of Dexmedetomidine on Human Isolated Endothelium-Denuded Gastroepiploic Arteries. Anesth Analg 2002. [DOI: 10.1213/00000539-200206000-00010] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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18
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Hamasaki J, Tsuneyoshi I, Katai R, Hidaka T, Boyle WA, Kanmura Y. Dual alpha(2)-adrenergic agonist and alpha(1)-adrenergic antagonist actions of dexmedetomidine on human isolated endothelium-denuded gastroepiploic arteries. Anesth Analg 2002; 94:1434-40, table of contents. [PMID: 12032002 DOI: 10.1097/00000539-200206000-00010] [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: 11/26/2022]
Abstract
UNLABELLED The actions of dexmedetomidine (DEX) on human vascular smooth muscle are unclear. We investigated its effects on isolated, endothelium-denuded human gastroepiploic arteries in vitro and compared them with clonidine (CLO). DEX had little direct effect on resting tension, whereas CLO produced small contractile responses, an effect which is blocked by the alpha(1)-adrenergic antagonist prazosin. DEX markedly enhanced the high K(+) (40 mmol/L)-induced contraction, and this effect was reversed by the alpha(2)-adrenergic antagonists yohimbine and rauwolscine but unaffected by prazosin. However, CLO had little effect on the K(+) contractions. Interestingly, larger concentrations (>10(-7) mol/L) of both alpha(2)-adrenergic stimulants significantly inhibited the contractions elicited by the alpha(1)-adrenergic agonist phenylephrine (10(-6) mol/L) and, to a lesser extent, those elicited by the alpha(1)/alpha(2)-agonist norepinephrine (10(-6) mol/L). These results suggest the possibility that DEX and CLO each have a high affinity for alpha(1)-adrenoceptors in human isolated gastroepiploic arteries, resulting in a reduced efficacy of alpha(1)-adrenergic activation by alpha-agonists. The differing affinities of the drugs for alpha(1)- and alpha(2)-adrenoceptors may help explain their additional actions: 1) DEX enhances the high K(+)-induced contraction presumably through alpha(2)-adrenoceptor activation, and 2) CLO acts on alpha(1)-adrenoceptors as a partial agonist when present alone. IMPLICATIONS Dexmedetomidine may not directly affect smooth muscle in human peripheral resistance vessels within the usual range of plasma concentrations (<10(-7) mol/L) achieved in clinical practice. However, in large doses, it could enhance the response to nonadrenergic vasoconstrictor agonists while antagonizing the vasoconstrictor response to alpha(1)-adrenoceptor agonists.
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Affiliation(s)
- Junichirou Hamasaki
- Department of Anesthesiology and Critical Care Medicine, Kagoshima University School of Medicine, 8-35-1 Sakuragaoka, Kagoshima 890-8520, Japan.
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19
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Abstract
The number of G protein-coupled receptors (GPCRs) displayed at the cell surface is a critical determinant of physiological responsiveness to native ligands and drugs. Downregulation of the number of adrenergic and dopaminergic receptors present on specific neurons can be induced by receptor agonists or by drugs that increase extracellular concentrations of catecholamines such as dopamine. Thus agonist-induced downregulation of GPCRs is of potentially great importance to the treatment of Parkinson's Disease. However, little is known about biochemical mechanisms that mediate GPCR downregulation. Recent studies of cloned GPCRs have provided exciting insights into specific mechanisms that control endocytosis of receptors from the plasma membrane and regulate proteolytic degradation of receptors. In this review we briefly survey representative studies establishing that multiple mechanisms of GPCR membrane trafficking can function in downregulation function both in neural and non-neural cell types. Then we focus on our present view of mechanisms mediating regulated proteolysis of GPCRs, highlighting recent progress in understanding membrane trafficking of GPCRs from the cell surface to lysosomes. Finally we discuss emerging evidence regarding a specific mechanism that modulates sorting of certain GPCRs between recycling and degradative pathways.
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Affiliation(s)
- M von Zastrow
- Department of Psychiatry, University of California, San Francisco, CA, USA
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20
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Tsao P, Cao T, von Zastrow M. Role of endocytosis in mediating downregulation of G-protein-coupled receptors. Trends Pharmacol Sci 2001; 22:91-6. [PMID: 11166853 DOI: 10.1016/s0165-6147(00)01620-5] [Citation(s) in RCA: 195] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Many G-protein-coupled receptors (GPCRs) undergo agonist-induced endocytosis. Such endocytosis has been implicated in diverse processes of receptor regulation, including reversible sequestration of receptors in endosomes and proteolytic downregulation of receptors in lysosomes. The precise relationships between membrane pathways that mediate receptor sequestration and downregulation remain controversial. Recent studies suggest that GPCRs can be segregated within distinct microdomains of the plasma membrane before endocytosis occurs, and others suggest that certain GPCRs are sorted between divergent membrane pathways after endocytosis by clathrin-coated pits. Furthermore, emerging data implicate a specific role of the actin cytoskeleton and receptor phosphorylation in controlling endocytic sorting of a particular GPCR. In this article, recent research into endocytosis of GPCRs will be discussed together with some important and unresolved questions regarding the diversity and specificity of mechanisms that mediate downregulation of GPCRs.
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Affiliation(s)
- P Tsao
- Dept of Biochemistry and Biophysics, University of California, San Francisco, CA 94143-0984, USA
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21
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Meyer H, Palchaudhuri M, Scheinin M, Flügge G. Regulation of alpha(2A)-adrenoceptor expression by chronic stress in neurons of the brain stem. Brain Res 2000; 880:147-58. [PMID: 11032999 DOI: 10.1016/s0006-8993(00)02787-6] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Alpha(2)-Adrenoceptors are supposed to be important regulatory elements in responses to stress. Previous receptor binding studies in male tree shrews have shown that chronic psychosocial stress down-regulates binding sites for alpha(2)-adrenergic ligands in several brain stem nuclei. The aim of the present study was to quantify effects of chronic subordination stress on expression of the alpha(2)-adrenoceptor subtype A gene in identified neurons of the brain stem. We partially cloned the alpha(2A)-adrenoceptor cDNA of the tree shrew (1.22 kb) and localized receptor RNA expression in brain stem neurons by in situ hybridization using a 35S-labeled cRNA probe (1.06 kb). To identify neurons expressing receptor mRNA, brain sections were first immunocytochemically stained with antibodies against tyrosine hydroxylase, phenylethanolamine-N-methyltransferase, or glutamate, and then processed for in situ hybridization. Furthermore, expression of receptor-specific RNA was quantified in single neurons of animals which had been psychosocially stressed during 4 weeks and in unstressed controls. We found strong in situ hybridization in the noradrenergic neurons of the locus coeruleus, but only weak labeling of A2 neurons in the solitary tract nucleus and no labeling of A1 neurons in the caudal ventrolateral medulla. Adrenergic neurons in the solitary tract nucleus (group C2) did not express the alpha(2A)-adrenoceptor, and C1 neurons in the rostral ventrolateral medulla showed only a minor labeling by the in situ probe. In contrast, large glutamatergic neurons in the lateral reticular nucleus were strongly labeled by the probe. Chronic psychosocial stress reduced alpha(2A)-adrenoceptor RNA expression in locus coeruleus neurons (-24.0%), in solitary tract neurons (-31.0%), and in neurons of the lateral reticular nucleus (-18.8%). These findings show that stress not only decreases the expression of the alpha(2A)-adrenergic autoreceptor in the locus coeruleus but also of alpha(2A)-heteroreceptors in glutamatergic neurons.
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Affiliation(s)
- H Meyer
- Division of Neurobiology, German Primate Center, Kellnerweg 4, D-37077, Göttingen, Germany
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22
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Dutton JL, Poronnik P, Li GH, Holding CA, Worthington RA, Vandenberg RJ, Cook DI, Barden JA, Bennett MR. P2X(1) receptor membrane redistribution and down-regulation visualized by using receptor-coupled green fluorescent protein chimeras. Neuropharmacology 2000; 39:2054-66. [PMID: 10963749 DOI: 10.1016/s0028-3908(00)00058-7] [Citation(s) in RCA: 73] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The P2X(1) purinergic receptor subtype occurs on smooth muscle cells of the vas deferens and urinary bladder where it is localized in two different size receptor clusters, with the larger beneath autonomic nerve terminal varicosities. We have sought to determine whether these synaptic-size clusters only form in the presence of varicosities and whether they are labile when exposed to agonists. P2X(1) and a chimera of P2X(1) and green fluorescent protein (GFP) were delivered into cells using microinjection, transient transfection or infection with a replication-deficient adenovirus. The P2X(1)-GFP chimera was used to study the time course of P2X(1) receptor clustering in plasma membranes and the internalization of the receptor following prolonged exposure to ATP. Both P2X(1) and P2X(1)-GFP clustered in the plasma membranes of Xenopus oocytes, forming patches 4-6 microm in diameter. Human embryonic kidney 293 (HEK293) cells, infected with the adenovirus, possessed P2X(1) antibody-labeled regions in the membrane colocalized with GFP fluorescence. The ED(50) for the binding of alpha,beta-methylene adenosine triphosphate (alpha,beta-meATP) to the P2X(1)-GFP chimera was similar to native P2X(1) receptors. ATP-generated whole-cell currents in oocytes or HEK293 cells expressing either P2X(1) or P2X(1)-GFP were similar. Exposure of HEK293 cells to alpha, beta-meATP for 10-20 min in the presence of 5 microM monensin led to the disappearance of P2X(1)-GFP fluorescence from the surface of the cells. These observations using the P2X(1)-GFP chimera demonstrate that P2X(1) receptors spontaneously form synaptic-size clusters in the plasma membrane that are internalized on exposure to agonists.
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Affiliation(s)
- J L Dutton
- Neurobiology Laboratory, Department of Physiology, Institute for Biomedical Research, University of Sydney, NSW 2006, Australia
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23
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Miller AF, Harvey SA, Thies RS, Olson MS. Bone morphogenetic protein-9. An autocrine/paracrine cytokine in the liver. J Biol Chem 2000; 275:17937-45. [PMID: 10849432 DOI: 10.1074/jbc.275.24.17937] [Citation(s) in RCA: 127] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Bone morphogenetic proteins (BMPs) occupy important roles during development serving to direct cells through specific differentiation programs. While several BMPs are essential for embryonic viability, their significance in mediating intercellular communication in the context of adult organ systems remains largely unknown. In the adult rat we characterized the tissue- and cell-specific transcription and translation of BMP-9. Utilizing a ribonuclease protection assay, we determined that in the adult animal, BMP-9 expression occurs predominantly in the liver. Furthermore, we determined that the non-parenchymal cells of the liver, i.e. endothelial, Kupffer, and stellate cells, are the major sources of this message. Western analyses corroborate the ribonuclease protection assay results, confirming that LEC and KC contain an abundance of immunoreactive BMP-9. Using [(125)I]BMP-9, a receptor with specific binding affinity for BMP-9 was characterized in primary cultures of hepatic endothelial cells and Kupffer cells. BMP-9 binding to these cell types was observed to be fully reversible and highly specific for this ligand. Additionally, we demonstrate that BMP-9 is specifically internalized upon binding to its receptor. This may represent a novel BMP receptor and is the first to be characterized in primary cultures of mature liver non-parenchymal cells. Our results depict BMP-9 as a potential autocrine/paracrine mediator in the hepatic reticuloendothelial system.
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Affiliation(s)
- A F Miller
- Department of Biochemistry, University of Texas Health Science Center, San Antonio, Texas 78284-7600, USA
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24
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Abstract
Major advances have been made in understanding mechanisms mediating downregulation of G protein-coupled receptors. Recent studies emphasize the role of multiple proteolytic mechanisms in downregulation. A specific mechanism of downregulation, mediated by endocytosis of receptors via clathrin-coated pits followed by sorting to lysosomes, has been examined in detail. Specific protein interactions that control the specificity of G-protein-coupled receptor trafficking in this pathway are beginning to be elucidated.
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Affiliation(s)
- P Tsao
- Department of Psychiatry and Cellular and Molecular Pharmacology, Box 0984 IRE, Room LP-A104, University of California, San Francisco, San Francisco, CA 94143-0984, USA
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25
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Edwards SW, Limbird LE. Role for the third intracellular loop in cell surface stabilization of the alpha2A-adrenergic receptor. J Biol Chem 1999; 274:16331-6. [PMID: 10347190 DOI: 10.1074/jbc.274.23.16331] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Previous studies have shown that alpha2A-adrenergic receptor (alpha2A-AR) retention at the basolateral surface of polarized MDCKII cells involves its third intracellular (3i loop). The present studies examining mutant alpha2A-ARs possessing short deletions of the 3i loop indicate that no single region can completely account for the accelerated surface turnover of the Delta3ialpha2A-AR, suggesting that the entire 3i loop is involved in basolateral retention. Both wild-type and Delta3i loop alpha2A-ARs are extracted from polarized Madin-Darby canine kidney (MDCK) cells with 0.2% Triton X-100 and with a similar concentration/response profile, suggesting that Triton X-100-resistant interactions of the alpha2A-AR with cytoskeletal proteins are not involved in receptor retention on the basolateral surface. The indistinguishable basolateral t(1)/(2) for either the wild-type or nonsense 3i loop alpha2A-AR suggests that the stabilizing properties of the alpha2A-AR 3i loop are not uniquely dependent on a specific sequence of amino acids. The accelerated turnover of Delta3i alpha2A-AR cannot be attributed to alteration in agonist-elicited alpha2A-AR redistribution, because alpha2A-ARs are not down-regulated in response to agonist. Taken together, the present studies show that stabilization of the alpha2A-AR on the basolateral surface of MDCKII cells involves multiple mechanisms, with the third intracellular loop playing a central role in regulating these processes.
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Affiliation(s)
- S W Edwards
- Department of Pharmacology, Vanderbilt University Medical Center, Nashville, Tennessee 37232, USA
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