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Velasquez-Martinez MC, Santos-Vera B, Velez-Hernandez ME, Vazquez-Torres R, Jimenez-Rivera CA. Alpha-1 Adrenergic Receptors Modulate Glutamate and GABA Neurotransmission onto Ventral Tegmental Dopamine Neurons during Cocaine Sensitization. Int J Mol Sci 2020; 21:E790. [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] [MESH Headings] [Grants] [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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Affiliation(s)
- Maria Carolina Velasquez-Martinez
- Grupo de Neurociencias y Comportamiento, Departamento de Ciencias Básicas, Facultad de Salud, Universidad Industrial de Santander, Bucaramanga 680006, Colombia;
| | - Bermary Santos-Vera
- Department of Biology, Cayey Campus, University of Puerto Rico, Cayey, PR 00737, USA;
| | - Maria E. Velez-Hernandez
- Department of Biological and Health Sciences, Texas A&M University-Kingsville, Kingsville, TX 78363, USA;
| | - Rafael Vazquez-Torres
- Department of Physiology, Medical Sciences Campus, University of Puerto Rico, San Juan, PR 00925, USA;
| | - Carlos A. Jimenez-Rivera
- Department of Physiology, Medical Sciences Campus, University of Puerto Rico, San Juan, PR 00925, USA;
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Roles of the G protein-coupled receptor kinase 2 and Rab5 in α 1B-adrenergic receptor function and internalization. Eur J Pharmacol 2020; 867:172846. [PMID: 31811856 DOI: 10.1016/j.ejphar.2019.172846] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2019] [Revised: 11/21/2019] [Accepted: 12/03/2019] [Indexed: 11/23/2022]
Abstract
Cells expressing eGFP-tagged Rab5 (wild-type or the GDP-Rab5 mutant) and the DsRed-tagged α1B-adrenergic receptors were employed and the roles of GRK2 were studied utilizing paroxetine and the dominant-negative mutant of GRK2 (DN-GRK2). The following parameters were studied: a) FRET (as an index of α1B-adrenergic receptor-Rab5 interaction): b) intracellular accumulation of DsRed fluorescence (receptor internalization); c) α1B-adrenergic receptor phosphorylation, and d) noradrenaline-induced increase in intracellular calcium concentration. Noradrenaline increased α1B-adrenergic receptor-Rab5 interaction, which was blocked by paroxetine and by expression of the dominant-negative GRK2 mutant. Similarly, paroxetine and expression of the DN-GRK2 or the GDP-Rab5 mutants markedly decreased receptor internalization, α1B-adrenergic receptor phosphorylation, and attenuated the ability of the adrenergic agonist to induce homologous desensitization (calcium signaling). The S406, 410,412A α1B-adrenergic receptor mutant did not reproduce the actions of GRK2 inhibition. The data indicate that GRK2 and Rab5 play key roles in α1B-adrenergic receptor phosphorylation, internalization, and desensitization. The possibility that Rab5 might form part of a signaling complex is suggested, as well as that GDP-Rab5 might interfere with the ability of GRK2 to catalyze α1B-adrenergic receptor phosphorylation.
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Hernández-Espinosa DA, Carmona-Rosas G, Alfonzo-Méndez MA, Alcántara-Hernández R, García-Sáinz JA. Sites phosphorylated in human α 1B-adrenoceptors in response to noradrenaline and phorbol myristate acetate. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2019; 1866:1509-1519. [PMID: 31325464 DOI: 10.1016/j.bbamcr.2019.07.006] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/26/2019] [Revised: 06/27/2019] [Accepted: 07/14/2019] [Indexed: 01/11/2023]
Abstract
Phosphorylation of the human α1B-adrenergic receptor (fused with the green fluorescent protein) was studied employing the inducible Flp-ln HEK293 T-Rex system for expression. Serine/alanine substitutions were performed in five sites corresponding to those previously identified as phosphorylation targets in the hamster ortholog. Desensitization was decreased in these mutants but receptor phosphorylation was still clearly detected. The protein phosphorylation of the wild-type receptor (fused to the green fluorescent protein) was studied, using mass spectrometry, under baseline and stimulated conditions (noradrenaline or phorbol myristate acetate). Basal phosphorylation was detected at sites located at the intracellular loop 3 and carboxyl terminus, and the number of sites detected increased under agonist activation and stimulation of protein kinase C. The phosphorylation patterns differed under the distinct conditions. Three of the phosphorylation sites detected in this work corresponded to those observed in the hamster receptor. The phosphorylation sites detected included the following: a) at the intracellular loop 3: serines 246, 248, 257, 267, and 277; and threonines 252, 264, and 268, and b) at the carboxyl terminus: serines 396, 400, 402, 406, 423, 425, 427, 455, and 470, and threonines 387, 392, 420, and 475. Our data indicate that complex phosphorylation patterns exist and suggest the possibility that such differences could be relevant in receptor function and subcellular localization.
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Affiliation(s)
- David A Hernández-Espinosa
- Departamento de Biología Celular y Desarrollo, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Ap. Postal 70-248, Ciudad de México CP 04510, Mexico
| | - Gabriel Carmona-Rosas
- Departamento de Biología Celular y Desarrollo, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Ap. Postal 70-248, Ciudad de México CP 04510, Mexico
| | - Marco A Alfonzo-Méndez
- Departamento de Biología Celular y Desarrollo, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Ap. Postal 70-248, Ciudad de México CP 04510, Mexico
| | - Rocío Alcántara-Hernández
- Departamento de Biología Celular y Desarrollo, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Ap. Postal 70-248, Ciudad de México CP 04510, Mexico
| | - J Adolfo García-Sáinz
- Departamento de Biología Celular y Desarrollo, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Ap. Postal 70-248, Ciudad de México CP 04510, Mexico.
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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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Alcántara-Hernández R, Adolfo García-Sáinz J. Effect of inhibitors of mitogen-activated protein kinase kinase on alpha(1B)-adrenoceptor phosphorylation. AUTONOMIC & AUTACOID PHARMACOLOGY 2009; 29:13-23. [PMID: 19302552 DOI: 10.1111/j.1474-8673.2009.00427.x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
1 Mitogen-activated protein kinases mediate hormone/neurotransmitter action on proliferation and differentiation and participate in receptor regulation. The effect of inhibitors of mitogen-activated kinase kinase (MEK) on alpha(1B)-adrenoceptor phosphorylation state and function was studied using different cell lines. It was observed that at nanomolar concentrations the MEK inhibitors, PD98059 (2'-amino-3'-methoxyflavone) and UO126 [1,4-(diamino-2,3-dicyano/1,4-bis-(2-aminophenylthio)-butadiene], increased alpha(1B)-adrenoceptor phosphorylation and diminished the functional response of this receptor to noradrenaline. These agents did not alter the action of lysophosphatidic acid. 2 Staurosporine (IC(50) approximately 0.8 nm) (a general protein kinase inhibitor) and bis-indolyl-maleimide I (IC(50) approximately 200 nm) (a selective protein kinase C inhibitor) inhibited PD98059-induced alpha(1B)-adrenoceptor phosphorylation. In contrast, neither wortmannin (phosphoinositide 3-kinase inhibitor) nor genistein (protein tyrosine kinase inhibitor) had any effect. The data suggest the possibility that MEK might exert control on the activity of the enzymes that regulate receptor phosphorylation, such as G-protein-coupled receptor kinases, protein kinase C or serine/threonine protein phosphatases. 3 Coimmunoprecipitation studies showed a constant association of total extracellular signal-regulated kinase 2 (ERK2) with alpha(1B)-adrenoceptors. Association of phospho-ERK 1/2 to alpha(1B)-adrenoceptors increased not only in response to agonist but also in response to agents that increase alpha(1B)-adrenoceptor and ERK1/2 phosphorylation [such as endothelin-1, phorbol 12-myristate-13-acetate (PMA) and epidermal growth factor (EGF)]; not surprisingly, PD98059 decreased this effect. 4 Our data show that blockade of MEK activity results in increased alpha(1B)-adrenoceptor phosphorylation, diminished adrenoceptor function and perturbation of receptor-ERK1/2 interaction.
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Affiliation(s)
- R Alcántara-Hernández
- Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, D.F., Mexico
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Molina-Muñoz T, Romero-Avila MT, Avendaño-Vázquez SE, García-Sáinz JA. Phosphorylation, desensitization and internalization of human alpha1B-adrenoceptors induced by insulin-like growth factor-I. Eur J Pharmacol 2007; 578:1-10. [PMID: 17915215 DOI: 10.1016/j.ejphar.2007.08.047] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2007] [Revised: 08/21/2007] [Accepted: 08/24/2007] [Indexed: 10/22/2022]
Abstract
The effect of insulin-like growth factor-I (IGF-I) on human alpha(1B)-adrenoceptor function, phosphorylation state and cellular location was studied. Rat-1 fibroblasts were transfected with a plasmid construction containing enhanced green fluorescent protein joined to the carboxyl terminus of the human alpha(1B)-adrenoceptor. Receptors were identified by radioligand binding and photoaffinity labeling, and were immunoprecipitated with an antiserum generated against the enhanced green fluorescent protein. The receptor was functional, as evidenced by noradrenaline action on intracellular calcium and inositol phosphate production. IGF-I had no significant effect by itself on these parameters but markedly reduced the effects of noradrenaline. IGF-I induced alpha(1B)-adrenoceptor phosphorylation, which was markedly reduced by the following agents: pertussis toxin, a metalloproteinase inhibitor, diphtheria toxin mutant CRM 197, an epidermal growth factor (EGF) receptor intrinsic kinase activity inhibitor, and by phosphoinositide 3-kinase and protein kinase C inhibitors. IGF-I action appears to involve activation of a pertussis toxin-sensitive G protein, shedding of heparin-binding EGF and autocrine activation of EGF receptors. G protein subunits and phosphotyrosine residues stimulate phosphoinositide 3-kinase activity leading to activation of protein kinase C, which in turn phosphorylates alpha(1B)-adrenoceptors. Confocal fluorescent microscopy showed that alpha(1B)-adrenoceptors fussed to the green fluorescent protein were located in plasma membrane and intracellular vesicles in the basal state. IGF-I induced receptor redistribution favoring the intracellular location; this effect was blocked by hypertonic sucrose and concanavalin A. Our data show that IGF-I induces alpha(1B)-adrenoceptor desensitization associated to receptor phosphorylation and internalization.
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Affiliation(s)
- Tzindilú Molina-Muñoz
- Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Apartado Postal 70-248, México D. F. 04510, Mexico
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García-Sáinz JA, Rodríguez-Pérez CE, Romero-Avila MT. Human alpha1D-adrenoceptor phosphorylation and desensitization. Biochem Pharmacol 2004; 67:1853-8. [PMID: 15130762 DOI: 10.1016/j.bcp.2004.01.025] [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] [Received: 11/14/2003] [Accepted: 01/23/2004] [Indexed: 11/17/2022]
Abstract
Rat-1 fibroblast were transfected with a plasmid containing the cDNA of the human alpha(1D)-adrenoceptor. A cell line was isolated that stably expressed the receptor as evidenced by BMY 7378-sensitive noradrenaline-induced increases in intracellular calcium concentration. The effect of noradrenaline was blocked by active phorbol esters; such blockade was mediated by protein kinase C (PKC) as evidenced by its inhibition by staurosporine or the downregulation of this protein kinase. Radioligand binding experiments showed expression of receptors with high affinity for [3H]tamsulosin (K(D) 0.30 +/- 0.05 nM) but low density (B(max) 35 +/- 4 fmol/mg protein). The receptors had the expected orders of potency for agonists (adrenaline = noradrenaline > oxymetazoline) and antagonists (BMY 7378 > 5-methyl-urapidil = phentolamine). Photoaffinity labeling identified the receptor as a band of M(r) 70-80kDa, which could be immunoprecipitated with a selective anti-alpha(1D)-adrenoceptor antiserum. In cells metabolically labeled with radioactive phosphate the adrenoceptor was identified as a phosphoprotein whose phosphorylation state was increased by the agonist, noradrenaline, and by phorbol myristate acetate. The data indicate that the human alpha(1D)-adrenoceptor function was regulated through phosphorylation by PKC.
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Affiliation(s)
- J Adolfo García-Sáinz
- Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Apartado Postal 70-248, Mexico D.F. 04510, Mexico.
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Romero-Avila MT, Flores-Jasso CF, García-Sáinz JA. alpha1B-Adrenergic receptor phosphorylation and desensitization induced by transforming growth factor-beta. Biochem J 2002; 368:581-7. [PMID: 12234252 PMCID: PMC1223020 DOI: 10.1042/bj20021052] [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: 07/03/2002] [Revised: 09/11/2002] [Accepted: 09/17/2002] [Indexed: 01/11/2023]
Abstract
Transforming growth factor-beta (TGF-beta) induced alpha(1B)-adrenergic receptor phosphorylation in Rat-1 fibroblasts stably expressing these adrenoceptors. This effect of TGF-beta was rapid, reaching a maximum within 30 min and decreasing thereafter, and concentration-dependent (EC(50) 0.3 pM). The phosphoinositide 3-kinase inhibitors wortmannin and LY294002, and the protein kinase C inhibitors staurosporine, Ro 318220 and bisindolylmaleimide, blocked the effect of this growth factor. alpha(1B)-Adrenergic receptor phosphorylation was associated with desensitization, as indicated by a reduction in the adrenergic-mediated production of [(3)H]inositol phosphates. Phosphorylation of alpha(1B)-adrenergic receptors by TGF-beta was also observed in Cos-1 cells transfected with the receptor. Co-transfection of the dominant-negative mutant of the regulatory subunit of phosphoinositide 3-kinase (Deltap85) inhibited the phosphorylation of alpha(1B)-adrenergic receptors induced by TGF-beta. Our results indicate that activation of TGF-beta receptors induces alpha(1B)-adrenergic receptor phosphorylation and desensitization. The data suggest that phosphoinositide 3-kinase and protein kinase C play key roles in this effect of TGF-beta.
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Affiliation(s)
- M Teresa Romero-Avila
- Instituto de Fisiologi;a Celular, Universidad Nacional Autónoma de México, Apartado Postal 70-248, México D.F. 04510
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Baker TL, Fuller DD, Zabka AG, Mitchell GS. Respiratory plasticity: differential actions of continuous and episodic hypoxia and hypercapnia. RESPIRATION PHYSIOLOGY 2001; 129:25-35. [PMID: 11738644 DOI: 10.1016/s0034-5687(01)00280-8] [Citation(s) in RCA: 83] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
The objectives of this paper are: (1) to review advances in our understanding of the mechanisms of respiratory plasticity elicited by episodic versus continuous hypoxia in short to intermediate time domains (min to h); and (2) to present new data suggesting that different patterns of hypercapnia also elicit distinct forms of respiratory plasticity. Episodic, but not continuous hypoxia elicits long-term facilitation (LTF) of respiratory motor output. Phrenic LTF is a serotonin-dependent central neural mechanism that requires: (a) activation of spinal serotonin receptors; and (b) spinal protein synthesis. Continuous and episodic hypercapnia also elicit different mechanisms of plasticity. Continuous, severe hypercapnia (25 min of approximately 10% inspired CO(2)) elicits long-term depression (LTD) of phrenic motor output (-33+/-8% at 60 min post-hypercapnia) in anesthetized rats. In contrast, 3,5 min hypercapnic episodes do not elicit LTD (9+/-17% at 60 min). We hypothesize that the response of respiratory motoneurons to serotonergic and noradrenergic modulation may contribute to pattern sensitivity to hypoxia and hypercapnia.
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Affiliation(s)
- T L Baker
- Center for Neuroscience, University of Wisconsin, 2015 Linden Drive West, Madison, WI 53706, USA.
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Bundey RA, Nahorski SR. Homologous and heterologous uncoupling of muscarinic M(3) and alpha(1B) adrenoceptors to Galpha(q/11) in SH-SY5Y human neuroblastoma cells. Br J Pharmacol 2001; 134:257-64. [PMID: 11564643 PMCID: PMC1572941 DOI: 10.1038/sj.bjp.0704229] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
1. The present study employed a [(35)S]-GTPgammaS binding protocol in conjunction with immunoprecipitation (IP) of the Galpha subunits to investigate the desensitization of G(q/11)-coupled receptors at the level of the G-protein activation. Membranes from SH-SY5Y cells expressing the recombinant human alpha(1B)-adrenoceptor (alpha(1B)-AR) (and endogenously expressing the M(3) muscarinic acetylcholine receptor (M(3)-AChR)) exhibited G(q/11) activation in a concentration-dependent manner in response to noradrenaline or methacholine. 2. Pre-treatment of intact cells with agonist prior to membrane preparation and use in the [(35)S]-GTPgammaS IP assay demonstrated that both receptors were homologously desensitized by pre-treatment with agonist since the G(q/11) activation in response to a secondary challenge with agonist was markedly reduced. Stimulation of alpha(1B)-AR was effective at heterologously desensitizing the M(3)-AChR. The PKC inhibitor, Ro-31-8220 (10 microM) was ineffective at preventing the agonist-mediated receptor desensitization. 3. [(32)P]P(i)-labelled cells allowed the detection of increases in receptor phosphorylation. Phorbol 12,13 dibutyrate (PDBu) (1 microM) was effective at producing a Ro-31-8220 (10 microM)-sensitive, detectable increase in alpha(1B)-AR but not M(3)-AChR phosphorylation. Noradrenaline (30 microM) stimulated alpha(1B)-AR phosphorylation, which could be partially inhibited by Ro-31-8220 (10 microM). The phosphorylation of M(3)-AChR was increased by methacholine (100 microM) incubation and this effect appeared to be insensitive to Ro-31-8220 (10 microM). 4. These findings demonstrate that [(35)S]-GTPgammaS-Galpha-subunit IP can be used to estimate receptor desensitization as a decline in receptor-G-protein coupling. Both the alpha(1B)-AR and M(3)-AChR undergo rapid homologous desensitization that is associated with an increase in receptor phosphorylation. The heterologous desensitization of M(3)-AChR produced by alpha(1B)-AR stimulation is not associated with a detectable increase in M(3)-AChR phosphorylation, suggesting that receptor phosphorylation is not necessarily a prerequisite for desensitization.
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Affiliation(s)
- R A Bundey
- Department of Cell Physiology and Pharmacology, Medical Sciences Building, University of Leicester, Leicester, LE1 9HN.
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García-Sáinz JA, Vázquez-Cuevas FG, Romero-Avila MT. Phosphorylation and desensitization of alpha1d-adrenergic receptors. Biochem J 2001; 353:603-10. [PMID: 11171057 PMCID: PMC1221606 DOI: 10.1042/0264-6021:3530603] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
In rat-1 fibroblasts stably expressing rat alpha(1d)-adrenoceptors, noradrenaline and PMA markedly decreased alpha(1d)-adrenoceptor function (noradrenaline-elicited increases in calcium in whole cells and [(35)S]guanosine 5'-[gamma-thio]triphosphate binding in membranes), suggesting homologous and heterologous desensitizations. Photoaffinity labelling, Western blotting and immunoprecipitation identified alpha(1d)-adrenoceptors as a broad band of 70-80 kDa. alpha(1d)-Adrenoceptors were phosphorylated in the basal state and noradrenaline and PMA increased it. The effect of noradrenaline was concentration-dependent (EC(50) 75 nM), rapid (maximum at 1 min) and transient. Phorbol ester-induced phosphorylation was concentration-dependent (EC(50) 25 nM), slightly slower (maximum at 5 min) and stable for at least 60 min. Inhibitors of protein kinase C decreased the effect of phorbol esters but not that of noradrenaline. Evidence of cross-talk of alpha(1d)-adrenoceptors with receptors endogenously expressed in rat-1 fibroblasts was given by the ability of endothelin, lysophosphatidic acid and bradykinin to induce alpha(1d)-adrenoceptor phosphorylation. In summary, it is shown for the first time here that alpha(1d)-adrenoceptors are phosphoproteins and that receptor phosphorylation is increased by the natural ligand, noradrenaline, by direct activation of protein kinase C and via cross-talk with other receptors endogenously expressed in rat-1 fibroblasts. Receptor phosphorylation has functional repercussions.
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Affiliation(s)
- J A García-Sáinz
- Departamento de Biología Celular, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Apartado Postal 70-248, México D.F. 04510.
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García-Sáinz JA, Vázquez-Prado J, del Carmen Medina L. Alpha 1-adrenoceptors: function and phosphorylation. Eur J Pharmacol 2000; 389:1-12. [PMID: 10686290 DOI: 10.1016/s0014-2999(99)00896-1] [Citation(s) in RCA: 91] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
This review focuses on alpha(1)-adrenoceptor phosphorylation and function. Most of what is currently known is based on studies on the hamster alpha(1B)-adrenoceptor. It is known that agonist stimulation leads to homologous desensitization of these receptors and current evidence indicates that such decrease in receptor activity is associated with receptor phosphorylation. Such receptor phosphorylation seems to involve G protein-receptor kinases and the receptor phosphorylation sites have been located in the carboxyl tail (Ser(404), Ser(408), and Ser(410)). There is also evidence showing that in addition to desensitization, receptor phosphorylation is associated with internalization and roles of beta-arrestins have been observed. Direct activation of protein kinase C leads to receptor desensitization/internalization associated with phosphorylation; the protein-kinase-C-catalyzed receptor phosphorylation sites have been also located in the carboxyl tail (Ser(394) and Ser(400)). Activation of G(q)-coupled receptors, such as the endothelin ET(A) receptor induces alpha(1B)-adrenoceptor phosphorylation and desensitization. Such effect involves protein kinase C and a yet unidentified tyrosine kinase. Activation of G(i)-coupled receptors, such as the lysophosphatidic acid receptor, also induces alpha(1B)-adrenoceptor phosphorylation and desensitization. These effects involve protein kinase C and phosphatidyl inositol 3-kinase. Interestingly, activation of epidermal growth factor receptors also induces alpha(1B)-adrenoceptor phosphorylation and desensitization involving protein kinase C and phosphatidyl inositol 3-kinase. A pivotal role of these kinases in heterologous desensitization is evidenced.
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Affiliation(s)
- J A García-Sáinz
- Departamento de Biología Celular, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México. Apartado postal 70-248, México, Mexico.
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