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Liao J, Li K, Su X, Chen Y, Wang Y, Tang X, Xing Y, Xu Y, Dai X, Teng J, Li H, Wang H, Lv X, Wang Y. Dexmedetomidine Promotes Lipopolysaccharide-Induced Differentiation of Cardiac Fibroblasts and Collagen I/III Synthesis through α 2A Adrenoreceptor-Mediated Activation of the PKC-p38-Smad2/3 Signaling Pathway in Mice. Int J Mol Sci 2021; 22:ijms222312749. [PMID: 34884552 PMCID: PMC8657501 DOI: 10.3390/ijms222312749] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2021] [Revised: 10/31/2021] [Accepted: 11/23/2021] [Indexed: 02/05/2023] Open
Abstract
Dexmedetomidine (DEX), a selective α2 adrenergic receptor (AR) agonist, is commonly used as a sedative drug during critical illness. In the present study, we explored a novel accelerative effect of DEX on cardiac fibroblast (CF) differentiation mediated by LPS and clarified its potential mechanism. LPS apparently increased the expression of α-SMA and collagen I/III and the phosphorylation of p38 and Smad-3 in the CFs of mice. These effects were significantly enhanced by DEX through increasing α2A-AR expression in CFs after LPS stimulation. The CFs from α2A-AR knockout mice were markedly less sensitive to DEX treatment than those of wild-type mice. Inhibition of protein kinase C (PKC) abolished the enhanced effects of DEX on LPS-induced differentiation of CFs. We also found that the α-SMA level in the second-passage CFs was much higher than that in the nonpassage and first-passage CFs. However, after LPS stimulation, the TNF-α released from the nonpassage CFs was much higher than that in the first- and second-passage CFs. DEX had no effect on LPS-induced release of TNF-α and IL-6 from CFs. Further investigation indicated that DEX promoted cardiac fibrosis and collagen I/III synthesis in mice exposed to LPS for four weeks. Our results demonstrated that DEX effectively accelerated LPS-induced differentiation of CFs to myofibroblasts through the PKC-p38-Smad2/3 signaling pathway by activating α2A-AR.
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Lv P, Chen T, Liu P, Zheng L, Tian J, Tan F, Chen J, Deng Y, Li J, Cai J, Chi X. Dexmedetomidine Attenuates Orthotopic Liver Transplantation-Induced Acute Gut Injury via α 2-Adrenergic Receptor-Dependent Suppression of Oxidative Stress. Oxid Med Cell Longev 2019; 2019:9426368. [PMID: 31827710 PMCID: PMC6885230 DOI: 10.1155/2019/9426368] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/23/2019] [Revised: 09/04/2019] [Accepted: 09/17/2019] [Indexed: 12/13/2022]
Abstract
Patients with orthotopic liver transplantation (OLT) frequently develop acute gut injury (AGI), and dexmedetomidine (Dex) has been reported to exert a protective effect against AGI. We investigated whether Dex protects against AGI through antioxidative stress effects by the Nrf2/HO-1 antioxidative signaling pathway. Rats were randomly allocated into a sham group and six orthotopic autologous liver transplantation (OALT) groups receiving different doses of Dex together with/without α 2-adrenergic receptor (AR) blockers. Intestinal tissues were collected to visualize the barrier damage and to measure the indexes of oxidative stress. For in vitro studies, rat intestinal recess epithelial cells (IEC-6) underwent hypoxia/reoxygenation (H/R), and the protective role of Dex was evaluated after α 2A-AR siRNA silencing. OALT resulted in increased oxidative stress, significant intestinal injury, and barrier dysfunction. Dex attenuated OALT-induced oxidative stress and intestinal injury, which was abolished by the pretreatment with the nonspecific α 2A-AR siRNA blocker atipamezole and the specific α 2A-AR siRNA blocker BRL-44408, but not by the specific 2B/C-AR siRNA blocker ARC239. Silencing of α 2A-AR siRNA also attenuated the protective role of Dex on alleviating oxidative stress in IEC-6 cells subjected to H/R. Dex exerted its protective effects by activating Nrf2/HO-1 antioxidative signaling. Collectively, Dex attenuates OALT-induced AGI via α 2A-AR-dependent suppression of oxidative stress, which might be a novel potential therapeutic target for OALT-induced AGI.
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Affiliation(s)
- Peibiao Lv
- Department of General Surgery, The Third Affiliated Hospital of Sun Yat-sen University, Yuedong Hospital, Meizhou, Guangdong 514700, China
| | - Tufeng Chen
- Department of Gastroenterological Surgery, The Third Affiliated Hospital of Sun Yat-sen University, Guangzhou, Guangdong 510630, China
| | - Peibin Liu
- Department of Anesthesiology, The Seventh Affiliated Hospital of Sun Yat-sen University, Shenzhen, Guangdong 518017, China
| | - Lei Zheng
- Department of Anesthesiology, The Seventh Affiliated Hospital of Sun Yat-sen University, Shenzhen, Guangdong 518017, China
| | - Jingling Tian
- Department of Anesthesiology, The Seventh Affiliated Hospital of Sun Yat-sen University, Shenzhen, Guangdong 518017, China
| | - Fan Tan
- Department of Anesthesiology, The Seventh Affiliated Hospital of Sun Yat-sen University, Shenzhen, Guangdong 518017, China
| | - Jiaxin Chen
- Department of Anesthesiology, The Seventh Affiliated Hospital of Sun Yat-sen University, Shenzhen, Guangdong 518017, China
| | - Yingqing Deng
- Department of Anesthesiology, The Seventh Affiliated Hospital of Sun Yat-sen University, Shenzhen, Guangdong 518017, China
| | - Jun Li
- Department of General Surgery, The Third Affiliated Hospital of Sun Yat-sen University, Yuedong Hospital, Meizhou, Guangdong 514700, China
| | - Jun Cai
- Department of Anesthesiology, The Third Affiliated Hospital of Sun Yat-sen University, Guangzhou, Guangdong 510630, China
| | - Xinjin Chi
- Department of Anesthesiology, The Seventh Affiliated Hospital of Sun Yat-sen University, Shenzhen, Guangdong 518017, China
- Department of Anesthesiology, The Third Affiliated Hospital of Sun Yat-sen University, Guangzhou, Guangdong 510630, China
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Yen HY, Hoi KK, Liko I, Hedger G, Horrell MR, Song W, Wu D, Heine P, Warne T, Lee Y, Carpenter B, Plückthun A, Tate CG, Sansom MSP, Robinson CV. PtdIns(4,5)P 2 stabilizes active states of GPCRs and enhances selectivity of G-protein coupling. Nature 2018; 559:423-427. [PMID: 29995853 PMCID: PMC6059376 DOI: 10.1038/s41586-018-0325-6] [Citation(s) in RCA: 190] [Impact Index Per Article: 31.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2017] [Accepted: 05/14/2018] [Indexed: 11/21/2022]
Abstract
G-protein-coupled receptors (GPCRs) are involved in many physiological processes and are therefore key drug targets1. Although detailed structural information is available for GPCRs, the effects of lipids on the receptors, and on downstream coupling of GPCRs to G proteins are largely unknown. Here we use native mass spectrometry to identify endogenous lipids bound to three class A GPCRs. We observed preferential binding of phosphatidylinositol-4,5-bisphosphate (PtdIns(4,5)P2) over related lipids and confirm that the intracellular surface of the receptors contain hotspots for PtdIns(4,5)P2 binding. Endogenous lipids were also observed bound directly to the trimeric Gαsβγ protein complex of the adenosine A2A receptor (A2AR) in the gas phase. Using engineered Gα subunits (mini-Gαs, mini-Gαi and mini-Gα12)2, we demonstrate that the complex of mini-Gαs with the β1 adrenergic receptor (β1AR) is stabilized by the binding of two PtdIns(4,5)P2 molecules. By contrast, PtdIns(4,5)P2 does not stabilize coupling between β1AR and other Gα subunits (mini-Gαi or mini-Gα12) or a high-affinity nanobody. Other endogenous lipids that bind to these receptors have no effect on coupling, highlighting the specificity of PtdIns(4,5)P2. Calculations of potential of mean force and increased GTP turnover by the activated neurotensin receptor when coupled to trimeric Gαiβγ complex in the presence of PtdIns(4,5)P2 provide further evidence for a specific effect of PtdIns(4,5)P2 on coupling. We identify key residues on cognate Gα subunits through which PtdIns(4,5)P2 forms bridging interactions with basic residues on class A GPCRs. These modulating effects of lipids on receptors suggest consequences for understanding function, G-protein selectivity and drug targeting of class A GPCRs.
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MESH Headings
- Animals
- GTP-Binding Protein alpha Subunits, Gi-Go/metabolism
- GTP-Binding Protein alpha Subunits, Gs/metabolism
- Heterotrimeric GTP-Binding Proteins/metabolism
- Humans
- Molecular Dynamics Simulation
- Phosphatidylinositol 4,5-Diphosphate/metabolism
- Protein Stability
- Rats
- Receptors, Adrenergic, alpha-2/chemistry
- Receptors, Adrenergic, alpha-2/genetics
- Receptors, Adrenergic, alpha-2/metabolism
- Receptors, Adrenergic, beta-1/chemistry
- Receptors, Adrenergic, beta-1/genetics
- Receptors, Adrenergic, beta-1/metabolism
- Receptors, G-Protein-Coupled/chemistry
- Receptors, G-Protein-Coupled/genetics
- Receptors, G-Protein-Coupled/metabolism
- Receptors, Neurotensin/chemistry
- Receptors, Neurotensin/genetics
- Receptors, Neurotensin/metabolism
- Single-Chain Antibodies/chemistry
- Single-Chain Antibodies/metabolism
- Substrate Specificity
- Turkeys
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Affiliation(s)
- Hsin-Yung Yen
- Chemical Research Laboratory, University of Oxford, Oxford, UK
- OMass Technologies, Kidlington, UK
| | - Kin Kuan Hoi
- Chemical Research Laboratory, University of Oxford, Oxford, UK
| | - Idlir Liko
- Chemical Research Laboratory, University of Oxford, Oxford, UK
- OMass Technologies, Kidlington, UK
| | - George Hedger
- Department of Biochemistry, University of Oxford, Oxford, UK
| | | | - Wanling Song
- Department of Biochemistry, University of Oxford, Oxford, UK
| | - Di Wu
- Chemical Research Laboratory, University of Oxford, Oxford, UK
| | - Philipp Heine
- Biochemisches Institut, Universität Zürich, Zurich, Switzerland
| | - Tony Warne
- MRC Laboratory of Molecular Biology, Cambridge, UK
| | - Yang Lee
- MRC Laboratory of Molecular Biology, Cambridge, UK
| | - Byron Carpenter
- MRC Laboratory of Molecular Biology, Cambridge, UK
- Warwick Integrative Synthetic Biology Centre, School of Life Sciences, The University of Warwick, Coventry, UK
| | | | | | - Mark S P Sansom
- Department of Biochemistry, University of Oxford, Oxford, UK.
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Shelkar GP, Gakare SG, Chakraborty S, Dravid SM, Ugale RR. Interactions of nitric oxide with α2 -adrenoceptors within the locus coeruleus underlie the facilitation of inhibitory avoidance memory by agmatine. Br J Pharmacol 2016; 173:2589-99. [PMID: 27273730 PMCID: PMC4978159 DOI: 10.1111/bph.13531] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2015] [Revised: 05/20/2016] [Accepted: 05/27/2016] [Indexed: 01/23/2023] Open
Abstract
BACKGROUND AND PURPOSE Agmatine, a putative neurotransmitter, plays a vital role in learning and memory. Although it is considered an endogenous ligand of imidazoline receptors, agmatine exhibits high affinity for α-adrenoceptors, NOS and NMDA receptors. These substrates within the locus coeruleus (LC) are critically involved in learning and memory processes. EXPERIMENTAL APPROACH The hippocampus and LC of male Wistar rat were stereotaxically cannulated for injection. Effects of agmatine, given i.p. or intra-LC, on acquisition, consolidation and retrieval of inhibitory avoidance (IA) memory were measured. The NO donor S-nitrosoglutathione, non-specific (L-NAME) and specific NOS inhibitors (L-NIL, 7-NI, L-NIO), the α2 -adrenoceptor antagonist (yohimbine) or the corresponding agonist (clonidine) were injected intra-LC before agmatine. Intra-hippocampal injections of the NMDA antagonist, MK-801 (dizocilpine), were used to modify the memory enhancing effects of agmatine, SNG and yohimbine. Expression of tyrosine hydroxylase (TH) and eNOS in the LC was assessed immunohistochemically. KEY RESULTS Agmatine (intra-LC or i.p.) facilitated memory retrieval in the IA test. S-nitrosoglutathione potentiated, while L-NAME and L-NIO decreased, these effects of agmatine. L-NIL and 7-NI did not alter the effects of agmatine. Yohimbine potentiated, whereas clonidine attenuated, effects of agmatine within the LC. The effects of agmatine, S-nitrosoglutathione and yohimbine were blocked by intra-hippocampal MK-801. Agmatine increased the population of TH- and eNOS-immunoreactive elements in the LC. CONCLUSIONS AND IMPLICATIONS The facilitation of memory retrieval in the IA test by agmatine is probably mediated by interactions between eNOS, NO and noradrenergic pathways in the LC.
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Affiliation(s)
- Gajanan P Shelkar
- Division of Neuroscience, Department of Pharmacology, Shrimati Kishoritai Bhoyar College of Pharmacy, Nagpur, Maharashtra, India
- Department of Pharmaceutical Sciences, Rashtrasant Tukadoji Maharaj Nagpur University, Nagpur, India
| | - Sukanya G Gakare
- Department of Pharmaceutical Sciences, Rashtrasant Tukadoji Maharaj Nagpur University, Nagpur, India
| | - Suwarna Chakraborty
- Division of Neuroscience, Department of Pharmacology, Shrimati Kishoritai Bhoyar College of Pharmacy, Nagpur, Maharashtra, India
| | | | - Rajesh R Ugale
- Division of Neuroscience, Department of Pharmacology, Shrimati Kishoritai Bhoyar College of Pharmacy, Nagpur, Maharashtra, India
- Department of Pharmaceutical Sciences, Rashtrasant Tukadoji Maharaj Nagpur University, Nagpur, India
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Sansoè G, Aragno M, Mastrocola R, Mengozzi G, Parola M. Alpha-2A Adrenoceptor Agonist Guanfacine Restores Diuretic Efficiency in Experimental Cirrhotic Ascites: Comparison with Clonidine. PLoS One 2016; 11:e0158486. [PMID: 27384184 PMCID: PMC4934922 DOI: 10.1371/journal.pone.0158486] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2016] [Accepted: 06/16/2016] [Indexed: 01/09/2023] Open
Abstract
BACKGROUND In human cirrhosis, adrenergic hyperfunction causes proximal tubular fluid retention and contributes to diuretic-resistant ascites, and clonidine, a sympatholytic drug, improves natriuresis in difficult-to-treat ascites. AIM To compare clonidine (aspecific α2-adrenoceptor agonist) to SSP-002021R (prodrug of guanfacine, specific α2A-receptor agonist), both associated with diuretics, in experimental cirrhotic ascites. METHODS AND RESULTS Six groups of 12 rats were studied: controls (G1); controls receiving furosemide and potassium canrenoate (G2); rats with ascitic cirrhosis due to 14-week CCl4 treatment (G3); cirrhotic rats treated (over the 11th-14th CCl4 weeks) with furosemide and canrenoate (G4), furosemide, canrenoate and clonidine (G5), or diuretics and SSP002021R (G6). Three rats of each group had their hormonal status and renal function assessed at the end of 11th, 12th, 13th, and 14th weeks of respective treatments.Cirrhotic rats in G3 and G4 gained weight over the 12th-14th CCl4 weeks. In G4, brief increase in sodium excretion over the 11th-12th weeks preceded worsening of inulin clearance and natriuresis (diuretic resistance). In comparison with G4, the addition of clonidine (G5) or guanfacine (G6) to diuretics improved, respectively, sodium excretion over the 11th-12th CCl4 weeks, or GFR and electrolytes excretion over the 13th-14th CCl4 weeks. Natriuretic responses in G5 and G6 were accompanied by reduced catecholamine serum levels. CONCLUSIONS α2A-receptor agonists restore glomerular filtration rate and natriuresis, and delay diuretic-resistant ascites in experimental advanced cirrhosis. Clonidine ameliorates diuretic-dependent natriuresis just for a short time.
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Affiliation(s)
- Giovanni Sansoè
- Division of Gastroenterology, Gradenigo Hospital, Torino, Italy
- * E-mail:
| | - Manuela Aragno
- Department of Clinical and Biological Sciences, University of Torino, Torino, Italy
| | - Raffaella Mastrocola
- Department of Clinical and Biological Sciences, University of Torino, Torino, Italy
| | - Giulio Mengozzi
- Clinical Biochemistry Laboratory, San Giovanni Battista Hospital, Torino, Italy
| | - Maurizio Parola
- Department of Clinical and Biological Sciences, University of Torino, Torino, Italy
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Komiyama T, Hirokawa T, Sato K, Oka A, Kamiguchi H, Nagata E, Sakura H, Otsuka K, Kobayashi H. Relationship between human evolution and neurally mediated syncope disclosed by the polymorphic sites of the adrenergic receptor gene α2B-AR. PLoS One 2015; 10:e0120788. [PMID: 25860977 PMCID: PMC4393242 DOI: 10.1371/journal.pone.0120788] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2014] [Accepted: 02/06/2015] [Indexed: 11/18/2022] Open
Abstract
The objective of this study was to clarify the effects of disease on neurally mediated syncope (NMS) during an acute stress reaction. We analyzed the mechanism of the molecular interaction and the polymorphisms of the alpha-2 adrenoreceptor (α2B-AR) gene as the potential psychiatric cause of incentive stress. We focused on the following three genotypes of the repeat polymorphism site at Glu 301-303 in the α2B-AR gene: Glu12/12, Glu12/9, and Glu9/9. On the basis of our clinical research, NMS is likely to occur in people with the Glu12/9 heterotype. To verify this, we assessed this relationship with the interaction of Gi protein and adenylate cyclase by in silico analysis of the Glu12/9 heterotype. By measuring the difference in the dissociation time of the Gi-α subunit twice, we found that the Glu12/9 heterotype suppressed the action of adenylate cyclase longer than the Glu homotypes. As this difference in the Glu repeat number effect is thought to be one of the causes of NMS, we investigated the evolutionary significance of the Glu repeat number. Glu8 was originally repeated in simians, while the Glu12 repeats occurred over time during the evolution of bipedalism in humans. Taken with the Glu12 numbers, NMS would likely become a defensive measure to prevent significant blood flow to the human brain.
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MESH Headings
- Alleles
- Animals
- Base Sequence
- DNA/analysis
- DNA/isolation & purification
- DNA, Mitochondrial/analysis
- DNA, Mitochondrial/classification
- Epinephrine/blood
- Evolution, Molecular
- Female
- GTP-Binding Protein alpha Subunits, Gi-Go/metabolism
- Gene Frequency
- Genotype
- Humans
- Male
- Norepinephrine/blood
- Phylogeny
- Polymorphism, Single Nucleotide
- Primates/genetics
- Protein Binding
- Protein Structure, Secondary
- Protein Structure, Tertiary
- Receptors, Adrenergic, alpha-2/chemistry
- Receptors, Adrenergic, alpha-2/genetics
- Receptors, Adrenergic, alpha-2/metabolism
- Syncope, Vasovagal/metabolism
- Syncope, Vasovagal/pathology
- Thermodynamics
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Affiliation(s)
- Tomoyoshi Komiyama
- Department of Clinical Pharmacology, Tokai University School of Medicine, 143 Shimokasuya, Isehara, Kanagawa, 259–1193, Japan
| | - Takatsugu Hirokawa
- The National Institute of Advanced Industrial Science and Technology (AIST), Tokyo Waterfront Bio-IT Research Building 2-4-7 Aomi, Koto-ku, Tokyo, 135–0064, Japan
| | - Kyoko Sato
- Tokyo Women’s Medical University Medical Center East, 2-1-10 Higashiogu, Arakawa-ku, Tokyo, 116–8567, Japan
| | - Akira Oka
- The Institute of Medical Science, Tokai University, 143 Shimokasuya, Isehara, Kanagawa, 259–1193, Japan
| | - Hiroshi Kamiguchi
- Support Center for Medical Research and Education, Tokai University, 143 Shimokasuya, Isehara, Kanagawa, 259–1193, Japan
| | - Eiichiro Nagata
- Department of Neurology, Tokai University School of Medicine, 143 Shimokasuya, Isehara, Kanagawa, 259–1193, Japan
| | - Hiroshi Sakura
- Tokyo Women’s Medical University Medical Center East, 2-1-10 Higashiogu, Arakawa-ku, Tokyo, 116–8567, Japan
| | - Kuniaki Otsuka
- Tokyo Women’s Medical University Medical Center East, 2-1-10 Higashiogu, Arakawa-ku, Tokyo, 116–8567, Japan
| | - Hiroyuki Kobayashi
- Department of Clinical Pharmacology, Tokai University School of Medicine, 143 Shimokasuya, Isehara, Kanagawa, 259–1193, Japan
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Pawlowski M, Saraswathi S, Motawea HKB, Chotani MA, Kloczkowski A. In silico modeling of human α2C-adrenoreceptor interaction with filamin-2. PLoS One 2014; 9:e103099. [PMID: 25110951 PMCID: PMC4128582 DOI: 10.1371/journal.pone.0103099] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2014] [Accepted: 06/19/2014] [Indexed: 12/19/2022] Open
Abstract
Vascular smooth muscle α2C-adrenoceptors (α2C-ARs) mediate vasoconstriction of small blood vessels, especially arterioles. Studies of endogenous receptors in human arteriolar smooth muscle cells (referred to as microVSM) and transiently transfected receptors in heterologous HEK293 cells show that the α2C-ARs are perinuclear receptors that translocate to the cell surface under cellular stress and elicit a biological response. Recent studies in microVSM unraveled a crucial role of Rap1A-Rho-ROCK-F-actin pathways in receptor translocation, and identified protein-protein interaction of α2C-ARs with the actin binding protein filamin-2 as an essential step in the process. To better understand the molecular nature and specificity of this interaction, in this study, we constructed comparative models of human α2C-AR and human filamin-2 proteins. Finally, we performed in silico protein-protein docking to provide a structural platform for the investigation of human α2C-AR and filamin-2 interactions. We found that electrostatic interactions seem to play a key role in this complex formation which manifests in interactions between the C-terminal arginines of α2C-ARs (particularly R454 and R456) and negatively charged residues from filamin-2 region between residues 1979 and 2206. Phylogenetic and sequence analysis showed that these interactions have evolved in warm-blooded animals.
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Affiliation(s)
- Marcin Pawlowski
- Battelle Center for Mathematical Medicine, The Research Institute at Nationwide Children's Hospital, Columbus, Ohio, United States of America
| | - Saras Saraswathi
- Battelle Center for Mathematical Medicine, The Research Institute at Nationwide Children's Hospital, Columbus, Ohio, United States of America
| | - Hanaa K. B. Motawea
- Center for Cardiovascular and Pulmonary Research, The Research Institute at Nationwide Children's Hospital, Columbus, Ohio, United States of America
- Department of Pharmacology & Toxicology, Helwan University, Helwan, Egypt
| | - Maqsood A. Chotani
- Center for Cardiovascular and Pulmonary Research, The Research Institute at Nationwide Children's Hospital, Columbus, Ohio, United States of America
- Department of Pediatrics, The Ohio State University, Columbus, Ohio, United States of America
| | - Andrzej Kloczkowski
- Battelle Center for Mathematical Medicine, The Research Institute at Nationwide Children's Hospital, Columbus, Ohio, United States of America
- Department of Pediatrics, The Ohio State University, Columbus, Ohio, United States of America
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De Fusco M, Vago R, Striano P, Di Bonaventura C, Zara F, Mei D, Kim MS, Muallem S, Chen Y, Wang Q, Guerrini R, Casari G. The α2B-adrenergic receptor is mutant in cortical myoclonus and epilepsy. Ann Neurol 2014; 75:77-87. [PMID: 24114805 PMCID: PMC3932827 DOI: 10.1002/ana.24028] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2012] [Revised: 07/02/2013] [Accepted: 07/12/2013] [Indexed: 12/20/2022]
Abstract
OBJECTIVE Autosomal dominant cortical myoclonus and epilepsy (ADCME) is characterized by distal, fairly rhythmic myoclonus and epilepsy with variable severity. We have previously mapped the disease locus on chromosome 2p11.1-q12.2 by genome-wide linkage analysis. Additional pedigrees affected by similar forms of epilepsy have been associated with chromosomes 8q, 5p, and 3q, but none of the causing genes has been identified. We aim to identify the mutant gene responsible for this form of epilepsy. METHODS Genes included in the ADCME critical region were directly sequenced. Coimmunoprecipitation, immunofluorescent, and electrophysiologic approaches to transfected human cells have been utilized for testing the functional significance of the identified mutation. RESULTS Here we show that mutation in the α2 -adrenergic receptor subtype B (α2B -AR) is associated with ADCME by identifying a novel in-frame insertion/deletion in 2 Italian families. The mutation alters several conserved residues of the third intracellular loop, hampering neither the α2B -AR plasma membrane localization nor the arrestin-mediated internalization capacity, but altering the binding with the scaffolding protein spinophilin upon neurotransmitter activation. Spinophilin, in turn, regulates interaction of G protein coupled receptors with regulator of G protein signaling proteins. Accordingly, the mutant α2B -AR increases the epinephrine-stimulated calcium signaling. INTERPRETATION The identified mutation is responsible for ADCME, as the loss of α2B -AR/spinophilin interaction causes a gain of function effect. This work implicates for the first time the α-adrenergic system in human epilepsy and opens new ways of understanding the molecular pathway of epileptogenesis, widening the spectrum of possible therapeutic targets.
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Affiliation(s)
- Maurizio De Fusco
- Center for Translational Genomics and Bioinformatics, San Raffaele Scientific Institute, and Vita-Salute San Raffaele University, Milan, Italy
| | - Riccardo Vago
- Center for Translational Genomics and Bioinformatics, San Raffaele Scientific Institute, and Vita-Salute San Raffaele University, Milan, Italy
| | - Pasquale Striano
- Pediatric Neurology and Muscular Diseases Unit, Department of Neurosciences, Rehabilitation, Ophtalmology, Genetics, Maternal and Child Health, University of Genoa, “G. Gaslini” Institute, Genova, Italy
| | | | - Federico Zara
- Laboratory of Neurogenetics, Department of Neurosciences, “G. Gaslini” Institute, Genova, Italy
| | - Davide Mei
- Pediatric Neurology Unit and Laboratories, Children's Hospital A. Meyer-University of Florence, Florence
| | - Min Seuk Kim
- Department of Oral Physiology, School of Dentistry, Wonkwang University, Iksan, Jeonbuk, Republic of Korea
| | - Shmuel Muallem
- Epithelial Signaling and Transport Section, Molecular Physiology and Therapeutics Branch, National Institute of Dental and Craniofacial Research, National Institute of Health, Bethesda MD, 20892
| | - Yunjia Chen
- Department of Cell, Developmental and Integrative Biology, University of Alabama at Birmingham, Birmingham, AL, USA
| | - Qin Wang
- Department of Cell, Developmental and Integrative Biology, University of Alabama at Birmingham, Birmingham, AL, USA
| | - Renzo Guerrini
- Pediatric Neurology Unit and Laboratories, Children's Hospital A. Meyer-University of Florence, Florence
- IRCCS Stella Maris, Pisa, Italy
| | - Giorgio Casari
- Center for Translational Genomics and Bioinformatics, San Raffaele Scientific Institute, and Vita-Salute San Raffaele University, Milan, Italy
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Sandal M, Duy TP, Cona M, Zung H, Carloni P, Musiani F, Giorgetti A. GOMoDo: A GPCRs online modeling and docking webserver. PLoS One 2013; 8:e74092. [PMID: 24058518 PMCID: PMC3772745 DOI: 10.1371/journal.pone.0074092] [Citation(s) in RCA: 69] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2013] [Accepted: 07/26/2013] [Indexed: 11/19/2022] Open
Abstract
G-protein coupled receptors (GPCRs) are a superfamily of cell signaling membrane proteins that include >750 members in the human genome alone. They are the largest family of drug targets. The vast diversity and relevance of GPCRs contrasts with the paucity of structures available: only 21 unique GPCR structures have been experimentally determined as of the beginning of 2013. User-friendly modeling and small molecule docking tools are thus in great demand. While both GPCR structural predictions and docking servers exist separately, with GOMoDo (GPCR Online Modeling and Docking), we provide a web server to seamlessly model GPCR structures and dock ligands to the models in a single consistent pipeline. GOMoDo can automatically perform template choice, homology modeling and either blind or information-driven docking by combining together proven, state of the art bioinformatic tools. The web server gives the user the possibility of guiding the whole procedure. The GOMoDo server is freely accessible at http://molsim.sci.univr.it/gomodo.
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Affiliation(s)
- Massimo Sandal
- Department of Biotechnology, University of Verona, Ca’ Vignal 1, Verona, Italy
| | - Tran Phuoc Duy
- Laboratory of Computational Physics, University of Technology, Vietnam National University, Ho Chi Minh City, Vietnam
| | - Matteo Cona
- Department of Biotechnology, University of Verona, Ca’ Vignal 1, Verona, Italy
| | - Hoang Zung
- Laboratory of Computational Physics, University of Science, Vietnam National University, Ho Chi Minh City, Vietnam
| | - Paolo Carloni
- Computational Biophysics, German Research School for Simulation Sciences, Jülich, Germany
- Institute for Advanced Simulation, Forschungszentrum Jülich, Jülich, Germany
| | - Francesco Musiani
- Scuola Internazionale Superiore di Studi Avanzati (Sissa/ISAS), Trieste, Italy
| | - Alejandro Giorgetti
- Department of Biotechnology, University of Verona, Ca’ Vignal 1, Verona, Italy
- Computational Biophysics, German Research School for Simulation Sciences, Jülich, Germany
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10
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Fan Y, Li C, Guo J, Hu G, Wu G. A single lys residue on the first intracellular loop modulates the endoplasmic reticulum export and cell-surface expression of α2A-adrenergic receptor. PLoS One 2012; 7:e50416. [PMID: 23227171 PMCID: PMC3515576 DOI: 10.1371/journal.pone.0050416] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2012] [Accepted: 10/19/2012] [Indexed: 12/03/2022] Open
Abstract
Export from the endoplasmic reticulum (ER) represents an initial step in intracellular trafficking of G protein-coupled receptors (GPCRs). However, the underlying molecular mechanisms remain poorly understood. We have previously demonstrated that a highly conserved Leu residue on the first intracellular loop (ICL1) is required for exit of several GPCRs from the ER. Here we found that, in addition to Leu64 residue in the ICL1, the neighboring positively charged residue Lys65also modulates the cell-surface transport of α2A-adrenergic receptor (α2A-AR). Mutation of Lys65 to Ala, Glu and Gln significantly attenuated, whereas mutation of Lys65 to Arg strongly augmented α2A-AR expression at the cell surface. Consistent with the effects on the cell-surface expression of α2A-AR, mutation of Lys65 to Ala and Arg produced opposing effects on α2A-AR-mediated ERK1/2 activation. Furthermore, confocal microscopy revealed that the α2A-AR mutant K65A displayed a strong intracellular expression pattern and was extensively co-localized with the ER marker DsRed2-ER, suggestive of ER accumulation. These data provide the first evidence indicating an important function for a single Lys residue on the ICL1 in the ER export and cell-surface expression of α2A-AR. These data also suggest that the ICL1 may possess multiple signals that control the cell-surface targeting of GPCRs via distinct mechanisms.
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Affiliation(s)
- Yi Fan
- Department of Pharmacology and Toxicology, Georgia Health Sciences University, Augusta, Georgia, United States of America
| | - Chunman Li
- Department of Pharmacology and Toxicology, Georgia Health Sciences University, Augusta, Georgia, United States of America
| | - Jianhui Guo
- Department of Pharmacology and Toxicology, Georgia Health Sciences University, Augusta, Georgia, United States of America
| | - Gang Hu
- Department of Pharmacology, Nanjing Medical University, Nanjing, China
| | - Guangyu Wu
- Department of Pharmacology and Toxicology, Georgia Health Sciences University, Augusta, Georgia, United States of America
- * E-mail:
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11
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Affiliation(s)
- Ralf Gilsbach
- Pharmakologie und Toxikologie, Universität Freiburg, Albertstraße 25, D-79104 Freiburg i. Br
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12
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Ostopovici-Halip L, Curpăn R, Mracec M, Bologa CG. Structural determinants of the alpha2 adrenoceptor subtype selectivity. J Mol Graph Model 2011; 29:1030-8. [PMID: 21602069 PMCID: PMC3307019 DOI: 10.1016/j.jmgm.2011.04.011] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2010] [Revised: 04/26/2011] [Accepted: 04/27/2011] [Indexed: 11/18/2022]
Abstract
Alpha2-adrenergic receptor (α2-AR) subtypes, acting mainly on the central nervous and cardiovascular systems, represent important targets for drug design, confirmed by the high number of studies published so far. Presently, only a few α2-AR subtype selective compounds are known. Using homology modeling and ligand docking, the present study analyzes the similarities and differences between binding sites, and between extracellular loops of the three subtypes of α2-ARs. Several α2-AR subtype selective ligands were docked into the active sites of the three α2-AR subtypes, key interactions between ligands and receptors were mapped, and the predicted results were compared with the available experimental data. Binding site analysis reveals a strong identity between important amino acid residues in each receptor, the very few differences being the key toward modulating selectivity of α2-AR ligands. The observed differences between binding site residues provide an excellent starting point for virtual screening of chemical databases, in order to identify potentially selective ligands for α2-ARs.
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Affiliation(s)
- Liliana Ostopovici-Halip
- Computational Chemistry Department, Institute of Chemistry Timisoara, M. Viteazu 24, 300223, Romania.
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13
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Kurnik D, Muszkat M, Li C, Sofowora GG, Friedman EA, Scheinin M, Wood AJJ, Stein CM. Genetic variations in the α(2A)-adrenoreceptor are associated with blood pressure response to the agonist dexmedetomidine. ACTA ACUST UNITED AC 2011; 4:179-87. [PMID: 21325151 DOI: 10.1161/circgenetics.110.957662] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
BACKGROUND α(2A)-Adrenoceptors (α(2A)-ARs) have important roles in sympathetic cardiovascular regulation. Variants of ADRA2A affect gene transcription and expression and are associated with insulin release and risk for type 2 diabetes. We examined whether ADRA2A variants are also associated with cardiovascular responses to the selective α(2)-AR-agonist dexmedetomidine. METHODS AND RESULTS Seventy-three healthy subjects participated in a placebo-controlled, single-blind study. After 3 infusions of placebo, subjects received 3 incremental infusions of dexmedetomidine (cumulative dose, 0.4 μg/kg). Primary outcomes were changes in systolic blood pressure (SBP) and plasma norepinephrine concentrations, measured as difference of the area-under-the-curve during placebo and dexmedetomidine infusions (ΔAUC). We used multiple linear regression analysis to examine the associations between 9 ADRA2A tagging variants and 5 inferred haplotypes and ΔAUC after adjustment for covariates. Homozygous carriers of rs553668 and the corresponding haplotype 4, previously associated with increased α(2A)-AR expression, had a 2.2-fold greater decrease in AUC(SBP) after dexmedetomidine (adjusted P=0.006); similarly, the maximum decrease in SBP was 24.7±8.1 mm Hg compared with 13.6±5.9 mm Hg in carriers of the wild-type allele (P=0.007). Carriers of haplotype 3, previously associated with reduced α(2A)-AR expression, had a 44% smaller decrease in AUC(SBP) (P=0.013). Haplotype information significantly improved the model predicting the decrease in SBP (P<0.001). There were similar but nonsignificant trends for diastolic blood pressure and heart rate. Genotypes were not significantly associated with norepinephrine responses. CONCLUSIONS Common ADRA2A variants are associated with the hypotensive response to dexmedetomidine. Effects of specific variants/haplotypes in vivo are compatible with their known effects on gene expression in vitro.
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Affiliation(s)
- Daniel Kurnik
- Department of Medicine, Vanderbilt University School of Medicine, Nashville, TN 37232, USA
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14
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Ma G, Bavadekar SA, Schaneberg BT, Khan IA, Feller DR. Effects of synephrine and beta-phenethylamine on human alpha-adrenoceptor subtypes. Planta Med 2010; 76:981-986. [PMID: 20217639 DOI: 10.1055/s-0029-1240884] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Synephrine and beta-phenethylamine, two naturally occurring compounds, are structurally related to ephedrine. In this study, the effects of synephrine and beta-phenethylamine on alpha-adrenergic receptor (alpha-AR) subtypes are investigated in human embryonic kidney (HEK293) or Chinese hamster ovary (CHO) cells, and compared to that of 1R,2S-norephedrine. The rank order of binding affinities was found to be the same for the subtypes tested (alpha(1A)-, alpha(2A)-, and alpha(2C)-AR) viz, 1R,2S-norephedrine > beta-phenethylamine > synephrine. Functional studies on the alpha(1A)-AR subtype showed that synephrine was a partial agonist giving a maximal response at 100 microM that was equal to 55.3 % of the L-phenylephrine maximum. In contrast, neither 1R,2S-norephedrine nor beta-phenethylamine exhibited agonist activity at the highest concentration tested (300 microM). beta-Phenethylamine was more potent as an antagonist than 1R,2S-norephedrine and synephrine on the alpha(1A)-AR subtype. Functional studies on the alpha(2A)- and alpha(2C)-AR subtypes indicated that synephrine and beta-phenethylamine did not act as agonists. Similar to 1R,2S-norephedrine, both of these analogs reversed the effect of medetomidine against forskolin-induced cAMP elevations at 300 microM, and the rank order of antagonist potency was: 1R,2S-norephedrine = beta-phenethylamine > synephrine; and beta-phenethylamine > 1R,2S-norephedrine > synephrine, respectively. These differences suggest that the presence of a 4-hydroxy group, as in synephrine, reduced the potency in these subtypes. In conclusion, at the alpha(1A)-AR, synephrine acted as a partial agonist, while beta-phenethylamine did not exhibit any direct agonist activity. Both, synephrine and beta-phenethylamine, may act as antagonists of pre-synaptic alpha(2A/2C)-ARs present in nerve terminals.
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Affiliation(s)
- Guoyi Ma
- The National Center for Natural Products Research, The University of Mississippi, University, MS 38677, USA
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15
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Abstract
G-protein coupled receptors (GPCRs) form a ternary complex of agonist, receptor and G-proteins during primary signal transduction at the cell membrane. Downstream signalling is thought to be preceded by the process of dissociation of Galpha and Gbetagamma subunits, thus exposing new surfaces to interact with downstream effectors. We demonstrate here for the first time, the dissociation of heterotrimeric G-protein subunits (i.e., Galpha and Gbetagamma) following agonist-induced GPCR (alpha(2A)-adrenergic receptor; alpha(2A)-AR) activation in a cell-free assay system. alpha(2A)-AR membranes were reconstituted with the G-proteins (+/-hexahistidine-tagged) Galpha(i1) and Gbeta1gamma2 and functional signalling was determined following activation of the reconstituted receptor:G-protein complex with the potent agonist UK-14304, and [35S]GTPgammaS. In the presence of Ni(2+)-coated agarose beads, the activated his-tagged Galpha(i1)his-[35S]GTPgammaS complex was captured on the Ni(2+)-presenting surface. When his-tagged Gbeta1gamma2 (Gbeta1gamma2his) was used with Galpha(i1), the [35S]GTPgammaS-bound Galpha(i1) was not present on the Ni(2+)-coated beads, but rather, it was separated from the beta1gamma2(his)-beads, demonstrating receptor-induced dissociation of Galpha and Gbetagamma subunits. Treatment of the reconstituted alpha(2A)-AR membranes containing Gbeta1gamma2his:Galpha(i1) with imidazole confirmed the specificity for the Ni2+:G-protein surface dissociation of Galpha(i1) from Gbeta1gamma2his. These data demonstrate for the first time, the complete dissociation of the G-protein subunits and extend observations on the role of G-proteins in the assembly and disassembly of the ternary complex in the primary events of GPCR signalling.
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Affiliation(s)
- Wayne R Leifert
- CSIRO Molecular and Health Technologies, Adelaide, SA, Australia.
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16
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Grunewald GL, Seim MR, Bhat SR, Wilson ME, Criscione KR. Synthesis of 4,5,6,7-tetrahydrothieno[3,2-c]pyridines and comparison with their isosteric 1,2,3,4-tetrahydroisoquinolines as inhibitors of phenylethanolamine N-methyltransferase. Bioorg Med Chem 2008; 16:542-59. [PMID: 18024134 PMCID: PMC2269732 DOI: 10.1016/j.bmc.2007.08.066] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2007] [Revised: 08/23/2007] [Accepted: 08/28/2007] [Indexed: 11/30/2022]
Abstract
A series of substituted 4,5,6,7-tetrahydrothieno[3,2-c]pyridines (THTPs) was synthesized and evaluated for their human phenylethanolamine N-methyltransferase (hPNMT) inhibitory potency and affinity for the alpha(2)-adrenoceptor. The THTP nucleus was suggested as an isosteric replacement for the 1,2,3,4-tetrahydroisoquinoline (THIQ) ring system on the basis that 3-thienylmethylamine (18) was more potent as an inhibitor of hPNMT and more selective toward the alpha(2)-adrenoceptor than benzylamine (15). Although the isosterism was confirmed, with similar influence of functional groups and chirality in both systems on hPNMT inhibitory potency and selectivity, the THTP compounds proved, in general, to be less potent as inhibitors of hPNMT than their THIQ counterparts, with the drop in potency being primarily attributed to the electronic properties of the thiophene ring. A hypothesis for the reduced hPNMT inhibitory potency of these compounds has been formed on the basis of molecular modeling and docking studies using the X-ray crystal structures of hPNMT co-crystallized with THIQ-type inhibitors and S-adenosyl-L-homocysteine as a template.
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Affiliation(s)
- Gary L Grunewald
- Department of Medicinal Chemistry, The University of Kansas, Lawrence, KS 66045, USA.
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17
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Knaus AE, Muthig V, Schickinger S, Moura E, Beetz N, Gilsbach R, Hein L. α2-Adrenoceptor subtypes—Unexpected functions for receptors and ligands derived from gene-targeted mouse models. Neurochem Int 2007; 51:277-81. [PMID: 17664025 DOI: 10.1016/j.neuint.2007.06.036] [Citation(s) in RCA: 90] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2007] [Indexed: 11/22/2022]
Abstract
Alpha2-adrenoceptors belong to the group of nine adrenoceptors which mediate the biological actions of the endogenous catecholamines adrenaline and noradrenaline. Studies with gene-targeted mice carrying deletions in the genes encoding alpha2A-, alpha2B- or alpha2C-adrenoceptors have provided new insight into adrenergic receptor biology: (1) In principle, all three alpha2-receptor subtypes may operate as presynaptic inhibitory feedback receptors to control the release of noradrenaline and adrenaline or other transmitters from neurons. (2) Pharmacological effects of non-selective alpha2-ligands could be assigned to specific receptor subtypes, e.g. hypotension, sedation and analgesia are mediated via alpha2A-receptors. (3) Alpha2-adrenoceptor deficient mice have helped to uncover novel and unexpected functions of these receptor, e.g. feedback control of catecholamine release via alpha2C-receptors in adrenal chromaffin cells and control of angiogenesis during embryonic development. (4) Additional pharmacological targets for alpha2-adrenoceptor ligands were identified, e.g. inhibition of cardiac HCN2 and HCN4 pacemaker channels by clonidine.
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MESH Headings
- Animals
- Chromaffin Cells/metabolism
- Gene Targeting
- Ligands
- Mice
- Mice, Knockout
- Receptors, Adrenergic, alpha-2/chemistry
- Receptors, Adrenergic, alpha-2/drug effects
- Receptors, Adrenergic, alpha-2/genetics
- Receptors, Presynaptic/chemistry
- Receptors, Presynaptic/genetics
- Receptors, Presynaptic/metabolism
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Affiliation(s)
- Anne E Knaus
- Institute of Experimental and Clinical Pharmacology, University of Freiburg, Albertstrasse 25, 79104 Freiburg, Germany
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18
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Balogh B, Jójárt B, Wágner Z, Kovács P, Máté G, Gyires K, Zádori Z, Falkay G, Márki A, Viskolcz B, Mátyus P. 3D QSAR models for α2a-adrenoceptor agonists☆. Neurochem Int 2007; 51:268-76. [PMID: 17643557 DOI: 10.1016/j.neuint.2007.05.021] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2007] [Accepted: 05/25/2007] [Indexed: 11/28/2022]
Abstract
Three-dimensional structure-activity relationship studies of alpha2a-adrenoceptor agonists were carried out by Distance Comparison (DISCOthech) and Comparative Molecular Field Analysis (CoMFA) methods to define the pharmacophore and a quantitative model, respectively, of this class of compounds. The statistical validation of the CoMFA model indicates its high predictive performance for binding affinities of new alpha2a-adrenoceptor agonists.
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Affiliation(s)
- Balázs Balogh
- Department of Organic Chemistry, Semmelweis University, Hogyes E.u. 7, 1095 Budapest, Hungary
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19
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Balau LS, Vahlberg C, Petoral RM, Uvdal K. Mixed monolayers to promote g-protein adsorption: alpha2A-adrenergic receptor-derived peptides coadsorbed with formyl-terminated oligopeptides. Langmuir 2007; 23:8474-9. [PMID: 17622157 DOI: 10.1021/la063447f] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/16/2023]
Abstract
Pure and mixed monolayers of a synthetic peptide, GPR-i3n, derived from the third intracellular loop of the alpha2 adrenergic receptor and a shorter inactive oligopeptide, N-formyl-(Gly)3-(Cys) (called 3GC), were prepared on gold surfaces. The mixing ratio of the GPR-i3n and 3GC was used to control G-protein binding capability. The GPR-i3n peptide is specially designed for bovine G-protein selectivity and has been proven to have high affinity to G-proteins [Vahlberg, C.; Petoral, R. M., Jr.; Lindell, C.; Broo, K.; Uvdal, K. Langmuir 2006, 22 (17), 7260-7264]. Pure 3GC monolayers show very low protein adsorption capability. In this study, 3GC is chosen as a coadsorbent, with the aim to induce molecular conformational changes during monolayer formation to enhance G-protein adsorption. A full characterization of the mixed monolayers was done. The monolayer thickness and the mass-related surface coverage for both GPR-i3n and 3GC were investigated using radio labeling. The GPR-i3n was labeled by 125I-targeting tyrosine, and the activity was measured by using radioimmunoassay (RIA). The formation and chemical composition of GPR-i3n and 3GC monolayers were investigated using X-ray photoelectron spectroscopy, and it is shown that both GPR-i3n and 3GC bind chemically to the gold surface. The interaction between the mixed monolayers and G-proteins was investigated by means of real-time surface plasmon resonance. There is a higher protein binding capacity to the monolayer when the GPR-i3n peptide is intermixed with the 3GC coadsorbent, despite the fact that the 3GC itself has a very low G-protein binding capability. This supports a molecular reorientation at the surface, while 3GC is intermixed with GPR-i3n.
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Affiliation(s)
- Luminita Savitchi Balau
- Division of Sensor Science and Molecular Physics, Department of Physics, Chemistry and Biology, IFM, Linköping University, SE-581 83 Linköping, Sweden
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20
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Affiliation(s)
- Balázs Balogh
- Department of Organic Chemistry, Semmelweis University, Hogyes E. u. 7. 1095 Budapest, Hungary
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21
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Weber B, Schaper C, Scholz J, Bein B, Rodde C, H Tonner P. Interaction of the amyloid precursor like protein 1 with the alpha2A-adrenergic receptor increases agonist-mediated inhibition of adenylate cyclase. Cell Signal 2006; 18:1748-57. [PMID: 16531006 DOI: 10.1016/j.cellsig.2006.01.017] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2005] [Revised: 01/24/2006] [Accepted: 01/24/2006] [Indexed: 10/24/2022]
Abstract
Alpha2-adrenergic receptor agonists exert potent analgesic and sedative/hypnotic effects. In addition, they have been shown to be neuroprotective, but the mechanisms of these actions are still poorly defined. To isolate proteins that may control alpha2-adrenergic receptor function or trafficking, we performed a two-hybrid screen using the carboxy-terminal fourth intracellular tail of the alpha2A-adrenergic receptor as bait. This screen identified the amyloid precursor like protein 1 (APLP1), a homologue of the beta-amyloid precursor protein involved in Alzheimer's disease, as alpha2A-adrenergic receptor-binding protein. GST affinity chromatography revealed that APLP1 specifically interacts with all three human alpha2-adrenergic receptor subtypes and deletion mutant analysis confined the APLP1 domain involved in binding to alpha2-adrenergic receptors to the 13 amino acid residues Ser599-Ala611. Coimmunoprecipitations of transiently transfected cells with epitope-tagged APLP1 and alpha2-adrenergic receptors confirmed the interaction. Agonist treatment tended to increase the amount of alpha2A-adrenergic receptor associated with APLP1 while coimmunoprecipitations were not affected by the state of receptor phosphorylation or cotransfection of arrestin-3. Confocal laser microscopy showed that APLP1 causes a considerable shift of the alpha2A-adrenergic receptor localization from plasma membrane to intracellular compartments. Furthermore, cotransfection of alpha2A-adrenergic receptor and APLP1 into HEK293 cells significantly increased norepinephrine mediated inhibition of adenylate cyclase activity. These results suggest a possible role of APLP1 in regulation of alpha2A-adrenergic receptor trafficking. Moreover, we speculate that this interaction may present one mechanism by which alpha2-adrenergic receptor agonists exert their neuroprotective effects.
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Affiliation(s)
- Bernd Weber
- Department of Anaesthesiology and Intensive Care Medicine, University Hospital Schleswig-Holstein, Campus Kiel, Schwanenweg 21, 24105 Kiel, Germany.
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22
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Abstract
The studies on the intrinsic structural determinants for export trafficking of G protein-coupled receptors (GPCRs) have been mainly focused on the C termini of the receptors. In this report we determined the role of the extracellular N termini of alpha(2)-adrenergic receptors (alpha(2)-ARs) in the anterograde transport from the endoplasmic reticulum (ER) through the Golgi to the cell surface. The N-terminal-truncated alpha(2B)-AR mutant is completely unable to target to the cell surface. A single Met-6 residue is essential for the export of alpha(2B)-AR from the ER, likely through modulating correct alpha(2B)-AR folding in the ER. The Tyr-Ser motif, highly conserved in the membrane-proximal N termini of all alpha(2)-AR subtypes, is required for the exit of alpha(2A)-AR and alpha(2B)-AR from the Golgi apparatus, thus representing a novel Tyr-based motif modulating GPCR transport at the Golgi level. These data provide the first evidence indicating an essential role of the N termini of GPCRs in the export from distinct intracellular compartments along the secretory pathway.
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Affiliation(s)
- Chunmin Dong
- Department of Pharmacology and Experimental Therapeutics, Louisiana State University Health Sciences Center, 1901 Perdido Street, New Orleans, LA 70112, USA
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23
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Vahlberg C, Petoral RM, Lindell C, Broo K, Uvdal K. alpha(2A)-adrenergic receptor derived peptide adsorbates: a G-protein interaction study. Langmuir 2006; 22:7260-4. [PMID: 16893224 DOI: 10.1021/la052801r] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
The affinity of alpha(2A)-adrenergic receptor (alpha(2A)-AR) derived peptide adsorbates for the functional bovine brain G-protein is studied in the search for the minimum sequence recognition. Three short peptides (GPR-i2c, GPR-i3n, and GPR-i3c) are designed to mimic the second and third intracellular loops of the receptor. X-ray photoelectron spectroscopy is used to study the chemical composition of the peptides and the binding strength to the surfaces. Chemisorption of the peptides to the gold substrates is observed. Infrared spectroscopy is used to study the characteristic absorption bands of the peptides. The presence of peptides on the surfaces is verified by prominent amide I and amide II bands. The interaction between the peptides and the G-protein is studied with surface plasmon resonance. It is shown that GPR-i3n has the highest affinity for the G-protein. Equilibrium analysis of the binding shows that the G-protein keeps its native conformation when interacting with GPR-i3c, but during the interaction with GPR-i2c and GPR-i3n the conformation of G-protein is changed, leading to the formation of aggregates and/or multilayers.
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Affiliation(s)
- Cecilia Vahlberg
- Division of Molecular Physics, Department of Physics, Chemistry and Biology (IFM), Linköping University, SE-58183 Linköping, Sweden
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24
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Nikolaev VO, Hoffmann C, Bünemann M, Lohse MJ, Vilardaga JP. Molecular basis of partial agonism at the neurotransmitter alpha2A-adrenergic receptor and Gi-protein heterotrimer. J Biol Chem 2006; 281:24506-11. [PMID: 16787921 DOI: 10.1074/jbc.m603266200] [Citation(s) in RCA: 82] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
To characterize the mechanism by which heterotrimeric G-proteins interpret the signals coming from various neurotransmitters of diverse efficacies (agonists and partial agonists) acting on alpha(2A)-adrenergic receptors, we used a fluorescent resonance energy transfer-based approach to study the effects of these partial agonists on the activation process of both the alpha(2A)-adrenergic receptor and its cognate G(i)-protein. We show that ligands of different efficacies switch the receptor into distinct conformational states, which in turn set the speed and extent of the G(i)-protein signaling. Thus, in cells the efficacy by which a receptor responds to diverse ligands is caused by the ability of the G-protein to differentiate between distinct receptor conformations. The data provide a new key characteristic underlying the mechanism of partial agonism at G-protein-coupled receptors.
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Affiliation(s)
- Viacheslav O Nikolaev
- Institute of Pharmacology and Toxicology, University of Würzburg, D-97078, Würzburg, Germany
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25
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Prinster SC, Holmqvist TG, Hall RA. Alpha2C-adrenergic receptors exhibit enhanced surface expression and signaling upon association with beta2-adrenergic receptors. J Pharmacol Exp Ther 2006; 318:974-81. [PMID: 16757535 DOI: 10.1124/jpet.106.106526] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The alpha(2C)-adrenergic receptor (alpha(2C)AR) is known to be poorly trafficked to the cell surface when expressed in a variety of cell types. We tested the hypothesis that the surface expression and signaling of alpha(2C)AR might be enhanced by heterodimerization with other G protein-coupled receptors (GPCRs). Cotransfection of alpha(2C)AR with more than 25 related GPCRs revealed that only coexpression with the beta(2)-adrenergic receptor (beta(2)AR) increased the surface localization of alpha(2C)AR in human embryonic kidney-293 cells. Coimmunoprecipitation of alpha(2C)AR with beta(2)AR confirmed a physical interaction between the two receptors. Confocal microscopy studies demonstrated that alpha(2C)AR expressed alone was mainly intracellular, whereas alpha(2C)AR coexpressed with beta(2)AR was predominantly localized to the plasma membrane. Ligand binding studies revealed a significant increase in alpha(2C)AR binding sites upon coexpression with beta(2)AR, with no apparent change in affinity for alpha(2)AR ligands. Functional assays with the alpha(2)AR-specific agonist brimonidine (UK 14,304) revealed that coexpression of beta(2)AR with alpha(2C)AR enhanced alpha(2C)AR-mediated activation of extracellular signal-regulated kinase 1/2. Furthermore, analyses of agonist-promoted receptor endocytosis demonstrated enhanced alpha(2C)AR internalization in response to alpha(2)AR agonists when alpha(2C)AR and beta(2)AR were coexpressed. In addition, substantial cointernalization of alpha(2C)AR in response to betaAR agonists was observed when alpha(2C)AR was coexpressed with beta(2)AR. These data reveal that alpha(2C)AR can interact with beta(2)AR in cells in a manner that regulates alpha(2C)AR surface expression, internalization, and functionality.
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MESH Headings
- Cells, Cultured
- Dimerization
- Humans
- Receptors, Adrenergic, alpha-2/analysis
- Receptors, Adrenergic, alpha-2/chemistry
- Receptors, Adrenergic, alpha-2/physiology
- Receptors, Adrenergic, beta-2/chemistry
- Receptors, Adrenergic, beta-2/physiology
- Receptors, G-Protein-Coupled/chemistry
- Signal Transduction/physiology
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Affiliation(s)
- Steven C Prinster
- Department of Pharmacology, Emory University School of Medicine, Atlanta, GA 30322, USA
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26
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Abstract
Using fluorescence resonance energy transfer (FRET) microscopy, we investigate how heterotrimeric G proteins interact with G protein-coupled receptors (GPCRs). In the absence of receptor activation, the alpha2A adrenergic and muscarinic M4 receptors are present on the cell membrane as dimers. Furthermore, there is an interaction between the G protein subunits alpha o, beta1, and gamma2 and a number of GPCRs including M4, alpha2A, the adenosine A1 receptor, and the dopamine D2 receptor under resting conditions. The interaction between GPCRs and Galpha proteins shows specificity: there is interaction between the alpha2A receptor and Go, but little interaction between the alpha2A receptor and Gs. In contrast, the predominantly Gs-coupled prostacyclin receptor interacted with Gs, but there was little interaction between the prostacyclin receptor and Go. Inverse agonists did not change the FRET ratio, whereas the addition of agonist resulted in a modest fall. Our work suggests that GPCR dimers and the G protein heterotrimer are present at the cell membrane in the resting state in a pentameric complex.
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Affiliation(s)
- Muriel Nobles
- British Heart Foundation Laboratories and Department of Medicine, University College London, 5 University Street, London WC1E 6JJ, United Kingdom
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27
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Jaakola VP, Vainio M, Sen S, Rehn M, Heimo H, Scheinin M, Goldman A. Intracellularly truncated human alpha2B-adrenoceptors: stable and functional GPCRs for structural studies. J Recept Signal Transduct Res 2005; 25:99-124. [PMID: 16149769 DOI: 10.1081/rrs-200068745] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
All three alpha2-adrenoceptor subtypes have a long third intracellular loop (3i), which is conserved by overall size and charge-hydrophobic properties but not by amino acid sequence similarity. These properties must be relevant for function and structure, because they have been preserved during hundreds of millions of years of evolution. The contribution of different loop portions to agonist/antagonist binding properties and G protein coupling of the human alpha2B-adrenoceptor (alpha2B-AR) was investigated with a series of 3i truncated constructs (delta3i). We used a variety of agonists/antagonists in competition binding assays. We stimulated alpha2B-AR delta3i with various agonists and measured [35S]GTPgammaS binding in isolated cell membranes with or without antagonist inhibition. We also evaluated the ability of oligopeptides, analogous to the amino and carboxyl terminal parts of 3i, to promote G protein activation, monitored with the [35S]GTPgammaS assay. Our results reveal that the carboxyl end residues of 3i, R360(6.24) to V372(6.36), are important for Gi/Go protein activation. Deletions in regions from G206(5.72) to R245(5.110) altered the binding of some alpha2B-AR agonists, indicating that agonist binding is dependent on the conformation of the 3i domain, possibly through the involvement of G protein interactions. The truncated receptor constructs may be more stable on purification and thus be useful for structural characterization of alpha2B-AR.
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Affiliation(s)
- Veli-Pekka Jaakola
- Institute of Biotechnology, Biocenter 3, University of Helsinki, Helsinki, Finland
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28
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Grunewald GL, Romero FA, Seim MR, Criscione KR, Deupree JD, Spackman CC, Bylund DB. Exploring the active site of phenylethanolamine N-methyltransferase with 3-hydroxyethyl- and 3-hydroxypropyl-7-substituted-1,2,3,4-tetrahydroisoquinolines. Bioorg Med Chem Lett 2005; 15:1143-7. [PMID: 15686930 DOI: 10.1016/j.bmcl.2004.12.013] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2004] [Revised: 11/30/2004] [Accepted: 12/06/2004] [Indexed: 11/16/2022]
Abstract
3-Hydroxyethyl- and 3-hydroxypropyl-7-substituted-tetrahydroisoquinolines (9, 10, 16, and 17) were synthesized and evaluated for their phenylethanolamine N-methyltransferase (PNMT) inhibitory potency and affinity for the alpha(2)-adrenoceptor. Although alpha(2)-adrenoceptor affinity decreased for these compounds, selectivity was not gained over the parent 3-hydroxymethyl compounds (1, 2) due to a loss in PNMT inhibitory potency.
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Affiliation(s)
- Gary L Grunewald
- Department of Medicinal Chemistry, University of Kansas, 1251 Wescoe Hall Drive, Lawrence, KS 66045, USA.
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29
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Zhou F, Filipeanu CM, Duvernay MT, Wu G. Cell-surface targeting of alpha2-adrenergic receptors -- inhibition by a transport deficient mutant through dimerization. Cell Signal 2005; 18:318-27. [PMID: 15961277 PMCID: PMC2718052 DOI: 10.1016/j.cellsig.2005.05.014] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2005] [Revised: 05/04/2005] [Accepted: 05/04/2005] [Indexed: 01/08/2023]
Abstract
We previously demonstrated that the alpha2B-adrenergic receptor mutant, in which the F(x)6IL motif in the membrane-proximal carboxyl terminus were mutated to alanines (alpha2B-ARm), is deficient in export from the endoplasmic reticulum (ER). In this report, we determined if alpha2B-ARm could modulate transport from the ER to the cell surface and signaling of its wild-type counterpart. Transient expression of alpha2B-ARm in HEK293T cells markedly inhibited cell-surface expression of wild-type alpha2B-AR, as measured by radioligand binding. Subcellular localization demonstrated that alpha2B-ARm trapped alpha2B-AR in the ER. The alpha2B-AR was shown to form homodimers and heterodimers with alpha2B-ARm as measured by co-immunoprecipitation of the receptors tagged with green fluorescent protein and hemagglutinin epitopes. In addition to alpha2B-AR, the transport of alpha2A-AR and alpha2C-AR to the cell surface was also inhibited by alpha2B-ARm. Furthermore, transient expression of alpha2B-ARm significantly reduced cell-surface expression of endogenous alpha2-AR in NG108-15 and HT29 cells. Consistent with its effect on alpha2-AR cell-surface expression, alpha2B-ARm attenuated alpha2A-AR- and alpha2B-AR-mediated ERK1/2 activation. These data demonstrated that the ER-retained mutant alpha2B-ARm conferred a dominant negative effect on the cell-surface expression of wild-type alpha2-AR, which is likely mediated through heterodimerization. These data indicate a crucial role of ER export in the regulation of cell-surface targeting and signaling of G protein-coupled receptors.
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Affiliation(s)
| | | | | | - Guangyu Wu
- Corresponding author. Tel.: +1 504 568 2236; fax: +1 504 568 2361. E-mail address: (G. Wu)
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30
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Ruuskanen JO, Laurila J, Xhaard H, Rantanen VV, Vuoriluoto K, Wurster S, Marjamäki A, Vainio M, Johnson MS, Scheinin M. Conserved structural, pharmacological and functional properties among the three human and five zebrafish alpha 2-adrenoceptors. Br J Pharmacol 2005; 144:165-77. [PMID: 15655522 PMCID: PMC1575993 DOI: 10.1038/sj.bjp.0706057] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
1. Zebrafish has five distinct alpha(2)-adrenoceptors. Two of these, alpha(2Da) and alpha(2Db), represent a duplicated, fourth alpha(2)-adrenoceptor subtype, while the others are orthologue of the human alpha(2A)-, alpha(2B)- and alpha(2C)-adrenoceptors. Here, we have compared the pharmacological properties of these receptors to infer structural determinants of ligand interactions. 2. The zebrafish alpha(2)-adrenoceptors were expressed in Chinese hamster ovary cells and tested in competitive ligand binding assays and in a functional assay (agonist-stimulated [(35)S]GTPgammaS binding). The affinity results were used to cluster the receptors and, separately, the ligands using both principal component analysis and binary trees. 3. The overall ligand binding characteristics, the order of potency and efficacy of the tested agonists and the G-protein coupling of the zebrafish and human alpha(2)-adrenoceptors, separated by approximately 350 million years of evolution, were found to be highly conserved. The binding affinities of the 20 tested ligands towards the zebrafish alpha(2)-adrenoceptors are generally comparable to those of their human counterparts, with a few compounds showing up to 40-fold affinity differences. 4. The alpha(2A) orthologues and the zebrafish alpha(2D) duplicates clustered as close pairs, but the relationships between the orthologues of alpha(2B) and alpha(2C) were not clearly defined. Applied to the ligands, our clustering methods segregated the ligands based on their chemical structures and functional properties. As the ligand binding pockets formed by the transmembrane helices show only minor differences among the alpha(2)-adrenoceptors, we suggest that the second extracellular loop--where significant sequence variability is located --might contribute significantly to the observed affinity differences.
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Affiliation(s)
- Jori O Ruuskanen
- Department of Pharmacology and Clinical Pharmacology, University of Turku, Itäinen Pitkäkatu 4 B, Turku FI-20520, Finland
- Turku Graduate School of Biomedical Sciences, University of Turku, Turku, Finland
| | - Jonne Laurila
- Department of Pharmacology and Clinical Pharmacology, University of Turku, Itäinen Pitkäkatu 4 B, Turku FI-20520, Finland
| | - Henri Xhaard
- Department of Biochemistry and Pharmacy, Åbo Akademi University, Turku, Finland
| | - Ville-Veikko Rantanen
- Department of Biochemistry and Pharmacy, Åbo Akademi University, Turku, Finland
- Department of Mathematics, University of Turku, Turku, Finland
| | - Karoliina Vuoriluoto
- Department of Pharmacology and Clinical Pharmacology, University of Turku, Itäinen Pitkäkatu 4 B, Turku FI-20520, Finland
| | | | - Anne Marjamäki
- Department of Pharmacology and Clinical Pharmacology, University of Turku, Itäinen Pitkäkatu 4 B, Turku FI-20520, Finland
| | - Minna Vainio
- Department of Pharmacology and Clinical Pharmacology, University of Turku, Itäinen Pitkäkatu 4 B, Turku FI-20520, Finland
| | - Mark S Johnson
- Department of Biochemistry and Pharmacy, Åbo Akademi University, Turku, Finland
| | - Mika Scheinin
- Department of Pharmacology and Clinical Pharmacology, University of Turku, Itäinen Pitkäkatu 4 B, Turku FI-20520, Finland
- Author for correspondence:
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31
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Chen WK, Chang NCA, Chang YH, Chang KL, Wu SC, Yang TS, Wu SM, Chang AC. Characterization of the regulatory region of Adra2c, the gene encoding the murine alpha2C adrenoceptor subtype. J Biomed Sci 2005; 11:886-901. [PMID: 15591786 DOI: 10.1007/bf02254374] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2004] [Accepted: 06/29/2004] [Indexed: 01/17/2023] Open
Abstract
The 5' flanking sequence (3,227 base pairs, bp) of the mouse Adra2c subtype gene was determined and characterized. The transcription start site was mapped to nucleotide 'A' of two initiator motifs in tandem array, i.e. 1,159 and 1,153 bp upstream from the initiation codon of the open reading frame (ORF) of Adra2c, respectively. One structural feature salient to the 5' regulatory region of Adra2c is present in the sequence 1 kb immediately upstream from the receptor ORF, which is highly enriched in GC content (76%) and CpG island counts (i.e. CpG/GpC, 146:177), and thus rich in Sp1-binding motifs. At the 3' flanking region, the polyadenylation signal was mapped to 481 bp downstream from the termination codon. The transcript defined by sequence data thereby is consistent with a size of 3 kb (brain form) determined by Northern blot analysis. The transgene, Adra2c-NN- lacZ, which links the promoter region of Adra2c to the lacZ reporter gene, was constructed in order to evaluate the functional capacity of the promoter and the putative motifs residing within the defined regulatory region (1.9 kb upstream from the ORF) in directing the reporter gene expression in vitro in transiently transfected cells and in vivo in transgenic (Tg) mice. Permissive cell types to Adra2c-NN include those derived from neural and kidney lineages. Significant Adra2c-NN-driven reporter expression in Tg mice established suggests that alpha2C adrenoceptor expression is permissive under Adra2c-NN in central (cerebral cortex, hippocampus, subthalamus, hypothalamus, superior colliculus, cerebellum, and brain stem) and peripheral (pancreatic beta-islets) tissues.
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MESH Headings
- Amino Acid Motifs
- Animals
- Base Sequence
- Blotting, Northern
- Blotting, Southern
- Brain/metabolism
- Central Nervous System/metabolism
- Cloning, Molecular
- Codon
- Computational Biology
- CpG Islands
- Gene Library
- Gene Transfer Techniques
- Genes, Reporter
- Humans
- Islets of Langerhans/metabolism
- Lac Operon
- Mice
- Mice, Transgenic
- Models, Genetic
- Molecular Sequence Data
- Nucleic Acid Hybridization
- Open Reading Frames
- Polymerase Chain Reaction
- Promoter Regions, Genetic
- Receptors, Adrenergic, alpha-2/chemistry
- Receptors, Adrenergic, alpha-2/metabolism
- Reverse Transcriptase Polymerase Chain Reaction
- Tissue Distribution
- Transcription Factors
- Transcription, Genetic
- Transfection
- Transgenes
- beta-Galactosidase/metabolism
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Affiliation(s)
- Wen-Kwei Chen
- Institute of Microbiology and Immunology, National Yang-Ming University, Taipei, ROC
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32
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Zhu Q, Qi LJ, Shi A, Abou-Samra A, Deth RC. Protein kinase C regulates alpha(2A/D)-adrenoceptor constitutive activity. Pharmacology 2005; 71:80-90. [PMID: 15118347 DOI: 10.1159/000076944] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2003] [Accepted: 10/14/2003] [Indexed: 11/19/2022]
Abstract
We investigated a possible role for protein kinases in the constitutive activity of alpha(2A/D) adrenoceptors in membranes from transfected PC12 cells, using a [35S]GTPgammaS binding assay. After treatment of intact cells with various protein kinase inhibitors, constitutive activity was assessed by the reduction in basal GTP binding caused by the inverse agonist rauwolscine (RAU). Inhibitors of protein kinase C (PKC) caused the loss of RAU-sensitive GTP binding, while inhibitors of other protein kinases were ineffective. Anti-G(alpha) antibody treatments showed that constitutive alpha(2A/D)-receptor activity is directed toward different G proteins than agonist-stimulated activity. T373A mutant receptors exhibited increased constitutive activity, including a component that was insensitive to PKC inhibition. Since T373 is located within a putative G(i/o) activator sequence, these results suggest that PKC-dependent phosphorylation of T373 increases alpha(2A/D)-adrenergic receptor constitutive activity and causes a switch in G protein preference.
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MESH Headings
- Adrenergic alpha-Antagonists/pharmacology
- Animals
- Antibodies/pharmacology
- Constitutive Androstane Receptor
- Epinephrine/pharmacology
- GTP-Binding Proteins/antagonists & inhibitors
- GTP-Binding Proteins/chemistry
- GTP-Binding Proteins/metabolism
- Humans
- Mutation, Missense
- PC12 Cells
- Protein Conformation
- Protein Kinase C/antagonists & inhibitors
- Protein Kinase C/genetics
- Protein Kinase C/metabolism
- Rats
- Receptors, Adrenergic, alpha-2/chemistry
- Receptors, Adrenergic, alpha-2/genetics
- Receptors, Adrenergic, alpha-2/metabolism
- Receptors, Cytoplasmic and Nuclear/chemistry
- Receptors, Cytoplasmic and Nuclear/genetics
- Receptors, Cytoplasmic and Nuclear/metabolism
- Receptors, G-Protein-Coupled/chemistry
- Receptors, G-Protein-Coupled/drug effects
- Receptors, G-Protein-Coupled/metabolism
- Sequence Analysis, Protein/methods
- Sulfur Radioisotopes/metabolism
- Threonine/chemistry
- Threonine/drug effects
- Threonine/metabolism
- Transcription Factors/chemistry
- Transcription Factors/genetics
- Transcription Factors/metabolism
- Transfection/methods
- Yohimbine/antagonists & inhibitors
- Yohimbine/metabolism
- Yohimbine/pharmacology
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Affiliation(s)
- Qingbing Zhu
- Department of Pharmaceutical Sciences, Northeastern University, Boston, MA 02115, USA
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33
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Xhaard H, Nyrönen T, Rantanen VV, Ruuskanen JO, Laurila J, Salminen T, Scheinin M, Johnson MS. Model structures of α-2 adrenoceptors in complex with automatically docked antagonist ligands raise the possibility of interactions dissimilar from agonist ligands. J Struct Biol 2005; 150:126-43. [PMID: 15866736 DOI: 10.1016/j.jsb.2004.12.008] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2004] [Revised: 12/20/2004] [Indexed: 11/28/2022]
Abstract
Antagonist binding to alpha-2 adrenoceptors (alpha2-ARs) is not well understood. Structural models were constructed for the three human alpha2-AR subtypes based on the bovine rhodopsin X-ray structure. Twelve antagonist ligands (including covalently binding phenoxybenzamine) were automatically docked to the models. A hallmark of agonist binding is the electrostatic interaction between a positive charge on the agonist and the negatively charged side chain of D3.32. For antagonist binding, ion-pair formation would require deviations of the models from the rhodopsin structural template, e.g., a rotation of TM3 to relocate D3.32 more centrally within the binding cavity, and/or creation of new space near TM2/TM7 such that antagonists would be shifted away from TM5. Thus, except for the quinazolines, antagonist ligands automatically docked to the model structures did not form ion-pairs with D3.32. This binding mode represents a valid alternative, whereby the positive charge on the antagonists is stabilized by cation-pi interactions with aromatic residues (e.g., F6.51) and antagonists interact with D3.32 via carboxylate-aromatic interactions. This binding mode is in good agreement with maps derived from a molecular interaction library that predicts favorable atomic contacts; similar interaction environments are seen for unrelated proteins in complex with ligands sharing similarities with the alpha2-AR antagonists.
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Affiliation(s)
- Henri Xhaard
- Department of Biochemistry and Pharmacy, Abo Akademi University, Tykistökatu 6 A, FIN-20520 Turku, Finland
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34
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Zhang YQ, Limbird LE. Hetero-oligomers of alpha2A-adrenergic and mu-opioid receptors do not lead to transactivation of G-proteins or altered endocytosis profiles. Biochem Soc Trans 2005; 32:856-60. [PMID: 15494033 DOI: 10.1042/bst0320856] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Complexes of alpha(2A)-ARs (alpha(2A)-adrenergic receptors) and MORs (mu-opioid receptors), probably hetero-oligomers, were detected by co-immunoisolation after extraction from HEK-293 cells (human embryonic kidney 293 cells). Functional communication between these receptors is revealed by alpha(2A)-AR activation of a pertussis toxin-insensitive G(i)alpha subunit (termed as G(i)1) when fused with the MOR and evaluated in membranes from pertussis toxin-treated cells. However, the alpha(2A)-AR does not require transactivation through MOR, since quantitatively indistinguishable results were observed in cells co-expressing alpha(2A)-AR and a fusion protein of G(i)1 with the first transmembrane span of MOR (myc-MOR-TM1). Functional cross-talk among these alpha(2A)-AR-MOR complexes does not occur for internalization profiles; incubation with adrenaline (epinephrine) leads to endocytosis of alpha(2A)-AR but not MOR, while incubation with DAMGO ([D-Ala,NMe-Phe,Gly-ol]enkephalin) leads to endocytosis of MOR but not alpha(2A)-AR in cells co-expressing both the receptors. Hence, alpha(2A)-AR and MOR hetero-oligomers, although they occur, do not have an obligatory functional influence on one another in the paradigms studied.
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Affiliation(s)
- Y Q Zhang
- Department of Pharmacology and Center for Molecular Neuroscience, Vanderbilt University Medical Center, 2200 Pierce Ave., 464A RRB, Nashville, TN 37232-6600, USA
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35
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Novi F, Stanasila L, Giorgi F, Corsini GU, Cotecchia S, Maggio R. Paired activation of two components within muscarinic M3 receptor dimers is required for recruitment of beta-arrestin-1 to the plasma membrane. J Biol Chem 2005; 280:19768-76. [PMID: 15769745 DOI: 10.1074/jbc.m411281200] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
beta-Arrestins regulate the functioning of G protein-coupled receptors in a variety of cellular processes including receptor-mediated endocytosis and activation of signaling molecules such as ERK. A key event in these processes is the G protein-coupled receptor-mediated recruitment of beta-arrestins to the plasma membrane. However, despite extensive knowledge in this field, it is still disputable whether activation of signaling pathways via beta-arrestin recruitment entails paired activation of receptor dimers. To address this question, we investigated the ability of different muscarinic receptor dimers to recruit beta-arrestin-1 using both co-immunoprecipitation and fluorescence microscopy in COS-7 cells. Experimentally, we first made use of a mutated muscarinic M(3) receptor, which is deleted in most of the third intracellular loop (M(3)-short). Although still capable of activating phospholipase C, this receptor loses almost completely the ability to recruit beta-arrestin-1 following carbachol stimulation in COS-7 cells. Subsequently, M(3)-short was co-expressed with the M(3) receptor. Under these conditions, the M(3)/M(3)-short heterodimer could not recruit beta-arrestin-1 to the plasma membrane, even though the control M(3)/M(3) homodimer could. We next tested the ability of chimeric adrenergic muscarinic alpha(2)/M(3) and M(3)/alpha(2) heterodimeric receptors to co-immunoprecipitate with beta-arrestin-1 following stimulation with adrenergic and muscarinic agonists. beta-Arrestin-1 co-immunoprecipitation could be induced only when carbachol or clonidine were given together and not when the two agonists were supplied separately. Finally, we tested the reciprocal influence that each receptor may exert on the M(2)/M(3) heterodimer to recruit beta-arrestin-1. Remarkably, we observed that M(2)/M(3) heterodimers recruit significantly greater amounts of beta-arrestin-1 than their respective M(3)/M(3) or M(2)/M(2) homodimers. Altogether, these findings provide strong evidence in favor of the view that binding of beta-arrestin-1 to muscarinic M(3) receptors requires paired stimulation of two receptor components within the same receptor dimer.
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MESH Headings
- Animals
- Arrestins/metabolism
- Biological Transport, Active
- COS Cells
- Carbachol/pharmacology
- Cell Membrane/metabolism
- Chlorocebus aethiops
- Clonidine/pharmacology
- Dimerization
- Humans
- MAP Kinase Signaling System/drug effects
- Protein Binding/drug effects
- Protein Structure, Quaternary
- Receptor, Muscarinic M3/chemistry
- Receptor, Muscarinic M3/genetics
- Receptor, Muscarinic M3/metabolism
- Receptors, Adrenergic, alpha-2/chemistry
- Receptors, Adrenergic, alpha-2/genetics
- Receptors, Adrenergic, alpha-2/metabolism
- Recombinant Fusion Proteins/chemistry
- Recombinant Fusion Proteins/genetics
- Recombinant Fusion Proteins/metabolism
- Transfection
- beta-Arrestin 1
- beta-Arrestins
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36
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Abstract
G protein-coupled receptors (GPCRs) mediate the ability of a diverse array of extracellular stimuli to control intracellular signaling. Many GPCRs are phosphorylated by G protein-coupled receptor kinases (GRKs), a process that mediates agonist-specific desensitization in many cells. Although GRK binding to activated GPCRs results in kinase activation and receptor phosphorylation, relatively little is known about the mechanism of GRK/GPCR interaction or how this interaction results in kinase activation. Here, we used the alpha2A-adrenergic receptor (alpha(2A)AR) as a model to study GRK/receptor interaction because GRK2 phosphorylation of four adjacent serines within the large third intracellular loop of this receptor is known to mediate desensitization. Various domains of the alpha(2A)AR were expressed as glutathione S-transferase fusion proteins and tested for the ability to bind purified GRK2. The second and third intracellular loops of the alpha(2A)AR directly interacted with GRK2, whereas the first intracellular loop and C-terminal domain did not. Truncation mutagenesis identified three discrete regions within the third loop that contributed to GRK2 binding, the membrane proximal N- and C-terminal regions as well as a central region adjacent to the phosphorylation sites. Site-directed mutagenesis revealed a critical role for specific basic residues within these regions in mediating GRK2 interaction with the alpha(2A)AR. Mutation of these residues within the holo-alpha(2A)AR diminished GRK2-promoted phosphorylation of the receptor as well as the ability of the kinase to be activated by receptor binding. These studies provide new insight into the mechanism of interaction and activation of GRK2 by GPCRs and suggest that GRK2 binding is critical not only for receptor phosphorylation but also for full activity of the kinase.
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Affiliation(s)
- Christina S Pao
- Department of Microbiology and Immunology, Kimmel Cancer Center, Thomas Jefferson University, Philadelphia, Pennsylvania 19107, USA
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Gentili F, Ghelfi F, Giannella M, Piergentili A, Pigini M, Quaglia W, Vesprini C, Crassous PA, Paris H, Carrieri A. α2-Adrenoreceptors Profile Modulation. 2. Biphenyline Analogues as Tools for Selective Activation of the α2C-Subtype. J Med Chem 2004; 47:6160-73. [PMID: 15566287 DOI: 10.1021/jm0408215] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
A series of derivatives structurally related to biphenyline (3) was designed with the aim to modulate selectivity toward the alpha(2)-AR subtypes. The results obtained demonstrated that the presence of a correctly oriented function with positive electronic effect (+sigma) in portion X of the ligands is an important factor for significant alpha(2C)-subtype selectivity (imidazolines 5, 13, 16, and 19). Homology modeling and docking studies support experimental data and highlight the crucial role for the hydrogen bond between the pyridine nitrogen in position 3 of 5 and the NH-indole ring of Trp6.48, which is favorably oriented in the alpha(2C)-subtype, only.
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Affiliation(s)
- Francesco Gentili
- Dipartimento di Scienze Chimiche, Università degli Studi di Camerino, Via S. Agostino 1, 62032 Camerino, Italy
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Salt DW, Maccari L, Botta M, Ford MG. Variable selection and specification of robust QSAR models from multicollinear data: arylpiperazinyl derivatives with affinity and selectivity for ?2-adrenoceptors. J Comput Aided Mol Des 2004; 18:495-509. [PMID: 15729849 DOI: 10.1007/s10822-004-5203-7] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Two QSAR models have been identified that predict the affinity and selectivity of arylpiperazinyl derivatives for alpha1 and alpha2 adrenoceptors (ARs). The models have been specified and validated using 108 compounds whose structures and inhibition constants (Ki) are available in the literature [Barbaro et al., J. Med. Chem., 44 (2001) 2118; Betti et al., J. Med. Chem., 45 (2002) 3603; Barbaro et al., Bioorg. Med. Chem., 10 (2002) 361; Betti et al., J. Med. Chem., 46 (2003) 3555]. One hundred and forty-seven predictors have been calculated using the Cerius 2 software available from Accelrys. This set of variables exhibited redundancy and severe multicollinearity, which had to be identified and removed as appropriate in order to obtain robust regression models free of inflated errors for the beta estimates - so-called bouncing betas. Those predictors that contained information relevant to the alpha2 response were identified on the basis of their pairwise linear correlations with affinity (-log Ki) for alpha2 adrenoceptors; the remaining variables were discarded. Subsequent variable selection made use of Factor Analysis (FA) and Unsupervised Variable Selection (UzFS). The data was divided into test and training sets using cluster analysis. These two sets were characterised by similar and consistent distributions of compounds in a high dimensional, but relevant predictor space. Multiple regression was then used to determine a subset of predictors from which to determine QSAR models for affinity to alpha2-ARs. Two multivariate procedures, Continuum Regression (the Portsmouth formulation) and Canonical Correlation Analysis (CCA), have been used to specify models for affinity and selectivity, respectively. Reasonable predictions were obtained using these in silico screening tools.
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Affiliation(s)
- D W Salt
- The Centre for Molecular Design, IBBS, University of Porthsmouth, Porthsmouth POI 2D Y, UK
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39
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Brede M, Philipp M, Knaus A, Muthig V, Hein L. ?2-Adrenergic Receptor Subtypes ? Novel Functions Uncovered in Gene-Targeted Mouse Models. Biol Cell 2004; 96:343-8. [PMID: 15207902 DOI: 10.1016/j.biolcel.2004.03.006] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2004] [Accepted: 03/11/2004] [Indexed: 10/26/2022]
Abstract
The family of adrenergic receptors contains nine different subtypes of G protein-coupled receptors which mediate the biological effects of adrenaline and noradrenaline. With few exceptions, the full therapeutic potential of subtype-selective therapy has not yet been explored for the group of adrenergic receptors. In the absence of sufficiently subtype-selective ligands which can distinguish between individual receptor subtypes of the adrenergic family, gene-targeted mouse models with deletions in these receptor genes have recently been generated and characterized. These genetic mouse models have helped to assign specific pharmacological effects of alpha(2)-receptor agonists or antagonists to individual receptor subtypes. However, some unexpected and novel functions of alpha(2)-adrenergic receptors were also uncovered in these mouse models: Presynaptic control of catecholamine release from adrenergic nerves in the central and sympathetic nervous system may be regulated by three different alpha(2)-receptor subtypes, alpha(2A), alpha(2B), and alpha(2C). A similar feedback loop also controls the release of catecholamines from the adrenal gland. alpha(2B)-receptors are not only involved in regulating vascular tone in the adult organism, but they are essential for the development of the vascular system of the placenta during prenatal development. The challenge will now be to generate strategies to identify whether the findings obtained in gene-targeted mice may predict the action of receptor subtype-selective drugs in humans.
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Affiliation(s)
- Marc Brede
- Institut für Pharmakologie und Toxikologie, Universität Würzburg, Germany
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40
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Duvernay MT, Zhou F, Wu G. A conserved motif for the transport of G protein-coupled receptors from the endoplasmic reticulum to the cell surface. J Biol Chem 2004; 279:30741-50. [PMID: 15123661 DOI: 10.1074/jbc.m313881200] [Citation(s) in RCA: 132] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The structural determinants for the export trafficking of G protein-coupled receptors are poorly defined. In this report, we determined the role of carboxyl termini (CTs) of alpha2B-adrenergic receptor (AR) and angiotensin II type 1A receptor (AT1R) in their transport from the endoplasmic reticulum (ER) to the cell surface. The alpha2B-AR and AT1R mutants lacking the CTs were completely unable to transport to the cell surface and were trapped in the ER. Alanine-scanning mutagenesis revealed that residues Phe436 and Ile433-Leu444 in the CT were required for alpha2B-AR export. Insertion or deletion between Phe436 and Ile443-Leu444 as well as Ile443-Leu444 mutation to FF severely disrupted alpha2B-AR transport, indicating there is a defined spatial requirement, which is essential for their function as a single motif regulating receptor transport from the ER. Furthermore, the carboxyl-terminally truncated as well as Phe436 and Ile443-Leu444 mutants were unable to bind ligand and the alpha2B-AR CT conferred its transport properties to the AT1R mutant without the CT in a Phe436-Ile443-Leu444-dependent manner. These data suggest that the Phe436 and Ile443-Leu444 may be involved in both proper folding and export from the ER of the receptor. Similarly, residues Phe309 and Leu316-Leu317 in the CT were identified as essential for AT1R export. The sequence F(X)6LL (where X can be any residue, and L is leucine or isoleucine) is highly conserved in the membrane-proximal CTs of many G protein-coupled receptors and may function as a common motif mediating receptor transport from the ER to the cell surface.
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MESH Headings
- Alanine/chemistry
- Amino Acid Motifs
- Amino Acid Sequence
- Animals
- Cell Line
- Cell Membrane/metabolism
- Dose-Response Relationship, Drug
- Endoplasmic Reticulum/metabolism
- Flow Cytometry
- Humans
- Immunoblotting
- Isoleucine/chemistry
- Leucine/chemistry
- Ligands
- Microscopy, Fluorescence
- Mitogen-Activated Protein Kinase 1/metabolism
- Mitogen-Activated Protein Kinase 3
- Mitogen-Activated Protein Kinases/metabolism
- Molecular Sequence Data
- Mutagenesis, Site-Directed
- Mutation
- Phenylalanine/chemistry
- Plasmids/metabolism
- Protein Binding
- Protein Conformation
- Protein Structure, Tertiary
- Protein Transport
- Rats
- Receptor, Angiotensin, Type 1/chemistry
- Receptors, Adrenergic, alpha-2/chemistry
- Receptors, G-Protein-Coupled/chemistry
- Sequence Homology, Amino Acid
- Transfection
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Affiliation(s)
- Matthew T Duvernay
- Department of Pharmacology and Experimental Therapeutics, Louisiana State University Health Sciences Center, New Orleans, Louisiana 70112, USA
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Molderings GJ, Bonisch H, Bruss M, Gothert M. Alpha(2A)-adrenergic versus imidazoline receptor controversy in rilmenidine's action: alpha(2A)-antagonism in humans versus alpha(2A)-agonism in rabbits. Ann N Y Acad Sci 2004; 1009:279-82. [PMID: 15028600 DOI: 10.1196/annals.1304.036] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
At the alpha(2A)-autoreceptors on the sympathetic nerve terminals of the human atrial appendages and rabbit pulmonary artery, rilmenidine and oxymetazoline exhibit different properties (antagonism and agonism, respectively). These opposite pharmacodynamic properties of alpha(2)-adrenoceptor ligands seem to be due to substantial differences in the nucleotide and amino acid sequences between human and rabbit alpha(2A)-adrenoceptors. Hence, the rabbit alpha(2A)-adrenoceptor is not reliably predictive for the action of ligands at the human alpha(2A)-adrenoceptor.
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42
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Sen S, Jaakola VP, Heimo H, Engström M, Larjomaa P, Scheinin M, Lundstrom K, Goldman A. Functional expression and direct visualization of the human α2B-adrenergic receptor and α2B-AR-green fluorescent fusion protein in mammalian cell using Semliki Forest virus vectors. Protein Expr Purif 2003; 32:265-75. [PMID: 14965773 DOI: 10.1016/j.pep.2003.08.006] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2003] [Revised: 08/05/2003] [Indexed: 11/29/2022]
Abstract
The alpha 2B -adrenergic receptor ( alpha 2B -AR), a member of the G protein-coupled receptor (GPCR) superfamily, was expressed at high levels from Semliki Forest virus (SFV) vectors in mammalian cells. Constructs were engineered by fusing enhanced green fluorescent protein (eGFP) and the SFV capsid to opposite ends of the alpha 2B -AR. The receptor fusions alpha 2B -AR-eGFP and CAP- alpha 2B -AR expressed in CHO-K1 cells generated alpha 2B values of 176 and 122pmol/mg of membrane protein, respectively, and showed similar ligand binding characteristics, alpha 2B -AR subtype-selectivity, and G protein activation as reported for stable expression in CHO-K1 cells. Cryo-electron microscopy and eGFP-based fluorescence indicated the same subcellular receptor distribution. SFV expression is well suited for studies on the pharmacology, biochemistry, and cell biology of GPCRs, and for large-scale recombinant protein production in mammalian suspension culture to generate sufficient receptor quantities for structural biology.
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Affiliation(s)
- Saurabh Sen
- Institute of Biotechnology (Biocenter 3), University of Helsinki, P.O. Box 65, Viikinkaari 1, FIN-00014 Helsinki, Finland
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Peltonen JM, Nyrönen T, Wurster S, Pihlavisto M, Hoffrén AM, Marjamäki A, Xhaard H, Kanerva L, Savola JM, Johnson MS, Scheinin M. Molecular mechanisms of ligand-receptor interactions in transmembrane domain V of the alpha2A-adrenoceptor. Br J Pharmacol 2003; 140:347-58. [PMID: 12970108 PMCID: PMC1574035 DOI: 10.1038/sj.bjp.0705439] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
1. The structural determinants of catechol hydroxyl interactions with adrenergic receptors were examined using 12 alpha2-adrenergic agonists and a panel of mutated human alpha2A-adrenoceptors. The alpha2ASer201 mutant had a Cys --> Ser201 (position 5.43) amino-acid substitution, and alpha2ASer201Cys200 and alpha2ASer201Cys204 had Ser --> Cys200 (5.42) and Ser --> Cys204 (5.46) substitutions, respectively, in addition to the Cys --> Ser201 substitution. 2. Automated docking methods were used to predict the receptor interactions of the ligands. Radioligand-binding assays and functional [35S]GTPgammaS-binding assays were performed using transfected Chinese hamster ovary cells to experimentally corroborate the predicted binding modes. 3. The hydroxyl groups of phenethylamines were found to have different effects on ligand affinity towards the activated and resting forms of the wild-type alpha2A-adrenoceptor. Substitution of Ser200 or Ser204 with cysteine caused a deterioration in the capability of catecholamines to activate the alpha2A-adrenoceptor. The findings indicate that (i) Cys201 plays a significant role in the binding of catecholamine ligands and UK14,304 (for the latter, by a hydrophobic interaction), but Cys201 is not essential for receptor activation; (ii) Ser200 interacts with the meta-hydroxyl group of phenethylamine ligands, affecting both catecholamine binding and receptor activation; while (iii) substituting Ser204 with a cysteine interferes both with the binding of catecholamine ligands and with receptor activation, due to an interaction between Ser204 and the para-hydroxyl group of the catecholic ring.
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MESH Headings
- Adrenergic Agonists/metabolism
- Adrenergic Agonists/pharmacology
- Amino Acid Sequence
- Amino Acid Substitution
- Animals
- Binding Sites/genetics
- Binding, Competitive/drug effects
- Brimonidine Tartrate
- CHO Cells
- Catecholamines/chemistry
- Catecholamines/metabolism
- Cricetinae
- Guanosine 5'-O-(3-Thiotriphosphate)/metabolism
- Idazoxan/analogs & derivatives
- Idazoxan/metabolism
- Ligands
- Membrane Proteins/chemistry
- Membrane Proteins/genetics
- Membrane Proteins/metabolism
- Models, Molecular
- Molecular Structure
- Mutation
- Protein Structure, Tertiary
- Quinoxalines/chemistry
- Quinoxalines/metabolism
- Radioligand Assay
- Receptors, Adrenergic, alpha-2/chemistry
- Receptors, Adrenergic, alpha-2/genetics
- Receptors, Adrenergic, alpha-2/metabolism
- Sequence Homology, Amino Acid
- Sulfur Radioisotopes
- Tritium
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Affiliation(s)
- Juha M Peltonen
- Department of Pharmacology and Clinical Pharmacology, University of Turku, Finland
- Turku Graduate School of Biomedical Sciences, University of Turku, Finland
| | - Tommi Nyrönen
- Department of Biochemistry and Pharmacy, Åbo Akademi University, Turku, Finland
- Center for Scientific Computing, Espoo
| | | | - Marjo Pihlavisto
- Department of Pharmacology and Clinical Pharmacology, University of Turku, Finland
| | | | - Anne Marjamäki
- Department of Pharmacology and Clinical Pharmacology, University of Turku, Finland
| | - Henri Xhaard
- Department of Biochemistry and Pharmacy, Åbo Akademi University, Turku, Finland
| | - Liisa Kanerva
- Departments of Chemistry and Biomedicine, University of Turku, Turku, Finland
| | | | - Mark S Johnson
- Department of Biochemistry and Pharmacy, Åbo Akademi University, Turku, Finland
| | - Mika Scheinin
- Department of Pharmacology and Clinical Pharmacology, University of Turku, Finland
- Author for correspondence:
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Lin CY, Varma MG, Joubel A, Madabushi S, Lichtarge O, Barber DL. Conserved motifs in somatostatin, D2-dopamine, and alpha 2B-adrenergic receptors for inhibiting the Na-H exchanger, NHE1. J Biol Chem 2003; 278:15128-35. [PMID: 12566440 DOI: 10.1074/jbc.m212315200] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Receptor subtypes within families of G protein-coupled receptors that are activated by similar ligands can regulate distinct intracellular effectors. We identified conserved motifs within intracellular domains 2 and 3 of selective subtypes of several G protein-coupled receptor families that confer coupling to the Na-H exchanger, NHE1. A T(s,p)V motif within intracellular domain 2 and a QQ(r) motif within intracellular domain 3 are shared by the somatostatin receptor subtypes SSTR1, -3, and -4, which couple to the inhibition of NHE1, but not by SSTR2 and -5, which do not signal to NHE1. Only the collective substitution of cognate SSTR2 residues with these two motifs conferred the ability of mutant SSTR2 to inhibit NHE1. Both motifs are present in D(2)-dopamine receptors, which inhibit NHE1, and in alpha(2B)-adrenergic receptors, which couple to the inhibition of NHE1, but not in alpha(2A)-adrenergic receptors, which do not regulate NHE1. These findings indicate that motifs shared by different subfamilies of G protein-coupled receptors, but not necessarily by receptor subtypes within a subfamily, can confer coupling to a common effector.
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MESH Headings
- Amino Acid Motifs
- Amino Acid Sequence
- Animals
- Conserved Sequence
- Membrane Proteins
- Rats
- Receptors, Adrenergic, alpha-2/chemistry
- Receptors, Adrenergic, alpha-2/metabolism
- Receptors, Cell Surface/chemistry
- Receptors, Cell Surface/metabolism
- Receptors, Dopamine D2/chemistry
- Receptors, Dopamine D2/metabolism
- Receptors, Somatostatin/chemistry
- Receptors, Somatostatin/metabolism
- Sequence Alignment
- Signal Transduction
- Sodium-Hydrogen Exchangers/antagonists & inhibitors
- Sodium-Hydrogen Exchangers/metabolism
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Affiliation(s)
- Chin-Yu Lin
- University of California, San Francisco, San Francisco, California 94143, USA
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Abstract
beta- and alpha(2)-adrenergic receptors are known to exhibit substantial cross-talk and mutual regulation in tissues where they are expressed together. We have found that the beta(1)-adrenergic receptor (beta(1)AR) and alpha(2A)-adrenergic receptor (alpha(2A)AR) heterodimerize when coexpressed in cells. Immunoprecipitation studies with differentially tagged beta(1)AR and alpha(2A)AR expressed in HEK-293 cells revealed robust co-immunoprecipitation of the two receptors. Moreover, agonist stimulation of alpha(2A)AR was found to induce substantial internalization of coexpressed beta(1)AR, providing further evidence for a physical association between the two receptors in a cellular environment. Ligand binding assays examining displacement of [(3)H]dihydroalprenolol binding to the beta(1)AR by various ligands revealed that beta(1)AR pharmacological properties were significantly altered when the receptor was coexpressed with alpha(2A)AR. Finally, beta(1)AR/alpha(2A)AR heterodimerization was found to be markedly enhanced by a beta(1)AR point mutation (N15A) that blocks N-linked glycosylation of the beta(1)AR as well as by point mutations (N10A/N14A) that block N-linked glycosylation of the alpha(2A)AR. These data reveal an interaction between beta(1)AR and alpha(2A)AR that is regulated by glycosylation and that may play a key role in cross-talk and mutual regulation between these receptors.
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Affiliation(s)
- Jianguo Xu
- Department of Pharmacology, Rollins Research Center, Emory University School of Medicine, Atlanta, Georgia 30322, USA
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46
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Abstract
The present studies demonstrate that no single stretch of sequence in the third intracellular (3i) loop of the alpha(2A) adrenergic receptor (alpha(2A)-AR) can fully account for its previously described interactions with spinophilin (Richman, J. G., Brady, A. E., Wang, Q., Hensel, J. L., Colbran, R. J., and Limbird, L. E. (2001) J. Biol. Chem. 276, 15003-15008), 14-3-3zeta (Prezeau, L., Richman, J. G., Edwards, S. W., and Limbird, L. E. (1999) J. Biol. Chem. 274, 13462-13469), and arrestin 3 (Wu, G., Krupnick, J. G., Benovic, J. L., and Lanier, S. M. (1997) J. Biol. Chem. 272, 17836-17842), suggesting that a three-dimensional surface, rather than a linear sequence, provides the basis for these interactions as proposed for 3i loop tethering of the alpha(2A)-AR to the basolateral surface of Madin-Darby canine kidney cells (Edwards, S. W., and Limbird, L. E. (1999) J. Biol. Chem. 274, 16331-16336). Sequences at the extreme N-terminal and C-terminal ends of the 3i loop are critical for interaction with spinophilin but not for interaction with 14-3-3zeta or arrestin 3, for which the C-terminal half of the loop is more important. Competition binding for (35)S-labeled alpha(2A)-AR 3i loop binding to glutathione S-transferase (GST)-spinophilin amino acids 151-444 revealed a relative affinity of spinophilin congruent with arrestin > 14-3-3zeta for the unphosphorylated alpha(2A)-AR 3i loop. Agonist occupancy of the alpha(2A)-AR increases receptor association with spinophilin, and arrestin 3 appears to compete for this enrichment. However, when the G protein-coupled receptor kinase 2 substrate sequence was deleted from the 3i loop, arrestin 3 could not compete for the agonist-enriched binding of spinophilin to the mutant alpha(2A)-AR. These data are consistent with a model where sequential or competitive interactions among spinophilin, arrestin, and/or 14-3-3zeta play a role in alpha(2A)-AR functions.
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MESH Headings
- Amino Acid Substitution
- Animals
- Arrestins/metabolism
- Binding Sites
- Binding, Competitive
- Cell Line
- Dogs
- Kidney
- Kinetics
- Microfilament Proteins/metabolism
- Models, Molecular
- Nerve Tissue Proteins/metabolism
- Peptide Fragments/chemistry
- Protein Structure, Secondary
- Receptors, Adrenergic, alpha-2/chemistry
- Receptors, Adrenergic, alpha-2/genetics
- Receptors, Adrenergic, alpha-2/metabolism
- Recombinant Proteins/metabolism
- Sequence Alignment
- Sequence Deletion
- Sequence Homology, Amino Acid
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Affiliation(s)
- Qin Wang
- Department of Pharmacology, Vanderbilt University Medical Center, Nashville, Tennessee 37232-6600, USA
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47
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Abstract
The alpha 2B adrenergic receptor (A2AB) is a heptahelical G protein-coupled receptor for catecholamines. We compared the almost complete coding region (about 1,175 bp) of the A2AB gene from 48 mammalian species, including eight newly determined sequences, representing all the 18 eutherian and two marsupial orders. Comparison of the encoded proteins reveals that residues thought to be involved in agonist binding are highly conserved, as are the regions playing a role in G protein-coupling. The three extracellular loops are generally more variable than the transmembrane domains and two of the intracellular loops, indicating a lower functional constraint. However, the greatest variation is observed in the very long, third intracellular loop, where only a few residues and a polyglutamyl tract are preserved. Although this polyglutamyl domain displays a great variation in length, its presence in all described A2ABs confirms its proposed role in agonist-dependent phosphorylation of the third intracellular loop. Phylogenetic analyses of the A2AB data set, including Bayesian methods, recognized the superordinal clades Afrotheria, Laurasiatheria, and Euarchontoglires, in agreement with recent molecular evidence, albeit with lower support. Within Afrotheria, A2AB strongly supports the paenungulate clade and the association of the continental African otter shrew with Malagasy tenrecs. Among Laurasiatheria, A2AB confirms the nesting of whales within the artiodactyls, as a sister group to hippopotamus. Within the Euarchontoglires, there is constant support for rodent monophyly.
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Affiliation(s)
- Ole Madsen
- Department of Biochemistry 161, University of Nijmegen, 6500 HB Nijmegen, The Netherlands
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48
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DeGraff JL, Gurevich VV, Benovic JL. The third intracellular loop of alpha 2-adrenergic receptors determines subtype specificity of arrestin interaction. J Biol Chem 2002; 277:43247-52. [PMID: 12205092 DOI: 10.1074/jbc.m207495200] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Nonvisual arrestins (arrestin-2 and -3) serve as adaptors to link agonist-activated G protein-coupled receptors to the endocytic machinery. Although many G protein-coupled receptors bind arrestins, the molecular determinants involved in binding remain largely unknown. Because arrestins selectively promote the internalization of the alpha(2b)- and alpha(2c)-adrenergic receptors (ARs) while having no effect on the alpha(2a)AR, here we used alpha(2)ARs to identify molecular determinants involved in arrestin binding. Initially, we assessed the ability of purified arrestins to bind glutathione S-transferase fusions containing the third intracellular loops of the alpha(2a)AR, alpha(2b)AR, or alpha(2c)AR. These studies revealed that arrestin-3 directly binds to the alpha(2b)AR and alpha(2c)AR but not the alpha(2a)AR, whereas arrestin-2 only binds to the alpha(2b)AR. Truncation mutagenesis of the alpha(2b)AR identified two arrestin-3 binding domains in the third intracellular loop, one at the N-terminal end (residues 194-214) and the other at the C-terminal end (residues 344-368). Site-directed mutagenesis further revealed a critical role for several basic residues in arrestin-3 binding to the alpha(2b)AR third intracellular loop. Mutation of these residues in the holo-alpha(2b)AR and subsequent expression in HEK 293 cells revealed that the mutations had no effect on the ability of the receptor to activate ERK1/2. However, agonist-promoted internalization of the mutant alpha(2b)AR was significantly attenuated as compared with wild type receptor. These results demonstrate that arrestin-3 binds to two discrete regions within the alpha(2b)AR third intracellular loop and that disruption of arrestin binding selectively abrogates agonist-promoted receptor internalization.
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Affiliation(s)
- Jessica L DeGraff
- Department of Microbiology and Immunology, Kimmel Cancer Center, Thomas Jefferson University, Philadelphia, Pennsylvania 19107, USA
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49
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Abstract
BACKGROUND The opioid agonist meperidine has actions, such as antishivering, that are more pronounced than those of other opioid agonists and that are not blocked with nonselective opioid antagonists. Agonists at the alpha(2) adrenoceptors, such as clonidine, are very effective antishivering drugs. Preliminary evidence also indicates that meperidine interacts with alpha(2) adrenoceptors. The authors therefore studied the ability of meperidine to bind and activate each of the alpha(2)-adrenoceptor subtypes in a transfected cell system. METHODS The ability of meperidine to bind to and inhibit forskolin-stimulated cyclic adenosine monophosphate formation as mediated by the three alpha(2)-adrenoceptor subtypes transiently transfected into COS-7 cells has been tested. The ability of the opioid antagonist naloxone and the alpha(2)-adrenoceptor antagonists yohimbine and RX821002 to block the analgesic action of meperidine in the hot-plate test was also assessed. The ability of meperidine to fit into the alpha(2B) adrenoceptor was assessed using molecular modeling techniques. RESULTS Meperidine bound to all alpha2-adrenoceptor subtypes, with alpha(2B) having the highest affinity (alpha(2B), 8.6 +/- 0.3 microm; alpha(2C), 13.6 +/- 1.5 microm, P < 0.05; alpha(2A), 38.6 +/- 0.7 microm). Morphine was ineffective at binding to any of the receptor subtypes. Meperidine inhibited the production of forskolin-stimulated cyclic adenosine monophosphate mediated by all receptor subtypes but was most effective at the alpha(2B) adrenoceptor (alpha(2B), 0.6 microm; alpha(2A), 1.3 mm; alpha(2C), 0.3 mm), reaching the same level of inhibition (approximately 70%) as achieved with the alpha2-adrenoceptor agonist dexmedetomidine. The analgesic action of meperidine was blocked by naloxone but not by the alpha 2-adrenoceptor antagonists yohimbine and RX821002. The modeling studies demonstrated that meperidine can fit into the alpha(2B)-adrenoceptor subtype. CONCLUSION Meperidine is a potent agonist at the alpha2 adrenoceptors at its clinically relevant concentrations, especially at the alpha(2B)-adrenoceptor subtype. Activation of the alpha(2B) receptor does not contribute significantly to the analgesic action of meperidine. This raises the possibility that some of its actions, such as antishivering, are transduced by this mechanism.
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Affiliation(s)
- Koji Takada
- Department of Anesthesia, Toyonaka Municipal Hospital, Osaka, Japan
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Chung DA, Wade SM, Fowler CB, Woods DD, Abada PB, Mosberg HI, Neubig RR. Mutagenesis and peptide analysis of the DRY motif in the alpha2A adrenergic receptor: evidence for alternate mechanisms in G protein-coupled receptors. Biochem Biophys Res Commun 2002; 293:1233-41. [PMID: 12054508 DOI: 10.1016/s0006-291x(02)00357-1] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
In G protein-coupled receptors (GPCRs), a conserved aspartic acid in the DRY motif at the cytoplasmic end of helix 3 regulates the transition to the active state, while the adjacent arginine is crucial for G protein activation. To examine the functions of these two residues, we made D130I and R131Q mutations in the alpha2A adrenergic receptor (AR). We demonstrate that, unlike other GPCRs, the alpha2A AR is not constitutively activated by the D130I mutation, although the mutation increases agonist affinity. While the R131Q mutation severely disrupts function, it decreases rather than increasing agonist affinity as seen in other GPCRs. We then investigated the molecular effects of the same mutations in a peptide model and showed that Arg131 is not required for peptide-mediated G protein activation. These results indicate that the alpha2A AR does not follow the conventional GPCR mechanistic paradigm with respect to the function of the DRY motif.
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Affiliation(s)
- Duane A Chung
- Biophysics Research Division, The University of Michigan, Ann Arbor, MI 48109, USA
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