1
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Baker BW, Dougherty DA, Lummis SCR. Proline Residues Contribute to Efficient GABA p Receptor Function. ACS Chem Neurosci 2020; 11:4215-4222. [PMID: 33201686 DOI: 10.1021/acschemneuro.0c00483] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
GABAp receptors are homomeric pentameric ligand-gated ion channels (pLGICs) and are useful for probing the molecular details of the mechanism of action in this important protein family. Here, we explore the role of proline (Pro) residues by creating mutant receptors, expressing them in HEK293 cells, and using fluorescent membrane potential sensitive dye to monitor receptor activity. The data revealed that 3 of the Pro-to-alanine substitutions resulted in nonfunctional receptors (one in the Cys-loop, one in loop A and one in the β2-β3 loop), 7 resulted in increased EC50 values, and the remaining 13 resulted in receptors with properties similar to WT receptors. Further exploration of the nonfunctional mutants using expression in Xenopus laevis oocytes and whole-cell voltage-clamp electrophysiology, incorporating both canonical and noncanonical amino acids, revealed that the Pro in the Cys-loop had a preference for analogues with a high intrinsic cis bias, the Pro in loop A required a ring, and the β2-β3 loop Pro contributes to expression. The data from the Cys-loop Pro are consistent with those from other pLGICs, while those of the loop A Pro and some of the other Pros surprisingly differ. Thus, overall, the data clarify the roles of many of the Pros in the GABAp receptor and also suggest that caution must be applied in using data from one receptor to understand molecular details of all pLGICs.
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Affiliation(s)
- Benjamin W. Baker
- Department of Biochemistry, University of Cambridge, Tennis Court Road, Cambridge CB2 1GA, United Kingdom
| | - Dennis A. Dougherty
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, United States
| | - Sarah C. R. Lummis
- Department of Biochemistry, University of Cambridge, Tennis Court Road, Cambridge CB2 1GA, United Kingdom
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2
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Horsefield S, Burdett H, Zhang X, Manik MK, Shi Y, Chen J, Qi T, Gilley J, Lai JS, Rank MX, Casey LW, Gu W, Ericsson DJ, Foley G, Hughes RO, Bosanac T, von Itzstein M, Rathjen JP, Nanson JD, Boden M, Dry IB, Williams SJ, Staskawicz BJ, Coleman MP, Ve T, Dodds PN, Kobe B. NAD + cleavage activity by animal and plant TIR domains in cell death pathways. Science 2019; 365:793-799. [PMID: 31439792 DOI: 10.1126/science.aax1911] [Citation(s) in RCA: 291] [Impact Index Per Article: 58.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2019] [Accepted: 07/23/2019] [Indexed: 02/02/2023]
Abstract
SARM1 (sterile alpha and TIR motif containing 1) is responsible for depletion of nicotinamide adenine dinucleotide in its oxidized form (NAD+) during Wallerian degeneration associated with neuropathies. Plant nucleotide-binding leucine-rich repeat (NLR) immune receptors recognize pathogen effector proteins and trigger localized cell death to restrict pathogen infection. Both processes depend on closely related Toll/interleukin-1 receptor (TIR) domains in these proteins, which, as we show, feature self-association-dependent NAD+ cleavage activity associated with cell death signaling. We further show that SARM1 SAM (sterile alpha motif) domains form an octamer essential for axon degeneration that contributes to TIR domain enzymatic activity. The crystal structures of ribose and NADP+ (the oxidized form of nicotinamide adenine dinucleotide phosphate) complexes of SARM1 and plant NLR RUN1 TIR domains, respectively, reveal a conserved substrate binding site. NAD+ cleavage by TIR domains is therefore a conserved feature of animal and plant cell death signaling pathways.
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Affiliation(s)
- Shane Horsefield
- School of Chemistry and Molecular Biosciences, Institute for Molecular Bioscience and Australian Infectious Diseases Research Centre, University of Queensland, Brisbane, QLD 4072, Australia
| | - Hayden Burdett
- School of Chemistry and Molecular Biosciences, Institute for Molecular Bioscience and Australian Infectious Diseases Research Centre, University of Queensland, Brisbane, QLD 4072, Australia
| | - Xiaoxiao Zhang
- Agriculture and Food, Commonwealth Scientific and Industrial Research Organisation, Canberra, ACT 2601, Australia.,Plant Sciences Division, Research School of Biology, The Australian National University, Canberra ACT 2601, Australia
| | - Mohammad K Manik
- School of Chemistry and Molecular Biosciences, Institute for Molecular Bioscience and Australian Infectious Diseases Research Centre, University of Queensland, Brisbane, QLD 4072, Australia
| | - Yun Shi
- Institute for Glycomics, Griffith University, Southport, QLD 4222, Australia
| | - Jian Chen
- Agriculture and Food, Commonwealth Scientific and Industrial Research Organisation, Canberra, ACT 2601, Australia.,Plant Sciences Division, Research School of Biology, The Australian National University, Canberra ACT 2601, Australia
| | - Tiancong Qi
- Department of Plant and Microbial Biology, University of California Berkeley, Berkeley, CA 94720, USA
| | - Jonathan Gilley
- John van Geest Centre for Brain Repair, Department of Clinical Neurosciences, University of Cambridge, ED Adrian Building, Forvie Site, Robinson Way, Cambridge CB2 0PY, UK.,Babraham Institute, Babraham, Cambridge CB22 3AT, UK
| | - Jhih-Siang Lai
- School of Chemistry and Molecular Biosciences, Institute for Molecular Bioscience and Australian Infectious Diseases Research Centre, University of Queensland, Brisbane, QLD 4072, Australia
| | - Maxwell X Rank
- School of Chemistry and Molecular Biosciences, Institute for Molecular Bioscience and Australian Infectious Diseases Research Centre, University of Queensland, Brisbane, QLD 4072, Australia
| | - Lachlan W Casey
- School of Chemistry and Molecular Biosciences, Institute for Molecular Bioscience and Australian Infectious Diseases Research Centre, University of Queensland, Brisbane, QLD 4072, Australia.,Centre for Microscopy and Microanalysis, University of Queensland, Brisbane, QLD 4072, Australia
| | - Weixi Gu
- School of Chemistry and Molecular Biosciences, Institute for Molecular Bioscience and Australian Infectious Diseases Research Centre, University of Queensland, Brisbane, QLD 4072, Australia
| | - Daniel J Ericsson
- Macromolecular Crystallography (MX) Beamlines, Australian Synchrotron, Melbourne, VIC 3168, Australia
| | - Gabriel Foley
- School of Chemistry and Molecular Biosciences, Institute for Molecular Bioscience and Australian Infectious Diseases Research Centre, University of Queensland, Brisbane, QLD 4072, Australia
| | - Robert O Hughes
- Disarm Therapeutics, 400 Technology Square, Cambridge, MA 02139, USA
| | - Todd Bosanac
- Disarm Therapeutics, 400 Technology Square, Cambridge, MA 02139, USA
| | - Mark von Itzstein
- Institute for Glycomics, Griffith University, Southport, QLD 4222, Australia
| | - John P Rathjen
- Plant Sciences Division, Research School of Biology, The Australian National University, Canberra ACT 2601, Australia
| | - Jeffrey D Nanson
- School of Chemistry and Molecular Biosciences, Institute for Molecular Bioscience and Australian Infectious Diseases Research Centre, University of Queensland, Brisbane, QLD 4072, Australia
| | - Mikael Boden
- School of Chemistry and Molecular Biosciences, Institute for Molecular Bioscience and Australian Infectious Diseases Research Centre, University of Queensland, Brisbane, QLD 4072, Australia
| | - Ian B Dry
- Agriculture and Food, Commonwealth Scientific and Industrial Research Organisation, Urrbrae, SA 5064, Australia
| | - Simon J Williams
- Plant Sciences Division, Research School of Biology, The Australian National University, Canberra ACT 2601, Australia
| | - Brian J Staskawicz
- Department of Plant and Microbial Biology, University of California Berkeley, Berkeley, CA 94720, USA
| | - Michael P Coleman
- John van Geest Centre for Brain Repair, Department of Clinical Neurosciences, University of Cambridge, ED Adrian Building, Forvie Site, Robinson Way, Cambridge CB2 0PY, UK.,Babraham Institute, Babraham, Cambridge CB22 3AT, UK
| | - Thomas Ve
- School of Chemistry and Molecular Biosciences, Institute for Molecular Bioscience and Australian Infectious Diseases Research Centre, University of Queensland, Brisbane, QLD 4072, Australia. .,Institute for Glycomics, Griffith University, Southport, QLD 4222, Australia
| | - Peter N Dodds
- Agriculture and Food, Commonwealth Scientific and Industrial Research Organisation, Canberra, ACT 2601, Australia.
| | - Bostjan Kobe
- School of Chemistry and Molecular Biosciences, Institute for Molecular Bioscience and Australian Infectious Diseases Research Centre, University of Queensland, Brisbane, QLD 4072, Australia.
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3
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Plummer C, Driessen C, Szabo Z, Mateos MV. Management of cardiovascular risk in patients with multiple myeloma. Blood Cancer J 2019; 9:26. [PMID: 30808934 PMCID: PMC6391463 DOI: 10.1038/s41408-019-0183-y] [Citation(s) in RCA: 65] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2018] [Revised: 11/16/2018] [Accepted: 01/30/2019] [Indexed: 12/13/2022] Open
Abstract
Multiple myeloma (MM) is a plasma cell malignancy that accounts for 10% of hematological cancers. It predominantly affects elderly people; median age at diagnosis is 70 years. Consequently, many patients with MM have cardiovascular comorbidities or risk factors. MM can cause cardiac comorbidities such as cardiomyopathy and heart failure caused by cardiac amyloidosis and/or anemia. Some of the treatments used in MM can also affect cardiovascular health. Advances in pharmacotherapy for MM, such as the introduction of immunomodulators, proteasome inhibitors, histone deacetylase inhibitors, and monoclonal antibodies, have dramatically improved progression-free survival and life expectancy, but new agent classes are associated with adverse events that were not previously observed on a regular basis, including cardiovascular events. However, with careful risk assessment, monitoring, and prophylactic therapy, many of these cardiovascular complications can be managed or treated successfully. Most routine cardiovascular surveillance is undertaken by the treating hemato-oncologist, but a multidisciplinary approach involving cardiologists may help to optimize patient outcomes. In this review, we survey the cardiac complications commonly reported in patients with MM, discuss how they can be prevented and managed, and summarize the role cardiologists can play in delivering the best possible outcomes for patients with MM and cardiovascular comorbidities.
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Affiliation(s)
- Chris Plummer
- Department of Cardiology, Freeman Hospital, Freeman Road, Newcastle upon Tyne, NE7 7DN, UK.
| | - Christoph Driessen
- Department of Oncology and Hematology, Kantonsspital St Gallen, Rorschacher Strasse 95, CH-9007, St Gallen, Switzerland
| | - Zsolt Szabo
- Amgen (Europe) GmbH, Suurstoffi 22, 6343, Rotkreuz, Switzerland
| | - María-Victoria Mateos
- Hematology Service, University Hospital Salamanca, Casa del Bedel, Cardenal Pla y Deniel, 22, Planta Baja, Salamanca, 37008, Spain
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4
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Koludarov I, Aird SD. Snake venom NAD glycohydrolases: primary structures, genomic location, and gene structure. PeerJ 2019; 7:e6154. [PMID: 30755823 PMCID: PMC6368836 DOI: 10.7717/peerj.6154] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2018] [Accepted: 11/25/2018] [Indexed: 01/28/2023] Open
Abstract
NAD glycohydrolase (EC 3.2.2.5) (NADase) sequences have been identified in 10 elapid and crotalid venom gland transcriptomes, eight of which are complete. These sequences show very high homology, but elapid and crotalid sequences also display consistent differences. As in Aplysia kurodai ADP-ribosyl cyclase and vertebrate CD38 genes, snake venom NADase genes comprise eight exons; however, in the Protobothrops mucrosquamatus genome, the sixth exon is sometimes not transcribed, yielding a shortened NADase mRNA that encodes all six disulfide bonds, but an active site that lacks the catalytic glutamate residue. The function of this shortened protein, if expressed, is unknown. While many vertebrate CD38s are multifunctional, liberating both ADP-ribose and small quantities of cyclic ADP-ribose (cADPR), snake venom CD38 homologs are dedicated NADases. They possess the invariant TLEDTL sequence (residues 144–149) that bounds the active site and the catalytic residue, Glu228. In addition, they possess a disulfide bond (Cys121–Cys202) that specifically prevents ADP-ribosyl cyclase activity in combination with Ile224, in lieu of phenylalanine, which is requisite for ADPR cyclases. In concert with venom phosphodiesterase and 5′-nucleotidase and their ecto-enzyme homologs in prey tissues, snake venom NADases comprise part of an envenomation strategy to liberate purine nucleosides, and particularly adenosine, in the prey, promoting prey immobilization via hypotension and paralysis.
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Affiliation(s)
- Ivan Koludarov
- Ecology and Evolution Unit, Okinawa Institute of Science and Technology, Onna, Kunigami-gun, Okinawa, Japan
| | - Steven D Aird
- Ecology and Evolution Unit and Division of Faculty Affairs, Okinawa Institute of Science and Technology, Onna, Kunigami-gun, Okinawa, Japan
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5
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D’Agostino M, Salvini M, Palumbo A, Larocca A, Gay F. Novel investigational drugs active as single agents in multiple myeloma. Expert Opin Investig Drugs 2017; 26:699-711. [DOI: 10.1080/13543784.2017.1324571] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Affiliation(s)
- Mattia D’Agostino
- Myeloma Unit, Division of Hematology, University of Torino, Azienda Ospedaliero-Universitaria Città della Salute e della Scienza di Torino, Torino, Italy
| | - Marco Salvini
- Myeloma Unit, Division of Hematology, University of Torino, Azienda Ospedaliero-Universitaria Città della Salute e della Scienza di Torino, Torino, Italy
| | - Antonio Palumbo
- Myeloma Unit, Division of Hematology, University of Torino, Azienda Ospedaliero-Universitaria Città della Salute e della Scienza di Torino, Torino, Italy
- Currently Takeda employee
| | - Alessandra Larocca
- Myeloma Unit, Division of Hematology, University of Torino, Azienda Ospedaliero-Universitaria Città della Salute e della Scienza di Torino, Torino, Italy
| | - Francesca Gay
- Myeloma Unit, Division of Hematology, University of Torino, Azienda Ospedaliero-Universitaria Città della Salute e della Scienza di Torino, Torino, Italy
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6
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Naffaa MM, Hung S, Chebib M, Johnston GAR, Hanrahan JR. GABA-ρ receptors: distinctive functions and molecular pharmacology. Br J Pharmacol 2017; 174:1881-1894. [PMID: 28258627 DOI: 10.1111/bph.13768] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2016] [Revised: 02/26/2017] [Accepted: 03/01/2017] [Indexed: 01/14/2023] Open
Abstract
The homomeric GABA-ρ ligand-gated ion channels (also known as GABAC or GABAA -ρ receptors) are similar to heteromeric GABAA receptors in structure, function and mechanism of action. However, their distinctive pharmacological properties and distribution make them of special interest. This review focuses on GABA-ρ ion channel structure, ligand selectivity toward ρ receptors over heteromeric GABAA receptor sub-types and selectivity between different homomeric ρ sub-type receptors. Several GABA analogues show selectivity at homomeric GABA-ρ receptors over heteromeric GABAA receptors. More recently, some synthetic ligands have been found to show selectivity at receptors formed from one ρ subtype over others. The unique pharmacological profiles of these agents are discussed in this review. The classical binding site of GABA within the orthosteric site of GABA-ρ homomeric receptors is discussed in detail regarding the loops and residues that constitute the binding site. The ligand-residue interactions in this classical binding and those of mutant receptors are discussed. The structure and conformations of GABA are discussed in regard to its flexibility and molecular properties. Although the binding mode of GABA is difficult to predict, several interactions between GABA and the receptor assist in predicting its potential conformation and mode of action. The structure-activity relationships of GABA and structurally key ligands at ρ receptors are described and discussed.
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Affiliation(s)
- Moawiah M Naffaa
- Faculty of Pharmacy, University of Sydney, Sydney, NSW, Australia
| | - Sandy Hung
- Faculty of Pharmacy, University of Sydney, Sydney, NSW, Australia
| | - Mary Chebib
- Faculty of Pharmacy, University of Sydney, Sydney, NSW, Australia
| | | | - Jane R Hanrahan
- Faculty of Pharmacy, University of Sydney, Sydney, NSW, Australia
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7
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Mesquita I, Varela P, Belinha A, Gaifem J, Laforge M, Vergnes B, Estaquier J, Silvestre R. Exploring NAD+ metabolism in host-pathogen interactions. Cell Mol Life Sci 2016; 73:1225-36. [PMID: 26718485 PMCID: PMC11108276 DOI: 10.1007/s00018-015-2119-4] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2015] [Revised: 11/27/2015] [Accepted: 12/14/2015] [Indexed: 01/01/2023]
Abstract
Nicotinamide adenine dinucleotide (NAD(+)) is a vital molecule found in all living cells. NAD(+) intracellular levels are dictated by its synthesis, using the de novo and/or salvage pathway, and through its catabolic use as co-enzyme or co-substrate. The regulation of NAD(+) metabolism has proven to be an adequate drug target for several diseases, including cancer, neurodegenerative or inflammatory diseases. Increasing interest has been given to NAD(+) metabolism during innate and adaptive immune responses suggesting that its modulation could also be relevant during host-pathogen interactions. While the maintenance of NAD(+) homeostatic levels assures an adequate environment for host cell survival and proliferation, fluctuations in NAD(+) or biosynthetic precursors bioavailability have been described during host-pathogen interactions, which will interfere with pathogen persistence or clearance. Here, we review the double-edged sword of NAD(+) metabolism during host-pathogen interactions emphasizing its potential for treatment of infectious diseases.
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Affiliation(s)
- Inês Mesquita
- Microbiology and Infection Research Domain, Life and Health Sciences Research Institute (ICVS), School of Health Sciences, University of Minho, Braga, Portugal
- ICVS/3B's-PT Government Associate Laboratory, Braga/Guimarães, Portugal
| | - Patrícia Varela
- Microbiology and Infection Research Domain, Life and Health Sciences Research Institute (ICVS), School of Health Sciences, University of Minho, Braga, Portugal
- ICVS/3B's-PT Government Associate Laboratory, Braga/Guimarães, Portugal
| | - Ana Belinha
- Microbiology and Infection Research Domain, Life and Health Sciences Research Institute (ICVS), School of Health Sciences, University of Minho, Braga, Portugal
- ICVS/3B's-PT Government Associate Laboratory, Braga/Guimarães, Portugal
| | - Joana Gaifem
- Microbiology and Infection Research Domain, Life and Health Sciences Research Institute (ICVS), School of Health Sciences, University of Minho, Braga, Portugal
- ICVS/3B's-PT Government Associate Laboratory, Braga/Guimarães, Portugal
| | | | - Baptiste Vergnes
- MIVEGEC (IRD 224-CNRS 5290-Université Montpellier), Institut de Recherche pour le Développement (IRD), Montpellier, France
| | - Jérôme Estaquier
- CNRS FR 3636, Université Paris Descartes, 75006, Paris, France.
- Centre de Recherche du CHU de Québec, Université Laval, Quebec, G1V 4G2, Canada.
| | - Ricardo Silvestre
- Microbiology and Infection Research Domain, Life and Health Sciences Research Institute (ICVS), School of Health Sciences, University of Minho, Braga, Portugal.
- ICVS/3B's-PT Government Associate Laboratory, Braga/Guimarães, Portugal.
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8
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Galián JA, Mrowiec A, Muro M. Molecular targets on B-cells to prevent and treat antibody-mediated rejection in organ transplantation. Present and Future. Expert Opin Ther Targets 2016; 20:859-67. [DOI: 10.1517/14728222.2016.1135904] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Affiliation(s)
- Jose A. Galián
- Immunology Service, Clinical University Hospital Virgen de la Arrixaca-IMIB, Murcia, Spain
| | - Anna Mrowiec
- Immunology Service, Clinical University Hospital Virgen de la Arrixaca-IMIB, Murcia, Spain
| | - Manuel Muro
- Immunology Service, Clinical University Hospital Virgen de la Arrixaca-IMIB, Murcia, Spain
- Head of Regional Histocompatibility and Transplant Immunology Laboratory (LRHI), Clinical University Hospital Virgen de la Arrixaca-IMIB, Murcia, Spain
- Net of Biomedical Research in Digestive and Liver Diseases (CIBERehd), Barcelona, Spain
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9
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Magarotto V, Salvini M, Bonello F, Bringhen S, Palumbo A. Strategy for the treatment of multiple myeloma utilizing monoclonal antibodies: A new era begins. Leuk Lymphoma 2015; 57:537-56. [DOI: 10.3109/10428194.2015.1102245] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Affiliation(s)
- Valeria Magarotto
- Myeloma Unit, Division of Hematology, University of Torino, Azienda Ospedaliero-Universitaria Città della Salute e della Scienza di Torino, Torino, Italy
| | - Marco Salvini
- Myeloma Unit, Division of Hematology, University of Torino, Azienda Ospedaliero-Universitaria Città della Salute e della Scienza di Torino, Torino, Italy
| | - Francesca Bonello
- Myeloma Unit, Division of Hematology, University of Torino, Azienda Ospedaliero-Universitaria Città della Salute e della Scienza di Torino, Torino, Italy
| | - Sara Bringhen
- Myeloma Unit, Division of Hematology, University of Torino, Azienda Ospedaliero-Universitaria Città della Salute e della Scienza di Torino, Torino, Italy
| | - Antonio Palumbo
- Myeloma Unit, Division of Hematology, University of Torino, Azienda Ospedaliero-Universitaria Città della Salute e della Scienza di Torino, Torino, Italy
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10
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Naffaa MM, Chebib M, Hibbs DE, Hanrahan JR. Comparison of templates for homology model of ρ1 GABA C receptors: More insights to the orthosteric binding site’s structure and functionality. J Mol Graph Model 2015; 62:43-55. [DOI: 10.1016/j.jmgm.2015.09.002] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2015] [Revised: 08/27/2015] [Accepted: 09/01/2015] [Indexed: 11/25/2022]
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11
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Zhang W, Zhang H, Zhang T, Fan H, Hao Q. Protein-complex structure completion using IPCAS (Iterative Protein Crystal structure Automatic Solution). ACTA ACUST UNITED AC 2015; 71:1487-92. [PMID: 26143920 DOI: 10.1107/s1399004715008597] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2014] [Accepted: 05/02/2015] [Indexed: 11/10/2022]
Abstract
Protein complexes are essential components in many cellular processes. In this study, a procedure to determine the protein-complex structure from a partial molecular-replacement (MR) solution is demonstrated using a direct-method-aided dual-space iterative phasing and model-building program suite, IPCAS (Iterative Protein Crystal structure Automatic Solution). The IPCAS iteration procedure involves (i) real-space model building and refinement, (ii) direct-method-aided reciprocal-space phase refinement and (iii) phase improvement through density modification. The procedure has been tested with four protein complexes, including two previously unknown structures. It was possible to use IPCAS to build the whole complex structure from one or less than one subunit once the molecular-replacement method was able to give a partial solution. In the most challenging case, IPCAS was able to extend to the full length starting from less than 30% of the complex structure, while conventional model-building procedures were unsuccessful.
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Affiliation(s)
- Weizhe Zhang
- Department of Physiology, University of Hong Kong, Hong Kong
| | - Hongmin Zhang
- Department of Physiology, University of Hong Kong, Hong Kong
| | - Tao Zhang
- Institute of Physics, Chinese Academy of Sciences, Beijing 100080, People's Republic of China
| | - Haifu Fan
- Institute of Physics, Chinese Academy of Sciences, Beijing 100080, People's Republic of China
| | - Quan Hao
- Department of Physiology, University of Hong Kong, Hong Kong
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12
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Guedes AGP, Deshpande DA, Dileepan M, Walseth TF, Panettieri RA, Subramanian S, Kannan MS. CD38 and airway hyper-responsiveness: studies on human airway smooth muscle cells and mouse models. Can J Physiol Pharmacol 2014; 93:145-53. [PMID: 25594684 DOI: 10.1139/cjpp-2014-0410] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
Asthma is an inflammatory disease in which altered calcium regulation, contractility, and airway smooth muscle (ASM) proliferation contribute to airway hyper-responsiveness and airway wall remodeling. The enzymatic activity of CD38, a cell-surface protein expressed in human ASM cells, generates calcium mobilizing second messenger molecules such as cyclic ADP-ribose. CD38 expression in human ASM cells is augmented by cytokines (e.g., TNF-α) that requires the activation of MAP kinases and the transcription factors, NF-κB and AP-1, and is post-transcriptionally regulated by miR-140-3p and miR-708 by binding to 3' Untranslated Region of CD38 as well as by modulating the activation of signaling mechanisms involved in its regulation. Mice deficient in Cd38 exhibit reduced airway responsiveness to inhaled methacholine relative to the response in wild-type mice. Intranasal challenge of Cd38-deficient mice with TNF-α or IL-13, or the environmental fungus Alternaria alternata, causes significantly attenuated methacholine responsiveness compared with wild-type mice, with comparable airway inflammation. Reciprocal bone marrow transfer studies revealed partial restoration of airway hyper-responsiveness to inhaled methacholine in the Cd38-deficient mice. These studies provide evidence for CD38 involvement in the development of airway hyper-responsiveness; a hallmark feature of asthma. Future studies aimed at drug discovery and delivery targeting CD38 expression and (or) activity are warranted.
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Affiliation(s)
- Alonso G P Guedes
- a Department of Surgical & Radiological Sciences, University of California, Davis, CA 95616, USA
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13
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Carland JE, Yamamoto I, Hanrahan JR, Abdel-Halim H, Lewis TM, Absalom N, Chebib M. A hydrophobic area of the GABA ρ₁ receptor containing phenylalanine 124 influences both receptor activation and deactivation. J Mol Neurosci 2014; 55:305-13. [PMID: 24816654 DOI: 10.1007/s12031-014-0322-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2014] [Accepted: 04/30/2014] [Indexed: 10/25/2022]
Abstract
Experimental evidence suggests that GABA ρ1 receptors are potential therapeutic targets for the treatment of a range of neurological conditions, including anxiety and sleep disorders. Homology modelling of the GABA ρ1 extracellular N-terminal domain has revealed a novel hydrophobic area that extends beyond, but not including the GABA-binding site. Phenylalanine 124 (F124) is predicted to be involved in maintaining the structural integrity of the orthosteric-binding site. We have assessed the activity of a series of GABA ρ1 receptors that incorporate a mutation at F124. Wild-type and mutant human GABA ρ1 subunits were expressed in Xenopus laevis oocytes and AD293 cells, and the pharmacology and kinetic properties of the receptors were measured using electrophysiological analysis. Mutation of F124 had minimal effect on receptor pharmacology. However, the rate of deactivation was significantly increased compared to wild type. This study provides further information about the role of residues within a novel hydrophobic area of the GABA ρ1 receptor. This knowledge can help future studies into the design of potent and subtype-selective ligands with therapeutic value.
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Affiliation(s)
- J E Carland
- School of Medical Sciences, UNSW Medicine, The University of New South Wales, Kensington, NSW, 2052, Australia
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14
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Eyada TK, Hussein SK, Younan SA, Abd El Ghany WM, Malek RA. CD38 Gene polymorphisms and susceptibility to B cell chronic lymphocytic leukemia. COMPARATIVE CLINICAL PATHOLOGY 2013; 22:573-579. [DOI: 10.1007/s00580-012-1447-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/02/2023]
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15
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Planamente S, Moréra S, Faure D. In planta fitness-cost of the Atu4232-regulon encoding for a selective GABA-binding sensor in Agrobacterium. Commun Integr Biol 2013; 6:e23692. [PMID: 23710277 PMCID: PMC3656012 DOI: 10.4161/cib.23692] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2012] [Revised: 01/21/2013] [Accepted: 01/21/2013] [Indexed: 12/01/2022] Open
Abstract
GABA (gamma-aminobutyric acid) mediates cell-to-cell communication in eukaryotes and interspecies communication in host-microbe interactions. Agrobacterium tumefaciens induces the development of plant tumor in which GABA accumulates. Two periplasmic binding proteins Atu2422 and Atu4243 and their appropriate ABC-transporter are involved in the binding and importation of GABA. The structure of the selective GABA-binding Atu4243 reveals a GABA conformation similar to a proposed model of GABA bound to the mammalian GABAC receptor. The A. tumefaciens atu4243 mutant is affected for GABA uptake, aggressiveness on plant host and GABA-induced degradation of the quorum-sensing signal, hence for horizontal transfer of the tumor-inducing plasmid. Here, we report that a de-repression of atu4243 and its co-regulated neighbor genes affect the fitness of A. tumefaciens during tumor colonization. Atu4243-orthologs are present in several species of the Agrobacterium genus. This addendum highlights the recent data on the GABA transport in the A. tumefaciens plant-pathogen.
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Affiliation(s)
- Sara Planamente
- Institut des Sciences du Végétal (ISV); CNRS; Gif-sur-Yvette, France ; Laboratoire d'Enzymologie et Biochimie Structurales (LEBS); CNRS; Gif-sur-Yvette, France
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16
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A unified model of the GABA(A) receptor comprising agonist and benzodiazepine binding sites. PLoS One 2013; 8:e52323. [PMID: 23308109 PMCID: PMC3538749 DOI: 10.1371/journal.pone.0052323] [Citation(s) in RCA: 93] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2012] [Accepted: 11/16/2012] [Indexed: 11/19/2022] Open
Abstract
We present a full-length α(1)β(2)γ(2) GABA receptor model optimized for agonists and benzodiazepine (BZD) allosteric modulators. We propose binding hypotheses for the agonists GABA, muscimol and THIP and for the allosteric modulator diazepam (DZP). The receptor model is primarily based on the glutamate-gated chloride channel (GluCl) from C. elegans and includes additional structural information from the prokaryotic ligand-gated ion channel ELIC in a few regions. Available mutational data of the binding sites are well explained by the model and the proposed ligand binding poses. We suggest a GABA binding mode similar to the binding mode of glutamate in the GluCl X-ray structure. Key interactions are predicted with residues α(1)R66, β(2)T202, α(1)T129, β(2)E155, β(2)Y205 and the backbone of β(2)S156. Muscimol is predicted to bind similarly, however, with minor differences rationalized with quantum mechanical energy calculations. Muscimol key interactions are predicted to be α(1)R66, β(2)T202, α(1)T129, β(2)E155, β(2)Y205 and β(2)F200. Furthermore, we argue that a water molecule could mediate further interactions between muscimol and the backbone of β(2)S156 and β(2)Y157. DZP is predicted to bind with interactions comparable to those of the agonists in the orthosteric site. The carbonyl group of DZP is predicted to interact with two threonines α(1)T206 and γ(2)T142, similar to the acidic moiety of GABA. The chlorine atom of DZP is placed near the important α(1)H101 and the N-methyl group near α(1)Y159, α(1)T206, and α(1)Y209. We present a binding mode of DZP in which the pending phenyl moiety of DZP is buried in the binding pocket and thus shielded from solvent exposure. Our full length GABA(A) receptor is made available as Model S1.
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17
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Planamente S, Mondy S, Hommais F, Vigouroux A, Moréra S, Faure D. Structural basis for selective GABA binding in bacterial pathogens. Mol Microbiol 2012; 86:1085-99. [PMID: 23043322 DOI: 10.1111/mmi.12043] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/14/2012] [Indexed: 11/27/2022]
Abstract
GABA acts as an intercellular signal in eukaryotes and as an interspecies signal in host-microbe interactions. Structural characteristics of selective eukaryotic GABA receptors and bacterial GABA sensors are unknown. Here, we identified the selective GABA-binding protein, called Atu4243, in the plant pathogen Agrobacterium tumefaciens. A constructed atu4243 mutant was affected in GABA transport and in expression of the GABA-regulated functions, including aggressiveness on two plant hosts and degradation of the quorum-sensing signal. The GABA-bound Atu4243 structure at 1.28 Å reveals that GABA adopts a conformation never observed so far and interacts with two key residues, Arg(203) and Asp(226) of which the role in GABA binding and GABA signalling in Agrobacterium has been validated using appropriate mutants. The conformational GABA-analogue trans-4-aminocrotonic acid (TACA) antagonizes GABA activity, suggesting structural similarities between the binding sites of the bacterial sensor Atu4243 and mammalian GABA(C) receptors. Exploration of genomic databases reveals Atu4243 orthologues in several pathogenic and symbiotic proteobacteria, such as Rhizobium, Azospirillum, Burkholderia and Pseudomonas. Thus, this study establishes a structural basis for selective GABA sensors and offers opportunities for deciphering the role of the GABA-mediated communication in several host-pathogen interactions.
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Affiliation(s)
- Sara Planamente
- Institut des Sciences du Végétal, CNRS, avenue de la terrasse, 91198, Gif-sur-Yvette, France
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18
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Ashby JA, McGonigle IV, Price KL, Cohen N, Comitani F, Dougherty DA, Molteni C, Lummis SCR. GABA binding to an insect GABA receptor: a molecular dynamics and mutagenesis study. Biophys J 2012. [PMID: 23200041 DOI: 10.1016/j.bpj.2012.10.016] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
RDL receptors are GABA-activated inhibitory Cys-loop receptors found throughout the insect CNS. They are a key target for insecticides. Here, we characterize the GABA binding site in RDL receptors using computational and electrophysiological techniques. A homology model of the extracellular domain of RDL was generated and GABA docked into the binding site. Molecular dynamics simulations predicted critical GABA binding interactions with aromatic residues F206, Y254, and Y109 and hydrophilic residues E204, S176, R111, R166, S176, and T251. These residues were mutated, expressed in Xenopus oocytes, and their functions assessed using electrophysiology. The data support the binding mechanism provided by the simulations, which predict that GABA forms many interactions with binding site residues, the most significant of which are cation-π interactions with F206 and Y254, H-bonds with E204, S205, R111, S176, T251, and ionic interactions with R111 and E204. These findings clarify the roles of a range of residues in binding GABA in the RDL receptor, and also show that molecular dynamics simulations are a useful tool to identify specific interactions in Cys-loop receptors.
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19
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Carpenter TS, Lau EY, Lightstone FC. A role for loop F in modulating GABA binding affinity in the GABA(A) receptor. J Mol Biol 2012; 422:310-23. [PMID: 22659322 DOI: 10.1016/j.jmb.2012.05.025] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2011] [Revised: 05/08/2012] [Accepted: 05/17/2012] [Indexed: 10/28/2022]
Abstract
The brain's major inhibitory neuroreceptor is the ligand-gated ion channel γ-aminobutyric acid (GABA) type A receptor (GABAR). GABARs exist in a variety of different subunit combinations that act to modulate the physiological behavior of GABAR by altering its pharmacological profile, as well as its affinity for GABA. While the α(1)β(2)γ(2) subtype is one of the most prevalent GABARs, the less populous α(6)β(3)δ subtype has much higher GABA sensitivity. Previous studies identified residues crucial for GABA binding; however, the specific molecular differences responsible for this diverse sensitivity are not known. Furthermore, the role of loop F is a divisive subject, with conflicting evidence for ligand binding function. Using homology modeling, ligand docking, and molecular dynamics simulations, we investigated the GABA binding sites of the two receptor subtypes. Simulations identified seven residues that consistently interacted with GABA in both subtypes: αF65, αR132, βL99, βE155, βR/K196, βY205, and βR207. Residue substitution at position β196 (arginine in α(6)β(3)δ, lysine in α(1)β(2)γ(2)) resulted in a shift in GABA binding. However, the major difference between the two binding sites was the magnitude of loop F involvement, with a greater contribution in the α(6)β(3)δ receptor. Free energy calculations confirm that the α(6)β(3)δ binding pocket has an increased affinity for GABA. Thus, the possible role for loop F across the GABAR family is to modulate GABA affinity.
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Affiliation(s)
- Timothy S Carpenter
- Biosciences and Biotechnology Division, Lawrence Livermore National Laboratory, Livermore, CA 94550, USA
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20
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Lummis SCR, Harrison NJ, Wang J, Ashby JA, Millen KS, Beene DL, Dougherty DA. Multiple Tyrosine Residues Contribute to GABA Binding in the GABA(C) Receptor Binding Pocket. ACS Chem Neurosci 2012; 3:186-192. [PMID: 22448304 PMCID: PMC3309607 DOI: 10.1021/cn200103n] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2011] [Revised: 12/06/2011] [Indexed: 11/28/2022] Open
Abstract
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The ligand binding site of Cys-loop receptors is dominated
by aromatic
amino acids. In GABAC receptors, these are predominantly
tyrosine residues, with a number of other aromatic residues located
in or close to the binding pocket. Here we examine the roles of these
residues using substitution with both natural and unnatural amino
acids followed by functional characterization. Tyr198 (loop B) has
previously been shown to form a cation−π interaction
with GABA; the current data indicate that none of the other aromatic
residues form such an interaction, although the data indicate that
both Tyr102 and Phe138 may contribute to stabilization of the positively
charged amine of GABA. Tyr247 (loop C) was very sensitive to substitution
and, combined with data from a model of the receptor, suggest a π–π
interaction with Tyr241 (loop C); here again functional data show
aromaticity is important. In addition the hydroxyl group of Tyr241
is important, supporting the presence of a hydrogen bond with Arg104
suggested by the model. At position Tyr102 (loop D) size and aromaticity
are important; this residue may play a role in receptor gating and/or
ligand binding. The data also suggest that Tyr167, Tyr200, and Tyr208
have a structural role while Tyr106, Trp246, and Tyr251 are not critical.
Comparison of the agonist binding site “aromatic box”
across the superfamily of Cys-loop receptors reveals some interesting
parallels and divergences.
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Affiliation(s)
- Sarah C. R. Lummis
- Department of Biochemistry, University of Cambridge, Tennis Court Road, Cambridge
CB2 1QW, United Kingdom
| | - Neil J. Harrison
- Department of Biochemistry, University of Cambridge, Tennis Court Road, Cambridge
CB2 1QW, United Kingdom
| | - Jinti Wang
- Division of Chemistry and Chemical
Engineering, California Institute of Technology, Pasadena, California 91125, United States
| | - Jamie A. Ashby
- Department of Biochemistry, University of Cambridge, Tennis Court Road, Cambridge
CB2 1QW, United Kingdom
| | - Katherine S. Millen
- Department of Biochemistry, University of Cambridge, Tennis Court Road, Cambridge
CB2 1QW, United Kingdom
| | - Darren L. Beene
- Division of Chemistry and Chemical
Engineering, California Institute of Technology, Pasadena, California 91125, United States
| | - Dennis A. Dougherty
- Division of Chemistry and Chemical
Engineering, California Institute of Technology, Pasadena, California 91125, United States
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21
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Accardi MV, Beech RN, Forrester SG. Nematode cys-loop GABA receptors: biological function, pharmacology and sites of action for anthelmintics. INVERTEBRATE NEUROSCIENCE 2012; 12:3-12. [PMID: 22430311 DOI: 10.1007/s10158-012-0129-6] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/03/2012] [Accepted: 03/03/2012] [Indexed: 10/28/2022]
Abstract
Parasitic nematode infection of humans and livestock is a major problem globally. Attempts to control nematode populations have led to the development of several classes of anthelmintic, which target cys-loop ligand-gated ion channels. Unlike the vertebrate nervous system, the nematode nervous system possesses a large and diversified array of ligand-gated chloride channels that comprise key components of the inhibitory neurotransmission system. In particular, cys-loop GABA receptors have evolved to play many fundamental roles in nematode behaviour such as locomotion. Analysis of the genomes of several free-living and parasitic nematodes suggests that there are several groups of cys-loop GABA receptor subunits that, for the most part, are conserved among nematodes. Despite many similarities with vertebrate cys-loop GABA receptors, those in nematodes are quite distinct in sequence similarity, subunit composition and biological function. With rising anthelmintic resistance in many nematode populations worldwide, GABA receptors should become an area of increased scientific investigation in the development of the next generation of anthelmintics.
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Affiliation(s)
- Michael V Accardi
- Department of Pharmacology and Therapeutics, McGill University, Bellini Life Sciences Complex, 3649 Sir William Osler Promenade, Montreal, QC H3G 0B1, Canada
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22
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Shawl AI, Park KH, Kim BJ, Higashida C, Higashida H, Kim UH. Involvement of actin filament in the generation of Ca2+ mobilizing messengers in glucose-induced Ca2+ signaling in pancreatic β-cells. Islets 2012; 4:145-51. [PMID: 22627736 DOI: 10.4161/isl.19490] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Glucose is a metabolic regulator of insulin secretion from pancreatic β-cells, which is regulated by intracellular Ca(2+) signaling. We and others previously demonstrated that glucose activates CD38/ADP-ribosyl cyclase (ADPR-cyclase) to produce two Ca(2+) second messengers, cyclic ADP-ribose (cADPR) and nicotinic acid adenine dinucleotide phosphate (NAADP). Although F-actin remodeling is known to be an important step in glucose stimulated insulin secretion, the role of actin cytoskeleton in regulating Ca(2+) signaling in pancreatic β-cells remain to be solved. Here, we show that actin filaments are involved in the activation of CD38/ADPR-cyclase in pancreatic β-cells. Glucose induces a sequential formation of cADPR and NAADP. Pretreatment with jasplakinolide, an actin polymerizing agent, or a myosin heavy chain IIA (MHCIIA) blocker, blebbistatin, inhibited glucose-induced CD38 internalization, an essential step for cADPR formation. Blocking actin disassembly with jasplakinolide also abrogates glucose-induced cADPR and NAADP formation and sustained Ca(2+) signals. These results indicate that actin filaments along with MHCIIA play an important role in CD38 internalization for the generation of Ca(2+) mobilizing messengers for glucose-induced Ca(2+) signaling in pancreatic β-cells.
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Affiliation(s)
- Asif Iqbal Shawl
- Department of Biochemistry, Chonbuk National University Medical School, Jeonju, South Korea
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23
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Cantó C, Auwerx J. Targeting sirtuin 1 to improve metabolism: all you need is NAD(+)? Pharmacol Rev 2011; 64:166-87. [PMID: 22106091 DOI: 10.1124/pr.110.003905] [Citation(s) in RCA: 274] [Impact Index Per Article: 21.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
Sirtuin 1 (SIRT1) is an evolutionarily conserved NAD(+)-dependent deacetylase that is at the pinnacle of metabolic control, all the way from yeast to humans. SIRT1 senses changes in intracellular NAD(+) levels, which reflect energy level, and uses this information to adapt the cellular energy output such that it matches cellular energy requirements. The changes induced by SIRT1 activation are generally (but not exclusively) transcriptional in nature and are related to an increase in mitochondrial metabolism and antioxidant protection. These attractive features have validated SIRT1 as a therapeutic target in the management of metabolic disease and prompted an intensive search to identify pharmacological SIRT1 activators. In this review, we first give an overview of the SIRT1 biology with a particular focus on its role in metabolic control. We then analyze the pros and cons of the current strategies used to activate SIRT1 and explore the emerging evidence indicating that modulation of NAD(+) levels could provide an effective way to achieve such goals.
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Affiliation(s)
- Carles Cantó
- Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland
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24
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Two amino acid residues contribute to a cation-π binding interaction in the binding site of an insect GABA receptor. J Neurosci 2011; 31:12371-6. [PMID: 21865479 DOI: 10.1523/jneurosci.1610-11.2011] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
Cys-loop receptor binding sites characteristically possess an "aromatic box," where several aromatic amino acid residues surround the bound ligand. A cation-π interaction between one of these residues and the natural agonist is common, although the residue type and location are not conserved. Even in the closely related vertebrate GABA(A) and GABA(C) receptors, residues in distinct locations perform this role: in GABA(A) receptors, a Tyr residue in loop A forms a cation-π interaction with GABA, while in GABA(C) receptors it is a loop B residue. GABA-activated Cys-loop receptors also exist in invertebrates, where they have distinct pharmacologies and are the target of a range of pesticides. Here we examine the location of GABA in an insect binding site by incorporating a series of fluorinated Phe derivatives into the receptor binding pocket using unnatural amino acid mutagenesis, and evaluating the resulting receptors when expressed in Xenopus oocytes. A homology model suggests that two aromatic residues (in loops B and C) are positioned such that they could contribute to a cation-π interaction with the primary ammonium of GABA, and the data reveal a clear correlation between the GABA EC(50) and the cation-π binding ability both at Phe206 (loop B) and Tyr254 (loop C), demonstrating for the first time the contribution of two aromatic residues to a cation-π interaction in a Cys-loop receptor.
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25
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Xie A, Yan J, Yue L, Feng F, Mir F, Abdel-Halim H, Chebib M, Le Breton GC, Standaert RF, Qian H, Pepperberg DR. 2-Aminoethyl methylphosphonate, a potent and rapidly acting antagonist of GABA(A)-ρ1 receptors. Mol Pharmacol 2011; 80:965-78. [PMID: 21810922 DOI: 10.1124/mol.111.071225] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
2-Aminoethyl methylphosphonate (2-AEMP), an analog of GABA, has been found to exhibit antagonist activity at GABA(A)-ρ1 (also known as ρ1 GABA(C)) receptors. The present study was undertaken to elucidate 2-AEMP's action and to test the activities of 2-AEMP analogs. Whole-cell patch-clamp techniques were used to record membrane currents in neuroblastoma cells stably transfected with human GABA(A)-ρ1 receptors. The action of 2-AEMP was compared with that of 1,2,5,6-tetrahydropyridin-4-yl methylphosphinic acid (TPMPA), a commonly used GABA(A)-ρ1 antagonist. With 10 μM GABA, 2-AEMP's IC(50) (18 μM) differed by less than 2.5-fold from that of TPMPA (7 μM), and results obtained were consistent with a primarily competitive mode of inhibition by 2-AEMP. Terminating the presentation of 2-AEMP or TPMPA in the presence of GABA produced a release from inhibition. However, the rate of inhibition release upon the termination of 2-AEMP considerably exceeded that determined with termination of TPMPA. Moreover, when presented at concentrations near their respective IC(50) values, the preincubation period associated with 2-AEMP's onset of inhibition was much shorter than that for TPMPA. Analogs of 2-AEMP possessing a benzyl or n-butyl rather than a methyl substituent at the phosphorus atom, as well as analogs bearing a C-methyl substituent on the aminoethyl side chain, exhibited reduced potency relative to 2-AEMP. Of these analogs, only (R)-2-aminopropyl methylphosphonate significantly diminished the response to 10 μM GABA. Structure-activity relationships are discussed in the context of molecular modeling of ligand binding to the antagonist binding site of the GABA(A)-ρ1 receptor.
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Affiliation(s)
- An Xie
- Lions of Illinois Eye Research Institute, Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, College of Medicine, Chicago, Illinois 60612, USA
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26
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Martínez-Delgado G, Estrada-Mondragón A, Miledi R, Martínez-Torres A. An Update on GABAρ Receptors. Curr Neuropharmacol 2011; 8:422-33. [PMID: 21629448 PMCID: PMC3080597 DOI: 10.2174/157015910793358141] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2009] [Revised: 04/08/2010] [Accepted: 06/21/2010] [Indexed: 01/29/2023] Open
Abstract
The present review discusses the functional and molecular diversity of GABAρ receptors. These receptors were originally described in the mammalian retina, and their functional role in the visual pathway has been recently elucidated; however new studies on their distribution in the brain and spinal cord have revealed that they are more spread than originally thought, and thus it will be important to determine their physiological contribution to the GABAergic transmission in other areas of the central nervous system. In addition, molecular modeling has revealed peculiar traits of these receptors that have impacted on the interpretations of the latest pharmacolgical and biophysical findings. Finally, sequencing of several vertebrate genomes has permitted a comparative analysis of the organization of the GABAρ genes.
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Affiliation(s)
- Gustavo Martínez-Delgado
- Instituto de Neurbiología, Departamento de Neurobiología Celular y Molecular, Laboratorio D15, Campus UNAM Juriquilla. Querétaro 76230, México
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27
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Accardi MV, Forrester SG. The Haemonchus contortus UNC-49B subunit possesses the residues required for GABA sensitivity in homomeric and heteromeric channels. Mol Biochem Parasitol 2011; 178:15-22. [PMID: 21524670 DOI: 10.1016/j.molbiopara.2011.04.002] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2011] [Revised: 04/04/2011] [Accepted: 04/06/2011] [Indexed: 11/16/2022]
Abstract
Hco-UNC-49 is a GABA receptor from the parasitic nematode Haemonchus contortus that has a relatively low overall sequence similarity to vertebrate GABA receptors but is very similar to the UNC-49 receptor found in the free living nematode Caenorhabditis elegans. While the nematode receptors do share >80% sequence similarity they exhibit different sensitivities to GABA. In addition, the UNC-49C subunit appears to be a positive modulator of GABA sensitivity in the H. contortus heteromeric channel, but is a negative modulator in the C. elegans heteromeric channel. The cause(s) of these differences is currently unknown since the structural elements essential for GABA sensitivity in nematode receptors have been largely unexplored. Thus, the overall aim of this study was to investigate the residues that are important for UNC-49 receptor sensitivity through the use of homology modeling, site-directed mutagenesis, and two-electrode voltage clamp. This study revealed that Met(170) in Loop B of the GABA binding-site may partially account for the observed differences in GABA receptor sensitivity between the nematode species. Residues in Loops A-D that have been reported to form the GABA binding pocket in mammalian receptors, including those forming the conserved 'aromatic box', also appear to play analogous roles in Hco-UNC-49. In addition, the two mutations that produced the most significant reduction in GABA sensitivity were R66S and Y166S. Homology modeling indicates that these two residues share a hydrogen bond and are positioned close to the carboxyl end of the GABA molecule. However, of residues examined in this study, only those on the Hco-UNC-49B subunit and not its subunit partner, Hco-UNC-49C, appear important for GABA sensitivity. Overall, results from this study suggest that the binding site of the UNC-49 heteromeric GABA receptor exhibits some differences compared to classical vertebrate GABA(A) receptors.
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Affiliation(s)
- Michael V Accardi
- University of Ontario Institute of Technology, Faculty of Science, Oshawa, ON, Canada
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28
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Expression of CD38 with intracellular enzymatic activity: a possible explanation for the insulin release induced by intracellular cADPR. Mol Cell Biochem 2011; 352:293-9. [PMID: 21387169 DOI: 10.1007/s11010-011-0765-x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2010] [Accepted: 02/24/2011] [Indexed: 10/18/2022]
Abstract
CD38 is a transmembrane glycoprotein expressed in multiple cell types, including pancreatic β cells. It can serve as an enzyme that catalyzes the metabolism of two different Ca(2+)-mobilizing compounds, cyclic adenosine diphosphoribose (cADPR) and nicotinic acid adenine dinucleotide phosphate. One of these metabolites, cADPR, is known to be involved in glucose-induced insulin secretion from pancreatic β cells. Although the essential role of CD38 for endogenous cADPR synthesis has been established, the relationship between the proposed extracellular enzymatic activity of CD38 and the intracellular Ca(2+) modulation caused by the intracellular cADPR accumulation has not yet been fully explained. For a better understanding of the role of CD38 in the insulin secretion machinery, analysis of the intracellular localization of this molecule in pancreatic β cells is essential. In an attempt to provide a method to probe the N-terminal and C-terminal of CD38 separately, we generated an insulin-secreting MIN6 murine pancreatic β cell line expressing a human CD38 bearing an N-terminal FLAG epitope tag. We found a weak but consistent expression of the FLAG epitope outside of the cells, indicating the presence of a small amount of CD38 with cytoplasmic enzymatic activity. MIN6 cells transfected with human CD38 exhibited increased glucose-induced insulin release. In addition, anti-FLAG cross-linking further enhanced the insulin release, suggesting that the N-terminal of CD38 expressed on the cell surface functions as a receptor for an unknown ligand and triggers positive signals for insulin secretion.
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29
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Manrique M, Kozlowski PA, Cobo-Molinos A, Wang SW, Wilson RL, Montefiori DC, Mansfield KG, Carville A, Aldovini A. Long-term control of simian immunodeficiency virus mac251 viremia to undetectable levels in half of infected female rhesus macaques nasally vaccinated with simian immunodeficiency virus DNA/recombinant modified vaccinia virus Ankara. THE JOURNAL OF IMMUNOLOGY 2011; 186:3581-93. [PMID: 21317390 DOI: 10.4049/jimmunol.1002594] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
The efficacy of two SIV DNA plus recombinant modified vaccinia virus Ankara nasal vaccine regimens, one combined with plasmids expressing IL-2 and IL-15, the other with plasmids expressing GM-CSF, IL-12, and TNF-α, which may better stimulate humoral responses, was evaluated in two female rhesus macaque groups. Vaccination stimulated significant SIV-specific mucosal and systemic cell-mediated immunity in both groups, whereas SIV-specific IgA titers were sporadic and IgG titers negative. All vaccinated animals, except one, became infected after intravaginal SIV(mac251) low-dose challenge. Half of the vaccinated, infected animals (7/13) promptly controlled virus replication to undetectable viremia for the duration of the trial (130 wk) and displayed virological and immunological phenotypes similar to those of exposed, uninfected individuals. When all vaccinated animals were considered, a 3-log viremia reduction was observed, compared with controls. The excellent viral replication containment achieved in vaccinated animals translated into significant preservation of circulating α4β7(high+)/CD4(+) T cells and of circulating and mucosal CD4(+)/C(M) T cells and in reduced immune activation. A more significant long-term survival was also observed in these animals. Median survival was 72 wk for the control group, whereas >50% of the vaccinated animals were still disease free 130 wk postchallenge, when the trial was closed. There was a statistically significant correlation between levels of CD4(+)/IFN-γ(+) and CD8(+)/IFN-γ(+) T cell percentages on the day of challenge and the control of viremia at week 60 postchallenge or survival. Postchallenge immunological correlates of protection were systemic anti-SIV Gag + Env CD4(+)/IL-2(+), CD4(+)/IFN-γ(+), and CD8(+)/TNF-α(+) T cells and vaginal anti-SIV Gag + Env CD8(+) T cell total monofunctional responses.
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Affiliation(s)
- Mariana Manrique
- Department of Medicine, Children's Hospital, Boston, MA 02115, USA
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Yamamoto I, Deniau GP, Gavande N, Chebib M, Johnston GAR, O'Hagan D. Agonist responses of (R)- and (S)-3-fluoro-γ-aminobutyric acids suggest an enantiomeric fold for GABA binding to GABAC receptors. Chem Commun (Camb) 2011; 47:7956-8. [DOI: 10.1039/c1cc12141c] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
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Johnston GAR, Chebib M, Hanrahan JR, Mewett KN. Neurochemicals for the investigation of GABA(C) receptors. Neurochem Res 2010; 35:1970-7. [PMID: 20963487 DOI: 10.1007/s11064-010-0271-7] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/13/2010] [Indexed: 01/23/2023]
Abstract
GABA(C) receptors are being investigated for their role in many aspects of nervous system function including memory, myopia, pain and sleep. There is evidence for functional GABA(C) receptors in many tissues such as retina, hippocampus, spinal cord, superior colliculus, pituitary and the gut. This review describes a variety of neurochemicals that have been shown to be useful in distinguishing GABA(C) receptors from other receptors for the major inhibitory neurotransmitter GABA. Some selective agonists (including (+)-CAMP and 5-methyl-IAA), competitive antagonists (such as TPMPA, (±)-cis-3-ACPBPA and aza-THIP), positive (allopregnanolone) and negative modulators (epipregnanolone, loreclezole) are described. Neurochemicals that may assist in distinguishing between homomeric ρ1 and ρ2 GABA(C) receptors (2-methyl-TACA and cyclothiazide) are also covered. Given their less widespread distribution, lower abundance and relative structural simplicity compared to GABA(A) and GABA(B) receptors, GABA(C) receptors are attractive drug targets.
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Affiliation(s)
- Graham A R Johnston
- Adrien Albert Laboratory of Medicinal Chemistry, Department of Pharmacology D06, The University of Sydney, Sydney, NSW 2006, Australia.
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Nguyen MH, Dang VU, Luu BV. Computational characterization for catalytic activities of human CD38's wild type, E226 and E146 mutants. Interdiscip Sci 2010; 2:193-204. [PMID: 20640790 DOI: 10.1007/s12539-010-0091-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2009] [Revised: 02/16/2010] [Accepted: 03/04/2010] [Indexed: 11/26/2022]
Abstract
A series of the complexes of human CD38's wild type, E226 and E146 mutants as well have been simulated. The biosoftwares well simulate the penetration of nicotinamide-adenine-dinucleotide (NAD) into the active site. The nicotinamide end of NAD penetrates deep into the active site consistent with cleavage of the nicotinamide-glycosidic bond which is the first step of catalysis creating a Michaelis complex regarded as the intermediate product of NAD cyclase and hydrolysis reaction. The breaking down hydrogen bond between 2'-3' OH ribosyl and the residues replaced Glu(226) makes NAD to be less constrained in active site and nicotinamide (NA) becomes more difficult to be cleaved and eliminates the mutant catalytic activities. The large majority of the substrate NAD is hydrolyzed to ADPR while the conversion of NAD to cADPR is not the dominant reaction catalyzed by wild-type human CD38. The more strongly kept ribosyl group by hydrogen bonds the more NADase and the less cyclase activity. Breaking hydrogen bonds of ribosyl 2'- and 3'-OH by mutation will loosen it to promote the cyclase. The cyclic adenosine diphosphate-ribose (cADPR) could also penetrate deeply into active site to make some hydrogen bonds with Glu(146) and Glu(226); however, its docking poses are affected by a residue located at the entrance of the catalytic pocket (Lys(129)). These results are in good agreement with the previous crystallographic analysis and the experiments quantified the catalytic activities of human CD38 and its mutants.
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Affiliation(s)
- My H Nguyen
- Faculty of Chemistry, Hanoi University of Natural Science, VNU, 19 Le Thanh Tong, Hanoi, Vietnam
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Abstract
Functional studies of the ligand gated ion channel family (nicotinic acetylcholine, serotonin Type 3, glycine and GABA receptors) along with the crystal structure of the acetylcholine binding protein (AChBP) and molecular dynamics simulations of the nAChR structure have resulted in a structural model in which the agonist-binding pocket comprises six loops (A-F) contributed by adjacent subunits. It is presumed that the binding of agonist results in a local structural rearrangement that is then transduced to the gate, causing the pore to open. Efforts are underway to better define the specific roles of the six binding loops. Several studies have suggested Loop F may play a direct role in linking the structural rearrangement within the binding pocket to the gate, although other investigations have indicated Loop F may be crucial for locking the agonist molecule into the binding site. This review will focus on the controversy surrounding the role of Loop F during GABA receptor activation.
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Affiliation(s)
- Alpa Khatri
- Department of Physiology, University of Texas Health Science Center at San Antonio, San Antonio, TX 78229, USA
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Khatri A, Sedelnikova A, Weiss DS. Structural rearrangements in loop F of the GABA receptor signal ligand binding, not channel activation. Biophys J 2010; 96:45-55. [PMID: 19134470 DOI: 10.1016/j.bpj.2008.09.011] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2008] [Accepted: 09/24/2008] [Indexed: 02/06/2023] Open
Abstract
Structure-function studies of the Cys loop family of ionotropic neurotransmitter receptors (GABA, nACh, 5-HT(3), and glycine receptors) have resulted in a six-loop (A-F) model of the agonist-binding site. Key amino acids have been identified in these loops that associate with, and stabilize, bound ligand. The next step is to identify the structural rearrangements that couple agonist binding to channel opening. Loop F has been proposed to move upon receptor activation, although it is not known whether this movement is along the conformational pathway for channel opening. We test this hypothesis in the GABA receptor using simultaneous electrophysiology and site-directed fluorescence spectroscopy. The latter method reveals structural rearrangements by reporting changes in hydrophobicity around an environmentally sensitive fluorophore attached to defined positions of loop F. Using a series of ligands that span the range from full activation to full antagonism, we show there is no correlation between the rearrangements in loop F and channel opening. Based on these data and agonist docking simulations into a structural model of the GABA binding site, we propose that loop F is not along the pathway for channel opening, but rather is a component of the structural machinery that locks ligand into the agonist-binding site.
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Affiliation(s)
- Alpa Khatri
- Department of Physiology, University of Texas Health Science Center at San Antonio, San Antonio, Texas, USA. NS035291
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Adamian L, Gussin HA, Tseng YY, Muni NJ, Feng F, Qian H, Pepperberg DR, Liang J. Structural model of rho1 GABAC receptor based on evolutionary analysis: Testing of predicted protein-protein interactions involved in receptor assembly and function. Protein Sci 2010; 18:2371-83. [PMID: 19768800 DOI: 10.1002/pro.247] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
The homopentameric rho1 GABA(C) receptor is a ligand-gated ion channel with a binding pocket for gamma-aminobutyric acid (GABA) at the interfaces of N-terminal extracellular domains. We combined evolutionary analysis, structural modeling, and experimental testing to study determinants of GABA(C) receptor assembly and channel gating. We estimated the posterior probability of selection pressure at amino acid residue sites measured as omega-values and built a comparative structural model, which identified several polar residues under strong selection pressure at the subunit interfaces that may form intersubunit hydrogen bonds or salt bridges. At three selected sites (R111, T151, and E55), mutations disrupting intersubunit interactions had strong effects on receptor folding, assembly, and function. We next examined the role of a predicted intersubunit salt bridge for residue pair R158-D204. The mutant R158D, where the positively charged residue is replaced by a negatively charged aspartate, yielded a partially degraded receptor and lacked membrane surface expression. The membrane surface expression was rescued by the double mutant R158D-D204R, where positive and negative charges are switched, although the mutant receptor was inactive. The single mutants R158A, D204R, and D204A exhibited diminished activities and altered kinetic profiles with fast recovery kinetics, suggesting that R158-D204 salt bridge perhaps stabilizes the open state of the GABA(C) receptor. Our results emphasize the functional importance of highly conserved polar residues at the protein-protein interfaces in GABA(C) rho1 receptors and demonstrate how the integration of computational and experimental approaches can aid discovery of functionally important interactions.
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Affiliation(s)
- Larisa Adamian
- Department of Bioengineering, University of Illinois at Chicago, Chicago, Illinois 60612, USA
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Abstract
The Cys-loop family of ligand-gated ion channels contains both vertebrate and invertebrate members that are activated by GABA (gamma-aminobutyric acid). Many of the residues that are critical for ligand binding have been identified in vertebrate GABA(A) and GABA(C) receptors, and specific interactions between GABA and some of these residues have been determined. In the present paper, I show how a cation-pi interaction for one of the binding site residues has allowed the production of models of GABA docked into the binding site, and these orientations are supported by mutagenesis and functional data. Surprisingly, however, the residue that forms the cation-pi interaction is not conserved, suggesting that GABA occupies subtly different locations even in such closely related receptors.
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The evolution of pentameric ligand-gated ion channels. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2010; 683:11-23. [PMID: 20737785 DOI: 10.1007/978-1-4419-6445-8_2] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
Fast, ionotropic neurotransmission mediated by ligand-gated ion channels is essential for timely behavioral responses in multicellular organisms. Metazoa employ more ionotropic neurotransmitters in more types of synapses, inhibitory or excitatory, than is generally appreciated. It is becoming increasingly clear that the adaptability of a single neurotransmitter receptor superfamily, the pentameric ligand-gated ion channels (pLGICs), makes the diversity in ionotropic neurotransmission possible. Modification ofa common pLGIC structure generates channels that are gated by ligands as different as protons, histamine or zinc and that pair common neurotransmitters with both cation and anion permeability. A phylogeny of the pLGIC gene family from representative metazoa suggests that pLGIC diversity is ancient and evolution of contemporary phyla was characterized by a surprising loss of pLGIC diversity. The pLGIC superfamily reveals aspects of early metazoan evolution, may help us identify novel neurotransmitters and can inform our exploration of structure/function relationships.
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Fellner SK, Arendshorst WJ. Complex interactions of NO/cGMP/PKG systems on Ca2+ signaling in afferent arteriolar vascular smooth muscle. Am J Physiol Heart Circ Physiol 2009; 298:H144-51. [PMID: 19880669 DOI: 10.1152/ajpheart.00485.2009] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Little is known about the effects of nitric oxide (NO) and the cyclic GMP (cGMP)/protein kinase G (PKG) system on Ca(2+) signaling in vascular smooth muscle cells (VSMC) of resistance vessels in general and afferent arterioles in particular. We tested the hypotheses that cGMP-, Ca(2+)-dependent big potassium channels (BK(Ca(2+))) buffer the Ca(2+) response to depolarization by high extracellular KCl and that NO inhibits adenosine diphosphoribose (ADPR) cyclase, thereby reducing the Ca(2+)-induced Ca(2+) release. We isolated rat afferent arterioles, utilizing the magnetized microsphere method, and measured cytosolic Ca(2+) concentration ([Ca(2+)](i)) with fura-2, a preparation in which endothelial cells do not participate in [Ca(2+)](i) responses. KCl (50 mM)-induced depolarization causes an immediate increase in [Ca(2+)](i) of 151 nM. The blockers N(omega)-nitro-L-arginine methyl ester (of nitric oxide synthase), 1,2,4-oxodiazolo-[4,3-a]quinoxalin-1-one (ODQ, of guanylyl cyclase), KT-5823 (of PKG activation), and iberiotoxin (IBX, of BK(Ca(2+)) activity) do not alter the [Ca(2+)](i) response to KCl, suggesting no discernible endogenous NO production under basal conditions. The NO donor sodium nitroprusside (SNP) reduces the [Ca(2+)](i) response to 77 nM; IBX restores the response to control values. These data show that activation of BK(Ca(2+)) in the presence of NO/cGMP provides a brake on KCl-induced [Ca(2+)](i) responses. Experiments with the inhibitor of cyclic ADPR 8-bromo-cyclic ADPR (8-Br-cADPR) and SNP + downstream inhibitors of PKG and BK(Ca(2+)) suggest that NO inhibits ADPR cyclase in intact arterioles. When we pretreat afferent arterioles with 8-bromoguanosine 3',5'-cyclic monophosphate (8-Br-cGMP; 10 muM), the response to KCl is 143 nM. However, in the presence of both IBX and 8-Br-cGMP, we observe a surprising doubling of the [Ca(2+)](i) response to KCl. In summary, we present evidence for effects of the NO/cGMP/PKG system to reduce [Ca(2+)](i), via activation of BK(Ca(2+)) and possibly by inhibition of ADPR cyclase, and to increase [Ca(2+)](i), by a mechanism(s) yet to be defined.
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Affiliation(s)
- Susan K Fellner
- Department of Cell and Molecular Physiology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-7545, USA.
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Bensi T, Mele F, Ferretti M, Norelli S, El Daker S, Chiocchetti A, Maria Rojo J, Cauda R, Dianzani U, Savarino A. Evaluation of the antiretroviral effects of a PEG-conjugated peptide derived from human CD38. Expert Opin Ther Targets 2009; 13:141-52. [PMID: 19236233 DOI: 10.1517/14728220802637147] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
OBJECTIVE Cell infection by HIV-1 is inhibited by both the expression of CD38 and a soluble peptide (sCD38p) corresponding to its extracellular membrane-proximal amino acid sequence (amino acids 51 - 74). We show here the effects of PEG conjugation to sCD38p and provide new insights into the mechanisms behind the anti-HIV-1 effects of CD38 and derived peptides. RESEARCH DESIGN/METHODS In-vitro and in-silico study. RESULTS PEGylation of sCD38p increased its ability to inhibit replication of HIV-1 in MT-4 cells and syncytia formation in cocultures of MT-2 and persistently HIV-1(IIIB)-infected H9(IIIB) cells. In silico modeling suggests that sCD38p and CD4 form stable heterodimers involving, among others, an interaction between lysine 57 (K57) of CD38 and a groove in the CD4 receptor, which, in CD4/gp120 complexes, is partially occupied by a lysine residue of the HIV-1 envelope glycoprotein. K57 substitution with a glycine in sCD38p impaired its ability to inhibit syncytia formation in MT-2/H9(IIIB) cell cocultures and gp120 binding to CD4 in a mouse T cell line expressing human but not mouse CD4. CONCLUSIONS PEGylation significantly improves the anti-HIV-1 activity of sCD38p, whose effect is probably due to competition with gp120 for a common binding site on CD4 although other mechanisms cannot be excluded so far. The inhibitory concentrations of the sCD38p-PEG as well as its poor toxicity, merit further consideration in anti-HIV-1 strategies.
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Affiliation(s)
- Thea Bensi
- 1'A Avogadro' University of Eastern Piedmont, Interdisciplinary Research Center of Autoimmune Diseases (IRCAD), Department of Medical Science, Novara, Italy
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Osolodkin DI, Chupakhin VI, Palyulin VA, Zefirov NS. Molecular modeling of ligand-receptor interactions in GABA C receptor. J Mol Graph Model 2008; 27:813-21. [PMID: 19167917 DOI: 10.1016/j.jmgm.2008.12.004] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2008] [Revised: 11/24/2008] [Accepted: 12/12/2008] [Indexed: 10/21/2022]
Abstract
A new homology model of the GABA binding site of the GABA(C) receptor was built. Natural agonist GABA and antagonist TPMPA were docked into the receptor and molecular dynamics simulation of the complexes was performed to clarify binding poses of the ligands. It was shown that orientation of the ligand is defined by salt bridges between the ligand and the arginine (Arg104) and glutamate residues (Glu194 and Glu196) of the binding site. Different behavior and binding poses for agonist and antagonist was demonstrated by molecular dynamics simulation along with differential movement of the loop C during agonist and antagonist binding. Binding orientations of the ligands revealed that main binding forces in the GABA binding site should be electrostatic ones.
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Affiliation(s)
- Dmitry I Osolodkin
- Moscow State University, Department of Chemistry, Leninskie Gory 1/3, 119991 Moscow, Russia.
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42
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Horenstein AL, Sizzano F, Lusso R, Besso FG, Ferrero E, Deaglio S, Corno F, Malavasi F. CD38 and CD157 ectoenzymes mark cell subsets in the human corneal limbus. Mol Med 2008; 15:76-84. [PMID: 19052657 DOI: 10.2119/molmed.2008.00108] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2008] [Accepted: 11/19/2008] [Indexed: 11/06/2022] Open
Abstract
Nicotinamide adenine dinucleotide (NAD(+)), a precursor of molecules involved in cell regulatory processes, is released in extra-cellular compartments after stress or inflammation.This study investigates the expression in the human cornea of CD38 and CD157, two NAD(+)-consuming ectoenzymes and surface receptors. The analysis in corneal epithelial and stromal cells was performed by means of multiple approaches, which included immunofluorescence, reverse transcriptase polymerase chain reaction (RT-PCR), Western blot, and confocal microscopy. The presence of enzymatically active NAD(+)-consumers in intact corneal cells was analyzed by high performance liquid chromatography (HPLC)-based assays. The results obtained show that CD38 and CD157 are expressed constitutively by corneal cells: CD38 appears as a 45-kDa monomer, while CD157 is a 42- to 45-kDa doublet. The molecules are enzymatically active, with features reminiscent of those observed in human leukocytes. CD38 is expressed by cells of the suprabasal limbal epithelium, whereas it is not detectable in central corneal epithelium and stroma. CD157 is expressed by basal limbal clusters, a p63(+)/cytokeratin 19(+) cell subset reported to contain corneal stem cells, and by stromal cells. The results of the work indicates that the human cornea is equipped with molecular tools capable of consuming extracellular NAD(+), and that CD157 is a potential marker of corneal limbal cells in the stem cell niche. The presence and characteristics of these ectoenzymes may be exploited to design drugs for wound repair or for applications in tissue transplantation.
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Affiliation(s)
- Alberto L Horenstein
- Department of Genetics, Biology and Biochemistry, University of Torino Medical School, Torino, Italy.
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43
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Morgan AJ, Galione A. Investigating cADPR and NAADP in intact and broken cell preparations. Methods 2008; 46:194-203. [PMID: 18852050 DOI: 10.1016/j.ymeth.2008.09.013] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2008] [Accepted: 09/12/2008] [Indexed: 11/26/2022] Open
Abstract
The body of literature characterizing cyclic adenosine diphosphoribose (cADPR) and nicotinic acid adenine dinucleotide phosphate (NAADP) as Ca2+-mobilizing second messengers is growing apace. However, their unique properties may, for the uninitiated, make them difficult to work with. This article reviews many of the available techniques (and associated pitfalls) for investigating these nucleotide messengers, predominantly focusing upon optical techniques using fluorescent reporters to measure Ca2+ in the cytosol as well as Ca2+ or pH within the lumen of intracellular organelles.
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Affiliation(s)
- Anthony J Morgan
- Department of Pharmacology, University of Oxford, Mansfield Road, Oxford, Oxon OX1 3QT, UK.
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44
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Malavasi F, Deaglio S, Funaro A, Ferrero E, Horenstein AL, Ortolan E, Vaisitti T, Aydin S. Evolution and function of the ADP ribosyl cyclase/CD38 gene family in physiology and pathology. Physiol Rev 2008; 88:841-86. [PMID: 18626062 DOI: 10.1152/physrev.00035.2007] [Citation(s) in RCA: 619] [Impact Index Per Article: 38.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The membrane proteins CD38 and CD157 belong to an evolutionarily conserved family of enzymes that play crucial roles in human physiology. Expressed in distinct patterns in most tissues, CD38 (and CD157) cleaves NAD(+) and NADP(+), generating cyclic ADP ribose (cADPR), NAADP, and ADPR. These reaction products are essential for the regulation of intracellular Ca(2+), the most ancient and universal cell signaling system. The entire family of enzymes controls complex processes, including egg fertilization, cell activation and proliferation, muscle contraction, hormone secretion, and immune responses. Over the course of evolution, the molecules have developed the ability to interact laterally and frontally with other surface proteins and have acquired receptor-like features. As detailed in this review, the loss of CD38 function is associated with impaired immune responses, metabolic disturbances, and behavioral modifications in mice. CD38 is a powerful disease marker for human leukemias and myelomas, is directly involved in the pathogenesis and outcome of human immunodeficiency virus infection and chronic lymphocytic leukemia, and controls insulin release and the development of diabetes. Here, the data concerning diseases are examined in view of potential clinical applications in diagnosis, prognosis, and therapy. The concluding remarks try to frame all of the currently available information within a unified working model that takes into account both the enzymatic and receptorial functions of the molecules.
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Affiliation(s)
- Fabio Malavasi
- Laboratory of Immunogenetics, Department of Genetics, Biology, and Biochemistry and Centro di Ricerca in Medicina Sperimentale, University of Torino Medical School, Torino, Italy.
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45
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Schrlau MG, Brailoiu E, Patel S, Gogotsi Y, Dun NJ, Bau HH. Carbon nanopipettes characterize calcium release pathways in breast cancer cells. NANOTECHNOLOGY 2008; 19:325102. [PMID: 21828806 DOI: 10.1088/0957-4484/19/32/325102] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Carbon-based nanoprobes are attractive for minimally invasive cell interrogation but their application in cell physiology has thus far been limited. We have developed carbon nanopipettes (CNPs) with nanoscopic tips and used them to inject calcium-mobilizing messengers into cells without compromising cell viability. We identify pathways sensitive to cyclic adenosine diphosphate ribose (cADPr) and nicotinic acid adenine dinucleotide phosphate (NAADP) in breast carcinoma cells. Our findings demonstrate the superior utility of CNPs for intracellular delivery of impermeant molecules and, more generally, for cell physiology studies. The CNPs do not appear to cause any lasting damage to cells. Their advantages over commonly used glass pipettes include smaller size, breakage and clogging resistance, and potential for multifunctionality such as in concurrent injection and electrical measurements.
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Affiliation(s)
- Michael G Schrlau
- Department of Mechanical Engineering and Applied Mechanics, University of Pennsylvania, Philadelphia, PA 19104, USA
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46
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Abstract
GABA is the major inhibitory neurotransmitter in the nervous system and acts at a variety of receptors including GABAC receptors, which are a subclass of GABAA receptors. Here we have used molecular dynamics simulations of GABA docked into the extracellular domain of the GABAC receptor to explain the molecular interactions of the neurotransmitter with the residues that contribute to the binding site; in particular, we have explored the interaction of GABA with Arg104. The simulations suggest that the amine group of GABA forms cation-π interactions with Tyr102 and Tyr198, and hydrogen-bonds with Gln83, Glu220, Ser243, and Ser168, and, most prominently, with Arg104. Substituting Arg104 with Ala, Glu, or Lys, which experimentally disrupt GABAC receptor function, and repeating the simulation revealed fewer and different bonding patterns with GABA, or the rapid exit of GABA from the binding pocket. The simulations therefore unveil interactions of GABA within the binding pocket, and explain experimental data, which indicate that Arg104 is critical for the efficient functioning of the receptor.
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47
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Ci S, Ren T, Su Z. Investigating the putative binding-mode of GABA and diazepam within GABA A receptor using molecular modeling. Protein J 2008; 27:71-8. [PMID: 17805947 DOI: 10.1007/s10930-007-9109-9] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
The three-dimensional structure of the GABA A receptor that included the ligand/agonist binding site was constructed and validated by using molecular modeling technology. Moreover, the putative binding-mode of GABA and diazepam with GABAA receptor were investigated by means of docking studies. Based on an rmsd-tolerance of 1.0 angstroms, the docking of GABA to alpha1/beta2 interface resulted in three multi-member conformational clusters and model 2 was supported by homologous sequence alignment data and experimental evidence. On the other hand, the docking of diazepam to alpha1/gamma2 interface revealed five multi-member conformational clusters in the binding site and model 1 seemed to represent the correct orientation of diazepam in the binding site.
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Affiliation(s)
- Suqin Ci
- National Key Laboratory of Biochemical Engineering, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100080, P.R. China
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48
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Barranco WT, Kim DH, Stella SL, Eckhert CD. Boric acid inhibits stored Ca2+ release in DU-145 prostate cancer cells. Cell Biol Toxicol 2008; 25:309-20. [PMID: 18516691 DOI: 10.1007/s10565-008-9085-7] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2008] [Accepted: 04/22/2008] [Indexed: 10/22/2022]
Abstract
Boron (B) is a developmental and reproductive toxin. It is also essential for some organisms. Plants use uptake and efflux transport proteins to maintain homeostasis, and in humans, boron has been reported to reduce prostate cancer. Ca2+ signaling is one of the primary mechanisms used by cells to respond to their environment. In this paper, we report that boric acid (BA) inhibits NAD+ and NADP+ as well as mechanically induced release of stored Ca2+ in growing DU-145 prostate cancer cells. Cell proliferation was inhibited by 30% at 100 microM, 60% at 250 microM, and 97% at 1,000 microM BA. NAD+-induced Ca2+ transients were partly inhibited at 250 microM BA and completely at 1,000 microM BA, whereas both NADP+ and mechanically induced transients were inhibited by 1,000 microM BA. Expression of CD38 protein increased in proportion to BA exposure (0-1,000 microM). In vitro mass spectrometry analysis showed that BA formed adducts with the CD38 products and Ca2+ channel agonists cyclic adenosine diphosphate ribose (cADPR) and nicotinic acid adenine dinucleotide phosphate (NAADP). Vesicles positive for the Ca2+ fluorophore fluo-3 acetoxymethyl ester accumulated in cells exposed to 250 and 1,000 microM BA. The BA analog, methylboronic acid (MBA; 250 and 1,000 microM), did not inhibit cell proliferation or NAD+, NADP+, or mechanically stimulated Ca2+ store release. Nor did MBA increase CD38 expression or cause the formation of intracellular vesicles. Thus, mammalian cells can distinguish between BA and its synthetic analog MBA and exhibit graded concentration-dependent responses. Based on these observations, we hypothesize that toxicity of BA stems from the ability of high concentrations to impair Ca2+ signaling.
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Affiliation(s)
- Wade T Barranco
- Department of Pulmonary Medicine, Baylor College of Medicine, One Baylor Plaza, Suite 520B, Houston, TX 77030, USA
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49
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Abdel-Halim H, Hanrahan JR, Hibbs DE, Johnston GAR, Chebib M. A molecular basis for agonist and antagonist actions at GABA(C) receptors. Chem Biol Drug Des 2008; 71:306-27. [PMID: 18312293 DOI: 10.1111/j.1747-0285.2008.00642.x] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
We modelled the N-terminal ligand-binding domain of the rho1 GABA(C) receptor based on the Lymnaea stagnalis acetylcholine-binding protein (L-AChBP) crystal structure using comparative modelling and validated using flexible docking guided by known mutagenesis studies. A range of known rho1 GABA(C) receptor ligands comprising seven full agonists, 10 partial agonists, 43 antagonists and 12 inactive molecules were used to evaluate and validate the models. Of the 50 models identified, six models that allowed flexible ligand docking in accordance with the experimental data were selected and used to study detailed receptor-ligand interactions. The most refined model to accommodate all known active ligands featured a cavity comprising of a volume of 488 A(3). A detailed analysis of the interaction between the rho1 GABA(C) receptor model and the docked ligands revealed possible H-bonds and cation-pi interactions between the different ligands and binding site residues. Based on quantum mechanical/molecular mechanical (QM/MM) calculations, the model showed distinctive conformations of loop C that provided a molecular basis for agonist and antagonist actions. Agonists elicit loop C closure, while a more open loop C was observed upon antagonist binding. The model differentiates the role for key residues known to be involved in either binding and/or gating.
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Affiliation(s)
- Heba Abdel-Halim
- Faculty of Pharmacy, The University of Sydney, Sydney, NSW 2006, Australia
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Enantioselective actions of 4-amino-3-hydroxybutanoic acid and (3-amino-2-hydroxypropyl)methylphosphinic acid at recombinant GABAC receptors. Bioorg Med Chem Lett 2008; 18:402-4. [DOI: 10.1016/j.bmcl.2007.10.019] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2007] [Revised: 10/04/2007] [Accepted: 10/05/2007] [Indexed: 11/17/2022]
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