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Owji AP, Kittredge A, Zhang Y, Yang T. Structure and Function of the Bestrophin family of calcium-activated chloride channels. Channels (Austin) 2021; 15:604-623. [PMID: 34612806 PMCID: PMC8496536 DOI: 10.1080/19336950.2021.1981625] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022] Open
Abstract
Bestrophins are a family of calcium-activated chloride channels (CaCCs) with relevance to human physiology and a myriad of eye diseases termed "bestrophinopathies". Since the identification of bestrophins as CaCCs nearly two decades ago, extensive studies from electrophysiological and structural biology perspectives have sought to define their key channel features including calcium sensing, gating, inactivation, and anion selectivity. The initial X-ray crystallography studies on the prokaryotic homolog of Best1, Klebsiella pneumoniae (KpBest), and the Best1 homolog from Gallus gallus (chicken Best1, cBest1), laid the foundational groundwork for establishing the architecture of Best1. Recent progress utilizing single-particle cryogenic electron microscopy has further elucidated the molecular mechanism of gating in cBest1 and, separately, the structure of Best2 from Bos taurus (bovine Best2, bBest2). Meanwhile, whole-cell patch clamp, planar lipid bilayer, and other electrophysiologic analyses using these models as well as the human Best1 (hBest1) have provided ample evidence describing the functional properties of the bestrophin channels. This review seeks to consolidate these structural and functional results to paint a broad picture of the underlying mechanisms comprising the bestrophin family's structure-function relationship.
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Affiliation(s)
- Aaron P Owji
- Department of Pharmacology, Columbia University, NY, USA
| | - Alec Kittredge
- Department of Pharmacology, Columbia University, NY, USA
| | - Yu Zhang
- Department of Ophthalmology, Columbia University, NY, USA
| | - Tingting Yang
- Department of Ophthalmology, Columbia University, NY, USA
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Ravichandran G, Raju SV, Sarkar P, N. T. S, Al Olayan EM, Aloufi AS, Elokaby MA, Arshad A, Mala K, Arockiaraj J. Bestrophin‐derived peptide,
WP17
, elicits cell wall disruption‐mediated bactericidal activity against
Micrococcus luteus
and anti‐neoplastic effect against murine melanoma cells. Pept Sci (Hoboken) 2021. [DOI: 10.1002/pep2.24220] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Affiliation(s)
- Gayathri Ravichandran
- SRM Research Institute, SRM Institute of Science and Technology Chennai Tamil Nadu India
| | - Stefi V. Raju
- SRM Research Institute, SRM Institute of Science and Technology Chennai Tamil Nadu India
| | - Purabi Sarkar
- SRM Research Institute, SRM Institute of Science and Technology Chennai Tamil Nadu India
| | - Saraswathi N. T.
- Molecular Biophysics Lab School of Chemical and Biotechnology, SASTRA Deemed to be University Thanjavur Tamil Nadu India
| | - Ebtesam M. Al Olayan
- Department of Zoology College of Science, King Saud University Riyadh Saudi Arabia
| | - Abeer S. Aloufi
- Department of Zoology College of Science, King Saud University Riyadh Saudi Arabia
| | - Mohamed A. Elokaby
- Aquaculture Division National Institute of Oceanography and Fisheries (NIOF) Alexandria Egypt
| | - Aziz Arshad
- International Institute of Aquaculture and Aquatic Sciences (I‐AQUAS) Universiti Putra Malaysia Port Dickson Negeri Sembilan Malaysia
- Department of Aquaculture, Faculty of Agriculture University Putra Malaysia Serdang Selangor Malaysia
| | - Kanchana Mala
- Department of Medical Research Medical College Hospital & Research Centre, SRM Institute of Science & Technology Chennai Tamil Nadu India
| | - Jesu Arockiaraj
- SRM Research Institute, SRM Institute of Science and Technology Chennai Tamil Nadu India
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Kane Dickson V. Phasing and structure of bestrophin-1: a case study in the use of heavy-atom cluster compounds with multi-subunit transmembrane proteins. ACTA CRYSTALLOGRAPHICA SECTION D-STRUCTURAL BIOLOGY 2016; 72:319-25. [PMID: 26960119 PMCID: PMC4784663 DOI: 10.1107/s2059798315022524] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/12/2015] [Accepted: 11/25/2015] [Indexed: 11/16/2022]
Abstract
The structure of a eukaryotic ion channel solved using tantalum bromide SAD phasing is discussed in the context of basic challenges common to membrane proteins. The purification and three-dimensional crystallization of membrane proteins are commonly affected by a cumulation of pathologies that are less prevalent in their soluble counterparts. This may include severe anisotropy, poor spot shape, poor to moderate-resolution diffraction, crystal twinning, translational pseudo-symmetry and poor uptake of heavy atoms for derivatization. Such challenges must be circumvented by adaptations in the approach to crystallization and/or phasing. Here, an example of a protein that exhibited all of the above-mentioned complications is presented. Bestrophin-1 is a eukaryotic calcium-activated chloride channel, the structure of which was recently determined in complex with monoclonal antibody fragments using SAD phasing with tantalum bromide clusters (Ta6Br12·Br2). Some of the obstacles to obtaining improved diffraction and phasing for this particular channel are discussed, as well as the approach and adaptations that were key to determining the structure.
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Affiliation(s)
- Veronica Kane Dickson
- Cambridge Institute for Medical Research, University of Cambridge, Hills Road, Cambridge CB2 0XY, England
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Kane Dickson V, Pedi L, Long SB. Structure and insights into the function of a Ca(2+)-activated Cl(-) channel. Nature 2014; 516:213-8. [PMID: 25337878 DOI: 10.1038/nature13913] [Citation(s) in RCA: 154] [Impact Index Per Article: 15.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2014] [Accepted: 10/06/2014] [Indexed: 01/22/2023]
Abstract
Bestrophin calcium-activated chloride channels (CaCCs) regulate the flow of chloride and other monovalent anions across cellular membranes in response to intracellular calcium (Ca(2+)) levels. Mutations in bestrophin 1 (BEST1) cause certain eye diseases. Here we present X-ray structures of chicken BEST1-Fab complexes, at 2.85 Å resolution, with permeant anions and Ca(2+). Representing, to our knowledge, the first structure of a CaCC, the eukaryotic BEST1 channel, which recapitulates CaCC function in liposomes, is formed from a pentameric assembly of subunits. Ca(2+) binds to the channel's large cytosolic region. A single ion pore, approximately 95 Å in length, is located along the central axis and contains at least 15 binding sites for anions. A hydrophobic neck within the pore probably forms the gate. Phenylalanine residues within it may coordinate permeating anions via anion-π interactions. Conformational changes observed near the 'Ca(2+) clasp' hint at the mechanism of Ca(2+)-dependent gating. Disease-causing mutations are prevalent within the gating apparatus.
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Affiliation(s)
- Veronica Kane Dickson
- Structural Biology Program, Memorial Sloan Kettering Cancer Center, 1275 York Avenue, New York, New York 10065, USA
| | - Leanne Pedi
- Structural Biology Program, Memorial Sloan Kettering Cancer Center, 1275 York Avenue, New York, New York 10065, USA
| | - Stephen B Long
- Structural Biology Program, Memorial Sloan Kettering Cancer Center, 1275 York Avenue, New York, New York 10065, USA
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Yang T, Liu Q, Kloss B, Bruni R, Kalathur RC, Guo Y, Kloppmann E, Rost B, Colecraft HM, Hendrickson WA. Structure and selectivity in bestrophin ion channels. Science 2014; 346:355-9. [PMID: 25324390 DOI: 10.1126/science.1259723] [Citation(s) in RCA: 92] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Human bestrophin-1 (hBest1) is a calcium-activated chloride channel from the retinal pigment epithelium, where mutations are associated with vitelliform macular degeneration, or Best disease. We describe the structure of a bacterial homolog (KpBest) of hBest1 and functional characterizations of both channels. KpBest is a pentamer that forms a five-helix transmembrane pore, closed by three rings of conserved hydrophobic residues, and has a cytoplasmic cavern with a restricted exit. From electrophysiological analysis of structure-inspired mutations in KpBest and hBest1, we find a sensitive control of ion selectivity in the bestrophins, including reversal of anion/cation selectivity, and dramatic activation by mutations at the cytoplasmic exit. A homology model of hBest1 shows the locations of disease-causing mutations and suggests possible roles in regulation.
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Affiliation(s)
- Tingting Yang
- Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY 10032, USA
| | - Qun Liu
- New York Structural Biology Center, Synchrotron Beamlines, Brookhaven National Laboratory, Upton, NY 11973, USA
| | - Brian Kloss
- New York Consortium on Membrane Protein Structure, New York Structural Biology Center, 89 Convent Avenue, New York, NY 10027, USA
| | - Renato Bruni
- New York Consortium on Membrane Protein Structure, New York Structural Biology Center, 89 Convent Avenue, New York, NY 10027, USA
| | - Ravi C Kalathur
- New York Consortium on Membrane Protein Structure, New York Structural Biology Center, 89 Convent Avenue, New York, NY 10027, USA
| | - Youzhong Guo
- Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY 10032, USA
| | - Edda Kloppmann
- New York Consortium on Membrane Protein Structure, New York Structural Biology Center, 89 Convent Avenue, New York, NY 10027, USA. Department of Informatics, Bioinformatics and Computational Biology, TUM (Technische Universität München), Garching 85748, Germany
| | - Burkhard Rost
- New York Consortium on Membrane Protein Structure, New York Structural Biology Center, 89 Convent Avenue, New York, NY 10027, USA. Department of Informatics, Bioinformatics and Computational Biology, TUM (Technische Universität München), Garching 85748, Germany
| | - Henry M Colecraft
- Department of Physiology and Cellular Biophysics, Columbia University, New York, NY 10032, USA
| | - Wayne A Hendrickson
- Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY 10032, USA. New York Structural Biology Center, Synchrotron Beamlines, Brookhaven National Laboratory, Upton, NY 11973, USA. New York Consortium on Membrane Protein Structure, New York Structural Biology Center, 89 Convent Avenue, New York, NY 10027, USA. Department of Physiology and Cellular Biophysics, Columbia University, New York, NY 10032, USA.
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Effects of alternative splicing on the function of bestrophin-1 calcium-activated chloride channels. Biochem J 2014; 458:575-83. [PMID: 24341532 DOI: 10.1042/bj20121546] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
The proposed Ca2+-activated Cl- channel protein Best1 (bestrophin 1) is expressed and functionally important in the retina and in the brain. Human BEST1 has two known splice variants, Best1V1 and Best1V2, which arise from alternative splicing of two exons: exon 2 splicing results in a unique N-terminal domain, whereas alternative splicing of exon 11 produces two mutually exclusive C-termini. Prior studies were limited to Best1V1 and its clinically relevant mutations. In the present work, we cloned a novel splice variant of Best1V1 missing exon 2 (Best1V1Δex2) and differing from each of the two previously identified isoforms by one alternatively spliced domain. This finding allowed us to determine the role for alternative splicing of the Best1 N- and C-termini. We heteroexpressed Best1V1Δex2 in HEK (human embryonic kidney)-293 cells, and compared its properties with Best1V1 and Best1V2. Western blot analysis confirmed protein expression from all three splice variants. Both Best1V1 and Best1V1Δex2 successfully formed Ca2+-activated Cl- channels, demonstrating that the N-terminus encoded by exon 2 is not essential for channel function. In contrast, Best1V2-expressing cells had no detectable Ca2+-activated Cl- currents, pointing to a critical role for splicing of the C-terminus. Surface protein biotinylation demonstrated that Best1V1 and Best1V1Δex2 are trafficked to the plasma membrane, whereas Best1V2 is not. These results define the impact of alternative splicing on Best1 function, and should be taken into consideration in future modelling of the Best1 protein structure.
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Piccoli S, Suku E, Garonzi M, Giorgetti A. Genome-wide Membrane Protein Structure Prediction. Curr Genomics 2013; 14:324-9. [PMID: 24403851 PMCID: PMC3763683 DOI: 10.2174/13892029113149990009] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2013] [Revised: 07/19/2013] [Accepted: 07/22/2013] [Indexed: 01/25/2023] Open
Abstract
Transmembrane proteins allow cells to extensively communicate with the external world in a very accurate and specific way. They form principal nodes in several signaling pathways and attract large interest in therapeutic intervention, as the majority pharmaceutical compounds target membrane proteins. Thus, according to the current genome annotation methods, a detailed structural/functional characterization at the protein level of each of the elements codified in the genome is also required. The extreme difficulty in obtaining high-resolution three-dimensional structures, calls for computational approaches. Here we review to which extent the efforts made in the last few years, combining the structural characterization of membrane proteins with protein bioinformatics techniques, could help describing membrane proteins at a genome-wide scale. In particular we analyze the use of comparative modeling techniques as a way of overcoming the lack of high-resolution three-dimensional structures in the human membrane proteome.
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Affiliation(s)
- Stefano Piccoli
- Applied Bioinformatics Group, Dept. of Biotechnology, University of Verona, strada Le grazie 15, 37134, Verona,
Italy
| | - Eda Suku
- Applied Bioinformatics Group, Dept. of Biotechnology, University of Verona, strada Le grazie 15, 37134, Verona,
Italy
| | - Marianna Garonzi
- Applied Bioinformatics Group, Dept. of Biotechnology, University of Verona, strada Le grazie 15, 37134, Verona,
Italy
| | - Alejandro Giorgetti
- Applied Bioinformatics Group, Dept. of Biotechnology, University of Verona, strada Le grazie 15, 37134, Verona,
Italy
- German Research School for Simulation Sciences, Juelich, Germany
- Center for Biomedical Computing (CBMC), University of Verona, strada Le grazie 8, 37134, Verona, Italy
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8
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Doumanov JA, Zeitz C, Gimenez PD, Audo I, Krishna A, Alfano G, Diaz MLB, Moskova-Doumanova V, Lancelot ME, Sahel JA, Nandrot EF, Bhattacharya SS. Disease-causing mutations in BEST1 gene are associated with altered sorting of bestrophin-1 protein. Int J Mol Sci 2013; 14:15121-40. [PMID: 23880862 PMCID: PMC3742291 DOI: 10.3390/ijms140715121] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2013] [Revised: 07/02/2013] [Accepted: 07/04/2013] [Indexed: 01/03/2023] Open
Abstract
Mutations in BEST1 gene, encoding the bestrophin-1 (Best1) protein are associated with macular dystrophies. Best1 is predominantly expressed in the retinal pigment epithelium (RPE), and is inserted in its basolateral membrane. We investigated the cellular localization in polarized MDCKII cells of disease-associated Best1 mutant proteins to study specific sorting motifs of Best1. Real-time PCR and western blots for endogenous expression of BEST1 in MDCK cells were performed. Best1 mutant constructs were generated using site-directed mutagenesis and transfected in MDCK cells. For protein sorting, confocal microscopy studies, biotinylation assays and statistical methods for quantification of mislocalization were used. Analysis of endogenous expression of BEST1 in MDCK cells revealed the presence of BEST1 transcript but no protein. Confocal microscopy and quantitative analyses indicate that transfected normal human Best1 displays a basolateral localization in MDCK cells, while cell sorting of several Best1 mutants (Y85H, Q96R, L100R, Y227N, Y227E) was altered. In contrast to constitutively active Y227E, constitutively inactive Y227F Best1 mutant localized basolaterally similar to the normal Best1 protein. Our data suggest that at least three basolateral sorting motifs might be implicated in proper Best1 basolateral localization. In addition, non-phosphorylated tyrosine 227 could play a role for basolateral delivery.
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Affiliation(s)
- Jordan A. Doumanov
- Biological Faculty, Sofia University “Saint Kliment Ohridski”, 8 Dragan Tzankov str, Sofia 1164, Bulgaria; E-Mail:
- Author to whom correspondence should be addressed; E-Mail: ; Tel.: +359-2-8167-204; Fax: +359-2-8656-641
| | - Christina Zeitz
- Institut National de la Santé et de la Recherche Médicale (INSERM), UMR_S 968, Paris F-75012, France; E-Mails: (C.Z.); (I.A.); (M.-E.L.); (J.-A.S.); (E.F.N.); (S.S.B.)
- Centre National de la Recherche Scientifique (CNRS), UMR_7210, Paris F-75012, France
- Centre de Recherche Institut de la Vision, Université Pierre et Marie Curie-Paris 6, 17 rue Moreau, Paris F-75012, France
| | - Paloma Dominguez Gimenez
- Andalusian Center of Molecular Biology and Regenerative Medicine, Centro Andaluz de Biología Molecular y Medicina Regenerativa (CABIMER), Avda. Americo Vespucio s/n, Parque Cientifico y Tecnologico, Isla de la Cartuja 41092, Sevilla, Spain; E-Mails: (P.D.G.); (A.K.); (M.L.B.D.)
| | - Isabelle Audo
- Institut National de la Santé et de la Recherche Médicale (INSERM), UMR_S 968, Paris F-75012, France; E-Mails: (C.Z.); (I.A.); (M.-E.L.); (J.-A.S.); (E.F.N.); (S.S.B.)
- Centre National de la Recherche Scientifique (CNRS), UMR_7210, Paris F-75012, France
- Centre de Recherche Institut de la Vision, Université Pierre et Marie Curie-Paris 6, 17 rue Moreau, Paris F-75012, France
- Centre de Référence Maladies Rares/Centre d’Investigation Clinique (CMR/CIC), 503 INSERM, CHNO des Quinze-Vingts, Paris F-75012, France
| | - Abhay Krishna
- Andalusian Center of Molecular Biology and Regenerative Medicine, Centro Andaluz de Biología Molecular y Medicina Regenerativa (CABIMER), Avda. Americo Vespucio s/n, Parque Cientifico y Tecnologico, Isla de la Cartuja 41092, Sevilla, Spain; E-Mails: (P.D.G.); (A.K.); (M.L.B.D.)
| | - Giovanna Alfano
- Institute of Ophthalmology, University College London, 11-43 Bath Street, London EC1V 9EL, UK
| | - Maria Luz Bellido Diaz
- Andalusian Center of Molecular Biology and Regenerative Medicine, Centro Andaluz de Biología Molecular y Medicina Regenerativa (CABIMER), Avda. Americo Vespucio s/n, Parque Cientifico y Tecnologico, Isla de la Cartuja 41092, Sevilla, Spain; E-Mails: (P.D.G.); (A.K.); (M.L.B.D.)
| | - Veselina Moskova-Doumanova
- Biological Faculty, Sofia University “Saint Kliment Ohridski”, 8 Dragan Tzankov str, Sofia 1164, Bulgaria; E-Mail:
| | - Marie-Elise Lancelot
- Institut National de la Santé et de la Recherche Médicale (INSERM), UMR_S 968, Paris F-75012, France; E-Mails: (C.Z.); (I.A.); (M.-E.L.); (J.-A.S.); (E.F.N.); (S.S.B.)
- Centre National de la Recherche Scientifique (CNRS), UMR_7210, Paris F-75012, France
- Centre de Recherche Institut de la Vision, Université Pierre et Marie Curie-Paris 6, 17 rue Moreau, Paris F-75012, France
| | - José-Alain Sahel
- Institut National de la Santé et de la Recherche Médicale (INSERM), UMR_S 968, Paris F-75012, France; E-Mails: (C.Z.); (I.A.); (M.-E.L.); (J.-A.S.); (E.F.N.); (S.S.B.)
- Centre National de la Recherche Scientifique (CNRS), UMR_7210, Paris F-75012, France
- Centre de Recherche Institut de la Vision, Université Pierre et Marie Curie-Paris 6, 17 rue Moreau, Paris F-75012, France
- Centre de Référence Maladies Rares/Centre d’Investigation Clinique (CMR/CIC), 503 INSERM, CHNO des Quinze-Vingts, Paris F-75012, France
- Fondation Ophtalmologique Adolphe de Rothschild, Paris F-75019, France
| | - Emeline F. Nandrot
- Institut National de la Santé et de la Recherche Médicale (INSERM), UMR_S 968, Paris F-75012, France; E-Mails: (C.Z.); (I.A.); (M.-E.L.); (J.-A.S.); (E.F.N.); (S.S.B.)
- Centre National de la Recherche Scientifique (CNRS), UMR_7210, Paris F-75012, France
- Centre de Recherche Institut de la Vision, Université Pierre et Marie Curie-Paris 6, 17 rue Moreau, Paris F-75012, France
| | - Shomi S. Bhattacharya
- Institut National de la Santé et de la Recherche Médicale (INSERM), UMR_S 968, Paris F-75012, France; E-Mails: (C.Z.); (I.A.); (M.-E.L.); (J.-A.S.); (E.F.N.); (S.S.B.)
- Centre National de la Recherche Scientifique (CNRS), UMR_7210, Paris F-75012, France
- Centre de Recherche Institut de la Vision, Université Pierre et Marie Curie-Paris 6, 17 rue Moreau, Paris F-75012, France
- Andalusian Center of Molecular Biology and Regenerative Medicine, Centro Andaluz de Biología Molecular y Medicina Regenerativa (CABIMER), Avda. Americo Vespucio s/n, Parque Cientifico y Tecnologico, Isla de la Cartuja 41092, Sevilla, Spain; E-Mails: (P.D.G.); (A.K.); (M.L.B.D.)
- Institute of Ophthalmology, University College London, 11-43 Bath Street, London EC1V 9EL, UK
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Priya SSL, Devi PR, Eganathan P, Topno NS. Structure prediction of Bestrophin for the induced - fit docking of anthocyanins. Bioinformation 2012; 8:742-8. [PMID: 23055624 PMCID: PMC3449392 DOI: 10.6026/97320630008742] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2012] [Accepted: 08/13/2012] [Indexed: 11/23/2022] Open
Abstract
UNLABELLED Bestrophin, an integral membrane protein existing in basolateral region of the retina is a propitious target for drug discovery. Mutations in the Bestrophin protein cause Best Vitelliform Macular Dystrophy (BVMD) leading to retinal damages and loss of visual acuity. Owing to the lack of three dimensional structure and related structural homologs in the protein data bank, we modeled the bestrophin protein using Robetta ab initio method. Further, no treatment is available for the disease. In this situation, anthocyanins from natural sources are reported to combat retinal damages. Hence, we identified anthocyanins from Syzygium cumini fruit skin using Electrospray Ionization tandem mass spectrometry. These compounds were docked into the predicted bestrophin model to study the interactions within the active site. The results may provide a valuable insight into the structure of bestrophin and efficacy of anthocyanins in molecular docking studies. ABBREVIATIONS PTP - Putative transmembrane proteins, VMD - Vitelliform macular dystrophy, BVMD - Best's vitelliform macular dystrophy, RPE - Retinal pigment epithelium, ESI-MS/MS - Electrospray Ionization Tandem Mass Spectrometry, UNIPROT - Universal Protein Resource, PSIPRED - Protein secondary structure prediction, TMH - Transmembrane Helices, SCFS - Syzygium cumini fruit skin DP - Declustering Potential IFD - Induced Fit Docking.
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Affiliation(s)
| | - Ponnuswamy Renuka Devi
- Department of Biotechnology, Anna University of Technology, Coimbatore- 641 047, Tamilnadu, India
| | - Palanisami Eganathan
- Plant Tissue Culture and Bioprospecting Laboratory, M. S. Swaminathan Research Foundation, 3rd Cross Road, Institutional Area, Taramani, Chennai- 600113. India
| | - Nishith Saurav Topno
- Centre for Bioinformatics, School of Life Sciences, Pondicherry University, Kalapet, Puducherry- 605 014, India
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MacDonald IM, Gudiseva HV, Villanueva A, Greve M, Caruso R, Ayyagari R. Phenotype and genotype of patients with autosomal recessive bestrophinopathy. Ophthalmic Genet 2011; 33:123-9. [PMID: 21809908 DOI: 10.3109/13816810.2011.592172] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
PURPOSE To describe the phenotype and genotype of patients with autosomal recessive bestrophinopathy. METHODOLOGY The phenotype of the subjects was described after a complete ophthalmological examination, and in various cases, ancillary testing of the visual field, optical coherent tomography, full field electroretinography and electrophysiology. Genetic analysis was carried out by screening the Bestrophin-1 (BEST1) gene for mutations by dideoxy sequencing and segregation analysis. RESULTS We identified three previously described mutations (Ala195Val, Leu191Pro and Arg141His) and two potentially pathogenic changes (Trp93Pro and Trp287Ter) in the Best-1 gene. Two patients carried compound heterozygous mutations, Trp93Pro/Ala195Val, and Leu191Pro/Trp287Ter. Two sisters were homozygous for an Arg141His mutation. All individuals with Best1 gene mutations had signs of maculopathy. CONCLUSIONS Our observations expand the limited number of phenotypes associated with mutations in the Best1 gene. Patients with compound heteroyzygous Best1 mutations developed atypical forms of Best disease. Two siblings with homozygous Arg141His mutation developed symptoms of typical Best vitelliform dystrophy while their parents had clinical features of mild maculopathy.
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Autosomal recessive vitelliform macular dystrophy in a large cohort of vitelliform macular dystrophy patients. Retina 2011; 31:581-95. [PMID: 21273940 DOI: 10.1097/iae.0b013e318203ee60] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
PURPOSE To report 11 cases of autosomal recessive vitelliform macular dystrophy and to compare their molecular findings and phenotypic characteristics with those of patients with the more common and well-described dominant form of the disease. METHODS Blood samples were obtained from 435 unrelated individuals with a clinical diagnosis of vitelliform macular dystrophy and screened for mutations in the coding sequences of BEST1. Medical records and retinal photographs of selected patients were reviewed. RESULTS Nine of the 435 probands were found to have 2 plausible disease-causing variations in BEST1, while 198 individuals were found to have heterozygous variations compatible with autosomal dominant inheritance. Inheritance phase was determined in three of the recessive families. Six novel disease-causing mutations were identified among these recessive patients: Arg47Cys, IVS7-2A>G, IVS7+4G>A, Ile205del12ATCCTGCTCCAGAG, Pro274Arg, and Ile366delCAGGTGTGGC. Forty-four novel disease-causing mutations were identified among the patients with presumed autosomal dominant disease. The phenotype of patients with recessive alleles for BEST1 ranged from typical vitelliform lesions to extensive extramacular deposits. CONCLUSION The authors provide evidence that two abnormal BEST1 alleles, neither of which causes macular disease alone, can act in concert to cause early-onset vitelliform macular dystrophy.
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Zangerl B, Wickström K, Slavik J, Lindauer SJ, Ahonen S, Schelling C, Lohi H, Guziewicz KE, Aguirre GD. Assessment of canine BEST1 variations identifies new mutations and establishes an independent bestrophinopathy model (cmr3). Mol Vis 2010; 16:2791-804. [PMID: 21197113 PMCID: PMC3008713] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2010] [Accepted: 12/11/2010] [Indexed: 11/27/2022] Open
Abstract
PURPOSE Mutations in bestrophin 1 (BEST1) are associated with a group of retinal disorders known as bestrophinopathies in man and canine multifocal retinopathies (cmr) in the dog. To date, the dog is the only large animal model suitable for the complex characterization and in-depth studies of Best-related disorders. In the first report of cmr, the disease was described in a group of mastiff-related breeds (cmr1) and the Coton de Tulear (cmr2). Additional breeds, e.g., the Lapponian herder (LH) and others, subsequently were recognized with similar phenotypes, but linked loci are unknown. Analysis of the BEST1 gene aimed to identify mutations in these additional populations and extend our understanding of genotype-phenotype associations. METHODS Animals were subjected to routine eye exams, phenotypically characterized, and samples were collected for molecular studies. Known BEST1 mutations were assessed, and the canine BEST1 coding exons were amplified and sequenced in selected individuals that exhibited a cmr compatible phenotype but that did not carry known mutations. Resulting sequence changes were genotyped in several different breeds and evaluated in the context of the phenotype. RESULTS Seven novel coding variants were identified in exon 10 of cBEST1. Two linked mutations were associated with cmr exclusive to the LH breed (cmr3). Two individuals of Jämthund and Norfolk terrier breeds were heterozygous for two conservative changes, but these were unlikely to have disease-causing potential. Another three substitutions were found in the Bernese mountain dog that were predicted to have a deleterious effect on protein function. Previously reported mutations were excluded from segregation in these populations, but cmr1 was confirmed in another mastiff-related breed, the Italian cane corso. CONCLUSIONS A third independent canine model for human bestrophinopathies has been established in the LH breed. While exhibiting a phenotype comparable to cmr1 and cmr2, the novel cmr3 mutation is predicted to be based on a distinctly different molecular mechanism. So far cmr2 and cmr3 are exclusive to a single dog breed each. In contrast, cmr1 is found in multiple related breeds. Additional sequence alterations identified in exon 10 of cBEST1 in other breeds exhibit potential disease-causing features. The inherent genetic and phenotypic variation observed with retinal disorders in canines is complicated further by cmr3 being one of four distinct genetic retinal traits found to segregate in LH. Thus, a combination of phenotypic, molecular, and population analysis is required to establish a strong phenotype-genotype association. These results indicate that cmr has a larger impact on the general dog population than was initially suspected. The complexity of these models further confirms the similarity to human bestrophinopathies. Moreover, analyses of multiple canine models will provide additional insight into the molecular basis underlying diseases caused by mutations in BEST1.
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Affiliation(s)
- Barbara Zangerl
- Section of Ophthalmology, School of Veterinary Medicine, University of Pennsylvania, Philadelphia, PA
| | | | - Julianna Slavik
- Section of Ophthalmology, School of Veterinary Medicine, University of Pennsylvania, Philadelphia, PA
| | - Sarah J. Lindauer
- Section of Ophthalmology, School of Veterinary Medicine, University of Pennsylvania, Philadelphia, PA
| | - Saija Ahonen
- Department of Veterinary Biosciences, Department of Medical Genetics, Program in Molecular Medicine, University of Helsinki and Folkhälsan Research Institute, Helsinki, Finland
| | - Claude Schelling
- Department of Animal Sciences, Swiss Federal Institute of Technology Zurich and Vetsuisse Faculty Zurich, University of Zurich, Zurich, Switzerland
| | - Hannes Lohi
- Department of Veterinary Biosciences, Department of Medical Genetics, Program in Molecular Medicine, University of Helsinki and Folkhälsan Research Institute, Helsinki, Finland
| | - Karina E. Guziewicz
- Section of Ophthalmology, School of Veterinary Medicine, University of Pennsylvania, Philadelphia, PA
| | - Gustavo D. Aguirre
- Section of Ophthalmology, School of Veterinary Medicine, University of Pennsylvania, Philadelphia, PA
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Duran C, Thompson CH, Xiao Q, Hartzell HC. Chloride channels: often enigmatic, rarely predictable. Annu Rev Physiol 2010; 72:95-121. [PMID: 19827947 DOI: 10.1146/annurev-physiol-021909-135811] [Citation(s) in RCA: 241] [Impact Index Per Article: 17.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Until recently, anion (Cl(-)) channels have received considerably less attention than cation channels. One reason for this may be that many Cl(-) channels perform functions that might be considered cell-biological, like fluid secretion and cell volume regulation, whereas cation channels have historically been associated with cellular excitability, which typically happens more rapidly. In this review, we discuss the recent explosion of interest in Cl(-) channels, with special emphasis on new and often surprising developments over the past five years. This is exemplified by the findings that more than half of the ClC family members are antiporters, and not channels, as was previously thought, and that bestrophins, previously prime candidates for Ca(2+)-activated Cl(-) channels, have been supplanted by the newly discovered anoctamins and now hold a tenuous position in the Cl(-) channel world.
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Affiliation(s)
- Charity Duran
- Department of Cell Biology, Emory University School of Medicine, Atlanta, GA 30322, USA
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14
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Xiao Q, Hartzell HC, Yu K. Bestrophins and retinopathies. Pflugers Arch 2010; 460:559-69. [PMID: 20349192 DOI: 10.1007/s00424-010-0821-5] [Citation(s) in RCA: 85] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2010] [Revised: 03/01/2010] [Accepted: 03/04/2010] [Indexed: 10/19/2022]
Abstract
Best vitelliform macular dystrophy (BVMD, also called Best's disease) is a dominantly inherited, juvenile-onset form of macular degeneration, which is characterized by abnormal accumulation of yellow pigment in the outer retina and a depressed electro-oculogram light peak (LP). Over 100 disease-causing mutations in human bestrophin-1 (hBest1) are closely linked to BVMD and several other retinopathies. However, the physiological role of hBest1 and the mechanisms of retinal pathology remain obscure partly because hBest1 has been described as a protein with multiple functions including a Ca2+-activated Cl- channel, a Ca2+ channel regulator, a volume-regulated Cl- channel, and a HCO3- channel. This review focuses on how dysfunction of hBest1 is related to the accumulation of yellow pigment and a decreased LP. The dysfunction of hBest1 as a HCO3- channel or a volume-regulated Cl- channel may be associated with defective regulation of the subretinal fluid or phagocytosis of photoreceptor outer segments by retinal pigment epithelium cells, which may lead to fluid and pigment accumulation.
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Affiliation(s)
- Qinghuan Xiao
- Department of Cell Biology and Center for Neurodegenerative Disease, Emory University School of Medicine, Atlanta, GA 30322, USA.
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15
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Bestrophin and TMEM16-Ca(2+) activated Cl(-) channels with different functions. Cell Calcium 2009; 46:233-41. [PMID: 19783045 DOI: 10.1016/j.ceca.2009.09.003] [Citation(s) in RCA: 102] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2009] [Revised: 09/01/2009] [Accepted: 09/04/2009] [Indexed: 12/23/2022]
Abstract
In the past, a number of candidates have been proposed to form Ca(2+) activated Cl(-) currents, but it is only recently that two families of proteins, the bestrophins and the TMEM16-proteins, recapitulate reliably the properties of Ca(2+) activated Cl(-) currents. Bestrophin 1 is strongly expressed in the retinal pigment epithelium, but also at lower levels in other cell types. Bestrophin 1 may form Ca(2+) activated chloride channels and, at the same time, affect intracellular Ca(2+) signaling. In epithelial cells, bestrophin 1 probably controls receptor mediated Ca(2+) signaling. It may do so by facilitating Ca(2+) release from the endoplasmic reticulum, thereby indirectly activating membrane localized Ca(2+)-dependent Cl(-) channels. In contrast to bestrophin 1, the Ca(2+) activated Cl(-) channel TMEM16A (anoctamin 1, ANO1) shows most of the biophysical and pharmacological properties that have been attributed to Ca(2+)-dependent Cl(-) channels in various tissues. TMEM16A is broadly expressed in both mouse and human tissues and is of particular importance in epithelial cells. Thus exocrine gland secretion as well as electrolyte transport by both respiratory and intestinal epithelia requires TMEM16A. Because of its role for Ca(2+)-dependent Cl(-) secretion in human airways, it is likely to become a prime target for the therapy of cystic fibrosis lung disease, caused by defective cAMP-dependent Cl(-) secretion. It will be very exciting to learn, how TMEM16A and other TMEM16-proteins are activated upon increase in intracellular Ca(2+), and whether the other nine members of the TMEM16 family also form Cl(-) channels with properties similar to TMEM16A.
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