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Pospiech M, Owens SE, Miller DJ, Austin-Muttitt K, Mullins JGL, Cronin JG, Allemann RK, Sheldon IM. Bisphosphonate inhibitors of squalene synthase protect cells against cholesterol-dependent cytolysins. FASEB J 2021; 35:e21640. [PMID: 33991130 DOI: 10.1096/fj.202100164r] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2021] [Revised: 04/09/2021] [Accepted: 04/19/2021] [Indexed: 01/29/2023]
Abstract
Certain species of pathogenic bacteria damage tissues by secreting cholesterol-dependent cytolysins, which form pores in the plasma membranes of animal cells. However, reducing cholesterol protects cells against these cytolysins. As the first committed step of cholesterol biosynthesis is catalyzed by squalene synthase, we explored whether inhibiting this enzyme protected cells against cholesterol-dependent cytolysins. We first synthesized 22 different nitrogen-containing bisphosphonate molecules that were designed to inhibit squalene synthase. Squalene synthase inhibition was quantified using a cell-free enzyme assay, and validated by computer modeling of bisphosphonate molecules binding to squalene synthase. The bisphosphonates were then screened for their ability to protect HeLa cells against the damage caused by the cholesterol-dependent cytolysin, pyolysin. The most effective bisphosphonate reduced pyolysin-induced leakage of lactate dehydrogenase into cell supernatants by >80%, and reduced pyolysin-induced cytolysis from >75% to <25%. In addition, this bisphosphonate reduced pyolysin-induced leakage of potassium from cells, limited changes in the cytoskeleton, prevented mitogen-activated protein kinases cell stress responses, and reduced cellular cholesterol. The bisphosphonate also protected cells against another cholesterol-dependent cytolysin, streptolysin O, and protected lung epithelial cells and primary dermal fibroblasts against cytolysis. Our findings imply that treatment with bisphosphonates that inhibit squalene synthase might help protect tissues against pathogenic bacteria that secrete cholesterol-dependent cytolysins.
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Affiliation(s)
- Mateusz Pospiech
- Swansea University Medical School, Swansea University, Swansea, UK
| | - Siân E Owens
- Swansea University Medical School, Swansea University, Swansea, UK
| | | | | | | | - James G Cronin
- Swansea University Medical School, Swansea University, Swansea, UK
| | | | - I Martin Sheldon
- Swansea University Medical School, Swansea University, Swansea, UK
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Abdel-Khalik J, Hearn T, Dickson AL, Crick PJ, Yutuc E, Austin-Muttitt K, Bigger BW, Morris AA, Shackleton CH, Clayton PT, Iida T, Sircar R, Rohatgi R, Marschall HU, Sjövall J, Björkhem I, Mullins JGL, Griffiths WJ, Wang Y. Bile acid biosynthesis in Smith-Lemli-Opitz syndrome bypassing cholesterol: Potential importance of pathway intermediates. J Steroid Biochem Mol Biol 2021; 206:105794. [PMID: 33246156 PMCID: PMC7816163 DOI: 10.1016/j.jsbmb.2020.105794] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/30/2020] [Revised: 11/16/2020] [Accepted: 11/18/2020] [Indexed: 12/15/2022]
Abstract
Bile acids are the end products of cholesterol metabolism secreted into bile. They are essential for the absorption of lipids and lipid soluble compounds from the intestine. Here we have identified a series of unusual Δ5-unsaturated bile acids in plasma and urine of patients with Smith-Lemli-Opitz syndrome (SLOS), a defect in cholesterol biosynthesis resulting in elevated levels of 7-dehydrocholesterol (7-DHC), an immediate precursor of cholesterol. Using liquid chromatography - mass spectrometry (LC-MS) we have uncovered a pathway of bile acid biosynthesis in SLOS avoiding cholesterol starting with 7-DHC and proceeding through 7-oxo and 7β-hydroxy intermediates. This pathway also occurs to a minor extent in healthy humans, but elevated levels of pathway intermediates could be responsible for some of the features SLOS. The pathway is also active in SLOS affected pregnancies as revealed by analysis of amniotic fluid. Importantly, intermediates in the pathway, 25-hydroxy-7-oxocholesterol, (25R)26-hydroxy-7-oxocholesterol, 3β-hydroxy-7-oxocholest-5-en-(25R)26-oic acid and the analogous 7β-hydroxysterols are modulators of the activity of Smoothened (Smo), an oncoprotein that mediates Hedgehog (Hh) signalling across membranes during embryogenesis and in the regeneration of postembryonic tissue. Computational docking of the 7-oxo and 7β-hydroxy compounds to the extracellular cysteine rich domain of Smo reveals that they bind in the same groove as both 20S-hydroxycholesterol and cholesterol, known activators of the Hh pathway.
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Affiliation(s)
- Jonas Abdel-Khalik
- Swansea University Medical School, ILS1 Building, Singleton Park, Swansea, SA2 8PP, Wales, UK
| | - Thomas Hearn
- Swansea University Medical School, ILS1 Building, Singleton Park, Swansea, SA2 8PP, Wales, UK
| | - Alison L Dickson
- Swansea University Medical School, ILS1 Building, Singleton Park, Swansea, SA2 8PP, Wales, UK
| | - Peter J Crick
- Swansea University Medical School, ILS1 Building, Singleton Park, Swansea, SA2 8PP, Wales, UK
| | - Eylan Yutuc
- Swansea University Medical School, ILS1 Building, Singleton Park, Swansea, SA2 8PP, Wales, UK
| | - Karl Austin-Muttitt
- Swansea University Medical School, ILS1 Building, Singleton Park, Swansea, SA2 8PP, Wales, UK
| | - Brian W Bigger
- Stem Cell & Neurotherapies, Faculty of Biology, Medicine and Health, University of Manchester, Manchester, M13 9PT, UK
| | - Andrew A Morris
- Willink Unit, Manchester Centre for Genomic Medicine, Manchester University Hospitals, Manchester, M13 9WL, UK
| | - Cedric H Shackleton
- University of California San Francisco (UCSF) Benioff Children's Hospital, Oakland, CA 94609, USA
| | - Peter T Clayton
- Inborn Errors of Metabolism, Genetics and Genomic Medicine, UCL Great Ormond Street Institute of Child Health, 30 Guilford Street, London, WC1N 1EH, UK
| | - Takashi Iida
- Department of Chemistry, College of Humanities & Sciences, Nihon University, Sakurajousui, Setagaya, Tokyo, 156-8550, Japan
| | - Ria Sircar
- Departments of Biochemistry and Medicine, Stanford University School of Medicine, Stanford, CA, 94305, USA
| | - Rajat Rohatgi
- Departments of Biochemistry and Medicine, Stanford University School of Medicine, Stanford, CA, 94305, USA
| | - Hanns-Ulrich Marschall
- Department of Molecular and Clinical Medicine, University of Gothenburg, Sahlgrenska Academy, Institute of Medicine, Gothenburg, 41345, Sweden
| | - Jan Sjövall
- Department of Medical Biochemistry and Biophysics, Karolinska Institutet, Stockholm, 17177, Sweden
| | - Ingemar Björkhem
- Division of Clinical Chemistry, Department of Laboratory Medicine, Karolinska Institutet, Karolinska University Hospital Huddinge, Huddinge, 14186, Stockholm, Sweden
| | - Jonathan G L Mullins
- Swansea University Medical School, ILS1 Building, Singleton Park, Swansea, SA2 8PP, Wales, UK
| | - William J Griffiths
- Swansea University Medical School, ILS1 Building, Singleton Park, Swansea, SA2 8PP, Wales, UK.
| | - Yuqin Wang
- Swansea University Medical School, ILS1 Building, Singleton Park, Swansea, SA2 8PP, Wales, UK.
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Chen S, Austin-Muttitt K, Zhang LH, Mullins JGL, Lau AJ. In Vitro and In Silico Analyses of the Inhibition of Human Aldehyde Oxidase by Bazedoxifene, Lasofoxifene, and Structural Analogues. J Pharmacol Exp Ther 2019; 371:75-86. [DOI: 10.1124/jpet.119.259267] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2019] [Accepted: 07/05/2019] [Indexed: 11/22/2022] Open
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Skibinski DOF, Ghiselli F, Diz AP, Milani L, Mullins JGL. Structure-Related Differences between Cytochrome Oxidase I Proteins in a Stable Heteroplasmic Mitochondrial System. Genome Biol Evol 2018; 9:3265-3281. [PMID: 29149282 PMCID: PMC5726481 DOI: 10.1093/gbe/evx235] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/13/2017] [Indexed: 12/27/2022] Open
Abstract
Many bivalve species have two types of mitochondrial DNA passed independently through the female line (F genome) and male line (M genome). Here we study the cytochrome oxidase I protein in such bivalve species and provide evidence for differences between the F and M proteins in amino acid property values, particularly relating to hydrophobicity and helicity. The magnitude of these differences varies between different regions of the protein and the change from the ancestor is most marked in the M protein. The observed changes occur in parallel and in the same direction in the different species studied. Two possible causes are considered, first relaxation of purifying selection with drift and second positive selection. These may operate in different ways in different regions of the protein. Many different amino acid substitutions contribute in a small way to the observed variation, but substitutions involving alanine and serine have a quantitatively large effect. Some of these substitutions are potential targets for phosphorylation and some are close to residues of functional importance in the catalytic mechanism. We propose that the observed changes in the F and M proteins might contribute to functional differences between them relating to ATP production and mitochondrial membrane potential with implications for sperm function.
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Affiliation(s)
- David O F Skibinski
- Institute of Life Science, Swansea University Medical School, United Kingdom
| | - Fabrizio Ghiselli
- Department of Biological, Geological, and Environmental Sciences, University of Bologna, Italy
| | - Angel P Diz
- Department of Biochemistry, Genetics and Immunology, University of Vigo, Spain
| | - Liliana Milani
- Department of Biological, Geological, and Environmental Sciences, University of Bologna, Italy
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Fry AE, Fawcett KA, Zelnik N, Yuan H, Thompson BAN, Shemer-Meiri L, Cushion TD, Mugalaasi H, Sims D, Stoodley N, Chung SK, Rees MI, Patel CV, Brueton LA, Layet V, Giuliano F, Kerr MP, Banne E, Meiner V, Lerman-Sagie T, Helbig KL, Kofman LH, Knight KM, Chen W, Kannan V, Hu C, Kusumoto H, Zhang J, Swanger SA, Shaulsky GH, Mirzaa GM, Muir AM, Mefford HC, Dobyns WB, Mackenzie AB, Mullins JGL, Lemke JR, Bahi-Buisson N, Traynelis SF, Iago HF, Pilz DT. De novo mutations in GRIN1 cause extensive bilateral polymicrogyria. Brain 2018; 141:698-712. [PMID: 29365063 PMCID: PMC5837214 DOI: 10.1093/brain/awx358] [Citation(s) in RCA: 58] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2017] [Revised: 10/17/2017] [Accepted: 11/14/2017] [Indexed: 11/14/2022] Open
Abstract
Polymicrogyria is a malformation of cortical development. The aetiology of polymicrogyria remains poorly understood. Using whole-exome sequencing we found de novo heterozygous missense GRIN1 mutations in 2 of 57 parent-offspring trios with polymicrogyria. We found nine further de novo missense GRIN1 mutations in additional cortical malformation patients. Shared features in the patients were extensive bilateral polymicrogyria associated with severe developmental delay, postnatal microcephaly, cortical visual impairment and intractable epilepsy. GRIN1 encodes GluN1, the essential subunit of the N-methyl-d-aspartate receptor. The polymicrogyria-associated GRIN1 mutations tended to cluster in the S2 region (part of the ligand-binding domain of GluN1) or the adjacent M3 helix. These regions are rarely mutated in the normal population or in GRIN1 patients without polymicrogyria. Using two-electrode and whole-cell voltage-clamp analysis, we showed that the polymicrogyria-associated GRIN1 mutations significantly alter the in vitro activity of the receptor. Three of the mutations increased agonist potency while one reduced proton inhibition of the receptor. These results are striking because previous GRIN1 mutations have generally caused loss of function, and because N-methyl-d-aspartate receptor agonists have been used for many years to generate animal models of polymicrogyria. Overall, our results expand the phenotypic spectrum associated with GRIN1 mutations and highlight the important role of N-methyl-d-aspartate receptor signalling in the pathogenesis of polymicrogyria.
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Affiliation(s)
- Andrew E Fry
- Institute of Medical Genetics, University Hospital of Wales, Cardiff CF14 4XW, UK
- Division of Cancer and Genetics, School of Medicine, Cardiff University, Cardiff CF14 4XN, UK
| | - Katherine A Fawcett
- MRC Computational Genomics Analysis and Training Programme (CGAT), MRC Centre for Computational Biology, MRC Weatherall Institute of Molecular Medicine, John Radcliffe Hospital, Headington, Oxford OX3 9DS, UK
| | - Nathanel Zelnik
- Pediatric Neurology Unit, Carmel Medical Center, Haifa, Israel
- Bruce and Ruth Rappaport Faculty of Medicine, Technion, Haifa, Israel
| | - Hongjie Yuan
- Department of Pharmacology and Chemical Biology, Emory University School of Medicine, Atlanta, GA 30322, USA
- Center for Functional Evaluation of Rare Variants (CFERV), Emory University School of Medicine, Atlanta, GA 30322, USA
| | - Belinda A N Thompson
- Division of Cancer and Genetics, School of Medicine, Cardiff University, Cardiff CF14 4XN, UK
- Department of Pharmacy and Pharmacology, University of Bath, Claverton Down, Bath BA2 7AY, UK
| | | | - Thomas D Cushion
- Division of Cancer and Genetics, School of Medicine, Cardiff University, Cardiff CF14 4XN, UK
| | - Hood Mugalaasi
- Institute of Medical Genetics, University Hospital of Wales, Cardiff CF14 4XW, UK
| | - David Sims
- MRC Computational Genomics Analysis and Training Programme (CGAT), MRC Centre for Computational Biology, MRC Weatherall Institute of Molecular Medicine, John Radcliffe Hospital, Headington, Oxford OX3 9DS, UK
| | - Neil Stoodley
- Department of Neuroradiology, North Bristol NHS Trust, Frenchay Hospital, Bristol BS16 1LE, UK
| | - Seo-Kyung Chung
- Neurology and Molecular Neuroscience Research, Institute of Life Science, Swansea University Medical School, Swansea University, Swansea SA2 8PP, UK
| | - Mark I Rees
- Neurology and Molecular Neuroscience Research, Institute of Life Science, Swansea University Medical School, Swansea University, Swansea SA2 8PP, UK
| | - Chirag V Patel
- Genetic Health Queensland, Royal Brisbane and Women’s Hospital Campus, Herston, Brisbane, Queensland 4029, Australia
| | - Louise A Brueton
- West Midlands Regional Genetics Service, Clinical Genetics Unit, Birmingham Women’s Hospital, Birmingham B15 2TG, UK
| | - Valérie Layet
- Service de Génétique Médicale, Groupe Hospitalier du Havre, Hôpital Jacques Monod, Le Havre, France
| | - Fabienne Giuliano
- Service de Génétique Médicale, Centre Hospitalier Universitaire de Nice, Nice, France
| | - Michael P Kerr
- MRC Centre for Neuropsychiatric Genetics and Genomics, Institute of Psychological Medicine and Clinical Neurosciences, Cardiff University, Cardiff CF24 4HQ, UK
- Learning Disabilities Directorate, Abertawe Bro Morgannwg University NHS Trust, Treseder Way, Caerau, Cardiff CF5 5WF, UK
| | - Ehud Banne
- Clinical Genetics Institute, Kaplan Medical Centre, Rehovot, Israel
| | - Vardiella Meiner
- Department of Genetics and Metabolic Diseases, Hadassah-Hebrew University Hospital, Jerusalem, Israel
| | - Tally Lerman-Sagie
- Pediatric Neurology Unit, Wolfson Medical Centre, Holon, Sackler School of Medicine, Tel-Aviv University, Tel-Aviv, Israel
| | - Katherine L Helbig
- Division of Neurology, Children’s Hospital of Philadelphia, Philadelphia, PA 19104, USA
| | - Laura H Kofman
- Kaiser Permanente Mid-Atlantic States, McLean, VA 22102, USA
| | | | - Wenjuan Chen
- Department of Pharmacology and Chemical Biology, Emory University School of Medicine, Atlanta, GA 30322, USA
- Department of Neurology, Xiangya Hospital, Central South University, Changsha 410013, China
| | - Varun Kannan
- Department of Pharmacology and Chemical Biology, Emory University School of Medicine, Atlanta, GA 30322, USA
| | - Chun Hu
- Department of Pharmacology and Chemical Biology, Emory University School of Medicine, Atlanta, GA 30322, USA
| | - Hirofumi Kusumoto
- Department of Pharmacology and Chemical Biology, Emory University School of Medicine, Atlanta, GA 30322, USA
| | - Jin Zhang
- Department of Pharmacology and Chemical Biology, Emory University School of Medicine, Atlanta, GA 30322, USA
- Department of Neurology, the First Hospital of Shanxi Medical University, Taiyuan, 030001, China
| | - Sharon A Swanger
- Department of Pharmacology and Chemical Biology, Emory University School of Medicine, Atlanta, GA 30322, USA
| | - Gil H Shaulsky
- Department of Pharmacology and Chemical Biology, Emory University School of Medicine, Atlanta, GA 30322, USA
| | - Ghayda M Mirzaa
- Division of Genetic Medicine, Department of Pediatrics, University of Washington, Seattle, WA 98195, USA
- Center for Integrative Brain Research, Seattle Children’s Research Institute, Seattle, WA 98195, USA
| | - Alison M Muir
- Division of Genetic Medicine, Department of Pediatrics, University of Washington, Seattle, WA 98195, USA
| | - Heather C Mefford
- Division of Genetic Medicine, Department of Pediatrics, University of Washington, Seattle, WA 98195, USA
| | - William B Dobyns
- Division of Genetic Medicine, Department of Pediatrics, University of Washington, Seattle, WA 98195, USA
- Center for Integrative Brain Research, Seattle Children’s Research Institute, Seattle, WA 98195, USA
- Department of Neurology, University of Washington, Seattle, WA 98195, USA
| | - Amanda B Mackenzie
- Department of Pharmacy and Pharmacology, University of Bath, Claverton Down, Bath BA2 7AY, UK
| | - Jonathan G L Mullins
- Genome and Structural Bioinformatics Group, Institute of Life Science, Swansea University, Singleton Park, Swansea SA2 8PP, UK
| | - Johannes R Lemke
- Institute of Human Genetics, University Medical Center Leipzig, Leipzig 04103, Germany
| | - Nadia Bahi-Buisson
- Imagine Institute, INSERM UMR-1163, Laboratory Genetics and Embryology of Congenital Malformations, Paris Descartes University, Paris, France
| | - Stephen F Traynelis
- Department of Pharmacology and Chemical Biology, Emory University School of Medicine, Atlanta, GA 30322, USA
- Center for Functional Evaluation of Rare Variants (CFERV), Emory University School of Medicine, Atlanta, GA 30322, USA
| | - Heledd F Iago
- Genome and Structural Bioinformatics Group, Institute of Life Science, Swansea University, Singleton Park, Swansea SA2 8PP, UK
| | - Daniela T Pilz
- Division of Cancer and Genetics, School of Medicine, Cardiff University, Cardiff CF14 4XN, UK
- West of Scotland Clinical Genetics Service, Queen Elizabeth University Hospital, Glasgow G51 4TF, UK
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Mair WJ, Deng W, Mullins JGL, West S, Wang P, Besharat N, Ellwood SR, Oliver RP, Lopez-Ruiz FJ. Demethylase Inhibitor Fungicide Resistance in Pyrenophora teres f. sp. teres Associated with Target Site Modification and Inducible Overexpression of Cyp51. Front Microbiol 2016; 7:1279. [PMID: 27594852 PMCID: PMC4990540 DOI: 10.3389/fmicb.2016.01279] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2016] [Accepted: 08/03/2016] [Indexed: 12/18/2022] Open
Abstract
Pyrenophora teres f. sp. teres is the cause of net form of net blotch (NFNB), an economically important foliar disease in barley (Hordeum vulgare). Net and spot forms of net blotch are widely controlled using site-specific systemic fungicides. Although resistance to succinate dehydrogenase inhibitors and quinone outside inhibitors has been addressed before in net blotches, mechanisms controlling demethylation inhibitor resistance have not yet been reported at the molecular level. Here we report the isolation of strains of NFNB in Australia since 2013 resistant to a range of demethylase inhibitor fungicides. Cyp51A:KO103-A1, an allele with the mutation F489L, corresponding to the archetype F495I in Aspergillus fumigatus, was only present in resistant strains and was correlated with resistance factors to various demethylase inhibitors ranging from 1.1 for epoxiconazole to 31.7 for prochloraz. Structural in silico modeling of the sensitive and resistant CYP51A proteins docked with different demethylase inhibitor fungicides showed how the interaction of F489L within the heme cavity produced a localized constriction of the region adjacent to the docking site that is predicted to result in lower binding affinities. Resistant strains also displayed enhanced induced expression of the two Cyp51A paralogs and of Cyp51B genes. While Cyp51B was found to be constitutively expressed in the absence of fungicide, Cyp51A was only detected at extremely low levels. Under fungicide induction, expression of Cyp51B, Cyp51A2, and Cyp51A1 was shown to be 1.6-, 3,- and 5.3-fold higher, respectively in the resistant isolate compared to the wild type. These increased levels of expression were not supported by changes in the promoters of any of the three genes. The implications of these findings on demethylase inhibitor activity will require current net blotch management strategies to be reconsidered in order to avoid the development of further resistance and preserve the lifespan of fungicides in use.
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Affiliation(s)
- Wesley J Mair
- Department of Environment and Agriculture, Centre for Crop and Disease Management, Curtin University Bentley, WA, Australia
| | - Weiwei Deng
- Department of Environment and Agriculture, Centre for Crop and Disease Management, Curtin University Bentley, WA, Australia
| | | | - Samuel West
- Institute of Life Science, School of Medicine, Swansea University Swansea, UK
| | - Penghao Wang
- School of Veterinary and Life Sciences, Murdoch University Murdoch, WA, Australia
| | - Naghmeh Besharat
- Department of Environment and Agriculture, Centre for Crop and Disease Management, Curtin University Bentley, WA, Australia
| | - Simon R Ellwood
- Department of Environment and Agriculture, Centre for Crop and Disease Management, Curtin University Bentley, WA, Australia
| | - Richard P Oliver
- Department of Environment and Agriculture, Centre for Crop and Disease Management, Curtin University Bentley, WA, Australia
| | - Francisco J Lopez-Ruiz
- Department of Environment and Agriculture, Centre for Crop and Disease Management, Curtin University Bentley, WA, Australia
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Pickrell WO, Hope CHD, Higgins AT, Mullins JGL, Smith PEM, Rees MI, Chung SK. A NOVEL LGI1 VARIANT IN LATERAL TEMPORAL LOBE EPILEPSY. J Neurol Neurosurg Psychiatry 2015. [DOI: 10.1136/jnnp-2015-312379.62] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
BackgroundWe identified a family with autosomal dominant lateral temporal lobe epilepsy (ADLTLE). Given that LGI1 mutations account for around 50% of families with ADLTLE, we screened family members for LGI1 variants.MethodWe sequenced all exonic regions of LGI1 and used in-silico analysis tools to assess the potential affect of the novel variant. We screened 106 control samples for the variant and assessed the structural effect of the variant using a protein modelling platform.ResultsThe proband's seizures consist of an unilateral ‘buzzing’ sensation which progresses to unilateral limb numbness and secondarily generalised seizures. Some noises can provoke seizures. Her mother also has epilepsy with identical seizure semiology. We identified a novel heterozygous missense LGI1 variant in the proband and her mother which was not present in other family members or control samples. This variant is close to the splice site region of LGI1 exon 4 and is predicted to be deleterious. Protein modelling suggests that the variant causes conformational structural changes.ConclusionWe present a family with ADLTLE caused by a novel variant in LGI1. This variant is predicted to be deleterious, alters protein function and adds additional evidence for the role of LGI1 in ADLTLE.
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Oegema R, Cushion TD, Phelps IG, Chung SK, Dempsey JC, Collins S, Mullins JGL, Dudding T, Gill H, Green AJ, Dobyns WB, Ishak GE, Rees MI, Doherty D. Recognizable cerebellar dysplasia associated with mutations in multiple tubulin genes. Hum Mol Genet 2015; 24:5313-25. [PMID: 26130693 DOI: 10.1093/hmg/ddv250] [Citation(s) in RCA: 63] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2015] [Accepted: 06/24/2015] [Indexed: 01/06/2023] Open
Abstract
Mutations in alpha- and beta-tubulins are increasingly recognized as a major cause of malformations of cortical development (MCD), typically lissencephaly, pachygyria and polymicrogyria; however, sequencing tubulin genes in large cohorts of MCD patients has detected tubulin mutations in only 1-13%. We identified patients with a highly characteristic cerebellar dysplasia but without lissencephaly, pachygyria and polymicrogyria typically associated with tubulin mutations. Remarkably, in seven of nine patients (78%), targeted sequencing revealed mutations in three different tubulin genes (TUBA1A, TUBB2B and TUBB3), occurring de novo or inherited from a mosaic parent. Careful re-review of the cortical phenotype on brain imaging revealed only an irregular pattern of gyri and sulci, for which we propose the term tubulinopathy-related dysgyria. Basal ganglia (100%) and brainstem dysplasia (80%) were common features. On the basis of in silico structural predictions, the mutations affect amino acids in diverse regions of the alpha-/beta-tubulin heterodimer, including the nucleotide binding pocket. Cell-based assays of tubulin dynamics reveal various effects of the mutations on incorporation into microtubules: TUBB3 p.Glu288Lys and p.Pro357Leu do not incorporate into microtubules at all, whereas TUBB2B p.Gly13Ala shows reduced incorporation and TUBA1A p.Arg214His incorporates fully, but at a slower rate than wild-type. The broad range of effects on microtubule incorporation is at odds with the highly stereotypical clinical phenotype, supporting differential roles for the three tubulin genes involved. Identifying this highly characteristic phenotype is important due to the low recurrence risk compared with the other (recessive) cerebellar dysplasias and the apparent lack of non-neurological medical issues.
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Affiliation(s)
- Renske Oegema
- Department of Clinical Genetics, Erasmus MC University Medical Center, Rotterdam, The Netherlands,
| | | | | | - Seo-Kyung Chung
- Institute of Life Science, College of Medicine and Wales Epilepsy Research Network (WERN), College of Medicine, Swansea University, Swansea SA2 8PP, UK
| | | | - Sarah Collins
- Center for Integrative Brain Research, Seattle Children's Research Institute, Seattle, WA 98101, USA
| | | | - Tracy Dudding
- Hunter Genetics, Waratah, New South Wales, Australia, University of Newcastle, Callaghan, New South Wales, Australia
| | - Harinder Gill
- National Centre for Medical Genetics, Our Lady's Children's Hospital, Dublin 12, Ireland and
| | - Andrew J Green
- National Centre for Medical Genetics, Our Lady's Children's Hospital, Dublin 12, Ireland and School of Medicine and Medical Science, University College Dublin, Dublin 4, Ireland
| | - William B Dobyns
- Department of Pediatrics, Department of Neurology and Center for Integrative Brain Research, Seattle Children's Research Institute, Seattle, WA 98101, USA
| | - Gisele E Ishak
- Department of Radiology, Seattle Children's Hospital and University of Washington, Seattle, WA 98195, USA
| | - Mark I Rees
- Institute of Life Science, College of Medicine and Wales Epilepsy Research Network (WERN), College of Medicine, Swansea University, Swansea SA2 8PP, UK
| | - Dan Doherty
- Department of Pediatrics, Center for Integrative Brain Research, Seattle Children's Research Institute, Seattle, WA 98101, USA,
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Parker JE, Warrilow AGS, Price CL, Mullins JGL, Kelly DE, Kelly SL. Resistance to antifungals that target CYP51. J Chem Biol 2014; 7:143-61. [PMID: 25320648 DOI: 10.1007/s12154-014-0121-1] [Citation(s) in RCA: 101] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2014] [Accepted: 08/06/2014] [Indexed: 12/23/2022] Open
Abstract
Fungal diseases are an increasing global burden. Fungi are now recognised to kill more people annually than malaria, whilst in agriculture, fungi threaten crop yields and food security. Azole resistance, mediated by several mechanisms including point mutations in the target enzyme (CYP51), is increasing through selection pressure as a result of widespread use of triazole fungicides in agriculture and triazole antifungal drugs in the clinic. Mutations similar to those seen in clinical isolates as long ago as the 1990s in Candida albicans and later in Aspergillus fumigatus have been identified in agriculturally important fungal species and also wider combinations of point mutations. Recently, evidence that mutations originate in the field and now appear in clinical infections has been suggested. This situation is likely to increase in prevalence as triazole fungicide use continues to rise. Here, we review the progress made in understanding azole resistance found amongst clinically and agriculturally important fungal species focussing on resistance mechanisms associated with CYP51. Biochemical characterisation of wild-type and mutant CYP51 enzymes through ligand binding studies and azole IC50 determinations is an important tool for understanding azole susceptibility and can be used in conjunction with microbiological methods (MIC50 values), molecular biological studies (site-directed mutagenesis) and protein modelling studies to inform future antifungal development with increased specificity for the target enzyme over the host homologue.
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Affiliation(s)
- Josie E Parker
- Centre for Cytochrome P450 Biodiversity, Institute of Life Science, College of Medicine, Swansea University, Swansea, Wales SA2 8PP UK
| | - Andrew G S Warrilow
- Centre for Cytochrome P450 Biodiversity, Institute of Life Science, College of Medicine, Swansea University, Swansea, Wales SA2 8PP UK
| | - Claire L Price
- Centre for Cytochrome P450 Biodiversity, Institute of Life Science, College of Medicine, Swansea University, Swansea, Wales SA2 8PP UK
| | - Jonathan G L Mullins
- Centre for Cytochrome P450 Biodiversity, Institute of Life Science, College of Medicine, Swansea University, Swansea, Wales SA2 8PP UK
| | - Diane E Kelly
- Centre for Cytochrome P450 Biodiversity, Institute of Life Science, College of Medicine, Swansea University, Swansea, Wales SA2 8PP UK
| | - Steven L Kelly
- Centre for Cytochrome P450 Biodiversity, Institute of Life Science, College of Medicine, Swansea University, Swansea, Wales SA2 8PP UK
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10
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Cushion TD, Paciorkowski AR, Pilz DT, Mullins JGL, Seltzer LE, Marion RW, Tuttle E, Ghoneim D, Christian SL, Chung SK, Rees MI, Dobyns WB. De novo mutations in the beta-tubulin gene TUBB2A cause simplified gyral patterning and infantile-onset epilepsy. Am J Hum Genet 2014; 94:634-41. [PMID: 24702957 DOI: 10.1016/j.ajhg.2014.03.009] [Citation(s) in RCA: 82] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2013] [Accepted: 03/14/2014] [Indexed: 12/22/2022] Open
Abstract
Tubulins, and microtubule polymers into which they incorporate, play critical mechanical roles in neuronal function during cell proliferation, neuronal migration, and postmigrational development: the three major overlapping events of mammalian cerebral cortex development. A number of neuronally expressed tubulin genes are associated with a spectrum of disorders affecting cerebral cortex formation. Such "tubulinopathies" include lissencephaly/pachygyria, polymicrogyria-like malformations, and simplified gyral patterns, in addition to characteristic extracortical features, such as corpus callosal, basal ganglia, and cerebellar abnormalities. Epilepsy is a common finding in these related disorders. Here we describe two unrelated individuals with infantile-onset epilepsy and abnormalities of brain morphology, harboring de novo variants that affect adjacent amino acids in a beta-tubulin gene TUBB2A. Located in a highly conserved loop, we demonstrate impaired tubulin and microtubule function resulting from each variant in vitro and by using in silico predictive modeling. We propose that the affected functional loop directly associates with the alpha-tubulin-bound guanosine triphosphate (GTP) molecule, impairing the intradimer interface and correct formation of the alpha/beta-tubulin heterodimer. This study associates mutations in TUBB2A with the spectrum of "tubulinopathy" phenotypes. As a consequence, genetic variations affecting all beta-tubulin genes expressed at high levels in the brain (TUBB2B, TUBB3, TUBB, TUBB4A, and TUBB2A) have been linked with malformations of cortical development.
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Affiliation(s)
- Thomas D Cushion
- Neurology and Molecular Neuroscience Research Group, Institute of Life Science, College of Medicine, Swansea University, Swansea SA2 8PP, UK
| | - Alex R Paciorkowski
- Department of Neurology, University of Rochester Medical Center, Rochester, NY 14642, USA; Departments of Pediatrics and Biomedical Genetics, University of Rochester Medical Center, Rochester, NY 14641, USA; Center for Neural Development & Disease, University of Rochester Medical Center, Rochester, NY 14642, USA
| | - Daniela T Pilz
- Institute of Medical Genetics, University Hospital of Wales, Cardiff CF14 4XW, UK; Wales Epilepsy Research Network (WERN), College of Medicine, Swansea University, Swansea SA2 8PP, UK
| | - Jonathan G L Mullins
- Neurology and Molecular Neuroscience Research Group, Institute of Life Science, College of Medicine, Swansea University, Swansea SA2 8PP, UK
| | - Laurie E Seltzer
- Department of Neurology, University of Rochester Medical Center, Rochester, NY 14642, USA
| | - Robert W Marion
- The Children's Hospital at Montefiore, Bronx, NY 10467-2403, USA
| | - Emily Tuttle
- Center for Neural Development & Disease, University of Rochester Medical Center, Rochester, NY 14642, USA
| | - Dalia Ghoneim
- Center for Neural Development & Disease, University of Rochester Medical Center, Rochester, NY 14642, USA
| | - Susan L Christian
- Center for Integrative Brain Research, Seattle Children's Hospital, Seattle, WA 98101, USA
| | - Seo-Kyung Chung
- Neurology and Molecular Neuroscience Research Group, Institute of Life Science, College of Medicine, Swansea University, Swansea SA2 8PP, UK; Wales Epilepsy Research Network (WERN), College of Medicine, Swansea University, Swansea SA2 8PP, UK
| | - Mark I Rees
- Neurology and Molecular Neuroscience Research Group, Institute of Life Science, College of Medicine, Swansea University, Swansea SA2 8PP, UK; Wales Epilepsy Research Network (WERN), College of Medicine, Swansea University, Swansea SA2 8PP, UK.
| | - William B Dobyns
- Center for Integrative Brain Research, Seattle Children's Hospital, Seattle, WA 98101, USA; Departments of Pediatrics and Neurology, University of Washington, Seattle, WA 98195, USA.
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11
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Bode A, Wood SE, Mullins JGL, Keramidas A, Cushion TD, Thomas RH, Pickrell WO, Drew CJG, Masri A, Jones EA, Vassallo G, Born AP, Alehan F, Aharoni S, Bannasch G, Bartsch M, Kara B, Krause A, Karam EG, Matta S, Jain V, Mandel H, Freilinger M, Graham GE, Hobson E, Chatfield S, Vincent-Delorme C, Rahme JE, Afawi Z, Berkovic SF, Howell OW, Vanbellinghen JF, Rees MI, Chung SK, Lynch JW. New hyperekplexia mutations provide insight into glycine receptor assembly, trafficking, and activation mechanisms. J Biol Chem 2013; 288:33745-33759. [PMID: 24108130 DOI: 10.1074/jbc.m113.509240] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Hyperekplexia is a syndrome of readily provoked startle responses, alongside episodic and generalized hypertonia, that presents within the first month of life. Inhibitory glycine receptors are pentameric ligand-gated ion channels with a definitive and clinically well stratified linkage to hyperekplexia. Most hyperekplexia cases are caused by mutations in the α1 subunit of the human glycine receptor (hGlyR) gene (GLRA1). Here we analyzed 68 new unrelated hyperekplexia probands for GLRA1 mutations and identified 19 mutations, of which 9 were novel. Electrophysiological analysis demonstrated that the dominant mutations p.Q226E, p.V280M, and p.R414H induced spontaneous channel activity, indicating that this is a recurring mechanism in hGlyR pathophysiology. p.Q226E, at the top of TM1, most likely induced tonic activation via an enhanced electrostatic attraction to p.R271 at the top of TM2, suggesting a structural mechanism for channel activation. Receptors incorporating p.P230S (which is heterozygous with p.R65W) desensitized much faster than wild type receptors and represent a new TM1 site capable of modulating desensitization. The recessive mutations p.R72C, p.R218W, p.L291P, p.D388A, and p.E375X precluded cell surface expression unless co-expressed with α1 wild type subunits. The recessive p.E375X mutation resulted in subunit truncation upstream of the TM4 domain. Surprisingly, on the basis of three independent assays, we were able to infer that p.E375X truncated subunits are incorporated into functional hGlyRs together with unmutated α1 or α1 plus β subunits. These aberrant receptors exhibit significantly reduced glycine sensitivity. To our knowledge, this is the first suggestion that subunits lacking TM4 domains might be incorporated into functional pentameric ligand-gated ion channel receptors.
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Affiliation(s)
- Anna Bode
- University of Queensland, Queensland Brain Institute and School of Biomedical Sciences, Queensland 4072, Australia
| | - Sian-Elin Wood
- Department of Neurology Research and Molecular Neuroscience, Institute of Life Science, College of Medicine, Swansea University Swansea SA2 8PP, United Kingdom
| | - Jonathan G L Mullins
- Department of Neurology Research and Molecular Neuroscience, Institute of Life Science, College of Medicine, Swansea University Swansea SA2 8PP, United Kingdom
| | - Angelo Keramidas
- University of Queensland, Queensland Brain Institute and School of Biomedical Sciences, Queensland 4072, Australia
| | - Thomas D Cushion
- Department of Neurology Research and Molecular Neuroscience, Institute of Life Science, College of Medicine, Swansea University Swansea SA2 8PP, United Kingdom
| | - Rhys H Thomas
- Department of Neurology Research and Molecular Neuroscience, Institute of Life Science, College of Medicine, Swansea University Swansea SA2 8PP, United Kingdom; Wales Epilepsy Research Network, College of Medicine, Swansea University Swansea SA2 8PP, United Kingdom
| | - William O Pickrell
- Department of Neurology Research and Molecular Neuroscience, Institute of Life Science, College of Medicine, Swansea University Swansea SA2 8PP, United Kingdom; Wales Epilepsy Research Network, College of Medicine, Swansea University Swansea SA2 8PP, United Kingdom
| | - Cheney J G Drew
- Department of Neurology Research and Molecular Neuroscience, Institute of Life Science, College of Medicine, Swansea University Swansea SA2 8PP, United Kingdom; Wales Epilepsy Research Network, College of Medicine, Swansea University Swansea SA2 8PP, United Kingdom
| | - Amira Masri
- Department of Paediatrics, Division of Child Neurology, Faculty of Medicine, University of Jordan, Amman 11942, Jordan
| | - Elizabeth A Jones
- Manchester Centre for Genomic Medicine, Central Manchester University Hospitals National Health Service Foundation Trust, Manchester Academic Health Sciences Centre, Manchester M13 9WL, United Kingdom; Manchester Centre for Genomic Medicine, Institute of Human Development, Faculty of Medical and Human Sciences, University of Manchester, Manchester Academic Health Sciences Centre, Manchester M13 9WL, United Kingdom
| | - Grace Vassallo
- Royal Manchester Children's Hospital, Central Manchester University Hospitals National Health Service Foundation Trust, Manchester Academic Health Sciences Centre, Manchester M13 9WL, United Kingdom
| | - Alfred P Born
- Department of Pediatrics, Copenhagen University Hospital, Rigshospitalet, 2100 Copenhagen, Denmark
| | - Fusun Alehan
- Department of Pediatrics, Division of Child Neurology, Faculty of Medicine, Basşkent University, 06990 Ankara, Turkey
| | - Sharon Aharoni
- Institute of Pediatric Neurology, Schneider Children's Medical Center of Israel, Petah Tikva 49202, Israel; Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv 69987, Israel
| | - Gerald Bannasch
- Neurology Department, Affinity Medical Group, Menasha, Wisconsin 54952
| | - Marius Bartsch
- Department of Neonatology, University Medical Center of the Johannes Gutenberg University Mainz, D-55099 Mainz, Germany
| | - Bulent Kara
- Kocaeli University Medical Faculty, Department of Pediatrics, Division of Child Neurology, 41380 Kocaeli, Turkey
| | - Amanda Krause
- Division of Human Genetics, National Health Laboratory Service, and School of Pathology, Faculty of Health Sciences, University of the Witwatersrand, 2000 Johannesburg, South Africa
| | - Elie G Karam
- Department of Psychiatry and Clinical Psychology, Saint George Hospital University Medical Center, Balamand University, Faculty of Medicine, Beirut 1100 2807, Lebanon
| | - Stephanie Matta
- Department of Psychiatry and Clinical Psychology, Saint George Hospital University Medical Center, Balamand University, Faculty of Medicine, Beirut 1100 2807, Lebanon
| | - Vivek Jain
- Royal Children's Hospital Melbourne, Children's Neuroscience Centre, Royal Children's Hospital, Victoria 3052, Australia
| | - Hanna Mandel
- Metabolic Unit, Meyer Children's Hospital, Rambam Medical Center, Technion Faculty of Medicine, Haifa 31096, Israel
| | - Michael Freilinger
- Department of Pediatrics and Adolescent Medicine, Medical University of Vienna, 1090 Vienna, Austria
| | - Gail E Graham
- Department of Genetics, Children's Hospital of Eastern Ontario, Ottawa, Ontario K1H 8L1, Canada
| | - Emma Hobson
- Yorkshire Regional Genetic Service, Chapel Allerton Hospital, Leeds, West Yorkshire LS9 7TF, United Kingdom
| | - Sue Chatfield
- Neonatal Unit, Bradford Royal Infirmary, Bradford, West Yorkshire BD9 6RJ, United Kingdom
| | | | | | - Zaid Afawi
- Zlotowski Center for Neuroscience, Ben-Gurion University of the Negev, Beer-Sheva 8410501, Israel
| | - Samuel F Berkovic
- Epilepsy Research Centre, Melbourne Brain Centre, Austin Health, Heidelberg 3084, Victoria, Australia
| | - Owain W Howell
- Department of Neurology Research and Molecular Neuroscience, Institute of Life Science, College of Medicine, Swansea University Swansea SA2 8PP, United Kingdom; Wales Epilepsy Research Network, College of Medicine, Swansea University Swansea SA2 8PP, United Kingdom
| | | | - Mark I Rees
- Department of Neurology Research and Molecular Neuroscience, Institute of Life Science, College of Medicine, Swansea University Swansea SA2 8PP, United Kingdom; Wales Epilepsy Research Network, College of Medicine, Swansea University Swansea SA2 8PP, United Kingdom
| | - Seo-Kyung Chung
- Department of Neurology Research and Molecular Neuroscience, Institute of Life Science, College of Medicine, Swansea University Swansea SA2 8PP, United Kingdom; Wales Epilepsy Research Network, College of Medicine, Swansea University Swansea SA2 8PP, United Kingdom
| | - Joseph W Lynch
- University of Queensland, Queensland Brain Institute and School of Biomedical Sciences, Queensland 4072, Australia.
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12
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Kirshenbaum GS, Dawson N, Mullins JGL, Johnston TH, Drinkhill MJ, Edwards IJ, Fox SH, Pratt JA, Brotchie JM, Roder JC, Clapcote SJ. Alternating hemiplegia of childhood-related neural and behavioural phenotypes in Na+,K+-ATPase α3 missense mutant mice. PLoS One 2013; 8:e60141. [PMID: 23527305 PMCID: PMC3603922 DOI: 10.1371/journal.pone.0060141] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2013] [Accepted: 02/21/2013] [Indexed: 12/29/2022] Open
Abstract
Missense mutations in ATP1A3 encoding Na+,K+-ATPase α3 have been identified as the primary cause of alternating hemiplegia of childhood (AHC), a motor disorder with onset typically before the age of 6 months. Affected children tend to be of short stature and can also have epilepsy, ataxia and learning disability. The Na+,K+-ATPase has a well-known role in maintaining electrochemical gradients across cell membranes, but our understanding of how the mutations cause AHC is limited. Myshkin mutant mice carry an amino acid change (I810N) that affects the same position in Na+,K+-ATPase α3 as I810S found in AHC. Using molecular modelling, we show that the Myshkin and AHC mutations display similarly severe structural impacts on Na+,K+-ATPase α3, including upon the K+ pore and predicted K+ binding sites. Behavioural analysis of Myshkin mice revealed phenotypic abnormalities similar to symptoms of AHC, including motor dysfunction and cognitive impairment. 2-DG imaging of Myshkin mice identified compromised thalamocortical functioning that includes a deficit in frontal cortex functioning (hypofrontality), directly mirroring that reported in AHC, along with reduced thalamocortical functional connectivity. Our results thus provide validation for missense mutations in Na+,K+-ATPase α3 as a cause of AHC, and highlight Myshkin mice as a starting point for the exploration of disease mechanisms and novel treatments in AHC.
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Affiliation(s)
- Greer S. Kirshenbaum
- Samuel Lunenfeld Research Institute, Mount Sinai Hospital, Toronto, Ontario, Canada
- Institute of Medical Science, University of Toronto, Toronto, Ontario, Canada
| | - Neil Dawson
- Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, Glasgow, United Kingdom
| | - Jonathan G. L. Mullins
- Institute of Life Science, College of Medicine, Swansea University, Swansea, United Kingdom
| | - Tom H. Johnston
- Division of Brain, Imaging and Behaviour – Systems Neuroscience, Toronto Western Research Institute, Toronto, Ontario, Canada
| | - Mark J. Drinkhill
- Division of Cardiovascular and Neuronal Remodelling, Leeds Institute for Genetics, Health and Therapeutics, University of Leeds, Leeds, United Kingdom
| | - Ian J. Edwards
- School of Biomedical Sciences, University of Leeds, Leeds, United Kingdom
| | - Susan H. Fox
- Division of Brain, Imaging and Behaviour – Systems Neuroscience, Toronto Western Research Institute, Toronto, Ontario, Canada
| | - Judith A. Pratt
- Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, Glasgow, United Kingdom
| | - Jonathan M. Brotchie
- Division of Brain, Imaging and Behaviour – Systems Neuroscience, Toronto Western Research Institute, Toronto, Ontario, Canada
| | - John C. Roder
- Samuel Lunenfeld Research Institute, Mount Sinai Hospital, Toronto, Ontario, Canada
- Institute of Medical Science, University of Toronto, Toronto, Ontario, Canada
| | - Steven J. Clapcote
- School of Biomedical Sciences, University of Leeds, Leeds, United Kingdom
- * E-mail:
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13
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Cushion TD, Dobyns WB, Mullins JGL, Stoodley N, Chung SK, Fry AE, Hehr U, Gunny R, Aylsworth AS, Prabhakar P, Uyanik G, Rankin J, Rees MI, Pilz DT. Overlapping cortical malformations and mutations in TUBB2B and TUBA1A. ACTA ACUST UNITED AC 2013; 136:536-48. [PMID: 23361065 DOI: 10.1093/brain/aws338] [Citation(s) in RCA: 98] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Polymicrogyria and lissencephaly are causally heterogeneous disorders of cortical brain development, with distinct neuropathological and neuroimaging patterns. They can be associated with additional structural cerebral anomalies, and recurrent phenotypic patterns have led to identification of recognizable syndromes. The lissencephalies are usually single-gene disorders affecting neuronal migration during cerebral cortical development. Polymicrogyria has been associated with genetic and environmental causes and is considered a malformation secondary to abnormal post-migrational development. However, the aetiology in many individuals with these cortical malformations is still unknown. During the past few years, mutations in a number of neuron-specific α- and β-tubulin genes have been identified in both lissencephaly and polymicrogyria, usually associated with additional cerebral anomalies including callosal hypoplasia or agenesis, abnormal basal ganglia and cerebellar hypoplasia. The tubulin proteins form heterodimers that incorporate into microtubules, cytoskeletal structures essential for cell motility and function. In this study, we sequenced the TUBB2B and TUBA1A coding regions in 47 patients with a diagnosis of polymicrogyria and five with an atypical lissencephaly on neuroimaging. We identified four β-tubulin and two α-tubulin mutations in patients with a spectrum of cortical and extra-cortical anomalies. Dysmorphic basal ganglia with an abnormal internal capsule were the most consistent feature. One of the patients with a TUBB2B mutation had a lissencephalic phenotype, similar to that previously associated with a TUBA1A mutation. The remainder had a polymicrogyria-like cortical dysplasia, but the grey matter malformation was not typical of that seen in 'classical' polymicrogyria. We propose that the cortical malformations associated with these genes represent a recognizable tubulinopathy-associated spectrum that ranges from lissencephalic to polymicrogyric cortical dysplasias, suggesting shared pathogenic mechanisms in terms of microtubular function and interaction with microtubule-associated proteins.
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Affiliation(s)
- Thomas D Cushion
- Institute of Life Science, College of Medicine, Swansea University, Swansea SA2 8PP, UK
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14
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Davis C, Harris HJ, Hu K, Drummer HE, McKeating JA, Mullins JGL, Balfe P. In silico directed mutagenesis identifies the CD81/claudin-1 hepatitis C virus receptor interface. Cell Microbiol 2012; 14:1892-903. [PMID: 22897233 PMCID: PMC3549482 DOI: 10.1111/cmi.12008] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2012] [Revised: 07/19/2012] [Accepted: 08/06/2012] [Indexed: 12/12/2022]
Abstract
Hepatitis C virus (HCV) entry is dependent on host cell molecules tetraspanin CD81, scavenger receptor BI and tight junction proteins claudin-1 and occludin. We previously reported a role for CD81/claudin-1 receptor complexes in HCV entry; however, the molecular mechanism(s) driving association between the receptors is unknown. We explored the molecular interface between CD81 and claudin-1 using a combination of bioinformatic sequence-based modelling, site-directed mutagenesis and Fluorescent Resonance Energy Transfer (FRET) imaging methodologies. Structural modelling predicts the first extracellular loop of claudin-1 to have a flexible beta conformation and identifies a motif between amino acids 62-66 that interacts with CD81 residues T149, E152 and T153. FRET studies confirm a role for these CD81 residues in claudin-1 association and HCV infection. Importantly, mutation of these CD81 residues has minimal impact on protein conformation or HCV glycoprotein binding, highlighting a new functional domain of CD81 that is essential for virus entry.
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Affiliation(s)
- Christopher Davis
- School of Immunity and Infection, Institute of Biomedical Research, College of Medical and Dental Sciences, University of Birmingham, Birmingham B15 2TT, UK
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15
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Moody SC, Zhao B, Lei L, Nelson DR, Mullins JGL, Waterman MR, Kelly SL, Lamb DC. Investigating conservation of the albaflavenone biosynthetic pathway and CYP170 bifunctionality in streptomycetes. FEBS J 2012; 279:1640-9. [PMID: 22151149 DOI: 10.1111/j.1742-4658.2011.08447.x] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Albaflavenone, a tricyclic sesquiterpene antibiotic, is biosynthesized in Streptomyces coelicolor A3(2) by enzymes encoded in a two-gene operon. Initially, sesquiterpene cyclase catalyzes the cyclization of farnesyl diphosphate to the terpenoid epi-isozizaene, which is oxidized to the final albaflavenone by cytochrome P450 (CYP)170A1. Additionally, this CYP is a bifunctional enzyme, being able to also generate farnesene isomers from farnesyl diphosphate, owing to a terpene synthase active site moonlighting on the CYP molecule. To explore the functionality of this operon in other streptomycetes, we have examined culture extracts by GC/MS and established the presence of albaflavenone in five Streptomyces species. Bioinformatics examination of the predicted CYP170 primary amino acid sequences revealed substitutions in the CYP terpene synthase active site. To examine whether the terpene synthase site was catalytically active in another CYP170, we characterized the least related CYP170 orthologue from Streptomyces albus (CYP170B1). Following expression and purification, CYP170B1 showed a normal reduced CO difference spectrum at 450 nm, in contrast to the unusual 440-nm peak observed for S. coelicolor A3(2) CYP170A1. CYP170B1 can catalyze the conversion of epi-isozizaene to albaflavenone, but was unable to catalyze the conversion of farnesyl diphosphate to farnesene. Molecular modeling with our crystal structure of CYP170A1 suggests that the absence of key amino acids for binding the essential terpene synthase cofactor Mg(2+) may be the explanation for the loss of CYP170B1 bifunctionality.
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Affiliation(s)
- Suzy C Moody
- Institute of Life Science, Medical School, Swansea University, Swansea, UK
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16
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Abstract
Our capacity to reliably predict protein structure from sequence is steadily improving due to the increased numbers and better targeting of protein structures being experimentally determined by structural genomics projects, along with the development of better modeling methodologies. Template-based (homology) modeling and de novo modeling methods are being combined to fill in remaining gaps in template coverage, and powerful automated structural modeling pipelines are being applied to large data sets of protein sequences. The improved quality of 3D models of proteins has led to their routine use in assessing the functional impact of nonsynonymous single nucleotide polymorphisms (nsSNPs) in specific protein systems, with the development of approaches that may be applied in a predictive fashion to nsSNPs emerging from next-generation sequencing projects. The challenges encountered in deriving functionally meaningful deductions from structural modeling can be quite different for proteins of different protein functional classes. The specific challenges to the assessment of the structural and functional impact of nsSNPs in globular proteins such as binding and regulatory proteins, structural proteins, and enzymes are discussed, as well as membrane transport proteins and ion channels. The mapping of reliable predictions of the structural and functional impact of SNPs, generated from automated modeling pipelines, on to protein-protein interaction networks will facilitate new approaches to understanding complex polygenic disorders and predisposition to disease.
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Affiliation(s)
- Jonathan G L Mullins
- Genome and Structural Bioinformatics, Institute of Life Science, College of Medicine, Swansea University, Singleton Park, Swansea, Wales, UK.
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17
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Martel CM, Warrilow AGS, Jackson CJ, Mullins JGL, Togawa RC, Parker JE, Morris MS, Donnison IS, Kelly DE, Kelly SL. Expression, purification and use of the soluble domain of Lactobacillus paracasei beta-fructosidase to optimise production of bioethanol from grass fructans. Bioresour Technol 2010; 101:4395-402. [PMID: 20153640 DOI: 10.1016/j.biortech.2010.01.084] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/15/2009] [Revised: 01/13/2010] [Accepted: 01/19/2010] [Indexed: 05/21/2023]
Abstract
Microbial inulinases find application in food, pharmaceutical and biofuel industries. Here, a novel Lactobacillus paracasei beta-fructosidase was overexpressed as truncated cytosolic protein ((t)fosEp) in Escherichia coli. Purified (t)fosEp was thermostable (10-50 degrees C) with a pH optimum of 5; it showed highest affinity for bacterial levan (beta[2-6] linked fructose) followed by nystose, chicory inulin, 1-kestose (beta[2-1] linkages) and sucrose (K(m) values of 0.5, 15, 15.6, 49 and 398 mM, respectively). Hydrolysis of polyfructose moieties in agriculturally-sourced grass juice (GJ) with (t)fosEp resulted in the release of >13 mg/ml more bioavailable fructose than was measured in untreated GJ. Bioethanol yields from fermentation experiments with Brewer's yeast and GJ+(t)fosEp were >25% higher than those achieved using untreated GJ feedstock (36.5[+/-4.3] and 28.2[+/-2.7]mg ethanol/ml, respectively). This constitutes the first specific study of the potential to ferment ethanol from grass juice and the utility of a novel core domain of beta-fructosidase from L. paracasei.
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Affiliation(s)
- C M Martel
- Institute of Life Science and School of Medicine, Swansea University, Swansea SA2 8PP, Wales, UK
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18
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Harris HJ, Davis C, Mullins JGL, Hu K, Goodall M, Farquhar MJ, Mee CJ, McCaffrey K, Young S, Drummer H, Balfe P, McKeating JA. Claudin association with CD81 defines hepatitis C virus entry. J Biol Chem 2010; 285:21092-102. [PMID: 20375010 PMCID: PMC2898367 DOI: 10.1074/jbc.m110.104836] [Citation(s) in RCA: 158] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Viruses initiate infection by attaching to molecules or receptors at the cell surface. Hepatitis C virus (HCV) enters cells via a multistep process involving tetraspanin CD81, scavenger receptor class B member I, and the tight junction proteins Claudin-1 and Occludin. CD81 and scavenger receptor class B member I interact with HCV-encoded glycoproteins, suggesting an initial role in mediating virus attachment. In contrast, there are minimal data supporting Claudin-1 association with HCV particles, raising questions as to its role in the virus internalization process. In the present study we demonstrate a relationship between receptor active Claudins and their association and organization with CD81 at the plasma membrane by fluorescence resonance energy transfer and stoichiometric imaging methodologies. Mutation of residues 32 and 48 in the Claudin-1 first extracellular loop ablates CD81 association and HCV receptor activity. Furthermore, mutation of the same residues in the receptor-inactive Claudin-7 molecule enabled CD81 complex formation and virus entry, demonstrating an essential role for Claudin-CD81 complexes in HCV infection. Importantly, Claudin-1 associated with CD81 at the basolateral membrane of polarized HepG2 cells, whereas tight junction-associated pools of Claudin-1 demonstrated a minimal association with CD81. In summary, we demonstrate an essential role for Claudin-CD81 complexes in HCV infection and their localization at the basolateral surface of polarized hepatoma cells, consistent with virus entry into the liver via the sinusoidal blood and association with basal expressed forms of the receptors.
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Affiliation(s)
- Helen J Harris
- Institute for Biomedical Research, University of Birmingham, Birmingham B15 2TT, United Kingdom
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19
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Davies JS, Chung SK, Thomas RH, Robinson A, Hammond CL, Mullins JGL, Carta E, Pearce BR, Harvey K, Harvey RJ, Rees MI. The glycinergic system in human startle disease: a genetic screening approach. Front Mol Neurosci 2010; 3:8. [PMID: 20407582 PMCID: PMC2854534 DOI: 10.3389/fnmol.2010.00008] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2009] [Accepted: 03/08/2010] [Indexed: 11/17/2022] Open
Abstract
Human startle disease, also known as hyperekplexia (OMIM 149400), is a paroxysmal neurological disorder caused by defects in glycinergic neurotransmission. Hyperekplexia is characterised by an exaggerated startle reflex in response to tactile or acoustic stimuli which first presents as neonatal hypertonia, followed in some with episodes of life-threatening infantile apnoea. Genetic screening studies have demonstrated that hyperekplexia is genetically heterogeneous with several missense and nonsense mutations in the postsynaptic glycine receptor (GlyR) alpha1 subunit gene (GLRA1) as the primary cause. More recently, missense, nonsense and frameshift mutations have also been identified in the glycine transporter GlyT2 gene, SLC6A5, demonstrating a presynaptic component to this disease. Further mutations, albeit rare, have been identified in the genes encoding the GlyR beta subunit (GLRB), collybistin (ARHGEF9) and gephyrin (GPHN) - all of which are postsynaptic proteins involved in orchestrating glycinergic neurotransmission. In this review, we describe the clinical ascertainment aspects, phenotypic considerations and the downstream molecular genetic tools utilised to analyse both presynaptic and postsynaptic components of this heterogeneous human neurological disorder. Moreover, we will describe how the ancient startle response is the preserve of glycinergic neurotransmission and how animal models and human hyperekplexia patients have provided synergistic evidence that implicates this inhibitory system in the control of startle reflexes.
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Affiliation(s)
- Jeff S Davies
- Institute of Life Science, School of Medicine, Swansea University Singleton Park, Swansea, UK
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20
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Bowen AJ, Gonzalez D, Mullins JGL, Bhatt AM, Martinez A, Conlan RS. PAH-domain-specific interactions of the Arabidopsis transcription coregulator SIN3-LIKE1 (SNL1) with telomere-binding protein 1 and ALWAYS EARLY2 Myb-DNA binding factors. J Mol Biol 2010; 395:937-49. [PMID: 19962994 DOI: 10.1016/j.jmb.2009.11.065] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2009] [Revised: 09/25/2009] [Accepted: 11/29/2009] [Indexed: 11/17/2022]
Abstract
The eukaryotic SIN3 protein is the central component of the evolutionarily conserved multisubunit SIN3 complex that has roles in regulating gene expression and genome stability. Here we characterise the structure of the SIN3 protein in higher plants through the analysis of SNL1 (SIN3-LIKE1), SNL2, SNL3, SNL4, SNL5 and SNL6, a family of six SIN3 homologues in Arabidopsis thaliana. In an Arabidopsis-protoplast beta-glucuronidase reporter gene assay, as well as in a heterologous yeast repression assay, full-length SNL1 was shown to repress transcription in a histone-deacetylase-dependent manner, demonstrating the conserved nature of SIN3 function. Yeast two-hybrid screening identified a number of DNA binding proteins each containing a single Myb domain that included the Arabidopsis ALWAYS EARLY proteins AtALY2 and AtALY3, and two telomere binding proteins AtTBP1 and AtTRP2/TRFL1 as SNL1 partners, suggesting potential functions for SNL1 in development and telomere maintenance. The interaction with telomere-binding protein 1 was found to be mediated through the well-defined paired amphipathic helix domain PAH2. In contrast, the AtALY2 interaction was mediated through the PAH3 domain of SNL1, which is structurally distinct from PAH1 and PAH2, suggesting that evolution of this domain to a more novel structural motif has occurred. These findings support a diverse role of SNL1 in the regulation of transcription and genome stability.
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Affiliation(s)
- Adam J Bowen
- Institute of Life Science, School of Medicine, Swansea University, Singleton Park, Swansea SA2 8PP, UK
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21
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Yang T, Chung SK, Zhang W, Mullins JGL, McCulley CH, Crawford J, MacCormick J, Eddy CA, Shelling AN, French JK, Yang P, Skinner JR, Roden DM, Rees MI. Biophysical properties of 9 KCNQ1 mutations associated with long-QT syndrome. Circ Arrhythm Electrophysiol 2009; 2:417-26. [PMID: 19808498 DOI: 10.1161/circep.109.850149] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
BACKGROUND Inherited long-QT syndrome is characterized by prolonged QT interval on the ECG, syncope, and sudden death caused by ventricular arrhythmia. Causative mutations occur mostly in cardiac potassium and sodium channel subunit genes. Confidence in mutation pathogenicity is usually reached through family genotype-phenotype tracking, control population studies, molecular modeling, and phylogenetic alignments; however, biophysical testing offers a higher degree of validating evidence. METHODS AND RESULTS By using in vitro electrophysiological testing of transfected mutant and wild-type long-QT syndrome constructs into Chinese hamster ovary cells, we investigated the biophysical properties of 9 KCNQ1 missense mutations (A46T, T265I, F269S, A302V, G316E, F339S, R360G, H455Y, and S546L) identified in a New Zealand-based long-QT syndrome screening program. We demonstrate through electrophysiology and molecular modeling that 7 of the missense mutations have profound pathological dominant-negative loss-of-function properties, confirming their likely disease-causing nature. This supports the use of these mutations in diagnostic family screening. Two mutations (A46T, T265I) show suggestive evidence of pathogenicity within the experimental limits of biophysical testing, indicating that these variants are disease-causing via delayed- or fast-activation kinetics. Further investigation of the A46T family has revealed an inconsistent cosegregation of the variant with the clinical phenotype. CONCLUSIONS Electrophysiological characterization should be used to validate long-QT syndrome pathogenicity of novel missense channelopathies. When such results are inconclusive, great care should be taken with genetic counseling and screening of such families, and alternative disease-causing mechanisms should be considered.
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Affiliation(s)
- Tao Yang
- Department of Medicine and Pharmacology, Oates Institute for Experimental Therapeutics, Vanderbilt University School of Medicine, Nashville, Tenn, USA
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22
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Abstract
MOTIVATION Membrane dipping loops are sections of membrane proteins that reside in the membrane but do not traverse from one side to the other, rather they enter and leave the same side of the membrane. We applied a combinatorial pattern discovery approach to sets of sequences containing at least one characterised structure described as possessing a membrane dipping loop. Discovered patterns were found to be composed of residues whose biochemical role is known to be essential for function of the protein, thus validating our approach. TMLOOP (http://membraneproteins.swan.ac.uk/TMLOOP) was implemented to predict membrane dipping loops in polytopic membrane proteins. TMLOOP applies discovered patterns as weighted predictive rules in a collective motif method (a variation of the single motif method), to avoid inherent limitations of single motif methods in detecting distantly related proteins. The collective motif method applies several, partially overlapping patterns, which pertain to the same sequence region, allowing proteins containing small variations to be detected. The approach achieved 92.4% accuracy in sensitivity and 100% reliability in specificity. TMLOOP was applied to the Swiss-Prot database, identifying 1392 confirmed membrane dipping loops, 75 plausible membrane dipping loops hitherto uncharacterised by topology prediction methods or experimental approaches and 128 false positives (8.0%).
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Affiliation(s)
- Gorka Lasso
- Membrane Proteins Structural Bioinformatics Group, School of Medicine, Swansea University, Singleton Park, Swansea SA2 8PP, Wales, UK
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23
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Del Sol R, Mullins JGL, Grantcharova N, Flärdh K, Dyson P. Influence of CrgA on assembly of the cell division protein FtsZ during development of Streptomyces coelicolor. J Bacteriol 2006; 188:1540-50. [PMID: 16452438 PMCID: PMC1367258 DOI: 10.1128/jb.188.4.1540-1550.2006] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The product of the crgA gene of Streptomyces coelicolor represents a novel family of small proteins. A single orthologous gene is located close to the origin of replication of all fully sequenced actinomycete genomes and borders a conserved gene cluster implicated in cell growth and division. In S. coelicolor, CrgA is important for coordinating growth and cell division in sporogenic hyphae. In this study, we demonstrate that CrgA is an integral membrane protein whose peak expression is coordinated with the onset of development of aerial hyphae. The protein localizes to discrete foci away from growing hyphal tips. Upon overexpression, CrgA localizes to apical syncytial cells of aerial hyphae and inhibits the formation of productive cytokinetic rings of the bacterial tubulin homolog FtsZ, leading to proteolytic turnover of this major cell division determinant. In the absence of known prokaryotic cell division inhibitors in actinomycetes, CrgA may have an important conserved function influencing Z-ring formation in these bacteria.
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Affiliation(s)
- Ricardo Del Sol
- Institute of Life Science, School of Medicine, University of Wales Swansea, Singleton Park, Swansea SA2 8PP, United Kingdom
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24
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Hedfalk K, Bill RM, Mullins JGL, Karlgren S, Filipsson C, Bergstrom J, Tamás MJ, Rydström J, Hohmann S. A Regulatory Domain in the C-terminal Extension of the Yeast Glycerol Channel Fps1p. J Biol Chem 2004; 279:14954-60. [PMID: 14752103 DOI: 10.1074/jbc.m313126200] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The Saccharomyces cerevisiae gene FPS1 encodes an aquaglyceroporin of the major intrinsic protein (MIP) family. The main function of Fps1p seems to be the efflux of glycerol in the adaptation of the yeast cell to lower external osmolarity. Fps1p is an atypical member of the family, because the protein is much larger (669 amino acids) than most MIPs due to long hydrophilic extensions in both termini. We have shown previously that a short domain in the N-terminal extension of the protein is required for restricting glycerol transport through the channel (Tamás, M. J., Karlgren, S., Bill, R. M., Hedfalk, K., Allegri, L., Ferreira, M., Thevelein, J. M., Rydström, J., Mullins, J. G. L., and Hohmann, S. (2003) J. Biol. Chem. 278, 6337-6345). Deletion of the N-terminal domain results in an unregulated channel, loss of glycerol, and osmosensitivity. In this work we have investigated the role of the Fps1p C terminus (139 amino acids). A set of eight truncations has been constructed and tested in vivo in a yeast fps1Delta strain. We have performed growth tests, membrane localization following cell fractionation, and glycerol accumulation measurements as well as an investigation of the osmotic stress response. Our results show that the C-terminal extension is also involved in restricting transport through Fps1p. We have identified a sequence of 12 amino acids, residues 535-546, close to the sixth transmembrane domain. This element seems to be important for controlling Fps1p function. Similar to the N-terminal domain, the C-terminal domain is amphiphilic and has a potential to dip into the membrane.
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Affiliation(s)
- Kristina Hedfalk
- Department of Cell and Molecular Biology/Microbiology, Götegorg University, Götegorg, Sweden.
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25
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Karlgren S, Filipsson C, Mullins JGL, Bill RM, Tamás MJ, Hohmann S. Identification of residues controlling transport through the yeast aquaglyceroporin Fps1 using a genetic screen. ACTA ACUST UNITED AC 2004; 271:771-9. [PMID: 14764093 DOI: 10.1111/j.1432-1033.2004.03980.x] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Aquaporins and aquaglyceroporins mediate the transport of water and solutes across biological membranes. Saccharomyces cerevisiae Fps1 is an aquaglyceroporin that mediates controlled glycerol export during osmoregulation. The transport function of Fps1 is rapidly regulated by osmotic changes in an apparently unique way and distinct regions within the long N- and C-terminal extensions are needed for this regulation. In order to learn more about the mechanisms that control Fps1 we have set up a genetic screen for hyperactive Fps1 and isolated mutations in 14 distinct residues, all facing the inside of the cell. Five of the residues lie within the previously characterized N-terminal regulatory domain and two mutations are located within the approach to the first transmembrane domain. Three mutations cause truncation of the C-terminus, confirming previous studies on the importance of this region for channel control. Furthermore, the novel mutations identify two conserved residues in the channel-forming B-loop as critical for channel control. Structural modelling-based rationalization of the observed mutations supports the notion that the N-terminal regulatory domain and the B-loop could interact in channel control. Our findings provide a framework for further genetic and structural analysis to better understand the mechanism that controls Fps1 function by osmotic changes.
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Affiliation(s)
- Sara Karlgren
- Department of Cell and Molecular Biology/Microbiology, Göteborg University, Sweden
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26
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Tamás MJ, Karlgren S, Bill RM, Hedfalk K, Allegri L, Ferreira M, Thevelein JM, Rydström J, Mullins JGL, Hohmann S. A short regulatory domain restricts glycerol transport through yeast Fps1p. J Biol Chem 2003; 278:6337-45. [PMID: 12486125 DOI: 10.1074/jbc.m209792200] [Citation(s) in RCA: 78] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The controlled export of solutes is crucial for cellular adaptation to hypotonic conditions. In the yeast Saccharomyces cerevisiae glycerol export is mediated by Fps1p, a member of the major intrinsic protein (MIP) family of channel proteins. Here we describe a short regulatory domain that restricts glycerol transport through Fps1p. This domain is required for retention of cellular glycerol under hypertonic stress and hence acquisition of osmotolerance. It is located in the N-terminal cytoplasmic extension close to the first transmembrane domain. Several residues within that domain and its precise position are critical for channel control while the proximal residues 13-215 of the N-terminal extension are not required. The sequence of the regulatory domain and its position are perfectly conserved in orthologs from other yeast species. The regulatory domain has an amphiphilic character, and structural predictions indicate that it could fold back into the membrane bilayer. Remarkably, this domain has structural similarity to the channel forming loops B and E of Fps1p and other glycerol facilitators. Intragenic second-site suppressor mutations of the sensitivity to high osmolarity conferred by truncation of the regulatory domain caused diminished glycerol transport, confirming that elevated channel activity is the cause of the osmosensitive phenotype.
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Affiliation(s)
- Markus J Tamás
- Department of Cell and Molecular Biology/Microbiology, Göteborg University, Box 462, 40530 Göteborg, Sweden
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