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Schidlitzki A, Stanojlovic M, Fournier C, Käufer C, Feja M, Gericke B, Garzotti M, Welford RWD, Steiner MA, Angot E, Richter F. Double-Edged Effects of Venglustat on Behavior and Pathology in Mice Overexpressing α-Synuclein. Mov Disord 2023. [PMID: 37050861 DOI: 10.1002/mds.29398] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2022] [Revised: 03/01/2023] [Accepted: 03/21/2023] [Indexed: 04/14/2023] Open
Abstract
BACKGROUND Venglustat is a brain-penetrant, small molecule inhibitor of glucosylceramide synthase used in clinical testing for treatment of Parkinson's disease (PD). Despite beneficial effects in certain cellular and rodent models, patients with PD with mutations in GBA, the gene for lysosomal glucocerebrosidase, experienced worsening of their motor function under venglustat treatment (NCT02906020, MOVES-PD, phase 2 trial). OBJECTIVE The objective of this study was to evaluate venglustat in mouse models of PD with overexpression of wild-type α-synuclein. METHODS Mice overexpressing α-synuclein (Thy1-aSyn line 61) or Gba-mutated mice with viral vector-induced overexpression of α-synuclein in the substantia nigra were administered venglustat as food admixture. Motor and cognitive performance, α-synuclein-related pathology, and microgliosis were compared with untreated controls. RESULTS Venglustat worsened motor function in Thy1-aSyn transgenics on the challenging beam and the pole test. Although venglustat did not alter the cognitive deficit in the Y-maze test, it alleviated anxiety-related behavior in the novel object recognition test. Venglustat reduced soluble and membrane-bound α-synuclein in the striatum and phosphorylated α-synuclein in limbic brain regions. Although venglustat reversed the loss of parvalbumin immunoreactivity in the basolateral amygdala, it tended to increase microgliosis and phosphorylated α-synuclein in the substantia nigra. Furthermore, venglustat also partially worsened motor performance and tended to increase neurofilament light chain in the cerebrospinal fluid in the Gba-deficient model with nigral α-synuclein overexpression and neurodegeneration. CONCLUSIONS Venglustat treatment in two mouse models of α-synuclein overexpression showed that glucosylceramide synthase inhibition had differential detrimental or beneficial effects on behavior and neuropathology possibly related to brain region-specific effects. © 2023 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.
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Affiliation(s)
- Alina Schidlitzki
- Department of Pharmacology, Toxicology and Pharmacy, University of Veterinary Medicine Hannover, Hannover, Germany
| | - Milos Stanojlovic
- Department of Pharmacology, Toxicology and Pharmacy, University of Veterinary Medicine Hannover, Hannover, Germany
| | - Céline Fournier
- CNS Pharmacology and Drug Discovery, Idorsia Pharmaceuticals Ltd., Allschwil, Switzerland
- Roche Pharma Research and Early Development (pRED), F. Hoffman/La Roche Ltd, Basel, Switzerland
| | - Christopher Käufer
- Department of Pharmacology, Toxicology and Pharmacy, University of Veterinary Medicine Hannover, Hannover, Germany
| | - Malte Feja
- Department of Pharmacology, Toxicology and Pharmacy, University of Veterinary Medicine Hannover, Hannover, Germany
- Center for Systems Neuroscience Hannover, Hannover, Germany
| | - Birthe Gericke
- Department of Pharmacology, Toxicology and Pharmacy, University of Veterinary Medicine Hannover, Hannover, Germany
- Center for Systems Neuroscience Hannover, Hannover, Germany
| | - Marco Garzotti
- CNS Pharmacology and Drug Discovery, Idorsia Pharmaceuticals Ltd., Allschwil, Switzerland
- Matterhorn Biosciences AG, Basel, Switzerland
| | - Richard W D Welford
- CNS Pharmacology and Drug Discovery, Idorsia Pharmaceuticals Ltd., Allschwil, Switzerland
- Roche Pharma Research and Early Development (pRED), F. Hoffman/La Roche Ltd, Basel, Switzerland
| | | | - Elodie Angot
- CNS Pharmacology and Drug Discovery, Idorsia Pharmaceuticals Ltd., Allschwil, Switzerland
- Roche Pharma Research and Early Development (pRED), F. Hoffman/La Roche Ltd, Basel, Switzerland
| | - Franziska Richter
- Department of Pharmacology, Toxicology and Pharmacy, University of Veterinary Medicine Hannover, Hannover, Germany
- Center for Systems Neuroscience Hannover, Hannover, Germany
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Schäfer A, Haenig B, Erupathil J, Strickner P, Sabato D, Welford RWD, Klaeylé L, Simon E, Krepler C, Brafford P, Xiao M, Herlyn M, Gstaiger M, Lehembre F, Renz I. Inhibition of endothelin-B receptor signaling synergizes with MAPK pathway inhibitors in BRAF mutated melanoma. Oncogene 2021; 40:1659-1673. [PMID: 33500549 DOI: 10.1038/s41388-020-01628-x] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2020] [Revised: 12/03/2020] [Accepted: 12/15/2020] [Indexed: 01/30/2023]
Abstract
The clinical benefit of MAPK pathway inhibition in melanoma patients carrying BRAF mutations is temporal. After the initial response to treatment, the majority of tumors will develop resistance and patients will relapse. Here we demonstrate that the endothelin-endothelin receptor B (ETBR) signaling pathway confers resistance to MAPK pathway inhibitors in BRAF mutated melanoma. MAPK blockade, in addition to being anti-proliferative, induces a phenotypic change which is characterized by increased expression of melanocyte-specific genes including ETBR. In the presence of MAPK inhibitors, activation of ETBR by endothelin enables the sustained proliferation of melanoma cells. In mouse models of melanoma, including patient-derived xenograft models, concurrent inhibition of the MAPK pathway and ETBR signaling resulted in a more effective anti-tumor response compared to MAPK pathway inhibition alone. The combination treatment significantly reduced tumor growth and prolonged survival compared to therapies with MAPK pathway inhibitors alone. The phosphoproteomic analysis revealed that ETBR signaling did not induce resistance towards MAPK pathway inhibitors by restoring MAPK activity, but instead via multiple alternative signaling pathways downstream of the small G proteins GNAq/11. Together these data indicate that a combination of MAPK pathway inhibitors with ETBR antagonists could have a synergistically beneficial effect in melanoma patients with hyperactivated MAPK signaling pathways.
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Affiliation(s)
- Alexander Schäfer
- Department of Biology, Institute of Molecular Systems Biology, ETH Zürich, Otto-Stern-Weg 3, 8093, Zürich, Switzerland.,Swiss BioQuant AG, 4153, Reinach, Switzerland
| | - Benedicte Haenig
- Drug Discovery Biology, Idorsia Pharmaceuticals Ltd., Hegenheimermattweg 91, 4123, Allschwil, Switzerland
| | - Julie Erupathil
- Drug Discovery Biology, Idorsia Pharmaceuticals Ltd., Hegenheimermattweg 91, 4123, Allschwil, Switzerland
| | - Panja Strickner
- Drug Discovery Biology, Idorsia Pharmaceuticals Ltd., Hegenheimermattweg 91, 4123, Allschwil, Switzerland
| | - Daniela Sabato
- Drug Discovery Biology, Idorsia Pharmaceuticals Ltd., Hegenheimermattweg 91, 4123, Allschwil, Switzerland
| | - Richard W D Welford
- Drug Discovery Biology, Idorsia Pharmaceuticals Ltd., Hegenheimermattweg 91, 4123, Allschwil, Switzerland
| | - Lhéanna Klaeylé
- Drug Discovery Biology, Idorsia Pharmaceuticals Ltd., Hegenheimermattweg 91, 4123, Allschwil, Switzerland
| | - Elise Simon
- Drug Discovery Biology, Idorsia Pharmaceuticals Ltd., Hegenheimermattweg 91, 4123, Allschwil, Switzerland.,Novartis Institutes for BioMedical Research, 4002, Basel, Switzerland
| | - Clemens Krepler
- Molecular and Cellular Oncogenesis Program and Melanoma Research Center, The Wistar Institute, Philadelphia, PA, 19104, USA.,Merck, North Wales, PA, 19454, USA
| | - Patricia Brafford
- Molecular and Cellular Oncogenesis Program and Melanoma Research Center, The Wistar Institute, Philadelphia, PA, 19104, USA
| | - Min Xiao
- Molecular and Cellular Oncogenesis Program and Melanoma Research Center, The Wistar Institute, Philadelphia, PA, 19104, USA
| | - Meenhard Herlyn
- Molecular and Cellular Oncogenesis Program and Melanoma Research Center, The Wistar Institute, Philadelphia, PA, 19104, USA
| | - Matthias Gstaiger
- Department of Biology, Institute of Molecular Systems Biology, ETH Zürich, Otto-Stern-Weg 3, 8093, Zürich, Switzerland
| | - Francois Lehembre
- Drug Discovery Biology, Idorsia Pharmaceuticals Ltd., Hegenheimermattweg 91, 4123, Allschwil, Switzerland
| | - Imke Renz
- Drug Discovery Biology, Idorsia Pharmaceuticals Ltd., Hegenheimermattweg 91, 4123, Allschwil, Switzerland.
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Gehin M, Melchior M, Welford RWD, Sidharta PN, Dingemanse J. Assessment of Target Engagement in a First-in-Human Trial with Sinbaglustat, an Iminosugar to Treat Lysosomal Storage Disorders. Clin Transl Sci 2020; 14:558-567. [PMID: 33142037 PMCID: PMC7993281 DOI: 10.1111/cts.12911] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [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: 07/07/2020] [Accepted: 09/26/2020] [Indexed: 11/30/2022] Open
Abstract
In this first-in-human study, the tolerability, pharmacokinetics (PK), and pharmacodynamics (PD) of single and multiple oral doses of sinbaglustat, a dual inhibitor of glucosylceramide synthase (GCS) and non-lysosomal glucosyl ceramidase (GBA2), were investigated in healthy subjects. The single-ascending dose (SAD) and multiple-ascending dose (MAD) studies were randomized, double-blind, and placebo-controlled. Single doses from 10 to 2,000 mg in men and multiple doses from 30 to 1,000 mg twice daily for 7 days in male and female subjects were investigated. Tolerability, PK, and PD data were collected up to 3 days after (last) treatment administration and analyzed descriptively. Sinbaglustat was well-tolerated in the SAD and MAD studies, however, at the highest dose of the MAD, three of the four female subjects presented a similar pattern of general symptoms. In all cohorts, sinbaglustat was rapidly absorbed. Thereafter, plasma concentrations decreased biphasically. In the MAD study, steady-state conditions were reached on Day 2 without accumulation. During sinbaglustat treatment, plasma concentrations of glucosylceramide (GlcCer), lactosylceramide, and globotriaosylceramide decreased in a dose-dependent manner, reflecting GCS inhibition. The more complex the glycosphingolipid, the more time was required to elicit PD changes. After treatment stop, GlcCer levels returned to baseline and increased above baseline at lowest doses, probably due to the higher potency of sinbaglustat on GBA2 compared to GCS. Overall, sinbaglustat was welltolerated up to the highest tested doses. The PK profile is compatible with b.i.d. dosing. Sinbaglustat demonstrated target engagement in the periphery for GCS and GBA2.
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Affiliation(s)
- Martine Gehin
- Clinical Pharmacology, Idorsia Pharmaceuticals Ltd, Allschwil, Switzerland
| | - Meggane Melchior
- Clinical Pharmacology, Idorsia Pharmaceuticals Ltd, Allschwil, Switzerland
| | - Richard W D Welford
- Drug Discovery, Translational Biomarkers, Idorsia Pharmaceuticals Ltd, Allschwil, Switzerland
| | | | - Jasper Dingemanse
- Clinical Pharmacology, Idorsia Pharmaceuticals Ltd, Allschwil, Switzerland
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Schmidt A, Farine H, Keller MP, Sebastian A, Kozera L, Welford RWD, Strasser DS. Immunoaffinity Targeted Mass Spectrometry Analysis of Human Plasma Samples Reveals an Imbalance of Active and Inactive CXCL10 in Primary Sjögren's Syndrome Disease Patients. J Proteome Res 2020; 19:4196-4209. [PMID: 32870689 DOI: 10.1021/acs.jproteome.0c00494] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [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: 11/29/2022]
Abstract
One of the most important advantages of mass spectrometry is the ability to quantify proteins and their modifications in parallel to obtain a holistic picture of the protein of interest. Here, we present a hybrid immunoaffinity targeted mass spectrometry (MS) method that combines efficient pan-antibody enrichment of a specific protein from plasma with the selectivity of high-resolution targeted MS analysis to quantitate specific proteoforms of interest. We used this approach to quantify plasma levels of the chemokine CXCL10 that has been associated with many immunological disorders such as systemic lupus erythematosus and primary Sjögren's Syndrome (pSS). The hybrid approach enabled sensitive, specific, and simultaneous quantification of total, full-length (active) CXCL101-77 and DPP4-truncated (inactive) CXCL103-77 in human plasma down to the low pg/mL level, reaching ELISA sensitivities. Samples from 30 control subjects and 34 pSS patients (n = 64) were analyzed. The ratio of CXCL101-77 to truncated CXCL103-77 was significantly increased in patients with pSS and provided the highest correlation with pSS disease activity. Therefore, this CXCL10 proteoform ratio represents an interesting exploratory disease activity biomarker to further investigate. As this strategy can be readily adapted to other plasma proteins and proteoforms of interest, we are convinced that it will lead to a more detailed understanding of proteoforms in physiology and pathology yielding more relevant biomarkers and drug targets.
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Affiliation(s)
- Alexander Schmidt
- Biozentrum, University of Basel, Klingelbergstrasse 50/70, CH-4056 Basel, Switzerland
| | - Hervé Farine
- Idorsia Pharmaceuticals, Ltd, Hegenheimermattweg 91, CH-4123 Allschwil, Switzerland
| | - Marcel P Keller
- Idorsia Pharmaceuticals, Ltd, Hegenheimermattweg 91, CH-4123 Allschwil, Switzerland
| | - Agata Sebastian
- Department of Rheumatology and Internal Medicine, Wroclaw Medical University, Borowska 210, 50-556 Wroclaw, Poland
| | - Lukasz Kozera
- Lukasiewicz Research Network - PORT Polish Center for Technology Development, National Biobanking Node, Stablowicka 147, 50-066 Wroclaw, Poland
| | - Richard W D Welford
- Idorsia Pharmaceuticals, Ltd, Hegenheimermattweg 91, CH-4123 Allschwil, Switzerland
| | - Daniel S Strasser
- Idorsia Pharmaceuticals, Ltd, Hegenheimermattweg 91, CH-4123 Allschwil, Switzerland
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Welford RWD, Mühlemann A, Garzotti M, Rickert V, Groenen PMA, Morand O, Üçeyler N, Probst MR. Glucosylceramide synthase inhibition with lucerastat lowers globotriaosylceramide and lysosome staining in cultured fibroblasts from Fabry patients with different mutation types. Hum Mol Genet 2019; 27:3392-3403. [PMID: 29982630 PMCID: PMC6140777 DOI: 10.1093/hmg/ddy248] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [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: 05/25/2018] [Accepted: 06/29/2018] [Indexed: 12/31/2022] Open
Abstract
Fabry disease is an X-linked lysosomal storage disorder caused by mutations in the GLA gene coding for α-galactosidase A (α-GalA). The deleterious mutations lead to accumulation of α-GalA substrates, including globotriaosylceramide (Gb3) and globotriaosylsphingosine. Progressive glycolipid storage results in cellular dysfunction, leading to organ damage and clinical disease, i.e. neuropathic pain, impaired renal function and cardiomyopathy. Many Fabry patients are treated by bi-weekly intravenous infusions of replacement enzyme. While the only available oral therapy is an α-GalA chaperone, which is indicated for a limited number of patients with specific 'amenable' mutations. Lucerastat is an orally bioavailable inhibitor of glucosylceramide synthase (GCS) that is in late stage clinical development for Fabry disease. Here we investigated the ability of lucerastat to lower Gb3, globotriaosylsphingosine and lysosomal staining in cultured fibroblasts from 15 different Fabry patients. Patients' cells included 13 different pathogenic variants, with 13 cell lines harboring GLA mutations associated with the classic disease phenotype. Lucerastat dose dependently reduced Gb3 in all cell lines. For 13 cell lines the Gb3 data could be fit to an IC50 curve, giving a median IC50 [interquartile range (IQR)] = 11 μM (8.2-18); the median percent reduction (IQR) in Gb3 was 77% (70-83). Lucerastat treatment also dose dependently reduced LysoTracker Red staining of acidic compartments. Lucerastat's effects in the cell lines were compared to those with current treatments-agalsidase alfa and migalastat. Consequently, the GCS inhibitor lucerastat provides a viable mechanism to reduce Gb3 accumulation and lysosome volume, suitable for all Fabry patients regardless of genotype.
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Affiliation(s)
- R W D Welford
- Idorsia Pharmaceuticals, Hegenheimermattweg, Allschwil, Switzerland
| | - A Mühlemann
- Idorsia Pharmaceuticals, Hegenheimermattweg, Allschwil, Switzerland
| | - M Garzotti
- Idorsia Pharmaceuticals, Hegenheimermattweg, Allschwil, Switzerland
| | - V Rickert
- Department of Neurology, University of Würzburg, Würzburg, Germany
| | - P M A Groenen
- Idorsia Pharmaceuticals, Hegenheimermattweg, Allschwil, Switzerland
| | - O Morand
- Idorsia Pharmaceuticals, Hegenheimermattweg, Allschwil, Switzerland
| | - N Üçeyler
- Department of Neurology, University of Würzburg, Würzburg, Germany
| | - M R Probst
- Idorsia Pharmaceuticals, Hegenheimermattweg, Allschwil, Switzerland
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6
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Sieber P, Schäfer A, Lieberherr R, Le Goff F, Stritt M, Welford RWD, Gatfield J, Peter O, Nayler O, Lüthi U. Novel high-throughput myofibroblast assays identify agonists with therapeutic potential in pulmonary fibrosis that act via EP2 and EP4 receptors. PLoS One 2018; 13:e0207872. [PMID: 30485339 PMCID: PMC6261607 DOI: 10.1371/journal.pone.0207872] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2018] [Accepted: 11/06/2018] [Indexed: 12/15/2022] Open
Abstract
Pathological features of pulmonary fibrosis include accumulation of myofibroblasts and increased extracellular matrix (ECM) deposition in lung tissue. Contractile α–smooth muscle actin (α–SMA)–expressing myofibroblasts that produce and secrete ECM are key effector cells of the disease and therefore represent a viable target for potential novel anti–fibrotic treatments. We used primary normal human lung fibroblasts (NHLF) in two novel high–throughput screening assays to discover molecules that inhibit or revert fibroblast–to–myofibroblast differentiation. A phenotypic high–content assay (HCA) quantified the degree of myofibroblast differentiation, whereas an impedance–based assay, multiplexed with MS / MS quantification of α–SMA and collagen 1 alpha 1 (COL1) protein, provided a measure of contractility and ECM formation. The synthetic prostaglandin E1 (PGE1) alprostadil, which very effectively and potently attenuated and even reversed TGF–β1–induced myofibroblast differentiation, was identified by screening a library of approved drugs. In TGF–β1–induced myofibroblasts the effect of alprostadil was attributed to activation of prostanoid receptor 2 and 4 (EP2 and EP4, respectively). However, selective activation of the EP2 or the EP4 receptor was already sufficient to prevent or reverse TGF–β1–induced NHLF myofibroblast transition. Our high–throughput assays identified chemical structures with potent anti–fibrotic properties acting through potentially novel mechanisms.
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Affiliation(s)
- Patrick Sieber
- Idorsia Pharmaceuticals Ltd., Allschwil, Switzerland
- * E-mail:
| | - Anny Schäfer
- Idorsia Pharmaceuticals Ltd., Allschwil, Switzerland
| | | | | | - Manuel Stritt
- Idorsia Pharmaceuticals Ltd., Allschwil, Switzerland
| | | | - John Gatfield
- Idorsia Pharmaceuticals Ltd., Allschwil, Switzerland
| | - Oliver Peter
- Idorsia Pharmaceuticals Ltd., Allschwil, Switzerland
| | - Oliver Nayler
- Idorsia Pharmaceuticals Ltd., Allschwil, Switzerland
| | - Urs Lüthi
- Idorsia Pharmaceuticals Ltd., Allschwil, Switzerland
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Guérard N, Oder D, Nordbeck P, Zwingelstein C, Morand O, Welford RWD, Dingemanse J, Wanner C. Lucerastat, an Iminosugar for Substrate Reduction Therapy: Tolerability, Pharmacodynamics, and Pharmacokinetics in Patients With Fabry Disease on Enzyme Replacement. Clin Pharmacol Ther 2017; 103:703-711. [PMID: 28699267 DOI: 10.1002/cpt.790] [Citation(s) in RCA: 64] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2017] [Revised: 06/23/2017] [Accepted: 06/29/2017] [Indexed: 11/07/2022]
Abstract
Lucerastat is a glucosylceramide synthase inhibitor aimed at reducing production of glycosphingolipids (GSLs), including those accumulating in Fabry disease. The safety, tolerability, pharmacodynamics, and pharmacokinetics of oral lucerastat were evaluated in an exploratory study in patients with Fabry disease. In this single-center, open-label, randomized study, 10 patients received lucerastat 1,000 mg b.i.d. for 12 weeks in addition to enzyme replacement therapy (ERT; the lucerastat group). Four patients with Fabry disease received ERT only. Eight patients reported 17 adverse events (AEs) in the lucerastat group. No clinically relevant safety abnormalities were observed. The mean (SD) levels of the plasma GSLs, glucosylceramide, lactosylceramide, and globotriaosylceramide, were significantly decreased from baseline in the lucerastat group (-49.0% (16.5%), -32.7% (13.0%), and -55.0% (10.4%), respectively). Lucerastat 1,000 mg b.i.d. was well tolerated in patients with Fabry disease over 12 weeks. A marked decrease in plasma GSLs was observed, suggesting clinical potential for lucerastat in patients with Fabry disease.
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Affiliation(s)
- Nicolas Guérard
- Department of Global Clinical Pharmacology, Idorsia Pharmaceuticals Ltd, Allschwil, Switzerland
| | - Daniel Oder
- Fabry Center for Interdisciplinary Therapy (FAZiT), Comprehensive Heart Failure Center (CHFC), and Department of Internal Medicine I, Divisions of Cardiology and Nephrology, University Hospital Würzburg, Würzburg, Germany
| | - Peter Nordbeck
- Fabry Center for Interdisciplinary Therapy (FAZiT), Comprehensive Heart Failure Center (CHFC), and Department of Internal Medicine I, Divisions of Cardiology and Nephrology, University Hospital Würzburg, Würzburg, Germany
| | - Christian Zwingelstein
- Department of Clinical Pharmacology, Actelion Pharmaceuticals Ltd, Allschwil, Switzerland
| | - Olivier Morand
- Department of Global Clinical Science, Idorsia Pharmaceuticals Ltd, Allschwil, Switzerland
| | - Richard W D Welford
- DD Biology, Translational Science, Idorsia Pharmaceuticals Ltd, Allschwil, Switzerland
| | - Jasper Dingemanse
- Department of Global Clinical Pharmacology, Idorsia Pharmaceuticals Ltd, Allschwil, Switzerland
| | - Christoph Wanner
- Fabry Center for Interdisciplinary Therapy (FAZiT), Comprehensive Heart Failure Center (CHFC), and Department of Internal Medicine I, Divisions of Cardiology and Nephrology, University Hospital Würzburg, Würzburg, Germany
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Vanier MT, Gissen P, Bauer P, Coll MJ, Burlina A, Hendriksz CJ, Latour P, Goizet C, Welford RWD, Marquardt T, Kolb SA. Diagnostic tests for Niemann-Pick disease type C (NP-C): A critical review. Mol Genet Metab 2016; 118:244-54. [PMID: 27339554 DOI: 10.1016/j.ymgme.2016.06.004] [Citation(s) in RCA: 102] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/07/2016] [Revised: 06/03/2016] [Accepted: 06/03/2016] [Indexed: 12/14/2022]
Abstract
Niemann-Pick disease type C (NP-C) is a neurovisceral lysosomal cholesterol trafficking and lipid storage disorder caused by mutations in one of the two genes, NPC1 or NPC2. Diagnosis has often been a difficult task, due to the wide range in age of onset of NP-C and clinical presentation of the disease, combined with the complexity of the cell biology (filipin) laboratory testing, even in combination with genetic testing. This has led to substantial delays in diagnosis, largely depending on the access to specialist centres and the level of knowledge about NP-C of the physician in the area. In recent years, advances in mass spectrometry has allowed identification of several sensitive plasma biomarkers elevated in NP-C (e.g. cholestane-3β,5α,6β-triol, lysosphingomyelin isoforms and bile acid metabolites), which, together with the concomitant progress in molecular genetic technology, have greatly impacted the strategy of laboratory testing. Specificity of the biomarkers is currently under investigation and other pathologies are being found to also result in elevations. Molecular genetic testing also has its limitations, notably with unidentified mutations and the classification of new variants. This review is intended to increase awareness on the currently available approaches to laboratory diagnosis of NP-C, to provide an up to date, comprehensive and critical evaluation of the various techniques (cell biology, biochemical biomarkers and molecular genetics), and to briefly discuss ongoing/future developments. The use of current tests in proper combination enables a rapid and correct diagnosis in a large majority of cases. However, even with recent progress, definitive diagnosis remains challenging in some patients, for whom combined genetic/biochemical/cytochemical markers do not provide a clear answer. Expertise and reference laboratories thus remain essential, and further work is still required to fulfill unmet needs.
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Affiliation(s)
- Marie T Vanier
- INSERM Unit 820, 7 Rue Guillaume Paradin, 69008 Lyon, France; Laboratoire Gillet-Mérieux, Centre de Biologie et Pathologie Est, Hospices Civils de Lyon, 69500 Bron, France.
| | - Paul Gissen
- UCL Institute of Child Health, 30 Guilford Street, London WC1N 1EH, UK; Great Ormond Street Hospital, London WC1N 3JH, UK.
| | - Peter Bauer
- Institute of Medical Genetics and Applied Genomics, University Hospital of Tübingen, 72076 Tübingen, Germany.
| | - Maria J Coll
- Inborn Errors of Metabolism Section, Biochemistry and Molecular Genetics Service, Hospital Clínic of Barcelona, 08036 Barcelona, Spain; CIBERER, Spain.
| | - Alberto Burlina
- Division of Inherited Metabolic Diseases, Department of Pediatrics, University Hospital, 35129 Padova, Italy.
| | - Christian J Hendriksz
- The Mark Holland Metabolic Unit, Salford Royal Foundation NHS Trust, Salford, Manchester M68HD, UK; University of Pretoria, Steve Biko Academic Hospital, Department of Paediatrics and Child Health, Pretoria 0001, South Africa.
| | - Philippe Latour
- UF de Neurogénétique Moléculaire, Centre de Biologie et Pathologie Est, Hospices Civils de Lyon, 69500 Bron, France.
| | - Cyril Goizet
- CHU Bordeaux, Department of Medical Genetics, 33076 Bordeaux, France; INSERM Unit 1211, University of Bordeaux, 33076 Bordeaux, France.
| | - Richard W D Welford
- Actelion Pharmaceuticals Ltd., Gewerbestrasse 16, 4123 Allschwil, Switzerland.
| | - Thorsten Marquardt
- Unit for Inborn Errors of Metabolism, University Hospital Münster, 48149 Münster, Germany.
| | - Stefan A Kolb
- Actelion Pharmaceuticals Ltd., Gewerbestrasse 16, 4123 Allschwil, Switzerland.
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Welford RWD, Garzotti M, Marques Lourenço C, Mengel E, Marquardt T, Reunert J, Amraoui Y, Kolb SA, Morand O, Groenen P. Plasma lysosphingomyelin demonstrates great potential as a diagnostic biomarker for Niemann-Pick disease type C in a retrospective study. PLoS One 2014; 9:e114669. [PMID: 25479233 PMCID: PMC4257710 DOI: 10.1371/journal.pone.0114669] [Citation(s) in RCA: 68] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2014] [Accepted: 11/12/2014] [Indexed: 11/29/2022] Open
Abstract
Niemann-Pick disease type C (NP-C) is a devastating, neurovisceral lysosomal storage disorder which is characterised by variable manifestation of visceral signs, progressive neuropsychiatric deterioration and premature death, caused by mutations in the NPC1 and NPC2 genes. Due to the complexity of diagnosis and the availability of an approved therapy in the EU, improved detection of NP-C may have a huge impact on future disease management. At the cellular level dysfunction or deficiency of either the NPC1 or NPC2 protein leads to a complex intracellular endosomal/lysosomal trafficking defect, and organ specific patterns of sphingolipid accumulation. Lysosphingolipids have been shown to be excellent biomarkers of sphingolipidosis in several enzyme deficient lysosomal storage disorders. Additionally, in a recent study the lysosphingolipids, lysosphingomyelin (SPC) and glucosylsphingosine (GlcSph), appeared to be elevated in the plasma of three adult NP-C patients. In order to investigate the clinical utility of SPC and GlcSph as diagnostic markers, an in-depth fit for purpose biomarker assay validation for measurement of these biomarkers in plasma by liquid chromatography-tandem mass spectrometry was performed. Plasma SPC and GlcSph are stable and can be measured accurately, precisely and reproducibly. In a retrospective analysis of 57 NP-C patients and 70 control subjects, median plasma SPC and GlcSph were significantly elevated in NP-C by 2.8-fold and 1.4-fold respectively. For miglustat-naïve NP-C patients, aged 2–50 years, the area under the ROC curve was 0.999 for SPC and 0.776 for GlcSph. Plasma GlcSph did not correlate with SPC levels in NP-C patients. The data indicate excellent potential for the use of lysosphingomyelin in NP-C diagnosis, where it could be used to identify NP-C patients for confirmatory genetic testing.
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Affiliation(s)
| | | | | | - Eugen Mengel
- Department of Lysosomal Storage Disorder, Villa Metabolica, Center for Paediatric and Adolescent Medicine, University Medical Center of the Johannes Gutenberg University Mainz, Mainz, Germany
| | | | | | - Yasmina Amraoui
- Department of Lysosomal Storage Disorder, Villa Metabolica, Center for Paediatric and Adolescent Medicine, University Medical Center of the Johannes Gutenberg University Mainz, Mainz, Germany
| | | | | | - Peter Groenen
- Actelion Pharmaceuticals Ltd, Allschwil, Switzerland
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10
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Bauer P, Balding DJ, Klünemann HH, Linden DEJ, Ory DS, Pineda M, Priller J, Sedel F, Muller A, Chadha-Boreham H, Welford RWD, Strasser DS, Patterson MC. Genetic screening for Niemann-Pick disease type C in adults with neurological and psychiatric symptoms: findings from the ZOOM study. Hum Mol Genet 2013; 22:4349-56. [PMID: 23773996 PMCID: PMC3792693 DOI: 10.1093/hmg/ddt284] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.9] [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: 12/21/2022] Open
Abstract
Niemann–Pick disease type C (NP-C) is a rare, autosomal-recessive, progressive neurological disease caused by mutations in either the NPC1 gene (in 95% of cases) or the NPC2 gene. This observational, multicentre genetic screening study evaluated the frequency and phenotypes of NP-C in consecutive adult patients with neurological and psychiatric symptoms. Diagnostic testing for NP-C involved NPC1 and NPC2 exonic gene sequencing and gene dosage analysis. When available, results of filipin staining, plasma cholestane-3β,5α,6β-triol assays and measurements of relevant sphingolipids were also collected. NPC1 and NPC2 gene sequencing was completed in 250/256 patients from 30 psychiatric and neurological reference centres across the EU and USA [median (range) age 38 (18–90) years]. Three patients had a confirmed diagnosis of NP-C; two based on gene sequencing alone (two known causal disease alleles) and one based on gene sequencing and positive filipin staining. A further 12 patients displayed either single mutant NP-C alleles (8 with NPC1 mutations and 3 with NPC2 mutations) or a known causal disease mutation and an unclassified NPC1 allele variant (1 patient). Notably, high plasma cholestane-3β,5α,6β-triol levels were observed for all NP-C cases (n = 3). Overall, the frequency of NP-C patients in this study [1.2% (95% CI; 0.3%, 3.5%)] suggests that there may be an underdiagnosed pool of NP-C patients among adults who share common neurological and psychiatric symptoms.
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Affiliation(s)
- Peter Bauer
- Institute of Medical Genetics and Applied Genomics, Tübingen University, Tübingen, Germany
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11
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Brunner R, Ng CL, Aissaoui H, Akabas MH, Boss C, Brun R, Callaghan PS, Corminboeuf O, Fidock DA, Frame IJ, Heidmann B, Le Bihan A, Jenö P, Mattheis C, Moes S, Müller IB, Paguio M, Roepe PD, Siegrist R, Voss T, Welford RWD, Wittlin S, Binkert C. UV-triggered affinity capture identifies interactions between the Plasmodium falciparum multidrug resistance protein 1 (PfMDR1) and antimalarial agents in live parasitized cells. J Biol Chem 2013; 288:22576-83. [PMID: 23754276 DOI: 10.1074/jbc.m113.453159] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [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: 01/24/2023] Open
Abstract
A representative of a new class of potent antimalarials with an unknown mode of action was recently described. To identify the molecular target of this class of antimalarials, we employed a photo-reactive affinity capture method to find parasite proteins specifically interacting with the capture compound in living parasitized cells. The capture reagent retained the antimalarial properties of the parent molecule (ACT-213615) and accumulated within parasites. We identified several proteins interacting with the capture compound and established a functional interaction between ACT-213615 and PfMDR1. We surmise that PfMDR1 may play a role in the antimalarial activity of the piperazine-containing compound ACT-213615.
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Affiliation(s)
- Ralf Brunner
- Medical Parasitology and Infection Biology, Swiss Tropical and Public Health Institute, CH-4002 Basel, Switzerland
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12
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Welford RWD, Lam A, Mirica LM, Klinman JP. Partial conversion of Hansenula polymorpha amine oxidase into a "plant" amine oxidase: implications for copper chemistry and mechanism. Biochemistry 2007; 46:10817-27. [PMID: 17760423 DOI: 10.1021/bi700943r] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The mechanism of the first electron transfer from reduced cofactor to O2 in the catalytic cycle of copper amine oxidases (CAOs) remains controversial. Two possibilities have been proposed. In the first mechanism, the reduced aminoquinol form of the TPQ cofactor transfers an electron to the copper, giving radical semiquinone and Cu(I), the latter of which reduces O2 (pathway 1). The second mechanism invokes direct transfer of the first electron from the reduced aminoquinol form of the TPQ cofactor to O2 (pathway 2). The debate over these mechanisms has arisen, in part, due to variable experimental observations with copper amine oxidases from plant versus other eukaryotic sources. One important difference is the position of the aminoquinol/Cu(II) to semiquinone/Cu(I) equilibrium on anaerobic reduction with amine substrate, which varies from almost 0% to 40% semiquinone/Cu(I). In this study we have shown how protein structure controls this equilibrium by making a single-point mutation at a second-sphere ligand to the copper, D630N in Hansenula polymorpha amine oxidase, which greatly increases the concentration of the cofactor semiquinone/Cu(I) following anaerobic reduction by substrate. The catalytic properties of this mutant, including 18O kinetic isotope effects, point to a conservation of pathway 2, despite the elevated production of the cofactor semiqunone/Cu(I). Changes in kcat/Km[O2] are attributed to an impact of D630N on an increased affinity of O2 for its hydrophobic pocket. The data in this study indicate that changes in cofactor semiquinone/Cu(I) levels are not sufficient to alter the mechanism of O2 reduction and illuminate how subtle features are able to control the reduction potential of active site metals in proteins.
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Affiliation(s)
- Richard W D Welford
- Department of Chemistry, University of California, Berkeley, California 94720-1460, USA
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13
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Welford RWD, Kirkpatrick JM, McNeill LA, Puri M, Oldham NJ, Schofield CJ. Incorporation of oxygen into the succinate co-product of iron(II) and 2-oxoglutarate dependent oxygenases from bacteria, plants and humans. FEBS Lett 2005; 579:5170-4. [PMID: 16153644 DOI: 10.1016/j.febslet.2005.08.033] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2005] [Revised: 08/17/2005] [Accepted: 08/17/2005] [Indexed: 11/24/2022]
Abstract
The ferrous iron and 2-oxoglutarate (2OG) dependent oxygenases catalyse two electron oxidation reactions by coupling the oxidation of substrate to the oxidative decarboxylation of 2OG, giving succinate and carbon dioxide coproducts. The evidence available on the level of incorporation of one atom from dioxygen into succinate is inconclusive. Here, we demonstrate that five members of the 2OG oxygenase family, AlkB from Escherichia coli, anthocyanidin synthase and flavonol synthase from Arabidopsis thaliana, and prolyl hydroxylase domain enzyme 2 and factor inhibiting hypoxia-inducible factor-1 from Homo sapiens all incorporate a single oxygen atom, almost exclusively derived from dioxygen, into the succinate co-product.
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14
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Welford RWD, Clifton IJ, Turnbull JJ, Wilson SC, Schofield CJ. Structural and mechanistic studies on anthocyanidin synthase catalysed oxidation of flavanone substrates: the effect of C-2 stereochemistry on product selectivity and mechanism. Org Biomol Chem 2005; 3:3117-26. [PMID: 16106293 DOI: 10.1039/b507153d] [Citation(s) in RCA: 43] [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: 11/21/2022]
Abstract
During the biosynthesis of the tricyclic flavonoid natural products in plants, oxidative modifications to the central C-ring are catalysed by Fe(ii) and 2-oxoglutarate dependent oxygenases. The reactions catalysed by three of these enzymes; flavone synthase I, flavonol synthase and anthocyanidin synthase (ANS), are formally desaturations. In comparison, flavanone 3beta-hydroxylase catalyses hydroxylation at the C-3 pro-R position of 2S-naringenin. Incubation of ANS with the unnatural substrate (+/-)-naringenin results in predominantly C-3 hydroxylation to give cis-dihydrokaempferol as the major product; trans-dihydrokaempferol and the desaturation product, apigenin are also observed. Labelling studies have demonstrated that some of the formal desaturation reactions catalysed by ANS proceed via initial C-3 hydroxylation followed by dehydration at the active site. We describe analyses of the reaction of ANS with 2S- and 2R-naringenin substrates, including the anaerobic crystal structure of an ANS-Fe-2-oxoglutarate-naringenin complex. Together the results reveal that for the 'natural' C-2 stereochemistry of 2S-naringenin, C-3 hydroxylation predominates (>9 : 1) over desaturation, probably due to the inaccessibility of the C-2 hydrogen to the iron centre. For the 2R-naringenin substrate, desaturation is significantly increased relative to C-3 hydroxylation (ca. 1 : 1); this is probably a result of both the C-3 pro-S and C-2 hydrogen atoms being accessible to the reactive oxidising intermediate in this substrate. In contrast to the hydroxylation-elimination desaturation mechanism for some ANS substrates, the results imply that the ANS catalysed desaturation of 2R-naringenin to form apigenin proceeds with a syn-arrangement of eliminated hydrogen atoms and not via an oxygenated (gem-diol) flavonoid intermediate. Thus, by utilising flavonoid substrates with different C-2 stereochemistries, the balance between C-3 hydroxylation or C-2, C-3 desaturation mechanisms can be altered.
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Affiliation(s)
- Richard W D Welford
- Chemical Research Laboratory, Department of Chemistry and Oxford Centre for Molecular Sciences, Mansfield Road, Oxford OX1 3TA, UK
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15
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Hewitson KS, Granatino N, Welford RWD, McDonough MA, Schofield CJ. Oxidation by 2-oxoglutarate oxygenases: non-haem iron systems in catalysis and signalling. Philos Trans A Math Phys Eng Sci 2005; 363:807-28; discussion 1035-40. [PMID: 15901537 DOI: 10.1098/rsta.2004.1540] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/02/2023]
Abstract
The 2-oxoglutarate (2OG) and ferrous iron dependent oxygenases are a superfamily of enzymes that catalyse a wide range of reactions including hydroxylations, desaturations and oxidative ring closures. Recently, it has been discovered that they act as sensors in the hypoxic response in humans and other animals. Substrate oxidation is coupled to conversion of 2OG to succinate and carbon dioxide. Kinetic, spectroscopic and structural studies are consistent with a consensus mechanism in which ordered binding of (co)substrates enables control of reactive intermediates. Binding of the substrate to the active site triggers the enzyme for ligation of dioxygen to the metal. Oxidative decarboxylation of 2OG then generates the ferryl species thought to mediate substrate oxidation. Structural studies reveal a conserved double-stranded beta-helix core responsible for binding the iron, via a 2His-1carboxylate motif and the 2OG side chain. The rigidity of this core contrasts with the conformational flexibility of surrounding regions that are involved in binding the substrate. Here we discuss the roles of 2OG oxygenases in terms of the generic structural and mechanistic features that render the 2OG oxygenases suited for their functions.
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Affiliation(s)
- K S Hewitson
- The Department of Chemistry and The Oxford Centre for Molecular Sciences, Chemistry Research Laboratory, Mansfield Road, Oxford OX1 3TA, UK
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16
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Turnbull JJ, Nakajima JI, Welford RWD, Yamazaki M, Saito K, Schofield CJ. Mechanistic Studies on Three 2-Oxoglutarate-dependent Oxygenases of Flavonoid Biosynthesis. J Biol Chem 2004; 279:1206-16. [PMID: 14570878 DOI: 10.1074/jbc.m309228200] [Citation(s) in RCA: 113] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Anthocyanidin synthase (ANS), flavonol synthase (FLS), and flavanone 3beta-hydroxylase (FHT) are involved in the biosynthesis of flavonoids in plants and are all members of the family of 2-oxoglutarate- and ferrous iron-dependent oxygenases. ANS, FLS, and FHT are closely related by sequence and catalyze oxidation of the flavonoid "C ring"; they have been shown to have overlapping substrate and product selectivities. In the initial steps of catalysis, 2-oxoglutarate and dioxygen are thought to react at the ferrous iron center producing succinate, carbon dioxide, and a reactive ferryl intermediate, the latter of which can then affect oxidation of the flavonoid substrate. Here we describe work on ANS, FLS, and FHT utilizing several different substrates carried out in 18O2/16OH2, 16O2/18OH2, and 18O2/18OH2 atmospheres. In the 18O2/16OH2 atmosphere close to complete incorporation of a single 18O label was observed in the dihydroflavonol products (e.g. (2R,3R)-trans-dihydrokaempferol) from incubations of flavanones (e.g. (2S)naringenin) with FHT, ANS, and FLS. This and other evidence supports the intermediacy of a reactive oxidizing species, the oxygen of which does not exchange with that of water. In the case of products formed by oxidation of flavonoid substrates with a C-3 hydroxyl group (e.g. (2R,3R)-trans-dihydroquercetin), the results imply that oxygen exchange can occur at a stage subsequent to initial oxidation of the C-ring, probably via an enzyme-bound C-3 ketone/3,3-gem-diol intermediate.
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Affiliation(s)
- Jonathan J Turnbull
- The Dyson Perrins Laboratory and The Oxford Centre for Molecular Sciences, South Parks Road, Oxford OX1 3QY, United Kingdom
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17
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Turnbull JJ, Nagle MJ, Seibel JF, Welford RWD, Grant GH, Schofield CJ. The C-4 stereochemistry of leucocyanidin substrates for anthocyanidin synthase affects product selectivity. Bioorg Med Chem Lett 2003; 13:3853-7. [PMID: 14552794 DOI: 10.1016/s0960-894x(03)00711-x] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Anthocyanidin synthase (ANS), an iron(II) and 2-oxoglutarate (2OG) dependent oxygenase, catalyses the penultimate step in anthocyanin biosynthesis by oxidation of the 2R,3S,4S-cis-leucoanthocyanidins. It has been believed that in vivo the products of ANS are the anthocyanidins. However, in vitro studies on ANS using optically active cis- and trans-leucocyanidin substrates identified cyanidin as only a minor product; instead both quercetin and dihydroquercetin are products with the distribution being dependent on the C-4 stereochemistry of the leucocyanidin substrates.
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Affiliation(s)
- Jonathan J Turnbull
- The Oxford Centre for Molecular Sciences and The Dyson Perrins Laboratory, The Department of Chemistry, South Parks Road, Oxford OX1 3QY, UK
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18
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Abstract
AlkB is one of four proteins involved in the adaptive response to DNA alkylation damage in Escherichia coli and is highly conserved from bacteria to humans. Recent analyses have verified the prediction that AlkB is a member of the Fe(II) and 2-oxoglutarate (2OG)-dependent oxygenase family of enzymes. AlkB mediates repair of methylated DNA by direct demethylation of 1-methyladenine and 3-methylcytosine lesions. Other members of the Fe(II) and 2OG-dependent oxygenase family, including those involved in the hypoxic response, are targets for therapeutic intervention. Assays measuring 2OG turnover were used to investigate the selectivity of AlkB. 1-Methyladenosine, 1-methyl-2'-deoxyadenosine, 3-methylcytidine, and 3-methyl-2'-deoxycytidine all stimulated 2OG turnover by AlkB but were not demethylated indicating an uncoupling of 2OG and prime substrate oxidation and that oligomeric DNA is required for hydroxylation and subsequent demethylation. In contrast the equivalent unmethylated nucleosides did not stimulate 2OG turnover indicating that the presence of a methyl group in the substrate is important in initiating oxidation of 2OG. Stimulation of 2OG turnover by 1-methyladenosine was highly dependent on the presence of a reducing agent, ascorbate or dithiothreitol. Following the observation that AlkB is inhibited by high concentrations of 2OG, analogues of 2OG, including 2-mercaptoglutarate, were found to specifically inhibit AlkB. The flavonoid quercetin inhibits both AlkB and the 2OG oxygenase factor-inhibiting hypoxia-inducible factor (FIH) in vitro. FIH inhibition by quercetin occurs in the presence of excess iron indicating a specific interaction, while the inhibition of AlkB by quercetin is, predominantly, due to nonspecific iron chelation.
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Affiliation(s)
- Richard W D Welford
- Dyson Perrins Laboratory and The Oxford Centre for Molecular Sciences, United Kingdom
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19
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Abstract
Flavonoids are common colorants in plants and have long-established biomedicinal properties. Anthocyanidin synthase (ANS), a 2-oxoglutarate iron-dependent oxygenase, catalyzes the penultimate step in the biosynthesis of the anthocyanin class of flavonoids. The crystal structure of ANS reveals a multicomponent active site containing metal, cosubstrate, and two molecules of a substrate analog (dihydroquercetin). An additional structure obtained after 30 min exposure to dioxygen is consistent with the oxidation of the dihydroquercetin to quercetin and the concomitant decarboxylation of 2-oxoglutarate to succinate. Together with in vitro studies, the crystal structures suggest a mechanism for ANS-catalyzed anthocyanidin formation from the natural leucoanthocyanidin substrates involving stereoselective C-3 hydroxylation. The structure of ANS provides a template for the ubiquitous family of plant nonhaem oxygenases for future engineering and inhibition studies.
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Affiliation(s)
- Rupert C Wilmouth
- The Dyson Perrins Laboratory, Oxford Centre for Molecular Sciences, South Parks Road, Oxford OX1 3QY, United Kingdom.
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