1
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Vázquez Torres S, Leung PJY, Venkatesh P, Lutz ID, Hink F, Huynh HH, Becker J, Yeh AHW, Juergens D, Bennett NR, Hoofnagle AN, Huang E, MacCoss MJ, Expòsit M, Lee GR, Bera AK, Kang A, De La Cruz J, Levine PM, Li X, Lamb M, Gerben SR, Murray A, Heine P, Korkmaz EN, Nivala J, Stewart L, Watson JL, Rogers JM, Baker D. De novo design of high-affinity binders of bioactive helical peptides. Nature 2024; 626:435-442. [PMID: 38109936 PMCID: PMC10849960 DOI: 10.1038/s41586-023-06953-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2022] [Accepted: 12/07/2023] [Indexed: 12/20/2023]
Abstract
Many peptide hormones form an α-helix on binding their receptors1-4, and sensitive methods for their detection could contribute to better clinical management of disease5. De novo protein design can now generate binders with high affinity and specificity to structured proteins6,7. However, the design of interactions between proteins and short peptides with helical propensity is an unmet challenge. Here we describe parametric generation and deep learning-based methods for designing proteins to address this challenge. We show that by extending RFdiffusion8 to enable binder design to flexible targets, and to refining input structure models by successive noising and denoising (partial diffusion), picomolar-affinity binders can be generated to helical peptide targets by either refining designs generated with other methods, or completely de novo starting from random noise distributions without any subsequent experimental optimization. The RFdiffusion designs enable the enrichment and subsequent detection of parathyroid hormone and glucagon by mass spectrometry, and the construction of bioluminescence-based protein biosensors. The ability to design binders to conformationally variable targets, and to optimize by partial diffusion both natural and designed proteins, should be broadly useful.
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Affiliation(s)
- Susana Vázquez Torres
- Department of Biochemistry, University of Washington, Seattle, WA, USA
- Institute for Protein Design, University of Washington, Seattle, WA, USA
- Graduate Program in Biological Physics, Structure and Design, University of Washington, Seattle, WA, USA
| | - Philip J Y Leung
- Department of Biochemistry, University of Washington, Seattle, WA, USA
- Institute for Protein Design, University of Washington, Seattle, WA, USA
- Graduate Program in Molecular Engineering, University of Washington, Seattle, WA, USA
| | - Preetham Venkatesh
- Department of Biochemistry, University of Washington, Seattle, WA, USA
- Institute for Protein Design, University of Washington, Seattle, WA, USA
- Graduate Program in Biological Physics, Structure and Design, University of Washington, Seattle, WA, USA
| | - Isaac D Lutz
- Department of Biochemistry, University of Washington, Seattle, WA, USA
- Institute for Protein Design, University of Washington, Seattle, WA, USA
- Department of Bioengineering, University of Washington, Seattle, WA, USA
| | - Fabian Hink
- Department of Drug Design and Pharmacology, University of Copenhagen, Copenhagen, Denmark
| | - Huu-Hien Huynh
- Department of Laboratory Medicine and Pathology, University of Washington, Seattle, WA, USA
| | - Jessica Becker
- Department of Laboratory Medicine and Pathology, University of Washington, Seattle, WA, USA
| | - Andy Hsien-Wei Yeh
- Department of Biochemistry, University of Washington, Seattle, WA, USA
- Institute for Protein Design, University of Washington, Seattle, WA, USA
| | - David Juergens
- Department of Biochemistry, University of Washington, Seattle, WA, USA
- Institute for Protein Design, University of Washington, Seattle, WA, USA
- Graduate Program in Molecular Engineering, University of Washington, Seattle, WA, USA
| | - Nathaniel R Bennett
- Department of Biochemistry, University of Washington, Seattle, WA, USA
- Institute for Protein Design, University of Washington, Seattle, WA, USA
- Graduate Program in Molecular Engineering, University of Washington, Seattle, WA, USA
| | - Andrew N Hoofnagle
- Department of Laboratory Medicine and Pathology, University of Washington, Seattle, WA, USA
| | - Eric Huang
- Department of Genome Sciences, University of Washington, Seattle, WA, USA
| | - Michael J MacCoss
- Department of Genome Sciences, University of Washington, Seattle, WA, USA
| | - Marc Expòsit
- Department of Biochemistry, University of Washington, Seattle, WA, USA
- Institute for Protein Design, University of Washington, Seattle, WA, USA
- Graduate Program in Molecular Engineering, University of Washington, Seattle, WA, USA
| | - Gyu Rie Lee
- Department of Biochemistry, University of Washington, Seattle, WA, USA
- Institute for Protein Design, University of Washington, Seattle, WA, USA
| | - Asim K Bera
- Department of Biochemistry, University of Washington, Seattle, WA, USA
- Institute for Protein Design, University of Washington, Seattle, WA, USA
| | - Alex Kang
- Department of Biochemistry, University of Washington, Seattle, WA, USA
- Institute for Protein Design, University of Washington, Seattle, WA, USA
| | - Joshmyn De La Cruz
- Department of Biochemistry, University of Washington, Seattle, WA, USA
- Institute for Protein Design, University of Washington, Seattle, WA, USA
| | - Paul M Levine
- Department of Biochemistry, University of Washington, Seattle, WA, USA
- Institute for Protein Design, University of Washington, Seattle, WA, USA
| | - Xinting Li
- Department of Biochemistry, University of Washington, Seattle, WA, USA
- Institute for Protein Design, University of Washington, Seattle, WA, USA
| | - Mila Lamb
- Department of Biochemistry, University of Washington, Seattle, WA, USA
- Institute for Protein Design, University of Washington, Seattle, WA, USA
| | - Stacey R Gerben
- Department of Biochemistry, University of Washington, Seattle, WA, USA
- Institute for Protein Design, University of Washington, Seattle, WA, USA
| | - Analisa Murray
- Department of Biochemistry, University of Washington, Seattle, WA, USA
- Institute for Protein Design, University of Washington, Seattle, WA, USA
| | - Piper Heine
- Department of Biochemistry, University of Washington, Seattle, WA, USA
- Institute for Protein Design, University of Washington, Seattle, WA, USA
| | - Elif Nihal Korkmaz
- Department of Biochemistry, University of Washington, Seattle, WA, USA
- Institute for Protein Design, University of Washington, Seattle, WA, USA
| | - Jeff Nivala
- School of Computer Science and Engineering, University of Washington, Seattle, WA, USA
- Molecular Engineering and Sciences Institute, University of Washington, Seattle, WA, USA
| | - Lance Stewart
- Department of Biochemistry, University of Washington, Seattle, WA, USA
- Institute for Protein Design, University of Washington, Seattle, WA, USA
| | - Joseph L Watson
- Department of Biochemistry, University of Washington, Seattle, WA, USA.
- Institute for Protein Design, University of Washington, Seattle, WA, USA.
| | - Joseph M Rogers
- Department of Drug Design and Pharmacology, University of Copenhagen, Copenhagen, Denmark.
| | - David Baker
- Department of Biochemistry, University of Washington, Seattle, WA, USA.
- Institute for Protein Design, University of Washington, Seattle, WA, USA.
- Howard Hughes Medical Institute, University of Washington, Seattle, WA, USA.
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2
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Bolding JE, Nielsen AL, Jensen I, Hansen TN, Ryberg LA, Jameson ST, Harris P, Peters GHJ, Denu JM, Rogers JM, Olsen CA. Substrates and Cyclic Peptide Inhibitors of the Oligonucleotide-Activated Sirtuin 7. Angew Chem Int Ed Engl 2023; 62:e202314597. [PMID: 37873919 DOI: 10.1002/anie.202314597] [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] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2023] [Revised: 10/19/2023] [Accepted: 10/23/2023] [Indexed: 10/25/2023]
Abstract
The sirtuins are NAD+ -dependent lysine deacylases, comprising seven isoforms (SIRT1-7) in humans, which are involved in the regulation of a plethora of biological processes, including gene expression and metabolism. The sirtuins share a common hydrolytic mechanism but display preferences for different ϵ-N-acyllysine substrates. SIRT7 deacetylates targets in nuclei and nucleoli but remains one of the lesser studied of the seven isoforms, in part due to a lack of chemical tools to specifically probe SIRT7 activity. Here we expressed SIRT7 and, using small-angle X-ray scattering, reveal SIRT7 to be a monomeric enzyme with a low degree of globular flexibility in solution. We developed a fluorogenic assay for investigation of the substrate preferences of SIRT7 and to evaluate compounds that modulate its activity. We report several mechanism-based SIRT7 inhibitors as well as de novo cyclic peptide inhibitors selected from mRNA-display library screening that exhibit selectivity for SIRT7 over other sirtuin isoforms, stabilize SIRT7 in cells, and cause an increase in the acetylation of H3 K18.
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Affiliation(s)
- Julie E Bolding
- Center for Biopharmaceuticals & Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Jagtvej 160, 2100, Copenhagen, Denmark
| | - Alexander L Nielsen
- Center for Biopharmaceuticals & Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Jagtvej 160, 2100, Copenhagen, Denmark
- Current address: Institute of Chemical Sciences and Engineering, École Polytechnique Fédérale de Lausanne (EPFL), 1015, Lausanne, Switzerland
| | - Iben Jensen
- Center for Biopharmaceuticals & Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Jagtvej 160, 2100, Copenhagen, Denmark
| | - Tobias N Hansen
- Center for Biopharmaceuticals & Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Jagtvej 160, 2100, Copenhagen, Denmark
| | - Line A Ryberg
- Department of Chemistry, Technical University of Denmark, 2800, Kgs. Lyngby, Denmark
- Current address: Department of Immunology and Microbiology, University of Copenhagen, 2200, Copenhagen, Denmark
| | - Samuel T Jameson
- Center for Biopharmaceuticals & Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Jagtvej 160, 2100, Copenhagen, Denmark
| | - Pernille Harris
- Department of Chemistry, Technical University of Denmark, 2800, Kgs. Lyngby, Denmark
- Current address: Department of Chemistry, University of Copenhagen, 2200, Copenhagen, Denmark
| | - Günther H J Peters
- Department of Chemistry, Technical University of Denmark, 2800, Kgs. Lyngby, Denmark
| | - John M Denu
- Department of Biomolecular Chemistry, University of Wisconsin-Madison, Madison, WI 53706, USA
- Wisconsin Institute for Discovery, University of Wisconsin-Madison, Madison, WI 53715, USA
| | - Joseph M Rogers
- Center for Biopharmaceuticals & Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Jagtvej 160, 2100, Copenhagen, Denmark
| | - Christian A Olsen
- Center for Biopharmaceuticals & Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Jagtvej 160, 2100, Copenhagen, Denmark
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3
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Dreier JE, Prestel A, Martins JM, Brøndum SS, Nielsen O, Garbers AE, Suga H, Boomsma W, Rogers JM, Hartmann-Petersen R, Kragelund BB. A context-dependent and disordered ubiquitin-binding motif. Cell Mol Life Sci 2022; 79:484. [PMID: 35974206 PMCID: PMC9381478 DOI: 10.1007/s00018-022-04486-w] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [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: 03/25/2022] [Revised: 07/06/2022] [Accepted: 07/14/2022] [Indexed: 02/07/2023]
Abstract
Ubiquitin is a small, globular protein that is conjugated to other proteins as a posttranslational event. A palette of small, folded domains recognizes and binds ubiquitin to translate and effectuate this posttranslational signal. Recent computational studies have suggested that protein regions can recognize ubiquitin via a process of folding upon binding. Using peptide binding arrays, bioinformatics, and NMR spectroscopy, we have uncovered a disordered ubiquitin-binding motif that likely remains disordered when bound and thus expands the palette of ubiquitin-binding proteins. We term this motif Disordered Ubiquitin-Binding Motif (DisUBM) and find it to be present in many proteins with known or predicted functions in degradation and transcription. We decompose the determinants of the motif showing it to rely on features of aromatic and negatively charged residues, and less so on distinct sequence positions in line with its disordered nature. We show that the affinity of the motif is low and moldable by the surrounding disordered chain, allowing for an enhanced interaction surface with ubiquitin, whereby the affinity increases ~ tenfold. Further affinity optimization using peptide arrays pushed the affinity into the low micromolar range, but compromised context dependence. Finally, we find that DisUBMs can emerge from unbiased screening of randomized peptide libraries, featuring in de novo cyclic peptides selected to bind ubiquitin chains. We suggest that naturally occurring DisUBMs can recognize ubiquitin as a posttranslational signal to act as affinity enhancers in IDPs that bind to folded and ubiquitylated binding partners.
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Affiliation(s)
- Jesper E Dreier
- Structural Biology and NMR Laboratory, University of Copenhagen, Ole Maaloes Vej 5, 2200, Copenhagen N, Denmark.,REPIN, University of Copenhagen, Ole Maaloes Vej 5, 2200, Copenhagen N, Denmark
| | - Andreas Prestel
- Structural Biology and NMR Laboratory, University of Copenhagen, Ole Maaloes Vej 5, 2200, Copenhagen N, Denmark
| | - João M Martins
- Department of Computer Science, University of Copenhagen, Universitetsparken 1, 2100, Copenhagen Ø, Denmark
| | - Sebastian S Brøndum
- Structural Biology and NMR Laboratory, University of Copenhagen, Ole Maaloes Vej 5, 2200, Copenhagen N, Denmark
| | - Olaf Nielsen
- Functional Genomics, University of Copenhagen, Ole Maaloes Vej 5, 2200, Copenhagen N, Denmark
| | - Anna E Garbers
- Structural Biology and NMR Laboratory, University of Copenhagen, Ole Maaloes Vej 5, 2200, Copenhagen N, Denmark.,REPIN, University of Copenhagen, Ole Maaloes Vej 5, 2200, Copenhagen N, Denmark
| | - Hiroaki Suga
- Department of Chemistry, Graduate School of Science, The University of Tokyo, Tokyo, 113-0033, Japan
| | - Wouter Boomsma
- Department of Computer Science, University of Copenhagen, Universitetsparken 1, 2100, Copenhagen Ø, Denmark
| | - Joseph M Rogers
- Department of Drug Design and Pharmacology, University of Copenhagen, Jagtvej 160, 2100, Copenhagen Ø, Denmark
| | - Rasmus Hartmann-Petersen
- REPIN, University of Copenhagen, Ole Maaloes Vej 5, 2200, Copenhagen N, Denmark. .,The Linderstrøm Lang Centre for Protein Science, Department of Biology, University of Copenhagen, Ole Maaloes Vej 5, 2200, Copenhagen N, Denmark.
| | - Birthe B Kragelund
- Structural Biology and NMR Laboratory, University of Copenhagen, Ole Maaloes Vej 5, 2200, Copenhagen N, Denmark. .,REPIN, University of Copenhagen, Ole Maaloes Vej 5, 2200, Copenhagen N, Denmark. .,The Linderstrøm Lang Centre for Protein Science, Department of Biology, University of Copenhagen, Ole Maaloes Vej 5, 2200, Copenhagen N, Denmark.
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4
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Jeyandrabalan M, Punch A, Rogers JM, Jimenez YA. Insights into Diagnostic Radiography students' perception of clinical stressors. Radiography (Lond) 2022; 28:499-505. [PMID: 35031223 DOI: 10.1016/j.radi.2021.12.014] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2021] [Revised: 12/13/2021] [Accepted: 12/23/2021] [Indexed: 11/18/2022]
Abstract
INTRODUCTION Clinical placements are integral components of Diagnostic Radiography (DR) university training programs, providing students with necessary and unique learning experiences. Educators' understanding of the student experience on placement is growing, and it is important for educators to be attentive to students' reactions to their learning environments and to situations identified to reduce wellbeing. This study aimed to explore DR students' perceptions of challenges experienced during clinical placements and their use of coping strategies. METHODS Final year DR Students at the University of Sydney, were invited to participate in an online focus group. Three focus groups were conducted with a total of 13 participants. Participants were asked to narrate situations experienced while on clinical placement that reduced their emotional wellbeing, and coping strategies considered to support emotional wellbeing. An inductive thematic analysis of focus group transcripts was undertaken to identify the main discussion themes. RESULTS Three themes were identified regarding situations considered to reduce emotional wellbeing: adapting to the 'reality' of the clinical environment, forming effective relationships, and balancing student role expectations and responsibilities of patient care. Three themes were identified about coping strategies for emotionally challenging situations: support from clinical and academic staff, peer support and personal strategies, and growing knowledge and confidence over time. CONCLUSION Students' emotional wellbeing during experiential learning experiences is an underappreciated factor in their transformations into competent diagnostic radiographers. Academic training programs are therefore encouraged to be sensitive to the wellbeing of their trainees, and to take deliberate steps to equip students with the skills to navigate emotions and to normalise emotional responses that may be experienced in the clinical setting. IMPLICATIONS FOR PRACTICE Students' experience of challenges in the clinical environment is largely influenced by students' abilities to deal with negative experiences, hence students' concerns require implementation of focused interventions prior to first clinical placement.
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Affiliation(s)
- M Jeyandrabalan
- Faculty of Medicine and Health, Sydney School of Health Sciences, Discipline of Medical Imaging Science, The University of Sydney, NSW, Australia
| | - A Punch
- Faculty of Medicine and Health, Sydney School of Health Sciences, Discipline of Medical Imaging Science, The University of Sydney, NSW, Australia
| | - J M Rogers
- Faculty of Medicine and Health, Behavioural and Social Sciences in Health, The University of Sydney, NSW, Australia
| | - Y A Jimenez
- Faculty of Medicine and Health, Sydney School of Health Sciences, Discipline of Medical Imaging Science, The University of Sydney, NSW, Australia.
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5
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Rogers JM, Nawatha M, Lemma B, Vamisetti GB, Livneh I, Barash U, Vlodavsky I, Ciechanover A, Fushman D, Suga H, Brik A. Correction: In vivo modulation of ubiquitin chains by N-methylated non-proteinogenic cyclic peptides. RSC Chem Biol 2021; 2:944. [PMID: 34458819 PMCID: PMC8341468 DOI: 10.1039/d1cb90015c] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2021] [Accepted: 04/20/2021] [Indexed: 11/21/2022] Open
Abstract
Correction for ‘In vivo modulation of ubiquitin chains by N-methylated non-proteinogenic cyclic peptides’ by Joseph M. Rogers et al., RSC Chem. Biol., 2021, 2, 513–522, DOI: 10.1039/D0CB00179A.
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Affiliation(s)
- Joseph M Rogers
- Department of Chemistry, Graduate School of Science, The University of Tokyo 7-3-1 Hongo, Bunkyo-ku Tokyo 113-0033 Japan .,Department of Drug Design and Pharmacology, University of Copenhagen Copenhagen 2100 Denmark
| | - Mickal Nawatha
- Schulich Faculty of Chemistry, Technion-Israel Institute of Technology Haifa 3200008 Israel
| | - Betsegaw Lemma
- Department of Chemistry and Biochemistry, Center for Biomolecular Structure and Organization, University of Maryland College Park MD 20742 USA
| | - Ganga B Vamisetti
- Schulich Faculty of Chemistry, Technion-Israel Institute of Technology Haifa 3200008 Israel
| | - Ido Livneh
- The Rappaport Faculty of Medicine and Research Institute, Technion-Israel Institute of Technology Haifa 31096 Israel
| | - Uri Barash
- The Rappaport Faculty of Medicine and Research Institute, Technion-Israel Institute of Technology Haifa 31096 Israel
| | - Israel Vlodavsky
- The Rappaport Faculty of Medicine and Research Institute, Technion-Israel Institute of Technology Haifa 31096 Israel
| | - Aaron Ciechanover
- The Rappaport Faculty of Medicine and Research Institute, Technion-Israel Institute of Technology Haifa 31096 Israel
| | - David Fushman
- Department of Chemistry and Biochemistry, Center for Biomolecular Structure and Organization, University of Maryland College Park MD 20742 USA
| | - Hiroaki Suga
- Department of Chemistry, Graduate School of Science, The University of Tokyo 7-3-1 Hongo, Bunkyo-ku Tokyo 113-0033 Japan
| | - Ashraf Brik
- Schulich Faculty of Chemistry, Technion-Israel Institute of Technology Haifa 3200008 Israel
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6
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Wiedmann M, Dranchak PK, Aitha M, Queme B, Collmus CD, Kashipathy MM, Kanter L, Lamy L, Rogers JM, Tao D, Battaile KP, Rai G, Lovell S, Suga H, Inglese J. Structure-activity relationship of ipglycermide binding to phosphoglycerate mutases. J Biol Chem 2021; 296:100628. [PMID: 33812994 PMCID: PMC8113725 DOI: 10.1016/j.jbc.2021.100628] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [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: 12/31/2020] [Revised: 03/26/2021] [Accepted: 03/31/2021] [Indexed: 01/11/2023] Open
Abstract
Catalysis of human phosphoglycerate mutase is dependent on a 2,3-bisphosphoglycerate cofactor (dPGM), whereas the nonhomologous isozyme in many parasitic species is cofactor independent (iPGM). This mechanistic and phylogenetic diversity offers an opportunity for selective pharmacologic targeting of glycolysis in disease-causing organisms. We previously discovered ipglycermide, a potent inhibitor of iPGM, from a large combinatorial cyclic peptide library. To fully delineate the ipglycermide pharmacophore, herein we construct a detailed structure–activity relationship using 280 substituted ipglycermide analogs. Binding affinities of these analogs to immobilized Caenorhabditis elegans iPGM, measured as fold enrichment relative to the index residue by deep sequencing of an mRNA display library, illuminated the significance of each amino acid to the pharmacophore. Using cocrystal structures and binding kinetics, we show that the high affinity of ipglycermide for iPGM orthologs, from Brugia malayi, Onchocerca volvulus, Dirofilaria immitis, and Escherichia coli, is achieved by a codependence between (1) the off-rate mediated by the macrocycle Cys14 thiolate coordination to an active-site Zn2+ in the iPGM phosphatase domain and (2) shape complementarity surrounding the macrocyclic core at the phosphotransferase–phosphatase domain interface. Our results show that the high-affinity binding of ipglycermide to iPGMs freezes these structurally dynamic enzymes into an inactive, stable complex.
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Affiliation(s)
- Mareike Wiedmann
- Department of Chemistry, Graduate School of Sciences, The University of Tokyo, Tokyo, Japan
| | - Patricia K Dranchak
- National Center for Advancing Translational Sciences, National Institutes of Health, Rockville, Maryland, USA
| | - Mahesh Aitha
- National Center for Advancing Translational Sciences, National Institutes of Health, Rockville, Maryland, USA
| | - Bryan Queme
- National Center for Advancing Translational Sciences, National Institutes of Health, Rockville, Maryland, USA
| | - Christopher D Collmus
- National Center for Advancing Translational Sciences, National Institutes of Health, Rockville, Maryland, USA
| | - Maithri M Kashipathy
- Protein Structure Laboratory, Structural Biology Center, University of Kansas, Lawrence, Kansas, USA
| | - Liza Kanter
- National Center for Advancing Translational Sciences, National Institutes of Health, Rockville, Maryland, USA
| | - Laurence Lamy
- National Center for Advancing Translational Sciences, National Institutes of Health, Rockville, Maryland, USA
| | - Joseph M Rogers
- Department of Chemistry, Graduate School of Sciences, The University of Tokyo, Tokyo, Japan
| | - Dingyin Tao
- National Center for Advancing Translational Sciences, National Institutes of Health, Rockville, Maryland, USA
| | - Kevin P Battaile
- IMCA-CAT Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois, USA
| | - Ganesha Rai
- National Center for Advancing Translational Sciences, National Institutes of Health, Rockville, Maryland, USA
| | - Scott Lovell
- Protein Structure Laboratory, Structural Biology Center, University of Kansas, Lawrence, Kansas, USA
| | - Hiroaki Suga
- Department of Chemistry, Graduate School of Sciences, The University of Tokyo, Tokyo, Japan.
| | - James Inglese
- National Center for Advancing Translational Sciences, National Institutes of Health, Rockville, Maryland, USA; National Human Genome Research Institute, National Institutes of Health, Bethesda, Maryland, USA.
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7
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Rogers JM, Nawatha M, Lemma B, Vamisetti GB, Livneh I, Barash U, Vlodavsky I, Ciechanover A, Fushman D, Suga H, Brik A. In vivo modulation of ubiquitin chains by N-methylated non-proteinogenic cyclic peptides. RSC Chem Biol 2020; 2:513-522. [PMID: 34179781 PMCID: PMC8232551 DOI: 10.1039/d0cb00179a] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [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] [Indexed: 12/11/2022] Open
Abstract
Cancer and other disease states can change the landscape of proteins post-translationally tagged with ubiquitin (Ub) chains. Molecules capable of modulating Ub chains are potential therapeutic agents, but their discovery represents a significant challenge. Recently, it was shown that de novo cyclic peptides, selected from trillion-member random libraries, are capable of binding particular Ub chains. However, these peptides were overwhelmingly proteinogenic, so the prospect of in vivo activity was uncertain. Here, we report the discovery of small, non-proteinogenic cyclic peptides, rich in non-canonical features like N-methylation, which can tightly and specifically bind Lys48-linked Ub chains. These peptides engage three Lys48-linked Ub units simultaneously, block the action of deubiquitinases and the proteasome, induce apoptosis in vitro, and attenuate tumor growth in vivo. This highlights the potential of non-proteinogenic cyclic peptide screening to rapidly find in vivo-active leads, and the targeting of ubiquitin chains as a promising anti-cancer mechanism of action.
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Affiliation(s)
- Joseph M Rogers
- Department of Chemistry, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.,Department of Drug Design and Pharmacology, University of Copenhagen, Copenhagen 2100, Denmark
| | - Mickal Nawatha
- Schulich Faculty of Chemistry, Technion-Israel Institute of Technology, Haifa 3200008, Israel
| | - Betsegaw Lemma
- Department of Chemistry and Biochemistry, Center for Biomolecular Structure and Organization, University of Maryland, College Park, MD 20742, USA
| | - Ganga B Vamisetti
- Schulich Faculty of Chemistry, Technion-Israel Institute of Technology, Haifa 3200008, Israel
| | - Ido Livneh
- The Rappaport Faculty of Medicine and Research Institute, Technion-Israel Institute of Technology, Haifa 31096, Israel
| | - Uri Barash
- The Rappaport Faculty of Medicine and Research Institute, Technion-Israel Institute of Technology, Haifa 31096, Israel
| | - Israel Vlodavsky
- The Rappaport Faculty of Medicine and Research Institute, Technion-Israel Institute of Technology, Haifa 31096, Israel
| | - Aaron Ciechanover
- The Rappaport Faculty of Medicine and Research Institute, Technion-Israel Institute of Technology, Haifa 31096, Israel
| | - David Fushman
- Department of Chemistry and Biochemistry, Center for Biomolecular Structure and Organization, University of Maryland, College Park, MD 20742, USA
| | - Hiroaki Suga
- Department of Chemistry, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Ashraf Brik
- Schulich Faculty of Chemistry, Technion-Israel Institute of Technology, Haifa 3200008, Israel
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8
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Abstract
Many proteins and peptides fold upon binding another protein. Mutagenesis has proved an essential tool in the study of these multi-step molecular recognition processes. By comparing the biophysical behavior of carefully selected mutants, the concert of interactions and conformational changes that occur during folding and binding can be separated and assessed. Recently, this mutagenesis approach has been radically expanded by deep mutational scanning methods, which allow for many thousands of mutations to be examined in parallel. Furthermore, these high-throughput mutagenesis methods have been expanded to include mutations to non-canonical amino acids, returning peptide structure-activity relationships with unprecedented depth and detail. These developments are timely, as the insights they provide can guide the optimization of de novo cyclic peptides, a promising new modality for chemical probes and therapeutic agents.
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Affiliation(s)
- Joseph M Rogers
- Department of Drug Design and Pharmacology, University of Copenhagen, Copenhagen, Denmark
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9
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Huang Y, Nawatha M, Livneh I, Rogers JM, Sun H, Singh SK, Ciechanover A, Brik A, Suga H. Affinity Maturation of Macrocyclic Peptide Modulators of Lys48‐Linked Diubiquitin by a Twofold Strategy. Chemistry 2020; 26:8022-8027. [DOI: 10.1002/chem.202000273] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2020] [Indexed: 12/15/2022]
Affiliation(s)
- Yichao Huang
- Department of ChemistrySchool of ScienceThe University of Tokyo 7-3-1 Hongo Bunkyo Tokyo 113-0033 Japan
| | - Mickal Nawatha
- Schulich Faculty of ChemistryTechnion-Israel Institute of Technology Haifa 3200008 Israel
| | - Ido Livneh
- The Rappaport Faculty of Medicine and Research InstituteTechnion-Israel Institute of Technology Haifa 3200008 Israel
| | - Joseph M. Rogers
- Department of ChemistrySchool of ScienceThe University of Tokyo 7-3-1 Hongo Bunkyo Tokyo 113-0033 Japan
| | - Hao Sun
- Schulich Faculty of ChemistryTechnion-Israel Institute of Technology Haifa 3200008 Israel
| | - Sumeet K. Singh
- Schulich Faculty of ChemistryTechnion-Israel Institute of Technology Haifa 3200008 Israel
| | - Aaron Ciechanover
- The Rappaport Faculty of Medicine and Research InstituteTechnion-Israel Institute of Technology Haifa 3200008 Israel
| | - Ashraf Brik
- Schulich Faculty of ChemistryTechnion-Israel Institute of Technology Haifa 3200008 Israel
| | - Hiroaki Suga
- Department of ChemistrySchool of ScienceThe University of Tokyo 7-3-1 Hongo Bunkyo Tokyo 113-0033 Japan
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10
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Abstract
Ribosomal peptide synthesis begins almost exclusively with the amino acid methionine, across all domains of life. The ubiquity of methionine initiation raises the question; to what extent could polypeptide synthesis be realized with other amino acids, proteinogenic or otherwise? This highlight describes the breadth of building blocks now known to be accepted by the ribosome initiation machinery, from subtle methionine analogues to large exotic non-proteinogenic structures. We outline the key methodological developments that have enabled these discoveries, including the exploitation of methionyl-tRNA synthetase promiscuity, synthetase and tRNA engineering, and the utilization of artificial tRNA-loading ribozymes, flexizymes. Using these methods, the number and diversity of validated initiation building blocks is rapidly expanding permitting the use of the ribosome to synthesize ever more artificial polymers in search of new functional molecules.
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Affiliation(s)
- Christos Tsiamantas
- Department of Chemistry, School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-0033, Japan.
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11
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Tsiamantas C, Kwon S, Rogers JM, Douat C, Huc I, Suga H. Ribosomal Incorporation of Aromatic Oligoamides as Peptide Sidechain Appendages. Angew Chem Int Ed Engl 2020; 59:4860-4864. [PMID: 31894626 PMCID: PMC7496375 DOI: 10.1002/anie.201914654] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [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: 11/16/2019] [Revised: 12/24/2019] [Indexed: 01/06/2023]
Abstract
Derivatives of 4-aminomethyl-l-phenylalanine with aromatic oligoamide foldamers as sidechain appendages were successfully charged on tRNA by means of flexizymes. Their subsequent incorporation both at the C-terminus of, and within, peptide sequences by the ribosome, was demonstrated. These results expand the registry of chemical structures tolerated by the ribosome to sidechains significantly larger and more structurally defined than previously demonstrated.
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Affiliation(s)
- Christos Tsiamantas
- Department of ChemistrySchool of ScienceThe University of Tokyo7-3-1 HongoBunkyoTokyo113-0033Japan
| | - Sunbum Kwon
- Department of Pharmacy and Center for Integrated Protein ScienceLudwig-Maximilians-UniversitätButenandtstr. 5–1381377MünchenGermany
- Department of ChemistryChung-Ang University84 Heukseok-roDongjak-guSeoul06974Republic of Korea
| | - Joseph M. Rogers
- Department of ChemistrySchool of ScienceThe University of Tokyo7-3-1 HongoBunkyoTokyo113-0033Japan
| | - Céline Douat
- Department of Pharmacy and Center for Integrated Protein ScienceLudwig-Maximilians-UniversitätButenandtstr. 5–1381377MünchenGermany
| | - Ivan Huc
- Department of Pharmacy and Center for Integrated Protein ScienceLudwig-Maximilians-UniversitätButenandtstr. 5–1381377MünchenGermany
| | - Hiroaki Suga
- Department of ChemistrySchool of ScienceThe University of Tokyo7-3-1 HongoBunkyoTokyo113-0033Japan
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12
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Tsiamantas C, Kwon S, Rogers JM, Douat C, Huc I, Suga H. Ribosomal Incorporation of Aromatic Oligoamides as Peptide Sidechain Appendages. Angew Chem Int Ed Engl 2020. [DOI: 10.1002/ange.201914654] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Affiliation(s)
- Christos Tsiamantas
- Department of ChemistrySchool of ScienceThe University of Tokyo 7-3-1 Hongo Bunkyo Tokyo 113-0033 Japan
| | - Sunbum Kwon
- Department of Pharmacy and Center for Integrated Protein ScienceLudwig-Maximilians-Universität Butenandtstr. 5–13 81377 München Germany
- Department of ChemistryChung-Ang University 84 Heukseok-ro Dongjak-gu Seoul 06974 Republic of Korea
| | - Joseph M. Rogers
- Department of ChemistrySchool of ScienceThe University of Tokyo 7-3-1 Hongo Bunkyo Tokyo 113-0033 Japan
| | - Céline Douat
- Department of Pharmacy and Center for Integrated Protein ScienceLudwig-Maximilians-Universität Butenandtstr. 5–13 81377 München Germany
| | - Ivan Huc
- Department of Pharmacy and Center for Integrated Protein ScienceLudwig-Maximilians-Universität Butenandtstr. 5–13 81377 München Germany
| | - Hiroaki Suga
- Department of ChemistrySchool of ScienceThe University of Tokyo 7-3-1 Hongo Bunkyo Tokyo 113-0033 Japan
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13
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Rogers JM, Kwon S, Dawson SJ, Mandal PK, Suga H, Huc I. Publisher Correction: Ribosomal synthesis and folding of peptide-helical aromatic foldamer hybrids. Nat Chem 2018; 10:795. [DOI: 10.1038/s41557-018-0086-8] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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14
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Rogers JM, Kwon S, Dawson SJ, Mandal PK, Suga H, Huc I. Ribosomal synthesis and folding of peptide-helical aromatic foldamer hybrids. Nat Chem 2018; 10:405-412. [PMID: 29556052 DOI: 10.1038/s41557-018-0007-x] [Citation(s) in RCA: 65] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2017] [Accepted: 11/24/2017] [Indexed: 11/09/2022]
Abstract
Translation, the mRNA-templated synthesis of peptides by the ribosome, can be manipulated to incorporate variants of the 20 cognate amino acids. Such approaches for expanding the range of chemical entities that can be produced by the ribosome may accelerate the discovery of molecules that can perform functions for which poorly folded, short peptidic sequences are ill suited. Here, we show that the ribosome tolerates some artificial helical aromatic oligomers, so-called foldamers. Using a flexible tRNA-acylation ribozyme-flexizyme-foldamers were attached to tRNA, and the resulting acylated tRNAs were delivered to the ribosome to initiate the synthesis of non-cyclic and cyclic foldamer-peptide hybrid molecules. Passing through the ribosome exit tunnel requires the foldamers to unfold. Yet foldamers encode sufficient folding information to influence the peptide structure once translation is completed. We also show that in cyclic hybrids, the foldamer portion can fold into a helix and force the peptide segment to adopt a constrained and stretched conformation.
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Affiliation(s)
- Joseph M Rogers
- Department of Chemistry, Graduate School of Science, The University of Tokyo, Tokyo, Japan
| | - Sunbum Kwon
- CBMN Laboratory, Univ. Bordeaux, CNRS, IPB, Institut Européen de Chimie et Biologie, Pessac, France
| | - Simon J Dawson
- CBMN Laboratory, Univ. Bordeaux, CNRS, IPB, Institut Européen de Chimie et Biologie, Pessac, France
| | - Pradeep K Mandal
- CBMN Laboratory, Univ. Bordeaux, CNRS, IPB, Institut Européen de Chimie et Biologie, Pessac, France
| | - Hiroaki Suga
- Department of Chemistry, Graduate School of Science, The University of Tokyo, Tokyo, Japan.
| | - Ivan Huc
- CBMN Laboratory, Univ. Bordeaux, CNRS, IPB, Institut Européen de Chimie et Biologie, Pessac, France. .,Department of Pharmacy, Ludwig-Maximilians-Universität, München, Germany.
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15
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Paskaranandavadivel N, Cheng LK, Du P, Rogers JM, O'Grady G. High-resolution mapping of gastric slow-wave recovery profiles: biophysical model, methodology, and demonstration of applications. Am J Physiol Gastrointest Liver Physiol 2017; 313:G265-G276. [PMID: 28546283 DOI: 10.1152/ajpgi.00127.2017] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/20/2017] [Revised: 05/24/2017] [Accepted: 05/24/2017] [Indexed: 01/31/2023]
Abstract
Slow waves play a central role in coordinating gastric motor activity. High-resolution mapping of extracellular potentials from the stomach provides spatiotemporal detail on normal and dysrhythmic slow-wave patterns. All mapping studies to date have focused exclusively on tissue activation; however, the recovery phase contains vital information on repolarization heterogeneity, the excitable gap, and refractory tail interactions but has not been investigated. Here, we report a method to identify the recovery phase in slow-wave mapping data. We first developed a mathematical model of unipolar extracellular potentials that result from slow-wave propagation. These simulations showed that tissue repolarization in such a signal is defined by the steepest upstroke beyond the activation phase (activation was defined by accepted convention as the steepest downstroke). Next, we mapped slow-wave propagation in anesthetized pigs by recording unipolar extracellular potentials from a high-resolution array of electrodes on the serosal surface. Following the simulation result, a wavelet transform technique was applied to detect repolarization in each signal by finding the maximum positive slope beyond activation. Activation-recovery (ARi) and recovery-activation (RAi) intervals were then computed. We hypothesized that these measurements of recovery profile would differ for slow waves recorded during normal and spatially dysrhythmic propagation. We found that the ARi of normal activity was greater than dysrhythmic activity (5.1 ± 0.8 vs. 3.8 ± 0.7 s; P < 0.05), whereas RAi was lower (9.7 ± 1.3 vs. 12.2 ± 2.5 s; P < 0.05). During normal propagation, RAi and ARi were linearly related with negative unit slope indicating entrainment of the entire mapped region. This relationship was weakened during dysrhythmia (slope: -0.96 ± 0.2 vs -0.71 ± 0.3; P < 0.05).NEW & NOTEWORTHY The theoretical basis of the extracellular gastric slow-wave recovery phase was defined using mathematical modeling. A novel technique utilizing the wavelet transform was developed and validated to detect the extracellular slow-wave recovery phase. In dysrhythmic wavefronts, the activation-to-recovery interval (ARi) was shorter and recovery-to-activation interval (RAi) was longer compared with normal wavefronts. During normal activation, RAi vs. ARi had a slope of -1, whereas the weakening of the slope indicated a dysrhythmic propagation.
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Affiliation(s)
- N Paskaranandavadivel
- Auckland Bioengineering Institute, University of Auckland, Auckland, New Zealand; .,Department of Surgery, University of Auckland, Auckland, New Zealand
| | - L K Cheng
- Auckland Bioengineering Institute, University of Auckland, Auckland, New Zealand.,Department of Surgery, Vanderbilt University, Nashville, Tennessee; and
| | - P Du
- Auckland Bioengineering Institute, University of Auckland, Auckland, New Zealand
| | - J M Rogers
- Department of Biomedical Engineering, University of Alabama at Birmingham, Birmingham, Alabama
| | - G O'Grady
- Auckland Bioengineering Institute, University of Auckland, Auckland, New Zealand.,Department of Surgery, University of Auckland, Auckland, New Zealand
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16
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Rogers JM. Search for the missing lncs: gene regulatory networks in neural crest development and long non-coding RNA biomarkers of Hirschsprung's disease. Neurogastroenterol Motil 2016; 28:161-6. [PMID: 26806097 DOI: 10.1111/nmo.12776] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/20/2015] [Accepted: 12/22/2015] [Indexed: 12/12/2022]
Abstract
Hirschsprung's disease (HSCR), a birth defect characterized by variable aganglionosis of the gut, affects about 1 in 5000 births and is a consequence of abnormal development of neural crest cells, from which enteric ganglia derive. In the companion article in this issue (Shen et al., Neurogasterenterol Motil 28: 266-73), the authors search for long non-coding RNAs (lncRNAs) differentially expressed in bowel tissues of infants with HSCR. Microarray analysis of over 37 000 lncRNAs and 34 000 mRNAs was done. The key result was identification of a set of 5 lncRNAs that is a potential diagnostic biomarker of HSCR. In this minireview, I provide an overview of neural crest development and the gene regulatory networks involved in specification, epithelial-mesenchymal transition, and migration of neural crest cells. Genes involved in later development, proliferation, and differentiation of neural crest cells as they migrate into the gut are also reviewed. Many of these genes are associated with HSCR, including RET, GDNF, GFRα, EDN3, and EDNRB. LncRNAs and their roles in development and disease and their use as biomarkers are discussed. The authors of the companion article previously used a multipronged approach to elucidate the etiology of HSCR by examining the effects of specific miRNAs or lncRNAs and target genes on cell migration, proliferation, cell cycle, and apoptosis in vitro. These studies are discussed in terms of their elegance and limitations. The companion article identifies many new lncRNAs that, in addition to providing potential biomarkers of HSCR, may be a treasure trove for future investigations.
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Affiliation(s)
- J M Rogers
- Toxicity Assessment Division, National Health and Environmental Effects Research Laboratory, Office of Research and Development, United States Environmental Protection Agency, Research Triangle Park, NC, USA
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17
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Abstract
The protein synthesis machinery of the cell, the ribosome and associated factors, is able to accurately follow the canonical genetic code, that which maps RNA sequence to protein sequence, to assemble functional proteins from the twenty or so proteinogenic amino acids. A number of innovative methods have arisen to take advantage of this accurate, and efficient, machinery to direct the assembly of non-proteinogenic amino acids. We review and compare these routes to 'reprogram the genetic code' including in vitro translation, engineered aminoacyl tRNA synthetases, and RNA 'flexizymes'. These studies show that the ribosome is highly tolerant of unnatural amino acids, with hundreds of unusual substrates of varying structure and chemistries being incorporated into protein chains. We also discuss how these methods have been coupled to selection techniques, such as phage display and mRNA display, opening up an exciting new avenue for the production of proteins and peptides with properties and functions beyond that which is possible using proteins composed entirely of the proteinogenic amino acids.
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Affiliation(s)
- J M Rogers
- Department of Chemistry, The University of Tokyo, Graduate School of Science, Tokyo, Japan.
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18
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Jongkees SAK, Hipolito CJ, Rogers JM, Suga H. Model foldamers: applications and structures of stable macrocyclic peptides identified using in vitro selection. NEW J CHEM 2015. [DOI: 10.1039/c4nj01633e] [Citation(s) in RCA: 15] [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] [Indexed: 01/23/2023]
Abstract
A survey of crystal- and solution-structure information for macrocyclic peptides, illustrating common folding patterns and target binding effects.
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Affiliation(s)
- Seino A. K. Jongkees
- Department of Chemistry
- Graduate School of Science
- University of Tokyo
- Tokyo 113-0033
- Japan
| | | | - Joseph M. Rogers
- Department of Chemistry
- Graduate School of Science
- University of Tokyo
- Tokyo 113-0033
- Japan
| | - Hiroaki Suga
- Department of Chemistry
- Graduate School of Science
- University of Tokyo
- Tokyo 113-0033
- Japan
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19
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Huang PS, Oberdorfer G, Xu C, Pei XY, Nannenga BL, Rogers JM, DiMaio F, Gonen T, Luisi B, Baker D. High thermodynamic stability of parametrically designed helical bundles. Science 2014; 346:481-485. [PMID: 25342806 DOI: 10.1126/science.1257481] [Citation(s) in RCA: 203] [Impact Index Per Article: 20.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
We describe a procedure for designing proteins with backbones produced by varying the parameters in the Crick coiled coil-generating equations. Combinatorial design calculations identify low-energy sequences for alternative helix supercoil arrangements, and the helices in the lowest-energy arrangements are connected by loop building. We design an antiparallel monomeric untwisted three-helix bundle with 80-residue helices, an antiparallel monomeric right-handed four-helix bundle, and a pentameric parallel left-handed five-helix bundle. The designed proteins are extremely stable (extrapolated ΔGfold > 60 kilocalories per mole), and their crystal structures are close to those of the design models with nearly identical core packing between the helices. The approach enables the custom design of hyperstable proteins with fine-tuned geometries for a wide range of applications.
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Affiliation(s)
- Po-Ssu Huang
- Department of Biochemistry, University of Washington, Seattle, WA 98195, USA.,Institute for Protein Design, University of Washington, Seattle, WA 98195, USA
| | - Gustav Oberdorfer
- Department of Biochemistry, University of Washington, Seattle, WA 98195, USA.,Institute for Protein Design, University of Washington, Seattle, WA 98195, USA.,Institute of Molecular Biosciences, University of Graz, Humboldtstrasse 50/3, 8010-Graz, Austria
| | - Chunfu Xu
- Department of Biochemistry, University of Washington, Seattle, WA 98195, USA.,Institute for Protein Design, University of Washington, Seattle, WA 98195, USA
| | - Xue Y Pei
- Department of Biochemistry, University of Cambridge, Cambridge CB2 1GA, UK
| | - Brent L Nannenga
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA 20147, USA
| | - Joseph M Rogers
- Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, UK
| | - Frank DiMaio
- Department of Biochemistry, University of Washington, Seattle, WA 98195, USA.,Institute for Protein Design, University of Washington, Seattle, WA 98195, USA
| | - Tamir Gonen
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA 20147, USA
| | - Ben Luisi
- Department of Biochemistry, University of Cambridge, Cambridge CB2 1GA, UK
| | - David Baker
- Department of Biochemistry, University of Washington, Seattle, WA 98195, USA.,Institute for Protein Design, University of Washington, Seattle, WA 98195, USA.,Howard Hughes Medical Institute, University of Washington, Seattle, WA 98195, USA
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20
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Rogers JM, Oleinikovas V, Shammas SL, Wong CT, De Sancho D, Baker CM, Clarke J. Interplay between partner and ligand facilitates the folding and binding of an intrinsically disordered protein. Proc Natl Acad Sci U S A 2014; 111:15420-5. [PMID: 25313042 PMCID: PMC4217413 DOI: 10.1073/pnas.1409122111] [Citation(s) in RCA: 125] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Protein-protein interactions are at the heart of regulatory and signaling processes in the cell. In many interactions, one or both proteins are disordered before association. However, this disorder in the unbound state does not prevent many of these proteins folding to a well-defined, ordered structure in the bound state. Here we examine a typical system, where a small disordered protein (PUMA, p53 upregulated modulator of apoptosis) folds to an α-helix when bound to a groove on the surface of a folded protein (MCL-1, induced myeloid leukemia cell differentiation protein). We follow the association of these proteins using rapid-mixing stopped flow, and examine how the kinetic behavior is perturbed by denaturant and carefully chosen mutations. We demonstrate the utility of methods developed for the study of monomeric protein folding, including β-Tanford values, Leffler α, Φ-value analysis, and coarse-grained simulations, and propose a self-consistent mechanism for binding. Folding of the disordered protein before binding does not appear to be required and few, if any, specific interactions are required to commit to association. The majority of PUMA folding occurs after the transition state, in the presence of MCL-1. We also examine the role of the side chains of folded MCL-1 that make up the binding groove and find that many favor equilibrium binding but, surprisingly, inhibit the association process.
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Affiliation(s)
- Joseph M Rogers
- Department of Chemistry, University of Cambridge, Cambridge CB2 1EW, United Kingdom
| | | | - Sarah L Shammas
- Department of Chemistry, University of Cambridge, Cambridge CB2 1EW, United Kingdom
| | - Chi T Wong
- Department of Chemistry, University of Cambridge, Cambridge CB2 1EW, United Kingdom
| | - David De Sancho
- Department of Chemistry, University of Cambridge, Cambridge CB2 1EW, United Kingdom
| | - Christopher M Baker
- Department of Chemistry, University of Cambridge, Cambridge CB2 1EW, United Kingdom
| | - Jane Clarke
- Department of Chemistry, University of Cambridge, Cambridge CB2 1EW, United Kingdom
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21
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Jessop AB, Del Buono F, Solomon G, Mullen-Fortino M, Rogers JM. Police exposure to infectious agents: an audit of protective policies. Occup Med (Lond) 2014; 64:546-8. [PMID: 25114270 DOI: 10.1093/occmed/kqu112] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [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: 11/14/2022] Open
Abstract
BACKGROUND As first responders, police officers may be exposed to infectious agents such as hepatitis viruses and human immunodeficiency virus. Their risk of infection by these viruses can be reduced with training, monitoring and, with some viruses, vaccination. AIMS To examine infection prevention policies and practices among police departments and determine provision of vaccination and infection prevention education programmes. METHODS A questionnaire sent to all police departments in five counties of south-eastern Pennsylvania to capture information about department size, immunization policies and practices, record keeping, infection prevention education and monitoring of exposures. RESULTS Ninety-six of 168 departments responded (57%). Among these, policies requiring pre-employment physical examinations were almost universal (95%). Vaccination policies were less common with <15% requiring and 50% recommending hepatitis, tetanus or influenza vaccination for officers. Few departments took action to provide (2%) or cover the cost (21%) of vaccination. Fewer than 12% maintained vaccination records. Education about the risk of infectious agents was offered by 60% of the responding departments, but often just once at the start of employment. Fewer than half of the departments had systems to collect exposure information. CONCLUSIONS Police departments have opportunities to improve policies and practices for infection prevention and control. Accurate documentation of vaccination status is essential to ensure provision of appropriate post-exposure assessment and treatment. Better reporting of exposure will improve understanding of the infection transmission risk, enhancing the ability to offer targeted education and services to officers.
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Affiliation(s)
- A B Jessop
- HepTREC, 600 S. 43rd Street, Box 22, Philadelphia, PA 19003, USA, Department of Health Policy and Public Health, University of the Sciences in Philadelphia, Philadelphia, PA 19104, USA,
| | - F Del Buono
- Biomedical Writing Program, University of the Sciences in Philadelphia, Philadelphia, PA 19003, USA
| | - G Solomon
- Department of Health Policy and Public Health, University of the Sciences in Philadelphia, Philadelphia, PA 19104, USA
| | - M Mullen-Fortino
- Department of Health Policy and Public Health, University of the Sciences in Philadelphia, Philadelphia, PA 19104, USA
| | - J M Rogers
- Department of Political Science, Temple University, Philadelphia, PA 19122, USA
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22
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Abstract
Coupled folding and binding of intrinsically disordered proteins (IDPs) is prevalent in biology. As the first step toward understanding the mechanism of binding, it is important to know if a reaction is 'diffusion-limited' as, if this speed limit is reached, the association must proceed through an induced fit mechanism. Here, we use a model system where the 'BH3 region' of PUMA, an IDP, forms a single, contiguous α-helix upon binding the folded protein Mcl-1. Using stopped-flow techniques, we systematically compare the rate constant for association (k(+)) under a number of solvent conditions and temperatures. We show that our system is not 'diffusion-limited', despite having a k(+) in the often-quoted 'diffusion-limited' regime (10(5)-10(6) M(-1) s(-1) at high ionic strength) and displaying an inverse dependence on solvent viscosity. These standard tests, developed for folded protein-protein interactions, are not appropriate for reactions where one protein is disordered.
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Affiliation(s)
- Joseph M Rogers
- Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge, CB2 1EW, UK
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23
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Clarke J, Rogers JM, Hill SA, Shammas SL, Gruszka D, Steward A, Lee JC, Potts JR. Folding Upon Binding - Not a Simple Protein Folding Problem. Biophys J 2013. [DOI: 10.1016/j.bpj.2012.11.1069] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
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24
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Wensley BG, Kwa LG, Shammas SL, Rogers JM, Clarke J. Protein folding: adding a nucleus to guide helix docking reduces landscape roughness. J Mol Biol 2012; 423:273-83. [PMID: 22917971 PMCID: PMC3469821 DOI: 10.1016/j.jmb.2012.08.003] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [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: 05/30/2012] [Revised: 08/02/2012] [Accepted: 08/07/2012] [Indexed: 11/29/2022]
Abstract
The elongated three-helix‐bundle spectrin domains R16 and R17 fold and unfold unusually slowly over a rough energy landscape, in contrast to the homologue R15, which folds fast over a much smoother, more typical landscape. R15 folds via a nucleation–condensation mechanism that guides the docking of the A and C-helices. However, in R16 and R17, the secondary structure forms first and the two helices must then dock in the correct register. Here, we use variants of R16 and R17 to demonstrate that substitution of just five key residues is sufficient to alter the folding mechanism and reduce the landscape roughness. We suggest that, by providing access to an alternative, faster, folding route over their landscape, R16 and R17 can circumvent their slow, frustrated wild-type folding mechanism.
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Affiliation(s)
- Beth G Wensley
- Department of Chemistry, University of Cambridge, Cambridge CB2 1EW, UK
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25
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Rogers JM, Walcott GP, Gladden JD, Melnick SB, Ideker RE, Kay MW. Epicardial wavefronts arise from widely distributed transient sources during ventricular fibrillation in the isolated swine heart. New J Phys 2008; 10:015004. [PMID: 18552988 PMCID: PMC2429991 DOI: 10.1088/1367-2630/10/1/015004] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
It has been proposed that VF waves emanate from stable localized sources, often called "mother rotors." However, evidence for the existence of these rotors is conflicting. Using a new panoramic optical mapping system that can image nearly the entire ventricular epicardium, we recently excluded epicardial mother rotors as the drivers of Wiggers' stage II VF in the isolated swine heart. Furthermore, we were unable to find evidence that VF requires sustained intramural sources. The present study was designed to test the following hypotheses: 1. VF is driven by a specific region, and 2. Rotors that are long-lived, though not necessarily permanent, are the primary generators of VF wavefronts. Using panoramic optical mapping, we mapped VF wavefronts from 6 isolated swine hearts. Wavefronts were tracked to characterize their activation pathways and to locate their originating sources. We found that the wavefronts that participate in epicardial reentry were not confined to a compact region; rather they activated the entire epicardial surface. New wavefronts feeding into the epicardial activation pattern were generated over the majority of the epicardium and almost all of them were associated with rotors or repetitive breakthrough patterns that lasted for less than 2 s. These findings indicate that epicardial wavefronts in this model are generated by many transitory epicardial sources distributed over the entire surface of the heart.
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Affiliation(s)
- J M Rogers
- Department of Biomedical Engineering, University of Alabama at Birmingham, 1670 University Blvd., Volker Hall B140, Birmingham, AL 35294, USA
| | - G P Walcott
- Department of Medicine, University of Alabama at Birmingham, 1670 University Blvd., Volker Hall B140, Birmingham, AL 35294, USA
| | - J D Gladden
- Department of Biomedical Engineering, University of Alabama at Birmingham, 1670 University Blvd., Volker Hall B140, Birmingham, AL 35294, USA
| | - S B Melnick
- Department of Medicine, University of Alabama at Birmingham, 1670 University Blvd., Volker Hall B140, Birmingham, AL 35294, USA
| | - R E Ideker
- Department of Medicine, University of Alabama at Birmingham, 1670 University Blvd., Volker Hall B140, Birmingham, AL 35294, USA
| | - M W Kay
- Department of Biomedical Engineering, University of Alabama at Birmingham, 1670 University Blvd., Volker Hall B140, Birmingham, AL 35294, USA
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26
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Abstract
Experiments were conducted to study CCA-treated wood combustion over a range of temperature and oxygen concentrations with a view to understanding the factors affecting energy and metals recovery from waste treated timber. CCA-treated wood was burned in a furnace at temperatures from 400 to 940 degrees C and oxygen concentrations between 5 and 21%. The ash and condensed volatiles were digested for total concentrations of metals and subjected to leaching tests to determine the stabilized concentrations of metals. Arsenic volatilisation increased with increasing furnace temperature whereas the copper and chromium reported mainly to the ash product. The effect of oxygen concentration was weak although it appeared that more arsenic volatilises at higher oxygen concentrations. However, a larger proportion of the arsenic in the ash generated at lower oxygen concentrations is solubilised during leaching tests, with the result that the concentration of stabilized arsenic in the ash is relatively unaffected by oxygen concentration.
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Affiliation(s)
- Joseph M Rogers
- University of Sydney, Department of Chemical Engineering, Sydney, NSW 2006, Australia
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Plunkett AR, Brown DS, Rogers JM, Buckenmaier CC. Supraclavicular continuous peripheral nerve block in a wounded soldier: when ultrasound is the only option. Br J Anaesth 2006; 97:715-7. [PMID: 16914462 DOI: 10.1093/bja/ael218] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The complex nature of combat-related injuries requires frequent operative interventions and prolonged analgesic therapy. The application of continuous peripheral nerve block (CPNB) has been an important anaesthetic tool in the management of combat soldiers wounded from the current conflicts. The severe, destructive nature of combat injuries makes placement of CPNB difficult or impossible using more common neurostimulation approaches. The use of ultrasound technology has improved our success in placing CPNB in the presence of such injuries. We report the application of ultrasound technology in placing CPNB in a combat-injured soldier, whose injuries precluded other CPNB options.
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Affiliation(s)
- A R Plunkett
- Army Regional Anesthesia and Pain Management Initiative, Anesthesia and Operative Service Walter Reed Army Medical Center, Building 2, Ward 44, Room 4418, Washington, DC 20307-5001, USA.
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Hall LC, Rogers JM, Denison MS, Johnson ML. Identification of the herbicide Surflan and its active ingredient oryzalin, a dinitrosulfonamide, as xenoestrogens. Arch Environ Contam Toxicol 2005; 48:201-208. [PMID: 15696347 DOI: 10.1007/s00244-003-0164-8] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/25/2003] [Accepted: 05/28/2004] [Indexed: 05/24/2023]
Abstract
Numerous environmental contaminants have been identified as endocrine disruptors (EDs)--substances that alter endocrine homeostasis by interfering with the biological action, production, or pharmacokinetics of endogenous hormones. Xenoestrogens are those EDs whose biological activity is similar to endogenous estrogen. This report presents data that identified Surflan, a proprietary herbicide emulsion, and its active ingredient oryzalin as xenoestrogens. In vitro, Surflan and oryzalin activated an estrogen-inducible reporter gene, and oryzalin competitively displaced 17beta-estradiol from the estrogen receptor. In vivo, Surflan and oryzalin induced expression of estrogen-regulated high-molecular-weight choriogenin genes in medaka (Oryzias latipes). These results are consistent with the characteristics of previously identified xenoestrogens and indicate that Surflan and oryzalin have the potential to adversely affect numerous estrogen-regulated biological processes.
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Affiliation(s)
- L C Hall
- Lawrence Livermore National Laboratory, L-396, P. O. Box 808, Livermore, California 94550, USA.
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29
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Grasty RC, Bjork JA, Wallace KB, Wolf DC, Lau CS, Rogers JM. Effects of prenatal perfluorooctane sulfonate (PFOS) exposure on lung maturation in the perinatal rat. ACTA ACUST UNITED AC 2005; 74:405-16. [PMID: 16249997 DOI: 10.1002/bdrb.20059] [Citation(s) in RCA: 73] [Impact Index Per Article: 3.8] [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: 11/11/2022]
Abstract
BACKGROUND Perfluorooctane sulfonate (PFOS), found widely in wildlife and humans, is environmentally and metabolically stable. Environmental PFOS may be from its use as a surfactant, hydrolysis of perfluorooctanesulfonyl fluoride, and degradation of N-alkyl-perfluorooctanesulfonamide compounds formerly used in numerous applications. Prenatal exposure to PFOS in rodents causes neonatal mortality; treatment on gestation days (GD) 19-20 is sufficient to induce neonatal death in rats. Affected pups are born alive but present with labored breathing. Their lungs are pale and often do not expand fully on perfusion. METHODS Pregnant Sprague-Dawley rats received 0, 25, or 50 mg/kg/day PFOS/K+ orally on GD 19-20. Lungs from GD 21 fetuses and neonates were prepared for histology and morphometry. Rescue experiments included co-administration of dexamethasone or retinyl palmitate with PFOS. Pulmonary surfactant was investigated with mass spectrometry in GD 21 amniotic fluid and neonatal lungs. Microarray analysis was carried out on PND 0 lungs. RESULTS Histologically, alveolar walls were thicker in lungs of PFOS-exposed newborns compared to controls. The ratio of solid tissue:small airway was increased, suggesting immaturity. Rescue studies were ineffective. Phospholipid concentrations and molecular speciation were unaffected by PFOS. No changes in markers of alveolar differentiation were detected by microarray analysis. CONCLUSIONS Morphometric changes in lungs of PFOS exposed neonates were suggestive of immaturity, but the failure of rescue agents and normal pulmonary surfactant profile indicate that the labored respiration and mortality observed in PFOS-treated neonates was not due to lung immaturity.
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Affiliation(s)
- R C Grasty
- Reproductive Toxicology Division, NHEERL, Office of Research and Development, U.S. EPA, Research Triangle Park, North Carolina, USA
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Crane CEB, Luke CG, Rogers JM, Playford PE, Roder DM. An analysis of factors associated with interval as opposed to screen-detected breast cancers, including hormone therapy and mammographic density. Breast 2004; 11:131-6. [PMID: 14965659 DOI: 10.1054/brst.2001.0371] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2001] [Revised: 09/03/2001] [Accepted: 09/04/2001] [Indexed: 11/18/2022] Open
Abstract
A comparison of 270 interval breast cancers in South Australian women aged 50 years and over with 628 age-matched screen-detected cases indicated that the former had more advanced stages (P<0.001), higher grades (P<0.001), and more frequently a history of past breast problems (P<0.027). After adjusting for these factors, and presence of a self-reported breast lump at the last screen, using conditional logistic regression, hormone replacement therapy (HRT) exposure in the 6 months prior to this screen had a raised relative odds (95% CL) of an interval cancer of 1.48 (1.02, 2.14). For 479 women where breast density was measured, high density showed an elevated relative odds of an interval cancer of 2.62 (1.71, 4.02). The relative odds of a high density was raised to 2.02 (1.33, 3.06) when the HRT history was positive. Screeners should be aware when there is a history of HRT or past breast problems, or a high breast density, that there is an increased probability of a subsequent interval cancer.
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Affiliation(s)
- C E B Crane
- BreastScreen SA, Department of Human Services, South Australia
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31
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Rogers EH, Hunter ES, Rosen MB, Rogers JM, Lau C, Hartig PC, Francis BM, Chernoff N. Lack of evidence for intergenerational reproductive effects due to prenatal and postnatal undernutrition in the female CD-1 mouse. Reprod Toxicol 2003; 17:519-25. [PMID: 14555189 DOI: 10.1016/s0890-6238(03)00070-4] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The impacts of adverse environments during the prenatal and/or early postnatal periods may be manifested as functional deficits that occur later in life. Epidemiological studies have shown an association of sub-optimal pregnancy outcomes in one generation with similar events in the following one, a phenomenon termed the "intergenerational effect". Data indicate that the incidence of adverse pregnancy outcomes and/or low birth weight infants is more closely correlated with the mother's perinatal environment than with that during her pregnancy. However, epidemiological studies are inherently limited given the variability of lifestyles, ethnicity, nutritional status, and exposures to environmental factors. An appropriate animal model would permit control of parameters that may be impossible to evaluate in human populations. The current studies investigated the mouse as a possible animal model. Pregnant CD-1 mice were placed on an ad libitum or food-restricted diet (50% normal) throughout gestation to generate control (CON) and intrauterine growth retarded (IUGR) litters. At birth (postnatal day (PD) 1) pups (F1) were cross-fostered to control dams in litters of either 8 (CON) or 16 (postnatal food restriction (FR)). The experimental groups thus generated represented adequate nutrition (CON-CON) and undernutrition during the prenatal (IUGR-CON), or postnatal periods (CON-FR), or both (IUGR-FR). Pups of dams on a restricted diet during gestation had significant IUGR (P<0.001) as compared to controls (birth weights of 1.32 g versus 1.63 g). At weaning, the average weight of the pups was dependent on postnatal litter size and the difference in birth weights between IUGR and CON animals was not a significant factor. CON-CON pup weight was 24.1g and IUGR-CON was 22.2 g as compared to the CON-FR (17.0 g) and IUGR-FR (17.3 g) groups. The difference in weaning pup weights between the FR and CON groups was significant (P<0.01). The F1 FR females did not reach CON female weights at any time point through 11 months after weaning. At PD60, a single breeding period for all groups of females with CON males began and continued for 75 days with 17 opportunities for breeding. Animals that became pregnant during this time were removed and allowed to litter. No significant differences were noted in average F2 litter size or average pup weight at birth: (CON-CON 12.2/1.62 g; IUGR-CON 11.9/1.6 2 g; CON-FR 10.9/1.70 g; IUGR-FR 11.3/1.61 g). We conclude that body weight at birth in the CD-1 mouse is not correlated with growth through the period of weaning (PD28). We did not find any evidence for an intergenerational reproductive effect after developmental undernutrition.
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Affiliation(s)
- E H Rogers
- US Environmental Protection Agency, NHEERL, RTD, Research Triangle Park, NC 27711, USA
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Sarver RW, Rogers JM, Stockman BJ, Epps DE, DeZwaan J, Harris MS, Baldwin ET. Physical methods to determine the binding mode of putative ligands for hepatitis C virus NS3 helicase. Anal Biochem 2002; 309:186-95. [PMID: 12413450 DOI: 10.1016/s0003-2697(02)00301-9] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Several small molecules identified by high-throughput screening (HTS) were evaluated for their ability to bind to a nonstructural protein 3 (NS3) helicase from hepatitis C virus (HCV). Equilibrium dissociation constants (K(d)'s) of the compounds for this helicase were determined using several techniques including an assay measuring the kinetics of isothermal enzyme denaturation at several concentrations of the test molecule. Effects of two nonhydrolyzable ATP analogs on helicase denaturation were measured as controls using the isothermal denaturation (ITD) assay. Two compounds, 4-(2,4-dimethylphenyl)-2,7,8-trimethyl-4,5-quinolinediamine and 2-phenyl-N-(5-piperazin-1-ylpentyl)quinazolin-4-amine, were identified from screening that inhibited the enzyme and had low micromolar dissociation constants for NS3 helicase in the ITD assay. Low micromolar affinity of the quinolinediamine to helicase was also confirmed by nuclear magnetic resonance experiments. Unfortunately, isothermal titration calorimetry (ITC) experiments indicated that a more water-soluble analog bound to the 47/23-mer oligonucleotide helicase substrate with low micromolar affinity as did the substituted quinazolinamine. There was no further interest in these templates as helicase inhibitors due to the nonspecific binding to enzyme and substrate. A combination of physical methods was required to discern the mode of action of compounds identified by HTS and remove undesirable lead templates from further consideration.
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Affiliation(s)
- Ronald W Sarver
- Structural, Analytical and Medicinal Chemistry, 301 Henrietta Street, Kalamazoo, MI 49001, USA
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Sarver RW, Rogers JM, Epps DE. Determination of ligand-MurB interactions by isothermal denaturation: application as a secondary assay to complement high throughput screening. J Biomol Screen 2002; 7:21-8. [PMID: 11897052 DOI: 10.1177/108705710200700104] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
We used a temperature-jump isothermal denaturation procedure with various methods of detection to evaluate the quality of putative inhibitors of MurB discovered by high-throughput screening. Three optical methods of detection-ultraviolet hyperchromicity of absorbance, fluorescence of bound dyes, and circular dichroism-as well as differential scanning calorimetry were used to dissect the effects of two chemical compounds and a natural substrate on the enzyme. The kinetics of the denaturation process and binding of the compounds detected by quenching of flavin fluorescence were used to quantitate the dose dependencies of the ligand effects. We found that the first step in the denaturation of MurB is the rapid loss of flavin from the active site and that the two chemical inhibitors appeared to destabilize the interaction of the cofactor with the enzyme but stabilize the global unfolding. The kinetics of the denaturation process as well as the loss of flavin fluorescence on binding established that both compounds had nanomolar affinities for the enzyme. We showed that coupling of the various detection methods with isothermal denaturation yields a powerful regimen to provide analytical data for assessing inhibitor specificity for a protein target.
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Affiliation(s)
- Ronald W Sarver
- Structural and Medicinal Chemistry, Pharmacia Corporation, Kalamazoo, MI 49001, USA
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Sarver RW, Rogers JM, Epps DE. Determination of Ligand-MurB Interactions by Isothermal Denaturation: Application as a Secondary Assay to Complement High Throughput Screening. ACTA ACUST UNITED AC 2002. [DOI: 10.1089/108705702753520305] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
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Abstract
Methanol (MeOH), a widely used industrial solvent and alternative motor fuel, has been shown to be mutagenic and teratogenic. We have demonstrated that methanol is teratogenic in mice in vivo and causes dysmorphogenesis in cultured organogenesis stage mouse embryos. Although MeOH is a product of endogenous metabolism in the gut and can be found in humans following consumption of various foods, elevated levels of methanol could lead to methylation of cellular macromolecules. DNA methylation has been demonstrated to suppress transcription of fetal genes and may also play an important role in genetic imprinting. Embryonal proteins are also potential targets for methanol-induced methylation. We investigated the potential of administered methanol to incorporate into and/or alter the methylation of embryonal DNA or to affect specific protein methylation. Gestational day 8 CD-1 mouse embryos were grown for 24 h in culture medium (CM) with 0, 4, or 8 mg MeOH + 20 microCi (14)C-MeOH/mL. At the end of the culture period, yolk sacs and embryos were separated for each treatment group. The DNA was purified by cesium chloride gradient centrifugation in the presence of ethidium bromide and (14)C incorporation was determined. Methylation of a selected gene, Hoxc-8, was assessed by using methylation-specific restriction enzymes. The (14)C activity was found superimposed over the DNA-containing fraction, indicating incorporation. DNA from embryos treated with 4 mg MeOH/mL CM gave the highest incorporation of (14)C-MeOH (8 mg/mL was growth inhibiting). Methylation of Hoxc-8 appeared to be increased in embryos treated with 4 mg MeOH/mL CM, but not in embryos treated with 8 mg MeOH/mL. Lack of incorporation of methylation at the higher concentration may be due to the failure of embryos to grow at this concentration of MeOH. The incorporation of (14)C-MeOH into embryo proteins was investigated by polyacrylamide gel electrophoresis (PAGE) and autoradiography. Incorporation of (14)C-MeOH into specific proteins was observed but the labeling specificity was not methanol dose-related. These results indicate that methyl groups from (14)C-MeOH are incorporated into mouse embryo DNA and protein. Our results further suggest that methanol exposure may increase genomic methylation under certain conditions which could lead to altered gene expression.
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Affiliation(s)
- Y S Huang
- Experimental Toxicology Division, National Health and Environmental Effects Research Laboratory, Office of Research and Development, United States Environmental Protection Agency, Research Triangle Park, NC 27711, USA
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Affiliation(s)
- J M Rogers
- Developmental Biology Branch, Reproductive Toxicology Division, National Health and Environmental Effects Research Laboratory, U. S. Environmental Protection Agency, Research Triangle Park, North Carolina 27711, USA.
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Skinner JL, Digerness SB, Spruell RD, Rogers JM, Katholi CR, Walcott GP, Ideker RE, Holman WL. Novel methods to evaluate controlled reperfusion techniques in cardiac surgery. Int J Surg Investig 2001; 1:397-407. [PMID: 11341596] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Subscribe] [Scholar Register] [Indexed: 02/20/2023]
Abstract
BACKGROUND This manuscript describes two novel techniques that may be useful for comparing methods to reperfuse the heart during cardiac operations. These techniques are based on measurements of intra-myocyte ion content and the analysis of reperfusion arrhythmias. METHODS Myocyte ion content was measured in normal porcine hearts before and after ischemia (cardioplegic arrest, CP arrest) using atomic absorption spectroscopy. A cobalt-EDTA complex served as the extra-cellular marker. Cobalt-EDTA was infused into the aorta together with blood or cardioplegia (CP) solution. Myocardial biopsies were taken prior to CP arrest and upon successful defibrillation 5 min after initiating reperfusion. Ventricular fibrillation (VF) was recorded prior to ischemia, and then during reperfusion. VF wavefront (WF) morphology and propagation patterns were analyzed using computer algorithms. Electrophysiologic variables for measuring VF included the multiplicity index (a descriptor of VF organization), the number of WFs detected (nwaves/s) and the mean peak first derivative of electrogram voltage with respect to time (mp d V/dt). RESULTS Intra-cellular sodium content increased, while intra-cellular magnesium content decreased between control and reperfusion measurements (p < 0.05). Electrophysiologic recovery was characterized by increasingly rapid depolarization (i.e. more negative mp d V/dt) and an increasing nwaves/s during the first minute of post-CP reperfusion. CONCLUSIONS Atomic absorption spectroscopy and computer-based analysis of reperfusion VF successfully measured metabolic and electrophysiologic events that occurred during controlled reperfusion. These methods may be useful for comparing controlled reperfusion techniques.
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Affiliation(s)
- J L Skinner
- Department of Surgery, School of Medicine, University of Alabama at Birmingham 35294-0007, USA
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Abstract
An isothermal denaturation kinetic method was developed for identifying potential ligands of proteins and measuring their affinity. The method is suitable for finding ligands specific toward proteins of unknown function and for large-scale drug screening. It consists of analyzing the kinetics of isothermal denaturation of the protein-with and without the presence of potential specific ligands-as measured by long-wavelength fluorescent dyes whose quantum yield increases when bound to hydrophobic regions exposed upon unfolding of the proteins. The experimental procedure was developed using thymidylate kinase and stromelysin as target proteins. The kinetics of thermal unfolding of both of these enzymes were consistent with a pathway of two consecutive first-order rate-limiting steps. Reflecting the stabilizing effect of protein/ligand complexes, the presence of specific ligands decreased the value of the rate constants of both steps in a dose-dependent manner. The dependence of the rate constants on ligand concentration obeyed a simple binding isotherm, the analysis of which yielded an accurate equilibrium constant for ligand binding. The method was validated by comparing its results with those obtained under the same conditions by steady-state fluorescence spectroscopy, circular dichroism, and uv spectrophotometry: The corresponding rate constants were comparable for each of the analytical detection methods.
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Affiliation(s)
- D E Epps
- Pharmacia Corporation, 7000 Portage Road, Kalamazoo, Michigan 49001, USA
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Abstract
INTRODUCTION This study investigated a hybrid approach to reduce the atrial defibrillation threshold (ADFT) by determining the effect of a single linear radiofrequency ablation (RFA) lesion on both the ADFT and activation patterns during atrial fibrillation (AF). METHODS AND RESULTS In 18 open chest sheep (45 to 57 kg), coil defibrillation electrodes were placed in a superior vena cava/right ventricular configuration. AF was induced by burst pacing and maintained with acetyl beta-methylcholine (2 to 42 microL/min). ADFTs were obtained before and after a linear RFA lesion was created in the left atrium (LAL; n = 6), right atrium (RAL; n = 6), or neither atrium as a control (n = 6). In animals receiving an LAL, a 504-unipolar-electrode plaque was sutured to the LA. For animals receiving an RAL, two 504-electrode plaques were placed, one each on the LA and RA. From each plaque, activations were recorded before and after ADFT shocks, and organizational characteristics of activations were analyzed using algorithms that track individual wavefronts. In sham-treated controls, the ADFT did not change. In contrast, LAL reduced ADFT energy 29%, from 4.5 +/- 2.3 J to 3.2 +/- 2.0 J (P < 0.05). RAL reduced ADFT energy 25%, from 2.0 +/- 0.9 J to 1.5 +/- 0.7 J (P < 0.05). AF activation was substantially more organized after RFA than before RFA for both the RAL- and LAL-treated animals. CONCLUSION A single RFA lesion in either the RA or LA reduces the ADFT in this sheep model. This decrease is associated with an increase in fibrillatory organization.
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Affiliation(s)
- J B White
- Department of Biomedical Engineering, The University of Alabama at Birmingham, USA
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Huang J, Rogers JM, Killingsworth CR, Walcott GP, KenKnight BH, Smith WM, Ideker RE. Improvement of defibrillation efficacy and quantification of activation patterns during ventricular fibrillation in a canine heart failure model. Circulation 2001; 103:1473-8. [PMID: 11245655 DOI: 10.1161/01.cir.103.10.1473] [Citation(s) in RCA: 34] [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] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND Little is known about the effects of heart failure (HF) on the defibrillation threshold (DFT) and the characteristics of activation during ventricular fibrillation (VF). METHODS AND RESULTS HF was induced by rapid right ventricular (RV) pacing for at least 3 weeks in 6 dogs. Another 6 dogs served as controls. Catheter defibrillation electrodes were placed in the RV apex, the superior vena cava, and the great cardiac vein (CV). An active can coupled to the superior vena cava electrode served as the return for the RV and CV electrodes. DFTs were determined before and during HF for a shock through the RV electrode with and without a smaller auxiliary shock through the CV electrode. VF activation patterns were recorded in HF and control animals from 21x24 unipolar electrodes spaced 2 mm apart on the ventricular epicardium. Using these recordings, we computed a number of quantitative VF descriptors. DFT was unchanged in the control dogs. DFT energy was increased 79% and 180% (with and without auxiliary shock, respectively) in HF compared with control dogs. During but not before HF, DFT energy was significantly lowered (21%) by addition of the auxiliary shock. The VF descriptors revealed marked VF differences between HF and control dogs. The differences suggest decreased excitability and an increased refractory period during HF. Most, but not all, descriptors indicate that VF was less complex during HF, suggesting that VF complexity is multifactorial and cannot be expressed by a scalar quantity. CONCLUSIONS HF increases the DFT. This is partially reversed by an auxiliary shock. HF markedly changes VF activation patterns.
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Affiliation(s)
- J Huang
- Department of Medicine, University of Alabama at Birmingham, USA
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Abstract
INTRODUCTION Recent studies showed that pacing atrial and ventricular fibrillation (VF) is possible. The studies presented here determined which parameters influence the efficacy of a pacing train to capture fibrillating ventricular myocardium. Electrode type, current strength, order of pacing trains, polarity, and VF morphology preceding the pacing trains were investigated. METHODS AND RESULTS A 504-electrode recording plaque sutured to the right ventricle of pig hearts was used to record the activations of VF and those resulting from the pacing stimulation. Capture of VF by pacing was determined by observing an animated display of the first temporal derivative of the electrograms. A series of electrodes in a line captured the heart more frequently during VF than did a point electrode. Increasing the current strength to 10 x diastolic pacing threshold increased the incidence of capture, but increasing this strength further did not. The second or third train of 40 stimuli had greater capture rates than did the first train during the same VF episode. Anodal and cathodal unipolar, and bipolar stimulation were equally efficacious in capturing VF. VF activation during the 1-second interval preceding pacing was more organized for pacing trains that captured than those that did not. The highest incidence of capture, 46% to 61% of pacing trains, occurred with a line of electrodes at 10 x diastolic pacing threshold delivered by the second or third train. CONCLUSION The probability of a pacing train capturing fibrillating myocardium can be influenced by the pacing protocol parameters.
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Affiliation(s)
- J C Newton
- Department of Physiology and Biophysics, University of Alabama at Birmingham, 35294, USA
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Lau C, Mole ML, Copeland MF, Rogers JM, Kavlock RJ, Shuey DL, Cameron AM, Ellis DH, Logsdon TR, Merriman J, Setzer RW. Toward a biologically based dose-response model for developmental toxicity of 5-fluorouracil in the rat: acquisition of experimental data. Toxicol Sci 2001; 59:37-48. [PMID: 11134542 DOI: 10.1093/toxsci/59.1.37] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Biologically based dose-response (BBDR) models represent an emerging approach to improving the current practice of human health-risk assessment. The concept of BBDR modeling is to incorporate mechanistic information about a chemical that is relevant to the expression of its toxicity into descriptive mathematical terms, thereby providing a quantitative model that will enhance the ability for low-dose and cross-species extrapolation. Construction of a BBDR model for developmental toxicity is particularly complicated by the multitude of possible mechanisms. Thus, a few model assumptions were made. The current study illustrates the processes involved in selecting the relevant information for BBDR modeling, using an established developmental toxicant, 5-fluorouracil (5-FU), as a prototypic example. The primary BBDR model for 5-FU is based on inhibition of thymidylate synthetase (TS) and resultant changes in nucleotide pools, DNA synthesis, cell-cycle progression, and somatic growth. A single subcutaneous injection of 5-FU at doses ranging from 1 to 40 mg/kg was given to pregnant Sprague-Dawley rats at gestational day 14; controls received saline. 5-FU was absorbed rapidly into the maternal circulation, and AUC estimates were linear with administered doses. We found metabolites of 5-FU directly incorporated into embryonic nucleic acids, although the levels of incorporation were low and lacked correlation with administered doses. On the other hand, 5-FU produced dose-dependent inhibition of thymidylate synthetase in the whole embryo, and recovery from enzyme inhibition was also related to the administered dose. As a consequence of TS inhibition, embryonic dTTP and dGTP were markedly reduced, while dCTP was profoundly elevated, perhaps due to feedback regulation of intracellular nucleotide pools. The total contents of embryonic macromolecules (DNA and protein) were also reduced, most notably at the high doses. Correspondingly, dose-related reductions of fetal weight were seen as early as GD 15, and these deficits persisted for the remainder of gestation. These detailed dose-response parameters involved in the expression of 5-FU developmental toxicity were incorporated into mathematical terms for BBDR modeling. Such quantitative models should be instrumental to the improvement of high-to-low dose and cross-species extrapolation in health-risk assessment.
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Affiliation(s)
- C Lau
- Reproductive Toxicology Division and Experimental Toxicology Division, National Health and Environmental Effects Research Laboratory, U.S. Environmental Protection Agency, Research Triangle Park, North Carolina 27711, USA.
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Setzer RW, Lau C, Mole ML, Copeland MF, Rogers JM, Kavlock RJ. Toward a biologically based dose-response model for developmental toxicity of 5-fluorouracil in the rat: a mathematical construct. Toxicol Sci 2001; 59:49-58. [PMID: 11134543 DOI: 10.1093/toxsci/59.1.49] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Biologically based dose-response (BBDR) models comprise one way to incorporate mechanistic information into a dose-response assessment to be used for risk assessments. The chemotherapeutic drug 5-fluorouracil (5-FU) has been used as a prototypic compound for the construction of a BBDR model for developmental toxicity. Previous work has provided data and a general mechanistic framework for the developmental toxicity of 5-FU when it was administered to pregnant rats subcutaneously on gestation day 14. In this paper, a mathematical model relating maternally administered treatment with 5-FU to embryonal thymidylate synthetase inhibition and thymidylate synthetase inhibition to various measures of deoxyribonucleotide triphosphate (dNTP) pool perturbation is developed, and parameters are estimated using the data collected. The strategy used was to develop semi-empirical submodels for each of the intervening steps, and to estimate model parameters from previously described data. The models developed predict that there is no practical threshold for dNTP pool perturbation; that is, even minimal doses of 5-FU should result in some perturbation of dNTP pools. In particular, the relationship between dNTP pool perturbation and fetal weight deficit suggests that if there is a biological threshold for the effect of 5-FU on fetal weight, the responsible repair or compensation mechanism must be downstream of dNTP pool perturbation, and saturable at 5-FU doses lower than 10 mg/kg (the lowest dose examined for developmental effects in these studies).
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Affiliation(s)
- R W Setzer
- Experimental Toxicology Division and Reproductive Toxicology Division,Office of Research and Development, U.S. Environmental Protection Agency, Research Triangle Park, North Carolina 27711, USA.
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Abstract
INTRODUCTION The mechanisms that maintain ventricular fibrillation (VF) are not completely understood. It has been proposed that increased ventricular wall thickness destabilizes VF wavefronts and therefore is an important determinant of VF activation patterns. We hypothesized that if this is the case, then VF patterns on the thin-walled right ventricle (RV) should be simpler than those on the thick-walled left ventricle (LV). METHODS AND RESULTS In seven open chest pigs, we mapped VF simultaneously from two epicardial recording arrays, one on the RV and one on the LV. Each array contained 504 unipolar electrodes (in a 21 x 24 grid) spaced by 2 mm. We used specialized pattern analysis methods to compute quantitative descriptors of RV and LV activation patterns. Our data show that VF is more organized in the RV than the LV, containing fewer, larger wavefronts that follow fewer distinct pathways and are less likely to fragment or collide with other wavefronts. The incidence, size, and cycle length of reentrant circuits were similar in the two ventricles, but RV reentry persisted for more cycles. These results are not predicted by the differences in electrophysiologic properties between LV and RV that have been reported in mammalian hearts. CONCLUSION The geometry of the ventricular wall, particularly wall thickness, is an important determinant of VF activation patterns.
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Affiliation(s)
- J M Rogers
- Department of Biomedical Engineering, University of Alabama at Birmingham, 35294, USA.
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Abstract
This paper examines relationships between transmembrane potential (Vm), [Ca2+]i dependent membrane ionic currents, and [Ca2+]i handling by the sarcoplasmic reticulum (SR) in a two-dimensional model of cardiac tissue. Luo-Rudy dynamic (LRd) membrane equations were used because they include detailed formulations for triggered SR Ca2+ release dependent on membrane Ca2+ influx (CICR) and for spontaneous SR Ca2+ release following calsequestrin buffer overload (SCR). Reentry's rapid rate (110-ms cycle length) elevated [Ca2+]i and limited CICR, which in turn promoted SCR that occurred at intervals of 320-350 ms, was preferential at sites located inside the functional center, and destabilized the reentrant activation sequence. Although adjustment of LRd parameters for SR Ca2+ modified SCR interval and peak [Ca2+]i in voltage clamp simulations with a command waveform representing Vm time course within the functional center, SCR persisted. Using the same command waveform, SCR also occurred with an alternate SR Ca2+ formulation that represented subcellular details underlying CICR. LRd parameter adjustments to promote CICR and limit SCR in subsequent reentry simulations failed to eliminate SCR completely, as they modulated SCR intervals in a manner consistent with the voltage clamp simulations. Taken together, our findings support a destabilizing influence of functional reentry on [Ca2+]i handling. However, [Ca2+]i instabilities did not always fractionate depolarization wavefronts during reentry. Fractionation depended, in part, upon CICR and SCR parameters in the LRd formulation for SR Ca2+ release.
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Affiliation(s)
- A E Pollard
- Department of Biomedical Engineering and the Cardiac Rhythm Management Laboratory, University of Alabama at Birmingham 35294, USA.
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Rogers JM, Denison MS. Recombinant cell bioassays for endocrine disruptors: development of a stably transfected human ovarian cell line for the detection of estrogenic and anti-estrogenic chemicals. In Vitr Mol Toxicol 2000; 13:67-82. [PMID: 10900408] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Subscribe] [Scholar Register] [Indexed: 02/17/2023]
Abstract
The ability of a variety of compounds to disrupt normal endocrine homeostasis, and potentially, the physiological and reproductive capacity of an organism, has gained worldwide attention in recent years. In an attempt to identify such compounds, and to examine the mechanism(s) by which they may exert their actions, we have constructed reporter plasmid vectors that contain the firefly luciferase gene under hormone-inducible control of estrogen-, androgen-, or retinoic acid-responsive DNA enhancer elements. Transient transfection of these vectors into appropriate receptor-containing cell lines revealed their ability to respond to their respective hormones with the induction of luciferase. Here, we describe development and optimization of a recombinant human ovarian carcinoma (BG-1) line, which has been stably transfected with the estrogen responsive luciferase reporter plasmid. The resulting recombinant cell line (BG1Luc4E(2)) responds to 17beta-estradiol at concentrations as low as 1 pM. The utility of BG1Luc4E(2) cells as a bioassay screening system for environmental estrogens was demonstrated by their response to known xenoestrogens, and also by the putative identification of two polychlorinated biphenyls (2,3',4, 4,'-tetrachlorobiphenyl and 2,2',3,5',6-pentachlorobiphenyl) as novel estrogenic chemicals. These cell bioassay systems have applications for rapid screening, identification, and characterization of endocrine disrupting chemicals.
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Affiliation(s)
- J M Rogers
- Department of Environmental Toxicology, University of California, Davis 95616, USA
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Abstract
Action potential propagation simulations with physiologic membrane currents and macroscopic tissue dimensions are computationally expensive. We, therefore, analyzed distributed computing schemes to reduce execution time in workstation clusters by parallelizing solutions with message passing. Four schemes were considered in two-dimensional monodomain simulations with the Beeler-Reuter membrane equations. Parallel speedups measured with each scheme were compared to theoretical speedups, recognizing the relationship between speedup and code portions that executed serially. A data decomposition scheme based on total ionic current provided the best performance. Analysis of communication latencies in that scheme led to a load-balancing algorithm in which measured speedups at 89 +/- 2% and 75 +/- 8% of theoretical speedups were achieved in homogeneous and heterogeneous clusters of workstations. Speedups in this scheme with the Luo-Rudy dynamic membrane equations exceeded 3.0 with eight distributed workstations. Cluster speedups were comparable to those measured during parallel execution on a shared memory machine.
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Affiliation(s)
- D Porras
- Department of Biomedical Engineering, University of Alabama at Birmingham 35294, USA
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Affiliation(s)
- R M Zucker
- Reproductive Toxicology Division, US Environmental Protection Agency, Research Triangle Park, NC, USA
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49
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Affiliation(s)
- R M Zucker
- Reproductive Toxicology Division, US Environmental Protection Agency, Research Triangle Park, NC, USA
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Affiliation(s)
- M G Narotsky
- Reproductive Toxicology Division, US Department of Environmental Protection, Research Triangle Park, NC, USA
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