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Time-dependent botulinum neurotoxin serotype A metalloprotease inhibitors. Bioorg Med Chem 2011; 19:7338-48. [PMID: 22082667 DOI: 10.1016/j.bmc.2011.10.062] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2011] [Revised: 10/13/2011] [Accepted: 10/19/2011] [Indexed: 11/21/2022]
Abstract
Botulinum neurotoxins (BoNTs) are the most lethal of biological substances, and are categorized as class A biothreat agents by the Centers for Disease Control and Prevention. There are currently no drugs to treat the deadly flaccid paralysis resulting from BoNT intoxication. Among the seven BoNT serotypes, the development of therapeutics to counter BoNT/A is a priority (due to its long half-life in the neuronal cytosol and its ease of production). In this regard, the BoNT/A enzyme light chain (LC) component, a zinc metalloprotease responsible for the intracellular cleavage of synaptosomal-associated protein of 25 kDa, is a desirable target for developing post-BoNT/A intoxication rescue therapeutics. In an earlier study, we reported the high throughput screening of a library containing 70,000 compounds, and uncovered a novel class of benzimidazole acrylonitrile-based BoNT/A LC inhibitors. Herein, we present both structure-activity relationships and a proposed mechanism of action for this novel inhibitor chemotype.
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52
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Harper CB, Martin S, Nguyen TH, Daniels SJ, Lavidis NA, Popoff MR, Hadzic G, Mariana A, Chau N, McCluskey A, Robinson PJ, Meunier FA. Dynamin inhibition blocks botulinum neurotoxin type A endocytosis in neurons and delays botulism. J Biol Chem 2011; 286:35966-35976. [PMID: 21832053 DOI: 10.1074/jbc.m111.283879] [Citation(s) in RCA: 116] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The botulinum neurotoxins (BoNTs) are di-chain bacterial proteins responsible for the paralytic disease botulism. Following binding to the plasma membrane of cholinergic motor nerve terminals, BoNTs are internalized into an endocytic compartment. Although several endocytic pathways have been characterized in neurons, the molecular mechanism underpinning the uptake of BoNTs at the presynaptic nerve terminal is still unclear. Here, a recombinant BoNT/A heavy chain binding domain (Hc) was used to unravel the internalization pathway by fluorescence and electron microscopy. BoNT/A-Hc initially enters cultured hippocampal neurons in an activity-dependent manner into synaptic vesicles and clathrin-coated vesicles before also entering endosomal structures and multivesicular bodies. We found that inhibiting dynamin with the novel potent Dynasore analog, Dyngo-4a(TM), was sufficient to abolish BoNT/A-Hc internalization and BoNT/A-induced SNAP25 cleavage in hippocampal neurons. Dyngo-4a also interfered with BoNT/A-Hc internalization into motor nerve terminals. Furthermore, Dyngo-4a afforded protection against BoNT/A-induced paralysis at the rat hemidiaphragm. A significant delay of >30% in the onset of botulism was observed in mice injected with Dyngo-4a. Dynamin inhibition therefore provides a therapeutic avenue for the treatment of botulism and other diseases caused by pathogens sharing dynamin-dependent uptake mechanisms.
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Affiliation(s)
- Callista B Harper
- Queensland Brain Institute, the University of Queensland, Brisbane, Queensland 4072, Australia
| | - Sally Martin
- Queensland Brain Institute, the University of Queensland, Brisbane, Queensland 4072, Australia
| | - Tam H Nguyen
- Queensland Brain Institute, the University of Queensland, Brisbane, Queensland 4072, Australia
| | - Shari J Daniels
- Queensland Brain Institute, the University of Queensland, Brisbane, Queensland 4072, Australia
| | - Nickolas A Lavidis
- School of Biomedical Sciences, the University of Queensland, Brisbane, Queensland 4072, Australia
| | - Michel R Popoff
- Unité des Bactéries anaérobies et Toxines, Institut Pasteur, 28 rue du Dr. Roux, 75724 Paris cedex, France
| | - Gordana Hadzic
- Centre for Chemical Biology, Chemistry Building, the University of Newcastle, Callaghan, New South Wales 2308, Australia
| | - Anna Mariana
- Children's Medical Research Institute, the University of Sydney, Sydney, New South Wales 2145, Australia
| | - Ngoc Chau
- Children's Medical Research Institute, the University of Sydney, Sydney, New South Wales 2145, Australia
| | - Adam McCluskey
- Centre for Chemical Biology, Chemistry Building, the University of Newcastle, Callaghan, New South Wales 2308, Australia
| | - Phillip J Robinson
- Children's Medical Research Institute, the University of Sydney, Sydney, New South Wales 2145, Australia
| | - Frederic A Meunier
- Queensland Brain Institute, the University of Queensland, Brisbane, Queensland 4072, Australia.
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Whitby LR, Ando Y, Setola V, Vogt PK, Roth BL, Boger DL. Design, synthesis, and validation of a β-turn mimetic library targeting protein-protein and peptide-receptor interactions. J Am Chem Soc 2011; 133:10184-94. [PMID: 21609016 DOI: 10.1021/ja201878v] [Citation(s) in RCA: 67] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
The design and synthesis of a β-turn mimetic library as a key component of a small-molecule library targeting the major recognition motifs involved in protein-protein interactions is described. Analysis of a geometric characterization of 10,245 β-turns in the protein data bank (PDB) suggested that trans-pyrrolidine-3,4-dicarboxamide could serve as an effective and synthetically accessible library template. This was confirmed by initially screening select compounds against a series of peptide-activated GPCRs that recognize a β-turn structure in their endogenous ligands. This validation study was highlighted by identification of both nonbasic and basic small molecules with high affinities (K(i) = 390 and 23 nM, respectively) for the κ-opioid receptor (KOR). Consistent with the screening capabilities of collaborators and following the design validation, the complete library was assembled as 210 mixtures of 20 compounds, providing a total of 4200 compounds designed to mimic all possible permutations of 3 of the 4 residues in a naturally occurring β-turn. Unique to the design and because of the C(2) symmetry of the template, a typical 20 × 20 × 20-mix (8000 compounds prepared as 400 mixtures of 20 compounds) needed to represent 20 variations in the side chains of three amino acid residues reduces to a 210 × 20-mix, thereby simplifying the library synthesis and subsequent screening. The library was prepared using a solution-phase synthetic protocol with liquid-liquid or liquid-solid extractions for purification and conducted on a scale that insures its long-term availability for screening campaigns. Screening the library against the human opioid receptors (KOR, MOR, and DOR) identified not only the activity of library members expected to mimic the opioid receptor peptide ligands but also additional side-chain combinations that provided enhanced receptor binding selectivities (>100-fold) and affinities (as low as K(i) = 80 nM for KOR). A key insight to emerge from the studies is that the phenol of Tyr in endogenous ligands bearing the H-Tyr-Pro-Trp/Phe-Phe-NH(2) β-turn is important for MOR binding but may not be important for KOR (accommodated, but not preferred) and that the resulting selectivity for KOR observed with its removal can be increased by replacing the phenol OH with a chlorine substituent, further enhancing KOR affinity.
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Affiliation(s)
- Landon R Whitby
- Department of Chemistry and The Skaggs Institute for Chemical Biology, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, California 92037, USA
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Čapek P, Zhang Y, Barlow DJ, Houseknecht KL, Smith GR, Dickerson TJ. Enhancing the Pharmacokinetic Properties of Botulinum Neurotoxin Serotype A Protease Inhibitors Through Rational Design. ACS Chem Neurosci 2011; 2:288-293. [PMID: 21743830 DOI: 10.1021/cn200021q] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
Botulinum neurotoxin (BoNT), the etiological agent that causes the neuroparalytic disease botulism, has become a highly studied drug target in light of the potential abuse of this toxin as a weapon of bioterrorism. In particular, small molecule inhibitors of the light chain metalloprotease of BoNT serotype A have received significant attention and a number of small molecule and biologic inhibitors have been reported. However, all small molecules reported have been identified from either primary screens or medicinal chemistry follow-up studies, and the pharmacokinetic profiles of these compounds have not been addressed. In this study, we have removed the pharmacologic liabilities of one of the best compounds reported to date, 2,4-dichlorocinnamate hydroxamic acid, and in the process, uncovered a related class of benzothiophene hydroxamic acids that are significantly more potent inhibitors of the BoNT/A light chain, while also possessing greatly improved ADME properties, with the best compound showing the most potent inhibition of BoNT/A light chain reported (K(i) = 77 nM). Using a strategy of incorporating traditional drug development filters early into the discovery process, potential liabilities in BoNT/A lead compounds have been illuminated and removed, clearing the path for advancement into further pharmacologic optimization and in vivo efficacy testing.
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Affiliation(s)
- Petr Čapek
- Department of Chemistry and Worm Institute of Research and Medicine (WIRM), The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, California 92037, United States
| | - Yan Zhang
- Fox Chase Chemical Diversity Center, Doylestown, Pennsylvania, United States
| | - Deborah J. Barlow
- Department of Pharmaceutical Sciences, University of New England College of Pharmacy, Portland, Maine, United States
| | - Karen L. Houseknecht
- Department of Pharmaceutical Sciences, University of New England College of Pharmacy, Portland, Maine, United States
| | - Garry R. Smith
- Fox Chase Chemical Diversity Center, Doylestown, Pennsylvania, United States
| | - Tobin J. Dickerson
- Department of Chemistry and Worm Institute of Research and Medicine (WIRM), The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, California 92037, United States
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55
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Ruge DR, Dunning FM, Piazza TM, Molles BE, Adler M, Zeytin FN, Tucker WC. Detection of six serotypes of botulinum neurotoxin using fluorogenic reporters. Anal Biochem 2011; 411:200-9. [PMID: 21216216 DOI: 10.1016/j.ab.2011.01.002] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2010] [Revised: 01/03/2011] [Accepted: 01/04/2011] [Indexed: 12/01/2022]
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56
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Fighting bacterial infections—Future treatment options. Drug Resist Updat 2011; 14:125-39. [DOI: 10.1016/j.drup.2011.02.001] [Citation(s) in RCA: 122] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2011] [Revised: 01/31/2011] [Accepted: 01/31/2011] [Indexed: 12/13/2022]
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57
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Adekar SP, Segan AT, Chen C, Bermudez R, Elias MD, Selling BH, Kapadnis BP, Simpson LL, Simon PM, Dessain SK. Enhanced neutralization potency of botulinum neurotoxin antibodies using a red blood cell-targeting fusion protein. PLoS One 2011; 6:e17491. [PMID: 21399689 PMCID: PMC3047547 DOI: 10.1371/journal.pone.0017491] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2010] [Accepted: 02/03/2011] [Indexed: 01/17/2023] Open
Abstract
Botulinum neurotoxin (BoNT) potently inhibits cholinergic signaling at the neuromuscular junction. The ideal countermeasures for BoNT exposure are monoclonal antibodies or BoNT antisera, which form BoNT-containing immune complexes that are rapidly cleared from the general circulation. Clearance of opsonized toxins may involve complement receptor-mediated immunoadherence to red blood cells (RBC) in primates or to platelets in rodents. Methods of enhancing immunoadherence of BoNT-specific antibodies may increase their potency in vivo. We designed a novel fusion protein (FP) to link biotinylated molecules to glycophorin A (GPA) on the RBC surface. The FP consists of an scFv specific for murine GPA fused to streptavidin. FP:mAb:BoNT complexes bound specifically to the RBC surface in vitro. In a mouse model of BoNT neutralization, the FP increased the potency of single and double antibody combinations in BoNT neutralization. A combination of two antibodies with the FP gave complete neutralization of 5,000 LD50 BoNT in mice. Neutralization in vivo was dependent on biotinylation of both antibodies and correlated with a reduction of plasma BoNT levels. In a post-exposure model of intoxication, FP:mAb complexes gave complete protection from a lethal BoNT/A1 dose when administered within 2 hours of toxin exposure. In a pre-exposure prophylaxis model, mice were fully protected for 72 hours following administration of the FP:mAb complex. These results demonstrate that RBC-targeted immunoadherence through the FP is a potent enhancer of BoNT neutralization by antibodies in vivo.
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Affiliation(s)
- Sharad P. Adekar
- Lankenau Institute for Medical Research,
Wynnewood, Pennsylvania, United States of America
- Immunome, Inc., Wynnewood, Pennsylvania,
United States of America
- Augmenta Biologicals, LLC, Wynnewood,
Pennsylvania, United States of America
| | - Andrew T. Segan
- Lankenau Institute for Medical Research,
Wynnewood, Pennsylvania, United States of America
| | - Cindy Chen
- Lankenau Institute for Medical Research,
Wynnewood, Pennsylvania, United States of America
| | - Rodney Bermudez
- Immunome, Inc., Wynnewood, Pennsylvania,
United States of America
| | - M. D. Elias
- Division of Infectious Diseases and
Environmental Medicine, Thomas Jefferson University, Philadelphia, Pennsylvania,
United States of America
| | - Bernard H. Selling
- Impact Biologicals, Inc. Wallingford,
Pennsylvania, United States of America
| | - B. P. Kapadnis
- Department of Microbiology, University of
Pune, Pune, India
| | - Lance L. Simpson
- Division of Infectious Diseases and
Environmental Medicine, Thomas Jefferson University, Philadelphia, Pennsylvania,
United States of America
| | - Paul M. Simon
- Augmenta Biologicals, LLC, Wynnewood,
Pennsylvania, United States of America
- * E-mail: (SKD); (PMS)
| | - Scott K. Dessain
- Lankenau Institute for Medical Research,
Wynnewood, Pennsylvania, United States of America
- * E-mail: (SKD); (PMS)
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58
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Saunders MJ, Edwards BS, Zhu J, Sklar LA, Graves SW. Microsphere-based flow cytometry protease assays for use in protease activity detection and high-throughput screening. ACTA ACUST UNITED AC 2011; Chapter 13:Unit 13.12.1-17. [PMID: 20938917 DOI: 10.1002/0471142956.cy1312s54] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
This protocol describes microsphere-based protease assays for use in flow cytometry and high-throughput screening. This platform measures a loss of fluorescence from the surface of a microsphere due to the cleavage of an attached fluorescent protease substrate by a suitable protease enzyme. The assay format can be adapted to any site or protein-specific protease of interest and results can be measured in both real time and as endpoint fluorescence assays on a flow cytometer. Endpoint assays are easily adapted to microplate format for flow cytometry high-throughput analysis and inhibitor screening.
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Affiliation(s)
- Matthew J Saunders
- Department of Chemical and Nuclear Engineering, University of New Mexico, Center for Biomedical Engineering, Albuquerque, New Mexico, USA
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59
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McNutt P, Celver J, Hamilton T, Mesngon M. Embryonic stem cell-derived neurons are a novel, highly sensitive tissue culture platform for botulinum research. Biochem Biophys Res Commun 2011; 405:85-90. [PMID: 21215258 DOI: 10.1016/j.bbrc.2010.12.132] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2010] [Accepted: 12/29/2010] [Indexed: 12/23/2022]
Abstract
There are no pharmacological treatments to rescue botulinum neurotoxin (BoNT)-mediated paralysis of neuromuscular signaling. In part, this failure can be attributed to the lack of a cell culture model system that is neuron-based, allowing detailed elucidation of the mechanisms underlying BoNT pathogenesis, yet still compatible with modern cellular and molecular approaches. We have developed a method to derive highly enriched, glutamatergic neurons from suspension-cultured murine embryonic stem (ES) cells. Hypothesizing that ES cell-derived neurons (ESNs) might comprise a novel platform to investigate the neurotoxicology of BoNTs, we evaluated the susceptibility of ESNs to BoNT/A and BoNT/E using molecular and functional assays. ESNs express neuron-specific proteins, develop synapses and release glutamate in a calcium-dependent manner under depolarizing conditions. They express the BoNT substrate SNARE proteins SNAP25, VAMP2 and syntaxin, and treatment with BoNT/A and BoNT/E holotoxin results in proteolysis of SNAP25 within 24 h with EC50s of 0.81 and 68.6 pM, respectively. Intoxication with BoNT/A results in the functional inhibition of potassium-induced, calcium-dependent glutamate release. ESNs remain viable and susceptible to intoxication for up to 90 days after plating, enabling longitudinal screens exploring toxin-specific mechanisms underlying persistence of synaptic blockade. The evidence suggests that derived neurons are a novel, biologically relevant model system that combines the verisimilitude of primary neurons with the genetic tractability and scalable expansion of a continuous cell line, and thus should significantly accelerate BoNT research and drug discovery while dramatically decreasing animal use.
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Affiliation(s)
- Patrick McNutt
- The United States Army Medical Research Institute of Chemical Defense, APG, MD 21010, USA.
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60
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Cardinale SC, Butler MM, Ruthel G, Nuss JE, Wanner LM, Li B, Pai R, Peet NP, Bavari S, Bowlin TL. Novel Benzimidazole Inhibitors of Botulinum Neurotoxin/A Display Enzyme and Cell-Based Potency. ACTA ACUST UNITED AC 2011. [PMID: 23205055 DOI: 10.1504/tbj.2011.041813] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Botulinum Neurotoxins (BoNTs) are used therapeutically and in cosmetics, providing potential for bioterrorist activity, thus driving the search for small-molecule BoNT inhibitors. This report describes a 70,000-compound screen for inhibition of BoNT/A using a FRET assay to detect proteolysis of a peptide substrate. Hits were confirmed, followed by evaluation to determine compound specificity. Inhibitors fell into three main chemical classes, and on the basis of potency and specificity of inhibition, the activities of two chemotypes were examined further. Compounds exhibited specificity for BoNT/A LC inhibition with respect to other metalloproteases and displayed activity in a neuronal assay for botulinum intoxication.
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61
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Mayorov AV, Willis B, Di Mola A, Adler D, Borgia J, Jackson O, Wang J, Luo Y, Tang L, Knapp RJ, Natarajan C, Goodnough MC, Zilberberg N, Simpson LL, Janda KD. Symptomatic relief of botulinum neurotoxin/a intoxication with aminopyridines: a new twist on an old molecule. ACS Chem Biol 2010; 5:1183-91. [PMID: 20936877 DOI: 10.1021/cb1002366] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Botulinum neurotoxins (BoNT) are the etiological agents responsible for botulism, a disease characterized by peripheral neuromuscular blockade and a characteristic flaccid paralysis of humans. BoNT/A is the most toxic protein known to man and has been classified by the Centers of Disease Control (CDC) as one of the six highest-risk threat agents for bioterrorism. Of particular concern is the apparent lack of clinical interventions that can reverse cellular intoxication. Efforts to uncover molecules that can act within an intoxicated cell so as to provide symptomatic relief to BoNT/A are paramount. Aminopyridines have shown clinical efficacy for multiple sclerosis treatment as well as BoNT/A intoxication; yet, aminopyridines for BoNT/A treatment has been abandoned because of blood brain barrier (BBB) penetration producing undesired neurotoxic side effects. Two aminopyridines (5 and 11) exhibited inhibitory activity toward Shaker-IR voltage-gated potassium (K(V)1.x) channels with potencies similar to that of the previous "gold-standard", 3,4-diaminopyridine (3,4-DAP), including reversal of symptoms from BoNT-induced paralysis in phrenic nerve-hemidiaphragm preparations. Importantly, pharmacokinetic experiments revealed a lack of BBB penetration of 5, which is a significant advancement toward resolving the neurotoxicity issues associated with prolonged 3,4-DAP treatments. Finally, 5 was found to be as effective as 3,4-DAP in rescuing BoNT-poisoned mice in the mouse lethality assay, signifying an optimized balance between the undesired permeability across the BBB and the required permeability across lipid cellular membranes. The results demonstrate that 5 is the most promising small molecule K(+) channel inhibitor discovered to date for the treatment of BoNT/A intoxication.
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Affiliation(s)
- Alexander V. Mayorov
- Departments of Chemistry and Immunology, Skaggs Institute for Chemical Biology and Worm Institute of Research & Medicine (WIRM), The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, California 92037, United States
| | - Bert Willis
- Departments of Chemistry and Immunology, Skaggs Institute for Chemical Biology and Worm Institute of Research & Medicine (WIRM), The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, California 92037, United States
| | - Antonia Di Mola
- Departments of Chemistry and Immunology, Skaggs Institute for Chemical Biology and Worm Institute of Research & Medicine (WIRM), The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, California 92037, United States
| | - Derek Adler
- Sanofi-Aventis, Discovery Metabolism and Pharmacokinetics Safety Department, Bridgewater, New Jersey 08807, United States
| | - Jennifer Borgia
- Sanofi-Aventis, Discovery Metabolism and Pharmacokinetics Safety Department, Bridgewater, New Jersey 08807, United States
| | - Olin Jackson
- Sanofi-Aventis, Discovery Metabolism and Pharmacokinetics Safety Department, Bridgewater, New Jersey 08807, United States
| | - Jie Wang
- Sanofi-Aventis, Discovery Metabolism and Pharmacokinetics Safety Department, Bridgewater, New Jersey 08807, United States
| | - Yongyi Luo
- Sanofi-Aventis, Discovery Metabolism and Pharmacokinetics Safety Department, Bridgewater, New Jersey 08807, United States
| | - Lei Tang
- Sanofi-Aventis, Discovery Metabolism and Pharmacokinetics Safety Department, Bridgewater, New Jersey 08807, United States
| | - Richard J. Knapp
- Sanofi-Aventis, Discovery Metabolism and Pharmacokinetics Safety Department, Bridgewater, New Jersey 08807, United States
| | - Chandra Natarajan
- Sanofi-Aventis, Discovery Metabolism and Pharmacokinetics Safety Department, Bridgewater, New Jersey 08807, United States
| | | | - Noam Zilberberg
- Department of Life Sciences, Ben Gurion University, Beer Sheva 84105, Israel
| | - Lance L. Simpson
- Department of Medicine Jefferson Medical College, Thomas Jefferson University, 1020 Locust St, Rm 314-JAH, Philadelphia, Pennsylvania 19107, United States
| | - Kim D. Janda
- Departments of Chemistry and Immunology, Skaggs Institute for Chemical Biology and Worm Institute of Research & Medicine (WIRM), The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, California 92037, United States
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62
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Hale M, Oyler G, Swaminathan S, Ahmed SA. Basic tetrapeptides as potent intracellular inhibitors of type A botulinum neurotoxin protease activity. J Biol Chem 2010; 286:1802-11. [PMID: 20961849 DOI: 10.1074/jbc.m110.146464] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Botulinum neurotoxins (BoNT) are the most potent of all toxins that cause flaccid muscle paralysis leading to death. They are also potential biothreat agents. A systematic investigation of various short peptide inhibitors of the BoNT protease domain with a 17-residue peptide substrate led to arginine-arginine-glycine-cysteine having a basic tetrapeptide structure as the most potent inhibitor. When assayed in the presence of dithiothreitol (DTT), the inhibitory effect was drastically reduced. Replacing the terminal cysteine with one hydrophobic residue eliminated the DTT effect but with two hydrophobic residues made the pentapeptide a poor inhibitor. Replacing the first arginine with cysteine or adding an additional cysteine at the N terminus did not improve inhibition. When assessed using mouse brain lysates, the tetrapeptides also inhibited BoNT/A cleavage of the endogenous SNAP-25. The peptides penetrated the neuronal cell lines, N2A and BE(2)-M17, without adversely affecting metabolic functions as measured by ATP production and P-38 phosphorylation. Biological activity of the peptides persisted within cultured chick motor neurons and rat and mouse cerebellar neurons for more than 40 h and inhibited BoNT/A protease action inside the neurons in a dose- and time-dependent fashion. Our results define a tetrapeptide as the smallest peptide inhibitor in the backdrop of a large substrate protein of 200+ amino acids having multiple interaction regions with its cognate enzyme. The inhibitors should also be valuable candidates for drug development.
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Affiliation(s)
- Martha Hale
- Department Cell Biology and Biochemistry, Integrated Toxicology Division, United States Army Medical Research Institute of Infectious Diseases, Fort Detrick, Maryland 21702, USA
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63
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Shaginian A, Whitby LR, Hong S, Hwang I, Farooqi B, Searcey M, Chen J, Vogt PK, Boger DL. Design, synthesis, and evaluation of an alpha-helix mimetic library targeting protein-protein interactions. J Am Chem Soc 2010; 131:5564-72. [PMID: 19334711 DOI: 10.1021/ja810025g] [Citation(s) in RCA: 117] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The design and solution-phase synthesis of an alpha-helix mimetic library as an integral component of a small-molecule library targeting protein-protein interactions are described. The iterative design, synthesis, and evaluation of the candidate alpha-helix mimetic was initiated from a precedented triaryl template and refined by screening the designs for inhibition of MDM2/p53 binding. Upon identifying a chemically and biologically satisfactory design and consistent with the screening capabilities of academic collaborators, the corresponding complete library was assembled as 400 mixtures of 20 compounds (20 x 20 x 20-mix), where the added subunits are designed to mimic all possible permutations of the naturally occurring i, i + 4, i + 7 amino acid side chains of an alpha-helix. The library (8000 compounds) was prepared using a solution-phase synthetic protocol enlisting acid/base liquid-liquid extractions for purification on a scale that insures its long-term availability for screening campaigns. Screening of the library for inhibition of MDM2/p53 binding not only identified the lead alpha-helix mimetic upon which the library was based, but also suggests that a digestion of the initial screening results that accompany the use of such a comprehensive library can provide insights into the nature of the interaction (e.g., an alpha-helix mediated protein-protein interaction) and define the key residues and their characteristics responsible for recognition.
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Affiliation(s)
- Alex Shaginian
- Department of Chemistry and The Skaggs Institute for Chemical Biology, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, California 92037, USA
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64
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Identification of broad-based HIV-1 protease inhibitors from combinatorial libraries. Biochem J 2010; 429:527-32. [PMID: 20507280 DOI: 10.1042/bj20091645] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Clinically approved inhibitors of the HIV-1 protease function via a competitive mechanism. A particular vulnerability of competitive inhibitors is their sensitivity to increases in substrate concentration, as may occur during virion assembly, budding and processing into a mature infectious viral particle. Advances in chemical synthesis have led to the development of new high-diversity chemical libraries using rapid in-solution syntheses. These libraries have been shown previously to be effective at disrupting protein-protein and protein-nucleic acid interfaces. We have screened 44000 compounds from such a library to identify inhibitors of the HIV-1 protease. One compound was identified that inhibits wild-type protease, as well as a drug-resistant protease with six mutations. Moreover, analysis of this compound suggests an allosteric non-competitive mechanism of inhibition and may represent a starting point for an additional strategy for anti-retroviral therapy.
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65
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Affiliation(s)
- Mauricio Montal
- Section of Neurobiology, Division of Biological Sciences, University of California San Diego, La Jolla, California 92093-0366;
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66
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Thyagarajan B, Potian JG, Garcia CC, Hognason K, Čapková K, Moe ST, Jacobson AR, Janda KD, McArdle JJ. Effects of hydroxamate metalloendoprotease inhibitors on botulinum neurotoxin A poisoned mouse neuromuscular junctions. Neuropharmacology 2010; 58:1189-98. [PMID: 20211192 PMCID: PMC2867082 DOI: 10.1016/j.neuropharm.2010.02.014] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2010] [Accepted: 02/17/2010] [Indexed: 11/16/2022]
Abstract
Currently the only therapy for botulinum neurotoxin A (BoNT/A) poisoning is antitoxin. Antidotes that are effective after BoNT/A has entered the motor nerve terminals would dramatically benefit BoNT/A therapy. Inhibition of proteolytic activity of BoNT/A light chain by metalloendoprotease inhibitors (MEIs) is under development. We tested the effects of MEIs on in vitro as well as in vivo BoNT/A poisoned mouse nerve-muscle preparations (NMPs). The K(i) for inhibition of BoNT/A metalloendoprotease was 0.40 and 0.36 muM, respectively, for 2,4-dichlorocinnamic acid hydroxamate (DCH) and its methyl derivative, ABS 130. Acute treatment of nerve-muscle preparations with 10 pM BoNT/A inhibited nerve-evoked muscle twitches, reduced mean quantal content, and induced failures of endplate currents (EPCs). Bath application of 10 muM DCH or 5 muM ABS 130 reduced failures, increased the quantal content of EPCs, and partially restored muscle twitches after a delay of 40-90 min. The restorative effects of DCH and ABS 130, as well as 3,4 diaminopyridine (DAP) on twitch tension were greater at 22 degrees C compared to 37 degrees C. Unlike DAP, neither DCH nor ABS 130 increased Ca(2+) levels in cholinergic Neuro 2a cells. Injection of MEIs into mouse hind limbs before or after BoNT/A injection neither prevented the toe spread reflex inhibition nor improved muscle functions. We suggest that hydroxamate MEIs partially restore neurotransmission of acutely BoNT/A poisoned nerve-muscle preparations in vitro in a temperature dependent manner without increasing the Ca(2+) levels within motor nerve endings.
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Affiliation(s)
- Baskaran Thyagarajan
- Department of Pharmacology and Physiology, UMDNJ – New Jersey Medical School, Newark, NJ 07103
| | - Joseph G. Potian
- Department of Pharmacology and Physiology, UMDNJ – New Jersey Medical School, Newark, NJ 07103
| | - Carmen C. Garcia
- Department of Pharmacology and Physiology, UMDNJ – New Jersey Medical School, Newark, NJ 07103
| | - Kormakur Hognason
- Department of Pharmacology and Physiology, UMDNJ – New Jersey Medical School, Newark, NJ 07103
| | - Kateřina Čapková
- Department of Chemistry, The Skaggs Institute for Chemical Biology and the Worm Institute of Research and Medicine (WIRM), The Scripps Research Institute, La Jolla, CA 92037
| | | | | | - Kim D. Janda
- Department of Chemistry, The Skaggs Institute for Chemical Biology and the Worm Institute of Research and Medicine (WIRM), The Scripps Research Institute, La Jolla, CA 92037
| | - Joseph J. McArdle
- Department of Pharmacology and Physiology, UMDNJ – New Jersey Medical School, Newark, NJ 07103
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Saunders MJ, Graves SW, Sklar LA, Oprea TI, Edwards BS. High-throughput multiplex flow cytometry screening for botulinum neurotoxin type a light chain protease inhibitors. Assay Drug Dev Technol 2010; 8:37-46. [PMID: 20035615 DOI: 10.1089/adt.2009.0219] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Given their medical importance, proteases have been studied by diverse approaches and screened for small molecule protease inhibitors. Here, we present a multiplexed microsphere-based protease assay that uses high-throughput flow cytometry to screen for inhibitors of the light chain protease of botulinum neurotoxin type A (BoNTALC). Our assay uses a full-length substrate and several deletion mutants screened in parallel to identify small molecule inhibitors. The use of multiplex flow cytometry has the advantage of using full-length substrates, which contain already identified distal-binding elements for the BoNTALC, and could lead to a new class of BoNTALC inhibitors. In this study, we have screened 880 off patent drugs and bioavailable compounds to identify ebselen as an in vitro inhibitor of BoNTALC. This discovery demonstrates the validity of our microsphere-based approach and illustrates its potential for high-throughput screening for inhibitors of proteases in general.
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Affiliation(s)
- Matthew J Saunders
- The Center for Molecular Discovery and Department of Pathology, University of New Mexico, Albuquerque, New Mexico 87131, USA.
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68
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Chang TW, Blank M, Janardhanan P, Singh BR, Mello C, Blind M, Cai S. In vitro selection of RNA aptamers that inhibit the activity of type A botulinum neurotoxin. Biochem Biophys Res Commun 2010; 396:854-60. [PMID: 20452328 DOI: 10.1016/j.bbrc.2010.05.006] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2010] [Accepted: 05/03/2010] [Indexed: 10/19/2022]
Abstract
The category A agent, botulinum neurotoxin (BoNT), is the most toxic molecule known to mankind. The endopeptidase activity of light chain domain of BoNT is the cause for the inhibition of the neurotransmitter release and the flaccid paralysis that leads to lethality in botulism. Currently, antidotes are not available to reverse the flaccid paralysis caused by BoNT. In the present study, we have identified three RNA aptamers through SELEX-process, which bind strongly to the light chain of type A BoNT (BoNT/A) and inhibit the endopeptidase activity, with IC(50) in low nM range. Inhibition kinetic studies reveal low nM K(I) and non-competitive nature of their inhibition. Aptamers are unique group of molecules as therapeutics, and this is first report of their development as an antidote against botulism. These data on K(I) and IC(50) strongly suggest that the aptamers have strong potential as antidotes that can reverse the symptom caused by BoNT/A.
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Affiliation(s)
- Tzuu-Wang Chang
- Department of Chemistry and Biochemistry, and Botulinum Research Center, University of Massachusetts Dartmouth, North Dartmouth, MA 02747, USA
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69
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Lebeda FJ, Cer RZ, Mudunuri U, Stephens R, Singh BR, Adler M. The zinc-dependent protease activity of the botulinum neurotoxins. Toxins (Basel) 2010; 2:978-97. [PMID: 22069621 PMCID: PMC3153231 DOI: 10.3390/toxins2050978] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2010] [Revised: 04/30/2010] [Accepted: 05/05/2010] [Indexed: 12/11/2022] Open
Abstract
The botulinum neurotoxins (BoNT, serotypes A-G) are some of the most toxic proteins known and are the causative agents of botulism. Following exposure, the neurotoxin binds and enters peripheral cholinergic nerve endings and specifically and selectively cleaves one or more SNARE proteins to produce flaccid paralysis. This review centers on the kinetics of the Zn-dependent proteolytic activities of these neurotoxins, and briefly describes inhibitors, activators and factors underlying persistence of toxin action. Some of the structural, enzymatic and inhibitor data that are discussed here are available at the botulinum neurotoxin resource, BotDB (http://botdb.abcc.ncifcrf.gov).
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Affiliation(s)
- Frank J. Lebeda
- US Army Medical Research and Materiel Command, Ft. Detrick, MD 21702-5012, USA
| | - Regina Z. Cer
- Bioinformatics Support Group, Advanced Biomedical Computing Center, Information Systems Program, SAIC-Frederick Inc., NCI-Frederick, Frederick, MD 21702, USA; (R.Z.C.); (U.M.); (R.S.)
| | - Uma Mudunuri
- Bioinformatics Support Group, Advanced Biomedical Computing Center, Information Systems Program, SAIC-Frederick Inc., NCI-Frederick, Frederick, MD 21702, USA; (R.Z.C.); (U.M.); (R.S.)
| | - Robert Stephens
- Bioinformatics Support Group, Advanced Biomedical Computing Center, Information Systems Program, SAIC-Frederick Inc., NCI-Frederick, Frederick, MD 21702, USA; (R.Z.C.); (U.M.); (R.S.)
| | - Bal Ram Singh
- Botulinum Research Center, University of Massachusetts Dartmouth, 285 Old Westport Road, Dartmouth, MA 02747, USA; (B.R.S.)
| | - Michael Adler
- US Army Medical Research Institute of Chemical Defense, Aberdeen Proving Ground, MD 21010-5400, USA; (M.A.)
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70
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Pang YP, Davis J, Wang S, Park JG, Nambiar MP, Schmidt JJ, Millard CB. Small molecules showing significant protection of mice against botulinum neurotoxin serotype A. PLoS One 2010; 5:e10129. [PMID: 20405003 PMCID: PMC2854131 DOI: 10.1371/journal.pone.0010129] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2010] [Accepted: 03/21/2010] [Indexed: 11/30/2022] Open
Abstract
Botulinum neurotoxin serotype A (BoNTA) causes a life-threatening neuroparalytic disease known as botulism that could afflict large, unprotected populations if the toxin were employed in an act of bioterrorism. Current post-exposure therapy is limited to symptomatic treatment or passive immunization that is effective for treating infant botulism at a cost of US $45,300 per treatment regimen. Antibodies can neutralize the extracellular but not the intracellular BoNTA. Moreover, antibody production, storage, and administration in a mass casualty scenario pose logistical challenges. Alternatively, small-molecule inhibitors of BoNTA endopeptidase (BoNTAe) are sought to antagonize the extracellular or intracellular toxin. While several such molecules reportedly demonstrated efficacy in protecting cells against BoNTA, there is scant information to show that small molecules can significantly protect mammals against BoNTA. Herein we report the development of effective small-molecules BoNTAe inhibitors with promising in vivo pharmacokinetics. One such molecule has an in vivo half-life of 6.5 hours and is devoid of obvious sign of toxicity. Pre-treatment with this molecule at 2 mg/kg protected 100% and 70% of treated mice against BoNTA at 5 times of its median-lethal dose during the periods of 2 and 4 half-lives of the inhibitor, respectively. In contrast, 40% and 0% of untreated mice survived during the respective periods. Similar levels of protection were also observed with two other small molecules. These results demonstrate that small molecules can significantly protect mice against BoNTA and support the pursuit of small-molecule antagonists as a cost-effective alternative or as an adjunct to passive immunity for treating botulism.
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Affiliation(s)
- Yuan-Ping Pang
- Computer-Aided Molecular Design Laboratory, Mayo Clinic, Rochester, Minnesota, United States of America
- * E-mail: (Y-PP for chemistry); (CBM for biology)
| | - Jon Davis
- Division of Biochemistry, Walter Reed Army Institute of Research, Silver Spring, Maryland, United States of America
| | - Shaohua Wang
- Computer-Aided Molecular Design Laboratory, Mayo Clinic, Rochester, Minnesota, United States of America
| | - Jewn Giew Park
- Computer-Aided Molecular Design Laboratory, Mayo Clinic, Rochester, Minnesota, United States of America
| | - Madhusoodana P. Nambiar
- Division of Biochemistry, Walter Reed Army Institute of Research, Silver Spring, Maryland, United States of America
| | - James J. Schmidt
- Integrated Toxicology Division, United States Army Medical Research Institute of Infectious Diseases, Fort Detrick, Maryland, United States of America
| | - Charles B. Millard
- Division of Biochemistry, Walter Reed Army Institute of Research, Silver Spring, Maryland, United States of America
- * E-mail: (Y-PP for chemistry); (CBM for biology)
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71
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Kukreja RV, Sharma SK, Singh BR. Molecular basis of activation of endopeptidase activity of botulinum neurotoxin type E. Biochemistry 2010; 49:2510-9. [PMID: 20178376 DOI: 10.1021/bi902096r] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Botulinum neurotoxins (BoNTs) are a group of large proteins that are responsible for the clinical syndrome of botulism. The seven immunologically distinct serotypes of BoNTs (A-G), each produced by various strains of Clostridium botulinum, act on the neuromuscular junction by blocking the release of the neurotransmitter acetylcholine, thereby resulting in flaccid muscle paralysis. BoNTs are synthesized as single inactive polypeptide chains that are cleaved by endogenous or exogenous proteases to generate the active dichain form of the toxin. Nicking of the single chain BoNT/E to the dichain form is associated with 100-fold increase in toxicity. Here we investigated the activation mechanism of botulinum neurotoxin type E upon nicking and subsequent reduction of disulfide bond. It was observed that nicking of BoNT/E significantly enhances its endopeptidase activity and that at the physiological temperature of 37 degrees C the reduced form of nicked BoNT/E adopts a dynamically flexible conformation resulting from the exposure of hydrophobic segments and facilitating optimal cleavage of its substrate SNAP-25. Such reduction-induced increase in the flexibility of the polypeptide folding provides a rationale for the mechanism of BoNT/E endopeptidase against its intracellular substrate, SNAP-25, and complements current understanding of the mechanistics of interaction between the substrate and BoNT endopeptidase.
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Affiliation(s)
- Roshan V Kukreja
- Botulinum Research Center and Department of Chemistry and Biochemistry, University of Massachusetts Dartmouth, 285 Old Westport Road, North Dartmouth, Massachusetts 02747, USA
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72
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Burnett JC, Li B, Pai R, Cardinale SC, Butler MM, Peet NP, Moir D, Bavari S, Bowlin T. Analysis of Botulinum Neurotoxin Serotype A Metalloprotease Inhibitors: Analogs of a Chemotype for Therapeutic Development in the Context of a Three-Zone Pharmacophore. OPEN ACCESS BIOINFORMATICS 2010; 2010:11-18. [PMID: 21103387 PMCID: PMC2983112 DOI: 10.2147/oab.s7251] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Botulinum neurotoxins (BoNTs), and in particular serotype A, are the most poisonous of known biological substances, and are responsible for the flaccid paralysis of the disease state botulism. Because of the extreme toxicity of these enzymes, BoNTs are considered highest priority biothreat agents. To counter BoNT serotype A (BoNT/A) poisoning, the discovery and development of small molecule, drug-like inhibitors as post-intoxication therapeutic agents has been/is being pursued. Specifically, we are focusing on inhibitors of the BoNT/A light chain (LC) (ie, a metalloprotease) subunit, since such compounds can enter neurons and provide post-intoxication protection of the enzyme target substrate. To aid/facilitate this drug development effort, a pharmacophore for inhibition of the BoNT/A LC subunit was previously developed, and is continually being refined via the incorporation of novel and diverse inhibitor chemotypes. Here, we describe several analogs of a promising therapeutic chemotype in the context of the pharmacophore for BoNT/A LC inhibition. Specifically, we describe: 1) the pharmacophoric 'fits' of the analogs and how these 'fits' rationalize the in vitro inhibitory potencies of the analogs and 2) pharmacophore refinement via the inclusion of new components from the most potent of the presented analogs.
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Affiliation(s)
- James C. Burnett
- Target, Structure-Based Drug Discovery Group, SAIC-Frederick, Inc., National Cancer Institute at Frederick, Frederick, MD 21702 (USA)
| | - Bing Li
- Microbiotix, Inc., Worcester, MA 01605 (USA)
| | - Ramdas Pai
- Microbiotix, Inc., Worcester, MA 01605 (USA)
| | | | | | | | - Donald Moir
- Microbiotix, Inc., Worcester, MA 01605 (USA)
| | - Sina Bavari
- Division of Integrated Toxicology, United States Army Medical Research Institute of Infectious Diseases, Frederick, MD 21702 (USA)
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73
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Nakai Y, Pellett S, Tepp WH, Johnson EA, Janda KD. Toosendanin: synthesis of the AB-ring and investigations of its anti-botulinum properties (Part II). Bioorg Med Chem 2009; 18:1280-7. [PMID: 20044261 DOI: 10.1016/j.bmc.2009.12.030] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2009] [Revised: 12/04/2009] [Accepted: 12/08/2009] [Indexed: 10/20/2022]
Abstract
Botulinum neurotoxins (BoNTs) are the etiological agents responsible for botulism, a disease characterized by peripheral neuromuscular blockade and a characteristic flaccid paralysis of humans. The natural product toosendanin, a limonoid, is a traditional Chinese medicine that has reported anti-botulinum properties in animal models. Toosendanin effectively inhibits the biological activity of BoNT/A in neuronal cells at concentrations of 200 nM, and partial inhibition can be observed with concentrations as low as 8 nM. Mechanistically, toosendanin's inhibition is due to prevention of transduction of the BoNT LC through the HC channel. Intriguing questions as to the molecular architecture of toosendanin as related to its anti-botulinum properties have focused our attention on a synthesis of toosendanin's unusual AB-ring, containing a unique bridged hemi-acetal. Within the current work, a synthetic strategy allowing access to the AB-fragment of toosendanin was achieved from a trans-decalin system. In addition, this fragment was examined for its modulation of BoNT/A intoxication in a rat spinal cord cellular assay.
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Affiliation(s)
- Yuya Nakai
- Departments of Chemistry and Immunology and The Skaggs Institute for Chemical Biology, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037, USA
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74
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Nuss JE, Ruthel G, Tressler LE, Wanner LM, Torres-Melendez E, Hale ML, Bavari S. Development of cell-based assays to measure botulinum neurotoxin serotype A activity using cleavage-sensitive antibodies. ACTA ACUST UNITED AC 2009; 15:42-51. [PMID: 19965805 DOI: 10.1177/1087057109354779] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Botulinum neurotoxins (BoNTs) are zinc-metalloproteases that cleave components of the SNARE (soluble N-ethylmaleimide-sensitive factor attachment protein receptor) protein complex, inhibiting acetylcholine release into neuromuscular junctions, resulting in flaccid paralysis and eventual death. The potential for the malicious misuse of these toxins as bioweapons has created an urgent need to develop effective therapeutic countermeasures. Robust cell-based assays will be essential for lead identification and the optimization of therapeutic candidates. In this study, the authors developed novel BoNT serotype A (BoNT/A) cleavage-sensitive (BACS) antibodies that only interact with full-length SNAP-25 (synaptosomal-associated protein of 25 kDa), the molecular target of the BoNT/A serotype. These antibodies exhibit high specificity for full-length SNAP-25, allowing the BoNT/A-mediated proteolysis of this protein to be measured in diverse assay formats, including several variations of enzyme-linked immunosorbent assay and multiple immunofluorescence methods. Assays built around the BACS antibodies displayed excellent sensitivity, had excellent reproducibility, and were amenable to multiwell formats. Importantly, these assays provided novel methods for evaluating BoNT/A activity in cellular models of intoxication and allowed for the high-throughput evaluation of experimental compounds.
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Affiliation(s)
- Jonathan E Nuss
- US Army Medical Research Institute of Infectious Diseases, Frederick, Maryland 21702, USA
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75
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Thyagarajan B, Krivitskaya N, Potian JG, Hognason K, Garcia CC, McArdle JJ. Capsaicin protects mouse neuromuscular junctions from the neuroparalytic effects of botulinum neurotoxin a. J Pharmacol Exp Ther 2009; 331:361-71. [PMID: 19654265 PMCID: PMC2775269 DOI: 10.1124/jpet.109.156901] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2009] [Accepted: 08/03/2009] [Indexed: 11/22/2022] Open
Abstract
Botulinum neurotoxin A (BoNT/A), the most toxic, naturally occurring protein, cleaves synapse-associated protein of 25 kDa and inhibits acetylcholine release from motor nerve endings (MNEs). This leads to paralysis of skeletal muscles. Our study demonstrates that capsaicin protects mouse neuromuscular junctions from the neuroparalytic effects of BoNT/A. Bilateral injection of BoNT/A near the innervation of the Extensor digitorum longus (EDL) muscle of adult Swiss-Webster mice inhibited the toe spread reflex (TSR). However, when capsaicin was coinjected bilaterally, or injected 4 or 8 h before injecting BoNT/A, the TSR remained normal. In animals that were pretreated with capsazepine, capsaicin failed to protect against the neuroparalytic effects of BoNT/A. In vivo analyses demonstrated that capsaicin protected muscle functions and electromygraphic activity from the incapacitating effects of BoNT/A. The twitch response to nerve stimulation was greater for EDL preparations isolated from mice injected with capsaicin before BoNT/A. Capsaicin pretreatment also prevented the inhibitory effects of BoNT/A on end-plate currents. Furthermore, pretreatment of Neuro 2a cells with capsaicin significantly preserved labeling of synaptic vesicles by FM 1-43. This protective effect of capsaicin was observed only in the presence of extracellular Ca(2+) and was inhibited by capsazepine. Immunohistochemistry demonstrated that MNEs express transient receptor potential protein of the vanilloid subfamily, TRPV1, the capsaicin receptor. Capsaicin pretreatment, in vitro, reduced nerve stimulation or KCl-induced uptake of BoNT/A into motor nerve endings and cholinergic Neuro 2a cells. These data demonstrate that capsaicin interacts with TRPV1 receptors on MNEs to reduce BoNT/A uptake via a Ca(2+)-dependent mechanism.
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Affiliation(s)
- Baskaran Thyagarajan
- Department of Pharmacology and Physiology, University of Medicine and Dentistry of New Jersey, New Jersey MedicalSchool, Newark, New Jersey 07103, USA.
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76
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Cheng LW, Stanker LH, Henderson TD, Lou J, Marks JD. Antibody protection against botulinum neurotoxin intoxication in mice. Infect Immun 2009; 77:4305-13. [PMID: 19651864 PMCID: PMC2747958 DOI: 10.1128/iai.00405-09] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2009] [Revised: 05/21/2009] [Accepted: 07/25/2009] [Indexed: 11/20/2022] Open
Abstract
Adulteration of food or feed with any of the seven serotypes of botulinum neurotoxin (BoNT) is a potential bioterrorism concern. Currently, there is strong interest in the development of detection reagents, vaccines, therapeutics, and other countermeasures. A sensitive immunoassay for detecting BoNT serotype A (BoNT/A), based on monoclonal antibodies (MAbs) F1-2 and F1-40, has been developed and used in complex matrices. The epitope for F1-2 has been mapped to the heavy chain of BoNT/A, and the epitope of F1-40 has been mapped to the light chain. The ability of these MAbs to provide therapeutic protection against BoNT/A intoxication in mouse intravenous and oral intoxication models was tested. High dosages of individual MAbs protected mice well both pre- and postexposure to BoNT/A holotoxin. A combination therapy consisting of antibodies against both the light and heavy chains of the toxin, however, significantly increased protection, even at a lower MAb dosage. An in vitro peptide assay for measuring toxin activity showed that pretreatment of toxin with these MAbs did not block catalytic activity but instead blocked toxin entry into primary and cultured neuronal cells. The timing of antibody rescue in the mouse intoxication models revealed windows of opportunity for antibody therapeutic treatment that correlated well with the biologic half-life of the toxin in the serum. Knowledge of BoNT intoxication and antibody clearance in these mouse models and understanding of the pharmacokinetics of BoNT are invaluable for future development of antibodies and therapeutics against intoxication by BoNT.
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Affiliation(s)
- Luisa W Cheng
- Foodborne Contaminants Research Unit, Western Regional Research Center, USDA Agricultural Research Service, 800 Buchanan Street, Albany, CA 94710, USA.
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77
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Pires-Alves M, Ho M, Aberle KK, Janda KD, Wilson BA. Tandem fluorescent proteins as enhanced FRET-based substrates for botulinum neurotoxin activity. Toxicon 2009; 53:392-9. [PMID: 19168088 DOI: 10.1016/j.toxicon.2008.12.016] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2008] [Revised: 12/18/2008] [Accepted: 12/23/2008] [Indexed: 01/25/2023]
Abstract
The light chain of botulinum neurotoxin A (BoNT/A-LC) is a zinc-metalloprotease that requires two extended exosites for optimal substrate binding and recognition of its intracellular target SNAP25. CFP and YFP connected through SNAP25 peptide (141-206) containing both exosites (CsY) has been used in a FRET-based assay for BoNT/A. To further improve the FRET efficiency in this BoNT/A substrate for in vitro high-throughput assays, we explored the feasibility of enhancing the capture of CFP emission by doubling the number of YFP acceptors. In comparison to CsY, the tandem fluorescence substrates CsYY and YsCsY enhanced the ratiometric fluorescence signal between YFP and CFP. YsCsY, containing two substrate sites, offered the greatest fluorometric change upon toxin-catalyzed cleavage. In addition to known approaches for enhancing fluorescence yield through various mutations, this alternative tandem substrate approach can boost the FRET signal and is particularly useful for substrates requiring extensive exosite recognition for specificity.
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Affiliation(s)
- Melissa Pires-Alves
- Department of Microbiology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
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78
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Shi J, Stover JS, Whitby LR, Vogt PK, Boger DL. Small molecule inhibitors of Myc/Max dimerization and Myc-induced cell transformation. Bioorg Med Chem Lett 2009; 19:6038-41. [PMID: 19800226 DOI: 10.1016/j.bmcl.2009.09.044] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2009] [Revised: 09/12/2009] [Accepted: 09/14/2009] [Indexed: 10/20/2022]
Abstract
The preparation and evaluation of a series of inhibitors of Myc/Max dimerization and Myc-induced cell transformation are described providing mycmycin-1 (3) and mycmycin-2 (4).
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Affiliation(s)
- Jin Shi
- Department of Molecular and Experimental Medicine, The Skaggs Institute for Chemical Biology, The Scripps Research Institute, 10550 N. Torrey Pines Road, La Jolla, CA 92037, USA
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79
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Identification and biochemical characterization of small-molecule inhibitors of Clostridium botulinum neurotoxin serotype A. Antimicrob Agents Chemother 2009; 53:3478-86. [PMID: 19528275 DOI: 10.1128/aac.00141-09] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
An integrated strategy that combined in silico screening and tiered biochemical assays (enzymatic, in vitro, and ex vivo) was used to identify and characterize effective small-molecule inhibitors of Clostridium botulinum neurotoxin serotype A (BoNT/A). Virtual screening was initially performed by computationally docking compounds of the National Cancer Institute (NCI) database into the active site of BoNT/A light chain (LC). A total of 100 high-scoring compounds were evaluated in a high-performance liquid chromatography (HPLC)-based protease assay using recombinant full-length BoNT/A LC. Seven compounds that significantly inhibited the BoNT/A protease activity were selected. Database search queries of the best candidate hit [7-((4-nitro-anilino)(phenyl)methyl)-8-quinolinol (NSC 1010)] were performed to mine its nontoxic analogs. Fifty-five analogs of NSC 1010 were synthesized and examined by the HPLC-based assay. Of these, five quinolinol derivatives that potently inhibited both full-length BoNT/A LC and truncated BoNT/A LC (residues 1 to 425) were selected for further inhibition studies in neuroblastoma (N2a) cell-based and tissue-based mouse phrenic nerve hemidiaphragm assays. Consistent with enzymatic assays, in vitro and ex vivo studies revealed that these five quinolinol-based analogs effectively neutralized BoNT/A toxicity, with CB 7969312 exhibiting ex vivo protection at 0.5 microM. To date, this is the most potent BoNT/A small-molecule inhibitor that showed activity in an ex vivo assay. The reduced toxicity and high potency demonstrated by these five compounds at the biochemical, cellular, and tissue levels are distinctive among the BoNT/A small-molecule inhibitors reported thus far. This study demonstrates the utility of a multidisciplinary approach (in silico screening coupled with biochemical testing) for identifying promising small-molecule BoNT/A inhibitors.
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80
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Larsen JC. U.S. Army Botulinum Neurotoxin (BoNT) Medical Therapeutics Research Program: past accomplishments and future directions. Drug Dev Res 2009. [DOI: 10.1002/ddr.20304] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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81
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Pharmacophore-guided lead optimization: the rational design of a non-zinc coordinating, sub-micromolar inhibitor of the botulinum neurotoxin serotype a metalloprotease. Bioorg Med Chem Lett 2009; 19:5811-3. [PMID: 19703771 DOI: 10.1016/j.bmcl.2009.01.111] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2008] [Accepted: 01/07/2009] [Indexed: 11/22/2022]
Abstract
Botulinum neurotoxins, responsible for the neuroparalytic syndrome botulism, are the deadliest of known biological toxins. The work described in this study was based on a three-zone pharmacophore model for botulinum neurotoxin serotype A light chain inhibition. Specifically, the pharmacophore defined a separation between the overlaps of several different, non-zinc(II)-coordinating small molecule chemotypes, enabling the design and synthesis of a new structural hybrid possessing a Ki=600 nM (+/-100 nM).
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82
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Hermone AR, Burnett JC, Nuss JE, Tressler LE, Nguyen TL, Solaja BA, Vennerstrom JL, Schmidt JJ, Wipf P, Bavari S, Gussio R. Three-dimensional database mining identifies a unique chemotype that unites structurally diverse botulinum neurotoxin serotype A inhibitors in a three-zone pharmacophore. ChemMedChem 2009; 3:1905-12. [PMID: 19006141 DOI: 10.1002/cmdc.200800241] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
A search query consisting of two aromatic centers and two cationic centers was defined based on previously identified small molecule inhibitors of the botulinum neurotoxin serotype A light chain (BoNT/A LC) and used to mine the National Cancer Institute Open Repository. Ten small molecule hits were identified, and upon testing, three demonstrated inhibitory activity. Of these, one was structurally unique, possessing a rigid diazachrysene scaffold. The steric limitations of the diazachrysene imposed a separation between the overlaps of previously identified inhibitors, revealing an extended binding mode. As a result, the pharmacophore for BoNT/A LC inhibition has been modified to encompass three zones. To demonstrate the utility of this model, a novel three-zone inhibitor was mined and its activity was confirmed.
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Affiliation(s)
- Ann R Hermone
- Target Structure-Based Drug Discovery Group, SAIC-Frederick, Inc. National Cancer Institute at Frederick, P.O. Box B, Frederick, MD 21702, USA
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83
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Bimodal modulation of the botulinum neurotoxin protein-conducting channel. Proc Natl Acad Sci U S A 2009; 106:1330-5. [PMID: 19164566 DOI: 10.1073/pnas.0812839106] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Clostridium botulinum neurotoxin (BoNT) is the causative agent of botulism, a neuroparalytic disease. We describe here a semisynthetic strategy to identify inhibitors based on toosendanin, a traditional Chinese medicine reported to protect from BoNT intoxication. Using a single molecule assay of BoNT serotypes A and E light chain (LC) translocation through the heavy chain (HC) channel in neurons, we discovered that toosendanin and its tetrahydrofuran analog selectively arrest the LC translocation step of intoxication with subnanomolar potency, and increase the unoccluded HC channel propensity to open with micromolar efficacy. The inhibitory profile on LC translocation is accurately recapitulated in 2 different BoNT intoxication assays, namely the mouse protection and the primary rat spinal cord cell assays. Toosendanin has an unprecedented dual mode of action on the protein-conducting channel acting as a cargo-dependent inhibitor of translocation and as cargo-free channel activator. These results imply that the bimodal modulation by toosendanin depends on the dynamic interactions between channel and cargo, highlighting their tight interplay during the progression of LC transit across endosomes.
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84
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Wipf P, Wang C, Widom J, Petronijevic F, C. Burnett J, E. Nuss J, Bavari S, Gussio R. Synthesis and Biological Evaluation of Inhibitors of Botulinum Neurotoxin Metalloprotease. HETEROCYCLES 2009. [DOI: 10.3987/com-08-s(d)8] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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85
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Nakai Y, Tepp WH, Dickerson TJ, Johnson EA, Janda KD. Function-oriented synthesis applied to the anti-botulinum natural product toosendanin. Bioorg Med Chem 2008; 17:1152-7. [PMID: 19131252 DOI: 10.1016/j.bmc.2008.12.042] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2008] [Revised: 12/10/2008] [Accepted: 12/14/2008] [Indexed: 10/21/2022]
Abstract
Botulinum neurotoxins (BoNTs) are the etiological agents responsible for botulism, a disease characterized by peripheral neuromuscular blockade and a characteristic flaccid paralysis of humans. The natural product toosendanin is a traditional Chinese medicine which has been reported to have anti-botulinum properties in animal models. To establish what chemical functionalities are necessary for the anti-botulinum properties found within toosendanin, a study was initiated with the goal of using function-oriented synthesis (FOS) as a strategy to begin to unravel toosendanin's powerful anti-botulinum properties. From these studies a new synthetic strategy is put forth allowing access to a 4-acetoxy CD fragment analogue (14) of toosendanin, which was achieved from mesityl oxide and acetylacetone in 14 steps. Animal studies on this fragment are also reported.
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Affiliation(s)
- Yuya Nakai
- Department of Chemistry, The Skaggs Institute for Chemical Biology, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037, USA
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86
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Fischer A, Mushrush DJ, Lacy DB, Montal M. Botulinum neurotoxin devoid of receptor binding domain translocates active protease. PLoS Pathog 2008; 4:e1000245. [PMID: 19096517 PMCID: PMC2596314 DOI: 10.1371/journal.ppat.1000245] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2008] [Accepted: 11/19/2008] [Indexed: 01/04/2023] Open
Abstract
Clostridium botulinum neurotoxin (BoNT) causes flaccid paralysis by disabling synaptic exocytosis. Intoxication requires the tri-modular protein to undergo conformational changes in response to pH and redox gradients across endosomes, leading to the formation of a protein-conducting channel. The approximately 50 kDa light chain (LC) protease is translocated into the cytosol by the approximately 100 kDa heavy chain (HC), which consists of two modules: the N-terminal translocation domain (TD) and the C-terminal Receptor Binding Domain (RBD). Here we exploited the BoNT modular design to identify the minimal requirements for channel activity and LC translocation in neurons. Using the combined detection of substrate proteolysis and single-channel currents, we showed that a di-modular protein consisting only of LC and TD was sufficient to translocate active protease into the cytosol of target cells. The RBD is dispensable for cell entry, channel activity, or LC translocation; however, it determined a pH threshold for channel formation. These findings indicate that, in addition to its individual functions, each module acts as a chaperone for the others, working in concert to achieve productive intoxication.
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Affiliation(s)
- Audrey Fischer
- Section of Neurobiology, Division of Biological Sciences, University of California San Diego, La Jolla, California, United States of America
| | - Darren J. Mushrush
- Departments of Biochemistry, Microbiology and Immunology, and Center for Structural Biology, Vanderbilt University Medical Center, Nashville, Tennessee, United States of America
| | - D. Borden Lacy
- Departments of Biochemistry, Microbiology and Immunology, and Center for Structural Biology, Vanderbilt University Medical Center, Nashville, Tennessee, United States of America
| | - Mauricio Montal
- Section of Neurobiology, Division of Biological Sciences, University of California San Diego, La Jolla, California, United States of America
- * E-mail:
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87
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Willis B, Eubanks LM, Dickerson TJ, Janda KD. The strange case of the botulinum neurotoxin: using chemistry and biology to modulate the most deadly poison. Angew Chem Int Ed Engl 2008; 47:8360-79. [PMID: 18844202 DOI: 10.1002/anie.200705531] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
In the classic novella "The Strange Case of Dr. Jekyll and Mr. Hyde", Robert Louis Stevenson paints a stark picture of the duality of good and evil within a single man. Botulinum neurotoxin (BoNT), the most potent known toxin, possesses an analogous dichotomous nature: It shows a pronounced morbidity and mortality, but it is used with great effect in much lower doses in a wide range of clinical scenarios. Recently, tremendous strides have been made in the basic understanding of the structure and function of BoNT, which have translated into widespread efforts towards the discovery of biomacromolecules and small molecules that specifically modulate BoNT activity. Particular emphasis has been placed on the identification of inhibitors that can counteract BoNT exposure in the event of a bioterrorist attack. This Review summarizes the current advances in the development of therapeutics, including vaccines, peptides, and small-molecule inhibitors, for the prevention and treatment of botulism.
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Affiliation(s)
- Bert Willis
- Department of Chemistry, Skaggs Institute for Chemical Biology, 10550 North Torrey Pines Road, La Jolla, CA 92037, USA
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88
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Willis B, Eubanks L, Dickerson T, Janda K. Der seltsame Fall des Botulinum-Neurotoxins: chemische und biologische Modulierung des tödlichsten aller Gifte. Angew Chem Int Ed Engl 2008. [DOI: 10.1002/ange.200705531] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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89
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Neutralization of botulinum neurotoxin by a human monoclonal antibody specific for the catalytic light chain. PLoS One 2008; 3:e3023. [PMID: 18714390 PMCID: PMC2515629 DOI: 10.1371/journal.pone.0003023] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2008] [Accepted: 07/29/2008] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND Botulinum neurotoxins (BoNT) are a family of category A select bioterror agents and the most potent biological toxins known. Cloned antibody therapeutics hold considerable promise as BoNT therapeutics, but the therapeutic utility of antibodies that bind the BoNT light chain domain (LC), a metalloprotease that functions in the cytosol of cholinergic neurons, has not been thoroughly explored. METHODS AND FINDINGS We used an optimized hybridoma method to clone a fully human antibody specific for the LC of serotype A BoNT (BoNT/A). The 4LCA antibody demonstrated potent in vivo neutralization when administered alone and collaborated with an antibody specific for the HC. In Neuro-2a neuroblastoma cells, the 4LCA antibody prevented the cleavage of the BoNT/A proteolytic target, SNAP-25. Unlike an antibody specific for the HC, the 4LCA antibody did not block entry of BoNT/A into cultured cells. Instead, it was taken up into synaptic vesicles along with BoNT/A. The 4LCA antibody also directly inhibited BoNT/A catalytic activity in vitro. CONCLUSIONS An antibody specific for the BoNT/A LC can potently inhibit BoNT/A in vivo and in vitro, using mechanisms not previously associated with BoNT-neutralizing antibodies. Antibodies specific for BoNT LC may be valuable components of an antibody antidote for BoNT exposure.
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90
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Eubanks LM, Dickerson TJ. Investigating novel therapeutic targets and molecular mechanisms to treat botulinum neurotoxin A intoxication. Future Microbiol 2008; 2:677-87. [PMID: 18041908 DOI: 10.2217/17460913.2.6.677] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Botulinum neurotoxin (BoNT) has recently catapulted into the public consciousness in two seemingly disparate roles: potential use as a biological weapon and treatment of neuromuscular disorders. This bacterially produced protein is the most potent toxin known to humans, with a lethal dose estimated at approximately 1 ng/kg of body weight. BoNT intoxication occurs via a multistep process that includes recognition of peripheral neuronal cell membrane receptors, endocytosis and translocation of the light chain metalloprotease into the cytosol, and catalytic cleavage of soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) proteins critical for vesicle fusion and neurotransmitter release. Each of these distinct steps has been studied at the molecular level and is a valid target for the development of pharmacological interventions to prevent the considerable mortality associated with botulism. Alternatively, clinical uses of BoNT continue to expand at an ever-increasing rate; however, further optimization of BoNT therapy is critical to maximize efficacy.
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Affiliation(s)
- Lisa M Eubanks
- The Scripps Research Institute, Department of Chemistry, 10550 North Torrey Pines Road, La Jolla, CA 92037, USA.
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91
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Brunger AT, Breidenbach MA, Jin R, Fischer A, Santos JS, Montal M. Botulinum neurotoxin heavy chain belt as an intramolecular chaperone for the light chain. PLoS Pathog 2007; 3:1191-4. [PMID: 17907800 PMCID: PMC1994969 DOI: 10.1371/journal.ppat.0030113] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Affiliation(s)
- Axel T Brunger
- * To whom correspondence should be addressed. E-mail: (ATB), (MM)
| | | | | | | | | | - Mauricio Montal
- * To whom correspondence should be addressed. E-mail: (ATB), (MM)
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92
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Capková K, Yoneda Y, Dickerson TJ, Janda KD. Synthesis and structure-activity relationships of second-generation hydroxamate botulinum neurotoxin A protease inhibitors. Bioorg Med Chem Lett 2007; 17:6463-6. [PMID: 17951059 DOI: 10.1016/j.bmcl.2007.09.103] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2007] [Revised: 09/27/2007] [Accepted: 09/28/2007] [Indexed: 11/29/2022]
Abstract
Botulinum neurotoxins are the most toxic proteins currently known. Based on a recently identified potent lead structure, 2,4-dichlorocinnamic acid hydroxamate, herein we report on the structure-activity relationship of a series of hydroxamate BoNT/A inhibitors. Among them, 2-bromo-4-chlorocinnamic acid hydroxamate, 2-methyl-4-chlorocinnamic acid hydroxamate, and 2-trifluoromethyl-4-chlorocinnamic acid hydroxamate displayed comparable inhibitory activity to that of the lead structure.
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Affiliation(s)
- Katerina Capková
- Department of Chemistry, and The Skaggs Institute for Chemical Biology, 10550 North Torrey Pines Road, La Jolla, CA 92037, USA
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93
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Tang J, Park JG, Millard CB, Schmidt JJ, Pang YP. Computer-aided lead optimization: improved small-molecule inhibitor of the zinc endopeptidase of botulinum neurotoxin serotype A. PLoS One 2007; 2:e761. [PMID: 17712409 PMCID: PMC1942119 DOI: 10.1371/journal.pone.0000761] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2007] [Accepted: 07/16/2007] [Indexed: 11/23/2022] Open
Abstract
Optimization of a serotype-selective, small-molecule inhibitor of botulinum neurotoxin serotype A (BoNTA) endopeptidase is a formidable challenge because the enzyme-substrate interface is unusually large and the endopeptidase itself is a large, zinc-binding protein with a complex fold that is difficult to simulate computationally. We conducted multiple molecular dynamics simulations of the endopeptidase in complex with a previously described inhibitor (Kiapp of 7±2.4 µM) using the cationic dummy atom approach. Based on our computational results, we hypothesized that introducing a hydroxyl group to the inhibitor could improve its potency. Synthesis and testing of the hydroxyl-containing analog as a BoNTA endopeptidase inhibitor showed a twofold improvement in inhibitory potency (Kiapp of 3.8±0.8 µM) with a relatively small increase in molecular weight (16 Da). The results offer an improved template for further optimization of BoNTA endopeptidase inhibitors and demonstrate the effectiveness of the cationic dummy atom approach in the design and optimization of zinc protease inhibitors.
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Affiliation(s)
- Jing Tang
- Computer-Aided Molecular Design Laboratory, Mayo Clinic, Rochester, Minnesota, United States of America
| | - Jewn Giew Park
- Computer-Aided Molecular Design Laboratory, Mayo Clinic, Rochester, Minnesota, United States of America
| | - Charles B. Millard
- Division of Biochemistry, Walter Reed Army Institute of Research, Silver Spring, Maryland, United States of America
| | - James J. Schmidt
- Department of Cell Biology and Biochemistry, United States Army Medical Research Institute of Infectious Diseases, Frederick, Maryland, United States of America
- * To whom correspondence should be addressed. E-mail: (JS); (Y-PP)
| | - Yuan-Ping Pang
- Computer-Aided Molecular Design Laboratory, Mayo Clinic, Rochester, Minnesota, United States of America
- * To whom correspondence should be addressed. E-mail: (JS); (Y-PP)
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94
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Silvaggi NR, Boldt GE, Hixon MS, Kennedy JP, Tzipori S, Janda KD, Allen KN. Structures of Clostridium botulinum Neurotoxin Serotype A Light Chain complexed with small-molecule inhibitors highlight active-site flexibility. ACTA ACUST UNITED AC 2007; 14:533-42. [PMID: 17524984 DOI: 10.1016/j.chembiol.2007.03.014] [Citation(s) in RCA: 98] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2006] [Revised: 02/07/2007] [Accepted: 03/14/2007] [Indexed: 11/19/2022]
Abstract
The potential for the use of Clostridial neurotoxins as bioweapons makes the development of small-molecule inhibitors of these deadly toxins a top priority. Recently, screening of a random hydroxamate library identified a small-molecule inhibitor of C. botulinum Neurotoxin Serotype A Light Chain (BoNT/A-LC), 4-chlorocinnamic hydroxamate, a derivative of which has been shown to have in vivo efficacy in mice and no toxicity. We describe the X-ray crystal structures of BoNT/A-LC in complexes with two potent small-molecule inhibitors. The structures of the enzyme with 4-chlorocinnamic hydroxamate or 2,4-dichlorocinnamic hydroxamate bound are compared to the structure of the enzyme complexed with L-arginine hydroxamate, an inhibitor with modest affinity. Taken together, this suite of structures provides surprising insights into the BoNT/A-LC active site, including unexpected conformational flexibility at the S1' site that changes the electrostatic environment of the binding pocket. Information gained from these structures will inform the design and optimization of more effective small-molecule inhibitors of BoNT/A-LC.
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Affiliation(s)
- Nicholas R Silvaggi
- Department of Physiology and Biophysics, Boston University School of Medicine, Boston, MA 02118, USA
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95
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Auld D, Simeonov A, Thomas C. Literature Search and Review. Assay Drug Dev Technol 2007. [DOI: 10.1089/adt.2007.9995] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Affiliation(s)
- Doug Auld
- National Institutes of Health, Bethesda, MD
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