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Cai S, Kumar R, Singh BR. Clostridial Neurotoxins: Structure, Function and Implications to Other Bacterial Toxins. Microorganisms 2021; 9:2206. [PMID: 34835332 PMCID: PMC8618262 DOI: 10.3390/microorganisms9112206] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2021] [Revised: 10/19/2021] [Accepted: 10/19/2021] [Indexed: 01/20/2023] Open
Abstract
Gram-positive bacteria are ancient organisms. Many bacteria, including Gram-positive bacteria, produce toxins to manipulate the host, leading to various diseases. While the targets of Gram-positive bacterial toxins are diverse, many of those toxins use a similar mechanism to invade host cells and exert their functions. Clostridial neurotoxins produced by Clostridial tetani and Clostridial botulinum provide a classical example to illustrate the structure-function relationship of bacterial toxins. Here, we critically review the recent progress of the structure-function relationship of clostridial neurotoxins, including the diversity of the clostridial neurotoxins, the mode of actions, and the flexible structures required for the activation of toxins. The mechanism clostridial neurotoxins use for triggering their activity is shared with many other Gram-positive bacterial toxins, especially molten globule-type structures. This review also summarizes the implications of the molten globule-type flexible structures to other Gram-positive bacterial toxins. Understanding these highly dynamic flexible structures in solution and their role in the function of bacterial toxins not only fills in the missing link of the high-resolution structures from X-ray crystallography but also provides vital information for better designing antidotes against those toxins.
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Affiliation(s)
- Shuowei Cai
- Department of Chemistry and Biochemistry, University of Massachusetts Dartmouth, Dartmouth, MA 02747, USA
| | - Raj Kumar
- Botulinum Research Center, Institute of Advanced Sciences, Dartmouth, MA 02747, USA; (R.K.); (B.R.S.)
| | - Bal Ram Singh
- Botulinum Research Center, Institute of Advanced Sciences, Dartmouth, MA 02747, USA; (R.K.); (B.R.S.)
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Patel KB, Kononova O, Cai S, Barsegov V, Parmar VS, Kumar R, Singh BR. Botulinum neurotoxin inhibitor binding dynamics and kinetics relevant for drug design. Biochim Biophys Acta Gen Subj 2021; 1865:129933. [PMID: 34023445 DOI: 10.1016/j.bbagen.2021.129933] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2021] [Revised: 05/05/2021] [Accepted: 05/17/2021] [Indexed: 02/06/2023]
Abstract
BACKGROUND A natural product analog, 3-(4-nitrophenyl)-7H-furo[3,2-g]chromen-7-one, which is a nitrophenyl psoralen (NPP) was found to be an effective inhibitor of botulinum neurotoxin type A (BoNT/A). METHODS In this work, we performed enzyme inhibition kinetics and employed biochemical techniques such as isothermal calorimetry (ITC) and fluorescence spectroscopy as well as molecular modeling to examine the kinetics and binding mechanism of NPP inhibitor with BoNT/A LC. RESULTS Studies of inhibition mechanism and binding dynamics of NPP to BoNT/A light chain (BoNT/A LC) showed that NPP is a mixed type inhibitor for the zinc endopeptidase activity, implying that at least part of the inhibitor-enzyme binding site may be different from the substrate-enzyme binding site. By using biochemical techniques, we demonstrated NPP forms a stable complex with BoNT/A LC. These observations were confirmed by Molecular Dynamics (MD) simulation, which demonstrates that NPP binds to the site near the active site. CONCLUSION The NPP binding interferes with BoNT/A LC binding to the SNAP-25, hence, inhibits its cleavage. Based on these results, we propose a modified strategy for designing a molecule to enhance the efficiency of the inhibition against the neurotoxic effect of BoNT. GENERAL SIGNIFICANCE Insights into the interactions of NPP with BoNT/A LC using biochemical and computational approaches will aid in the future development of effective countermeasures and better pharmacological strategies against botulism.
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Affiliation(s)
- Kruti B Patel
- Botulinum Research Center, Institute of Advanced Sciences, Dartmouth, MA, USA; Department of Chemistry and Biochemistry, University of Massachusetts Dartmouth, North Dartmouth, MA, USA
| | - Olga Kononova
- Department of Chemistry and Biochemistry, University of Massachusetts Lowell, Lowell, MA, USA
| | - Shuowei Cai
- Department of Chemistry and Biochemistry, University of Massachusetts Dartmouth, North Dartmouth, MA, USA
| | - Valeri Barsegov
- Department of Chemistry and Biochemistry, University of Massachusetts Lowell, Lowell, MA, USA
| | - Virinder S Parmar
- Botulinum Research Center, Institute of Advanced Sciences, Dartmouth, MA, USA; Bioorganic Laboratory, Department of Chemistry, University of Delhi, Delhi, India
| | - Raj Kumar
- Botulinum Research Center, Institute of Advanced Sciences, Dartmouth, MA, USA
| | - Bal Ram Singh
- Botulinum Research Center, Institute of Advanced Sciences, Dartmouth, MA, USA; Department of Chemistry and Biochemistry, University of Massachusetts Dartmouth, North Dartmouth, MA, USA; Prime Bio Inc., Dartmouth, MA, USA.
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Wang H, Chen J, Gao C, Chen W, Chen G, Zhang M, Luo C, Wang T, Chen X, Tao L. TMT-based proteomics analysis to screen potential biomarkers of acute-phase TBI in rats. Life Sci 2020; 264:118631. [PMID: 33131748 DOI: 10.1016/j.lfs.2020.118631] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2020] [Revised: 10/09/2020] [Accepted: 10/17/2020] [Indexed: 01/19/2023]
Abstract
AIMS Traumatic brain injury (TBI) is a common nervous system injury. However, the detailed mechanisms about functional dysregulation and dignostic biomarkers post-TBI are still unclear. So we aimed to identify potential differentially expressed proteins and genes in TBI for clinical diagnosis and therapeutic purposes. MAIN METHODS Rat TBI model was established by the weight-drop method. First, through TMT-proteomics, we screened for the change in the proteins expression profile acute phase post-TBI. The DAVID and Reactome databases were used to analyze and visualize the dysregulation proteins. Then, using publicly available microarray datasets GSE45997, differentially expressed genes (DGEs) were identified for the 24 h post-TBI stage. Also, the proteomic data were compared with microarray data to analyze the similarity. KEY FINDINGS We found significant proteomics and transcriptomic changes in post-TBI samples. 989, 881, 832, 1057 proteins were quantitated at 1 h, 6 h, 24 h, and 3 d post-injury correspondingly. Concerning proteomics findings, oxygen transport, acute-phase response, and negative regulation of endopeptidase activity were influenced throughout the acute phrase of TBI. Also, pathways related to scavenging of heme from plasma, binding, and uptake of ligands by scavenger receptors were highly enriched in all time-points of TBI samples. SIGNIFICANCE We noticed that the interaction-networks trend to get complicated with more node connections following the progression of TBI. We inferred that Hk-1, PRKAR2A, and MBP could be novel candidate biomarkers related to time-injury in acute-phase TBI. Also, Ceruloplasmin and Complement C3 were found to be important proteins and genes are involved in the TBI.
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Affiliation(s)
- Haochen Wang
- Department of Forensic Medicine, Medical School of Soochow University, Suzhou 215123, China.
| | - Jie Chen
- Department of Forensic Medicine, Medical School of Soochow University, Suzhou 215123, China
| | - Cheng Gao
- Department of Forensic Medicine, Medical School of Soochow University, Suzhou 215123, China
| | - Wei Chen
- Department of Forensic Medicine, Medical School of Soochow University, Suzhou 215123, China
| | - Guang Chen
- Department of Forensic Medicine, Medical School of Soochow University, Suzhou 215123, China
| | - Mingyang Zhang
- Department of Forensic Medicine, Medical School of Soochow University, Suzhou 215123, China
| | - Chengliang Luo
- Department of Forensic Medicine, Medical School of Soochow University, Suzhou 215123, China
| | - Tao Wang
- Department of Forensic Medicine, Medical School of Soochow University, Suzhou 215123, China
| | - Xiping Chen
- Department of Forensic Medicine, Medical School of Soochow University, Suzhou 215123, China.
| | - Luyang Tao
- Department of Forensic Medicine, Medical School of Soochow University, Suzhou 215123, China.
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Natural Compounds and Their Analogues as Potent Antidotes against the Most Poisonous Bacterial Toxin. Appl Environ Microbiol 2018; 84:AEM.01280-18. [PMID: 30389764 DOI: 10.1128/aem.01280-18] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2018] [Accepted: 09/28/2018] [Indexed: 01/30/2023] Open
Abstract
Botulinum neurotoxins (BoNTs), the most poisonous proteins known to humankind, are a family of seven (serotype A to G) immunologically distinct proteins synthesized primarily by different strains of the anaerobic bacterium Clostridium botulinum Being the causative agents of botulism, the toxins block neurotransmitter release by specifically cleaving one of the three soluble N-ethylmaleimide-sensitive factor attachment receptor (SNARE) proteins, thereby inducing flaccid paralysis. The development of countermeasures and therapeutics against BoNTs is a high-priority research area for public health because of their extreme toxicity and potential for use as biowarfare agents. Extensive research has focused on designing antagonists that block the catalytic activity of BoNTs. In this study, we screened 300 small natural compounds and their analogues extracted from Indian plants for their activity against BoNT serotype A (BoNT/A) as well as its light chain (LCA) using biochemical and cellular assays. One natural compound, a nitrophenyl psoralen (NPP), was identified to be a specific inhibitor of LCA with an in vitro 50% inhibitory concentration (IC50) value of 4.74 ± 0.03 µM. NPP was able to rescue endogenous synaptosome-associated protein 25 (SNAP-25) from cleavage by BoNT/A in human neuroblastoma cells with an IC50 of 12.2 ± 1.7 µM, as well as to prolong the time to the blocking of neutrally elicited twitch tensions in isolated mouse phrenic nerve-hemidiaphragm preparations.IMPORTANCE The long-lasting endopeptidase activity of BoNT is a critical biological activity inside the nerve cell, as it prompts proteolysis of the SNARE proteins, involved in the exocytosis of the neurotransmitter acetylcholine. Thus, the BoNT endopeptidase activity is an appropriate clinical target for designing new small-molecule antidotes against BoNT with the potential to reverse the paralysis syndrome of botulism. In principle, small-molecule inhibitors (SMIs) can gain entry into BoNT-intoxicated cells if they have a suitable octanol-water partition coefficient (log P) value and other favorable characteristics (P. Leeson, Nature 481:455-456, 2012, https://doi.org/10.1038/481455a). Several efforts have been made in the past to develop SMIs, but inhibitors effective under in vitro conditions have not in general been effective in vivo or in cellular models (L. M. Eubanks, M. S. Hixon, W. Jin, S. Hong, et al., Proc Natl Acad Sci U S A 104:2602-2607, 2007, https://doi.org/10.1073/pnas.0611213104). The difference between the in vitro and cellular efficacy presumably results from difficulties experienced by the compounds in crossing the cell membrane, in conjunction with poor bioavailability and high cytotoxicity. The screened nitrophenyl psoralen (NPP) effectively antagonized BoNT/A in both in vitro and ex vivo assays. Importantly, NPP inhibited the BoNT/A light chain but not other general zinc endopeptidases, such as thermolysin, suggesting high selectivity for its target. Small-molecule (nonpeptidic) inhibitors have better oral bioavailability, better stability, and better tissue and cell permeation than antitoxins or peptide inhibitors.
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A Novel Surface Plasmon Resonance Biosensor for the Rapid Detection of Botulinum Neurotoxins. BIOSENSORS-BASEL 2017; 7:bios7030032. [PMID: 28783115 PMCID: PMC5618038 DOI: 10.3390/bios7030032] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/02/2017] [Revised: 07/28/2017] [Accepted: 08/01/2017] [Indexed: 11/16/2022]
Abstract
Botulinum neurotoxins (BoNTs) are Category A agents on the NIAID (National Institute of Allergy and Infectious Diseases) priority pathogen list owing to their extreme toxicity and the relative ease of production. These deadly toxins, in minute quantities (estimated human i.v. lethal dose LD50 of 1-2 ng/kg body weight), cause fatal flaccid paralysis by blocking neurotransmitter release. The current gold standard detection method, the mouse-bioassay, often takes days to confirm botulism. Furthermore, there are no effective antidotes known to reverse the symptoms of botulism, and as a result, patients with severe botulism often require meticulous care during the prolonged paralytic illness. To combat potential bio-terrorism incidents of botulinum neurotoxins, their rapid detection is paramount. Surface plasmon resonance (SPR) is a very sensitive technique to examine bio-molecular interactions. The label-free, real-time analysis, with high sensitivity and low sample consumption makes this technology particularly suitable for detection of the toxin. In this study, we demonstrated the feasibility in an assay with a newly designed SPR instrument for the rapid detection of botulinum neurotoxins. The LOD (limit of detection) of the Newton Photonics (NP) SPR based assay is 6.76 pg/mL for Botulinum Neurotoxin type A Light Chain (BoNT/A LC). We established that the detection sensitivity of the system is comparable to the traditional mouse LD50 bioassay in BoNT/A using this SPR technology.
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6
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Minnow YV, Goldberg R, Tummalapalli SR, Rotella DP, Goodey NM. Mechanism of inhibition of botulinum neurotoxin type A light chain by two quinolinol compounds. Arch Biochem Biophys 2017; 618:15-22. [DOI: 10.1016/j.abb.2017.01.006] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2016] [Revised: 01/06/2017] [Accepted: 01/12/2017] [Indexed: 11/26/2022]
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Bompiani KM, Caglič D, Krutein MC, Benoni G, Hrones M, Lairson LL, Bian H, Smith GR, Dickerson TJ. High-Throughput Screening Uncovers Novel Botulinum Neurotoxin Inhibitor Chemotypes. ACS COMBINATORIAL SCIENCE 2016; 18:461-74. [PMID: 27314875 DOI: 10.1021/acscombsci.6b00033] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Botulism is caused by potent and specific bacterial neurotoxins that infect host neurons and block neurotransmitter release. Treatment for botulism is limited to administration of an antitoxin within a short time window, before the toxin enters neurons. Alternatively, current botulism drug development targets the toxin light chain, which is a zinc-dependent metalloprotease that is delivered into neurons and mediates long-term pathology. Several groups have identified inhibitory small molecules, peptides, or aptamers, although no molecule has advanced to the clinic due to a lack of efficacy in advanced models. Here we used a homogeneous high-throughput enzyme assay to screen three libraries of drug-like small molecules for new chemotypes that modulate recombinant botulinum neurotoxin light chain activity. High-throughput screening of 97088 compounds identified numerous small molecules that activate or inhibit metalloprotease activity. We describe four major classes of inhibitory compounds identified, detail their structure-activity relationships, and assess their relative inhibitory potency. A previously unreported chemotype in any context of enzyme inhibition is described with potent submicromolar inhibition (Ki = 200-300 nM). Additional detailed kinetic analyses and cellular cytotoxicity assays indicate the best compound from this series is a competitive inhibitor with cytotoxicity values around 4-5 μM. Given the potency and drug-like character of these lead compounds, further studies, including cellular activity assays and DMPK analysis, are justified.
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Affiliation(s)
- Kristin M. Bompiani
- Department
of Chemistry, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, California 92037, United States
| | - Dejan Caglič
- Department
of Chemistry, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, California 92037, United States
| | - Michelle C. Krutein
- Department
of Chemistry, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, California 92037, United States
| | - Galit Benoni
- Department
of Chemistry, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, California 92037, United States
| | - Morgan Hrones
- Department
of Chemistry, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, California 92037, United States
| | - Luke L. Lairson
- Department
of Chemistry, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, California 92037, United States
| | - Haiyan Bian
- Fox Chase Chemical Diversity Center, 3805 Old Easton Road, Doylestown, Pennsylvania 18902, United States
| | - Garry R. Smith
- Fox Chase Chemical Diversity Center, 3805 Old Easton Road, Doylestown, Pennsylvania 18902, United States
| | - Tobin J. Dickerson
- Department
of Chemistry, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, California 92037, United States
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Selection of RNA Aptamers Against Botulinum Neurotoxin Type A Light Chain Through a Non-Radioactive Approach. Appl Biochem Biotechnol 2016; 180:10-25. [PMID: 27085355 DOI: 10.1007/s12010-016-2081-0] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2016] [Accepted: 04/07/2016] [Indexed: 12/15/2022]
Abstract
Botulinum neurotoxin (BoNT), a category A agent, 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, a non-radioactive-based systematic evolution of ligands by exponential enrichment (SELEX) process is developed by utilizing surface plasmon resonance to monitor the binding enrichment. Two RNA aptamers have been identified as strong binders against light chain of botulinum neurotoxin type A. These two aptamers showed strong inhibition activity on LCA, with IC50 in nanomolar range. Inhibition kinetic studies reveal mid nanomolar KI and non-competitive nature of their inhibition, suggesting that they have strong potential as antidotes that can reverse the symptom caused by BoNT/A. More importantly, we observed that the 2'-fluorine-pyrimidine-modified RNA aptamers identified here do not change their binding and biological activities. This observation could lead to a cost-effective way for SELEX, by using regular nucleotide during SELEX, and 2'-fluorine-pyrimidine-modified nucleotide for final application to enhance their RNase-resistance.
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Bandala C, Terán-Melo JL, Anaya-Ruiz M, Mejía-Barradas CM, Domínguez-Rubio R, la Garza-Montano PD, Alfaro-Rodríguez A, Lara-Padilla E. Effect of botulinum neurotoxin type A (BoNTA) on the morphology and viability of 3T3 murine fibroblasts. INTERNATIONAL JOURNAL OF CLINICAL AND EXPERIMENTAL PATHOLOGY 2015; 8:9458-9462. [PMID: 26464704 PMCID: PMC4583936] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Subscribe] [Scholar Register] [Received: 06/03/2015] [Accepted: 07/21/2015] [Indexed: 06/05/2023]
Abstract
AIM BoNTA is used in the treatment of ophthalmological disorders, muscular hyperactivity and pain. In recent years it has been described that BoNTA reduces cellular viability and induces apoptosis in prostate cells lines. Studies about the effect of BoNTA are no well known. There have been studies about the effect of BoNTA on the expression levels of collagenase in fibroblasts, but not on its morphological impact on these cells. The aim of this study was to determine the effect of BoNTA on the morphology and viability of the 3T3 fibroblast cell line. MATERIAL AND METHODS The 3T3 fibroblast cell line was cultured and the experimental group received 10 U BoNTA added to a 0.9% sterile saline solution in a reconstituted vial. The control group received saline solution only. Cultured cells were observed and photographed at 5, 10, 15 and 20 h. Cell viability was evaluated by means of the trypan blue test, and cell proliferation with the Proliferation Assay kit (PROMEGA). RESULTS The application of BoNTA to 3T3 fibroblast cells induced morphological changes, such as a loss of normal fibroblast morphology. Additionally, we observed the cytoplasmic retraction and spread phenomena. The nuclei showed other important changes with Giemsa staining. CONCLUSION The results indicate that BoNTA induced a loss of spindle form, increase in cytoplasmic vesicles, and the presence of nuclear vesicles (compacted chromatin surrounded by a nuclear envelope). This suggests an apoptotic process and decreased cell viability. Further studies are needed to explore the mechanisms of these alterations.
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Affiliation(s)
- Cindy Bandala
- Research Support Group, National Institute of RehabilitationMexico City, México
- Laboratory of Molecular Oncology and Oxidative Stress, Escuela Superior de Medicina, Instituto Politécnico NacionalMexico City, México
| | - Juan Luis Terán-Melo
- Laboratory of Molecular Oncology and Oxidative Stress, Escuela Superior de Medicina, Instituto Politécnico NacionalMexico City, México
| | - Maricruz Anaya-Ruiz
- Laboratory of Cell Biology, Centro de Investigación Biomédica de Oriente, Instituto Mexicano del Seguro SocialPuebla, México
| | - Cesar Miguel Mejía-Barradas
- Laboratory of Molecular Oncology and Oxidative Stress, Escuela Superior de Medicina, Instituto Politécnico NacionalMexico City, México
| | | | | | | | - Eleazar Lara-Padilla
- Laboratory of Molecular Oncology and Oxidative Stress, Escuela Superior de Medicina, Instituto Politécnico NacionalMexico City, México
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Montgomery VA, Ahmed SA, Olson MA, Mizanur RM, Stafford RG, Roxas-Duncan VI, Smith LA. Ex vivo inhibition of Clostridium botulinum neurotoxin types B, C, E, and F by small molecular weight inhibitors. Toxicon 2015; 98:12-9. [PMID: 25707753 DOI: 10.1016/j.toxicon.2015.02.012] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2014] [Revised: 02/06/2015] [Accepted: 02/19/2015] [Indexed: 11/28/2022]
Abstract
Two small molecular weight inhibitors, compounds CB7969312 and CB7967495, that displayed inhibition of botulinum neurotoxin serotype A in a previous study, were evaluated for inhibition of botulinum neurotoxin serotypes B, C, E, and F. The small molecular weight inhibitors were assessed by molecular modeling, UPLC-based peptide cleavage assay; and an ex vivo assay, the mouse phrenic nerve - hemidiaphragm assay (MPNHDA). While both compounds were inhibitors of botulinum neurotoxin (BoNT) serotypes B, C, and F in the MPNHDA, compound CB7969312 was effective at lower molar concentrations than compound CB7967495. However, compound CB7967495 was significantly more effective at preventing BoNTE intoxication than compound CB7969312. In the UPLC-based peptide cleavage assay, CB7969312 was also more effective against LcC. Both compounds inhibited BoNTE, but not BoNTF, LcE, or LcF in the UPLC-based peptide cleavage assay. Molecular modeling studies predicted that both compounds would be effective inhibitors of BoNTs B, C, E, and F. But CB7967495 was predicted to be a more effective inhibitor of the four serotypes (B, C, E, and F) than CB7969312. This is the first report of a small molecular weight compound that inhibits serotypes B, C, E, and F in the ex vivo assay.
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Affiliation(s)
- Vicki A Montgomery
- U.S. Army Medical Research Institute of Infectious Diseases, Division of Molecular and Translational Sciences, 1425 Porter St. Ft Detrick, Frederick, MD, USA.
| | - S Ashraf Ahmed
- U.S. Army Medical Research Institute of Infectious Diseases, Division of Molecular and Translational Sciences, 1425 Porter St. Ft Detrick, Frederick, MD, USA.
| | - Mark A Olson
- U.S. Army Medical Research Institute of Infectious Diseases, Division of Molecular and Translational Sciences, 1425 Porter St. Ft Detrick, Frederick, MD, USA.
| | - Rahman M Mizanur
- U.S. Army Medical Research Institute of Infectious Diseases, Biosurety Division, 1430 Veterans Dr, Ft Detrick, Frederick, MD, USA(1).
| | - Robert G Stafford
- U.S. Army Medical Research Institute of Infectious Diseases, Division of Molecular and Translational Sciences, 1425 Porter St. Ft Detrick, Frederick, MD, USA.
| | - Virginia I Roxas-Duncan
- U.S. Army Medical Research Institute of Infectious Diseases, Biosurety Division, 1430 Veterans Dr, Ft Detrick, Frederick, MD, USA(1).
| | - Leonard A Smith
- Medical Countermeasures Technology, U.S. Army Medical Research and Material Command, 1425 Porter St. Ft Detrick, Frederick, MD, USA.
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Mizanur RM, Stafford RG, Ahmed SA. Cleavage of SNAP25 and its shorter versions by the protease domain of serotype A botulinum neurotoxin. PLoS One 2014; 9:e95188. [PMID: 24769566 PMCID: PMC4000213 DOI: 10.1371/journal.pone.0095188] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2013] [Accepted: 03/25/2014] [Indexed: 11/18/2022] Open
Abstract
Various substrates, catalysts, and assay methods are currently used to screen inhibitors for their effect on the proteolytic activity of botulinum neurotoxin. As a result, significant variation exists in the reported results. Recently, we found that one source of variation was the use of various catalysts, and have therefore evaluated its three forms. In this paper, we characterize three substrates under near uniform reaction conditions using the most active catalytic form of the toxin. Bovine serum albumin at varying optimum concentrations stimulated enzymatic activity with all three substrates. Sodium chloride had a stimulating effect on the full length synaptosomal-associated protein of 25 kDa (SNAP25) and its 66-mer substrates but had an inhibitory effect on the 17-mer substrate. We found that under optimum conditions, full length SNAP25 was a better substrate than its shorter 66-mer or 17-mer forms both in terms of kcat, Km, and catalytic efficiency kcat/Km. Assay times greater than 15 min introduced large variations and significantly reduced the catalytic efficiency. In addition to characterizing the three substrates, our results identify potential sources of variations in previous published results, and underscore the importance of using well-defined reaction components and assay conditions.
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Affiliation(s)
- Rahman M. Mizanur
- Department of Cell Biology and Biochemistry, Molecular and Translational Sciences Division, United States Army Medical Research Institute of Infectious Diseases, Fort Detrick, Maryland, United States of America
| | - Robert G. Stafford
- Department of Cell Biology and Biochemistry, Molecular and Translational Sciences Division, United States Army Medical Research Institute of Infectious Diseases, Fort Detrick, Maryland, United States of America
| | - S. Ashraf Ahmed
- Department of Cell Biology and Biochemistry, Molecular and Translational Sciences Division, United States Army Medical Research Institute of Infectious Diseases, Fort Detrick, Maryland, United States of America
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Patel K, Cai S, Singh BR. Current strategies for designing antidotes against botulinum neurotoxins. Expert Opin Drug Discov 2014; 9:319-33. [DOI: 10.1517/17460441.2014.884066] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Affiliation(s)
- Kruti Patel
- University of Massachusetts Dartmouth, Department of Chemistry and Biochemistry, North Dartmouth, MA 02747, USA
| | - Shuowei Cai
- University of Massachusetts Dartmouth, Department of Chemistry and Biochemistry, North Dartmouth, MA 02747, USA
| | - Bal Ram Singh
- University of Massachusetts Dartmouth, Department of Chemistry and Biochemistry, North Dartmouth, MA 02747, USA
- Institute of Advanced Sciences and Prime Bio, Inc., Botulinum Research Center, 166 Chase Road, North Dartmouth, MA 02747, USA
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Dadgar S, Ramjan Z, Floriano WB. Paclitaxel is an inhibitor and its boron dipyrromethene derivative is a fluorescent recognition agent for botulinum neurotoxin subtype A. J Med Chem 2013; 56:2791-803. [PMID: 23484537 DOI: 10.1021/jm301829h] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
We have successfully identified one new inhibitor and one new fluorescent recognition agent for the botulinum neurotoxin subtype A (BoNT/A) using the virtual screening protocol "protein scanning with virtual ligand screening" (PSVLS). Hit selection used an in-house developed holistic binding scoring method. Selected hits were tested experimentally for inhibitory activity using fluorescence resonance energy transfer (FRET) assays against the light chain (catalytic domain) of BoNT/A. Ligand binding was determined against the light and heavy chain BoNT/A complex through either radiolabeled ligand binding assays (nonfluorescent ligands) or fluorescence intensity assays (fluorescent ligands). These experimental assays have confirmed one compound (paclitaxel) to inhibit BoNT/A's proteolytic activity experimentally with an IC50 of 5.2 μM. A fluorescent derivative was also confirmed to bind to the toxin and therefore is a suitable candidate for the rational design of new detection agents and for the development of fluorescence-based multiprobe detection assays.
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Affiliation(s)
- Saedeh Dadgar
- Department of Chemistry, Lakehead University and Thunder Bay Regional Research Institute, Thunder Bay, Ontario P7B 5E1, Canada
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Singh P, Singh MK, Chaudhary D, Chauhan V, Bharadwaj P, Pandey A, Upadhyay N, Dhaked RK. Small-molecule quinolinol inhibitor identified provides protection against BoNT/A in mice. PLoS One 2012; 7:e47110. [PMID: 23071727 PMCID: PMC3469547 DOI: 10.1371/journal.pone.0047110] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2012] [Accepted: 09/10/2012] [Indexed: 11/18/2022] Open
Abstract
Botulinum neurotoxins (BoNTs), etiological agents of the life threatening neuroparalytic disease botulism, are the most toxic substances currently known. The potential for the use as bioweapon makes the development of small-molecule inhibitor against these deadly toxins is a top priority. Currently, there are no approved pharmacological treatments for BoNT intoxication. Although an effective vaccine/immunotherapy is available for immuno-prophylaxis but this cannot reverse the effects of toxin inside neurons. A small-molecule pharmacological intervention, especially one that would be effective against the light chain protease, would be highly desirable. Similarity search was carried out from ChemBridge and NSC libraries to the hit (7-(phenyl(8-quinolinylamino)methyl)-8-quinolinol; NSC 84096) to mine its analogs. Several hits obtained were screened for in silico inhibition using AutoDock 4.1 and 19 new molecules selected based on binding energy and Ki. Among these, eleven quinolinol derivatives potently inhibited in vitro endopeptidase activity of botulinum neurotoxin type A light chain (rBoNT/A-LC) on synaptosomes isolated from rat brain which simulate the in vivo system. Five of these inhibitor molecules exhibited IC(50) values ranging from 3.0 nM to 10.0 µM. NSC 84087 is the most potent inhibitor reported so far, found to be a promising lead for therapeutic development, as it exhibits no toxicity, and is able to protect animals from pre and post challenge of botulinum neurotoxin type A (BoNT/A).
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Affiliation(s)
- Padma Singh
- Biotechnology Division, Defence Research and Development Establishment, Gwalior, Madhya Pradesh, India
| | - Manglesh Kumar Singh
- Biotechnology Division, Defence Research and Development Establishment, Gwalior, Madhya Pradesh, India
| | - Dilip Chaudhary
- Biotechnology Division, Defence Research and Development Establishment, Gwalior, Madhya Pradesh, India
| | - Vinita Chauhan
- Biotechnology Division, Defence Research and Development Establishment, Gwalior, Madhya Pradesh, India
| | - Pranay Bharadwaj
- Biotechnology Division, Defence Research and Development Establishment, Gwalior, Madhya Pradesh, India
| | - Apurva Pandey
- Biotechnology Division, Defence Research and Development Establishment, Gwalior, Madhya Pradesh, India
| | - Nisha Upadhyay
- Biotechnology Division, Defence Research and Development Establishment, Gwalior, Madhya Pradesh, India
| | - Ram Kumar Dhaked
- Biotechnology Division, Defence Research and Development Establishment, Gwalior, Madhya Pradesh, India
- * E-mail:
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Campagnola G, Gong P, Peersen OB. High-throughput screening identification of poliovirus RNA-dependent RNA polymerase inhibitors. Antiviral Res 2011; 91:241-51. [PMID: 21722674 PMCID: PMC3159743 DOI: 10.1016/j.antiviral.2011.06.006] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2011] [Revised: 05/11/2011] [Accepted: 06/14/2011] [Indexed: 11/26/2022]
Abstract
Viral RNA-dependent RNA polymerase (RdRP) enzymes are essential for the replication of positive-strand RNA viruses and established targets for the development of selective antiviral therapeutics. In this work we have carried out a high-throughput screen of 154,267 compounds to identify poliovirus polymerase inhibitors using a fluorescence based RNA elongation assay. Screening and subsequent validation experiments using kinetic methods and RNA product analysis resulted in the identification of seven inhibitors that affect the RNA binding, initiation, or elongation activity of the polymerase. X-ray crystallography data show clear density for five of the compounds in the active site of the poliovirus polymerase elongation complex. The inhibitors occupy the NTP binding site by stacking on the priming nucleotide and interacting with the templating base, yet competition studies show fairly weak IC50 values in the low μM range. A comparison with nucleotide bound structures suggests that weak binding is likely due to the lack of a triphosphate group on the inhibitors. Consequently, the inhibitors are primarily effective at blocking polymerase initiation and do not effectively compete with NTP binding during processive elongation. These findings are discussed in the context of the polymerase elongation complex structure and allosteric control of the viral RdRP catalytic cycle.
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Affiliation(s)
- Grace Campagnola
- Department of Biochemistry & Molecular Biology 1870 Campus Delivery Colorado State University Fort Collins, CO 80523-1870
| | - Peng Gong
- Department of Biochemistry & Molecular Biology 1870 Campus Delivery Colorado State University Fort Collins, CO 80523-1870
| | - Olve B. Peersen
- Department of Biochemistry & Molecular Biology 1870 Campus Delivery Colorado State University Fort Collins, CO 80523-1870
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Heeres JT, Hergenrother PJ. High-throughput screening for modulators of protein–protein interactions: use of photonic crystal biosensors and complementary technologies. Chem Soc Rev 2011; 40:4398-410. [DOI: 10.1039/b923660k] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
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18
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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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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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