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Lockridge O, Schopfer LM. Review: Organophosphorus toxicants, in addition to inhibiting acetylcholinesterase activity, make covalent adducts on multiple proteins and promote protein crosslinking into high molecular weight aggregates. Chem Biol Interact 2023; 376:110460. [PMID: 36963650 PMCID: PMC10100150 DOI: 10.1016/j.cbi.2023.110460] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2023] [Revised: 03/08/2023] [Accepted: 03/15/2023] [Indexed: 03/26/2023]
Abstract
The acute effects of exposure to organophosphorus toxicants are explained by inhibition of acetylcholinesterase activity. However, the mechanisms that explain long term illness associated with organophosphorus exposure are still under investigation. We find that organophosphorus nerve agents and organophosphorus pesticides make covalent adducts not only on the serine from acetylcholinesterase, but also on tyrosine, lysine, glutamate, serine and threonine from a variety of proteins. Almost any protein can be modified by a high dose of organophosphorus toxicant. A low dose of 10 μM chlorpyrifos oxon added to the serum-free culture medium of human neuroblastoma SH-SY5Y cells resulted in tyrosine adducts on 48 proteins immunopurified from the cell lysate. We identified the adducted proteins by mass spectrometry after immunopurifying modified proteins with a rabbit anti-diethoxyphospho-tyrosine monoclonal antibody which biased this study for tyrosine adducts. In cultured cells, the primary organophosphate targets are abundant proteins. Organophosphate-modified proteins may disrupt physiological processes. In separate experiments we identified organophosphate adducts on lysine. Organophosphylation activates the lysine for protein crosslinking. The activated lysine reacts with glutamic acid or aspartic acid protein side chains to form an isopeptide bond between proteins, resulting in high molecular weight crosslinked proteins. Crosslinked proteins form insoluble aggregates that may lead to neurogenerative disease.
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Affiliation(s)
- Oksana Lockridge
- Eppley Institute, University of Nebraska Medical Center, Omaha, NE, 68198, USA.
| | - Lawrence M Schopfer
- Eppley Institute, University of Nebraska Medical Center, Omaha, NE, 68198, USA.
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Muñoz-Torrero D, Schopfer LM, Lockridge O. Chlorpyrifos Oxon Activates Glutamate and Lysine for Protein Cross-linking. Chem Res Toxicol 2023; 36:112-121. [PMID: 36598934 PMCID: PMC9846825 DOI: 10.1021/acs.chemrestox.2c00333] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Chronic low-dose exposure to organophosphorus (OP) toxicants is correlated with an increase in the risk of impaired cognition and neurodegenerative diseases. A mechanism to explain this relationship is needed. We suggest that the formation of organophosphate-induced high-molecular-weight protein aggregates that disrupt cell function may be the missing link. It has been demonstrated that such aggregation can be promoted by OP-labeled lysine. Alternatively, OP-labeled glutamate may be the initiator. To test this hypothesis, we treated MAP-rich tubulin Sus scrofa and human transglutaminase with chlorpyrifos oxon. Trypsin-digested proteins were subjected to liquid chromatography-tandem mass spectrometry followed by Protein Prospector searches to identify diethyl phosphate adducts and cross-linked peptides. We report the presence of diethyl phosphate adducts on the side chains of glutamate, lysine, and tyrosine, as well as cross-links between glutamate and lysine. Glutamate-lysine cross-linking could be initiated either by diethyl phosphate-activated glutamate or by diethyl phosphate-activated lysine to form stable isopeptide bonds between and within proteins. It was concluded that organophosphate-induced high-molecular-weight protein aggregates could promote brain dysfunction.
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Affiliation(s)
- Diego Muñoz-Torrero
- Laboratory
of Medicinal Chemistry (CSIC Associated Unit), Faculty of Pharmacy
and Food Sciences, and Institute of Biomedicine (IBUB), University of Barcelona, Barcelona 08028, Spain
| | | | - Oksana Lockridge
- University
of Nebraska Medical Center, Omaha, Nebraska 68198, United States,. Phone +1-402-559-6032.
Fax: +1 402-559-4651
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Onder S, van Grol M, Fidder A, Xiao G, Noort D, Yerramalla U, Tacal O, Schopfer LM, Lockridge O. Rabbit Antidiethoxyphosphotyrosine Antibody, Made by Single B Cell Cloning, Detects Chlorpyrifos Oxon-Modified Proteins in Cultured Cells and Immunopurifies Modified Peptides for Mass Spectrometry. J Proteome Res 2021; 20:4728-4745. [PMID: 34469172 PMCID: PMC8491160 DOI: 10.1021/acs.jproteome.1c00383] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
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Chronic low-dose
exposure to organophosphorus pesticides is associated
with the risk of neurodegenerative disease. The mechanism of neurotoxicity
is independent of acetylcholinesterase inhibition. Adducts on tyrosine,
lysine, threonine, and serine can occur after exposure to organophosphorus
pesticides, the most stable being adducts on tyrosine. Rabbit monoclonal
1C6 to diethoxyphosphate-modified tyrosine (depY) was created by single
B cell cloning. The amino acid sequence and binding constant (Kd 3.2 × 10–8 M) were
determined. Cultured human neuroblastoma SH-SY5Y and mouse neuroblastoma
N2a cells incubated with a subcytotoxic dose of 10 μM chlorpyrifos
oxon contained depY-modified proteins detected by monoclonal 1C6 on
Western blots. depY-labeled peptides from tryptic digests of cell
lysates were immunopurified by binding to immobilized 1C6. Peptides
released with 50% acetonitrile and 1% formic acid were analyzed by
liquid chromatography tandem mass spectrometry (LC-MS/MS) on an Orbitrap
Fusion Lumos mass spectrometer. Protein Prospector database searches
identified 51 peptides modified on tyrosine by diethoxyphosphate in
SH-SY5Y cell lysate and 73 diethoxyphosphate-modified peptides in
N2a cell lysate. Adducts appeared most frequently on the cytoskeleton
proteins tubulin, actin, and vimentin. It was concluded that rabbit
monoclonal 1C6 can be useful for studies that aim to understand the
mechanism of neurotoxicity resulting from low-dose exposure to organophosphorus
pesticides.
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Affiliation(s)
- Seda Onder
- Department of Biochemistry, School of Pharmacy, Hacettepe University, Ankara 06100, Turkey
| | - Marco van Grol
- TNO Organisation for Applied Scientific Research, 2280 AA Rijswijk, The Netherlands
| | - Alex Fidder
- TNO Organisation for Applied Scientific Research, 2280 AA Rijswijk, The Netherlands
| | - Gaoping Xiao
- Syd Labs, Inc., Hopkinton, Massachusetts 01748, United States
| | - Daan Noort
- TNO Organisation for Applied Scientific Research, 2280 AA Rijswijk, The Netherlands
| | | | - Ozden Tacal
- Department of Biochemistry, School of Pharmacy, Hacettepe University, Ankara 06100, Turkey
| | - Lawrence M Schopfer
- Eppley Institute, University of Nebraska Medical Center, Omaha, Nebraska 68198, United States
| | - Oksana Lockridge
- Eppley Institute, University of Nebraska Medical Center, Omaha, Nebraska 68198, United States
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Onder S, Schopfer LM, Tacal O, Blake TA, Johnson RC, Lockridge O. Mass Spectral Detection of Diethoxyphospho-Tyrosine Adducts on Proteins from HEK293 Cells Using Monoclonal Antibody depY for Enrichment. Chem Res Toxicol 2018; 31:520-530. [PMID: 29775289 PMCID: PMC6008731 DOI: 10.1021/acs.chemrestox.8b00083] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
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Chronic illness from exposure to
organophosphorus toxicants is
hypothesized to involve modification of unknown proteins. Tyrosine
in proteins that have no active site serine readily reacts with organophosphorus
toxicants. We developed a monoclonal antibody, depY, that specifically
recognizes diethoxyphospho-tyrosine in proteins and peptides, independent
of the surrounding amino acid sequence. Our goal in the current study
was to identify diethoxyphosphorylated proteins in human HEK293 cell
lysate treated with chlorpyrifos oxon. Cell lysates treated with chlorpyrifos
oxon were recognized by depY antibody in ELISA and capillary electrophoresis
based Western blot. Tryptic peptides were analyzed by liquid chromatography
tandem mass spectrometry. Liquid chromatography tandem mass spectrometry
identified 116 diethoxyphospho-tyrosine peptides from 73 proteins
in immunopurified samples, but found only 15 diethoxyphospho-tyrosine
peptides from 12 proteins when the same sample was not immunopurified
on depY. The most abundant proteins in the cell lysate, histone H4,
heat shock 70 kDa protein 1A/1B, heat shock protein HSP 90 β,
and α-enolase, were represented by several diethoxyphospho-tyrosine
peptides. It was concluded that use of immobilized depY improved the
number of diethoxyphospho-tyrosine peptides identified in a complex
mixture. The mass spectrometry results confirmed the specificity of
depY for diethoxyphospho-tyrosine peptides independent of the context
of the modified tyrosine, which means depY could be used to analyze
modified proteins in any species. Use of the depY antibody could lead
to an understanding of chronic illness from organophosphorus pesticide
exposure.
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Affiliation(s)
- Seda Onder
- Department of Biochemistry, School of Pharmacy , Hacettepe University , Ankara 06100 , Turkey.,Eppley Institute , University of Nebraska Medical Center , Omaha , Nebraska 68198 , United States
| | - Lawrence M Schopfer
- Eppley Institute , University of Nebraska Medical Center , Omaha , Nebraska 68198 , United States
| | - Ozden Tacal
- Department of Biochemistry, School of Pharmacy , Hacettepe University , Ankara 06100 , Turkey
| | - Thomas A Blake
- Division of Laboratory Sciences, National Center for Environmental Health , Centers for Disease Control and Prevention , 4770 Buford Highway NE , Atlanta , Georgia 30341 , United States
| | - Rudolph C Johnson
- Division of Laboratory Sciences, National Center for Environmental Health , Centers for Disease Control and Prevention , 4770 Buford Highway NE , Atlanta , Georgia 30341 , United States
| | - Oksana Lockridge
- Eppley Institute , University of Nebraska Medical Center , Omaha , Nebraska 68198 , United States
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5
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Onder S, Dafferner AJ, Schopfer LM, Xiao G, Yerramalla U, Tacal O, Blake TA, Johnson RC, Lockridge O. Monoclonal Antibody That Recognizes Diethoxyphosphotyrosine-Modified Proteins and Peptides Independent of Surrounding Amino Acids. Chem Res Toxicol 2017; 30:2218-2228. [PMID: 29137457 DOI: 10.1021/acs.chemrestox.7b00288] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) are irreversibly inhibited by organophosphorus pesticides through formation of a covalent bond with the active site serine. Proteins that have no active site serine, for example albumin, are covalently modified on tyrosine and lysine. Chronic illness from pesticide exposure is not explained by inhibition of AChE and BChE. Our goal was to produce a monoclonal antibody that recognizes proteins diethoxyphosphorylated on tyrosine. Diethoxyphosphate-tyrosine adducts for 13 peptides were synthesized. The diethoxyphosphorylated (OP) peptides cross-linked to four different carrier proteins were used to immunize, boost, and screen mice. Monoclonal antibodies were produced with hybridoma technology. Monoclonal antibody depY was purified and characterized by ELISA, western blotting, Biacore, and Octet technology to determine binding affinity and binding specificity. DepY recognized diethoxyphosphotyrosine independent of the amino acid sequence around the modified tyrosine and independent of the identity of the carrier protein or peptide. It had an IC50 of 3 × 10-9 M in a competition assay with OP tubulin. Kd values measured by Biacore and OctetRED96 were 10-8 M for OP-peptides and 1 × 10-12 M for OP-proteins. The limit of detection measured on western blots hybridized with 0.14 μg/mL of depY was 0.025 μg of human albumin conjugated to YGGFL-OP. DepY was specific for diethoxyphosphotyrosine (chlorpyrifos oxon adduct) as it failed to recognize diethoxyphospholysine, phosphoserine, phosphotyrosine, phosphothreonine, dimethoxyphosphotyrosine (dichlorvos adduct), dimethoxyphosphoserine, monomethoxyphosphotyrosine (aged dichlorvos adduct), and cresylphosphoserine. In conclusion, a monoclonal antibody that specifically recognizes diethoxyphosphotyrosine adducts has been developed. The depY monoclonal antibody could be useful for identifying new biomarkers of OP exposure.
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Affiliation(s)
- Seda Onder
- Department of Biochemistry, School of Pharmacy, Hacettepe University , Ankara 06100, Turkey.,Eppley Institute, University of Nebraska Medical Center , Omaha, Nebraska 68198, United States
| | - Alicia J Dafferner
- Eppley Institute, University of Nebraska Medical Center , Omaha, Nebraska 68198, United States
| | - Lawrence M Schopfer
- Eppley Institute, University of Nebraska Medical Center , Omaha, Nebraska 68198, United States
| | - Gaoping Xiao
- Syd Labs, Inc. , Natick, Massachusetts 01760, United States
| | | | - Ozden Tacal
- Department of Biochemistry, School of Pharmacy, Hacettepe University , Ankara 06100, Turkey
| | - Thomas A Blake
- Division of Laboratory Sciences, National Center for Environmental Health, Centers for Disease Control and Prevention , 4770 Buford Highway NE, Chamblee, Georgia 30341, United States
| | - Rudolph C Johnson
- Division of Laboratory Sciences, National Center for Environmental Health, Centers for Disease Control and Prevention , 4770 Buford Highway NE, Chamblee, Georgia 30341, United States
| | - Oksana Lockridge
- Eppley Institute, University of Nebraska Medical Center , Omaha, Nebraska 68198, United States
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6
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Sabbioni G, Turesky RJ. Biomonitoring Human Albumin Adducts: The Past, the Present, and the Future. Chem Res Toxicol 2017; 30:332-366. [PMID: 27989119 PMCID: PMC5241710 DOI: 10.1021/acs.chemrestox.6b00366] [Citation(s) in RCA: 76] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2016] [Indexed: 12/21/2022]
Abstract
Serum albumin (Alb) is the most abundant protein in blood plasma. Alb reacts with many carcinogens and/or their electrophilic metabolites. Studies conducted over 20 years ago showed that Alb forms adducts with the human carcinogens aflatoxin B1 and benzene, which were successfully used as biomarkers in molecular epidemiology studies designed to address the role of these chemicals in cancer risk. Alb forms adducts with many therapeutic drugs or their reactive metabolites such as β-lactam antibiotics, acetylsalicylic acid, acetaminophen, nonsteroidal anti-inflammatory drugs, chemotherapeutic agents, and antiretroviral therapy drugs. The identification and characterization of the adduct structures formed with Alb have served to understand the generation of reactive metabolites and to predict idiosyncratic drug reactions and toxicities. The reaction of candidate drugs with Alb is now exploited as part of the battery of screening tools to assess the potential toxicities of drugs. The use of gas chromatography-mass spectrometry, liquid chromatography, or liquid chromatography-mass spectrometry (LC-MS) enabled the identification and quantification of multiple types of Alb xenobiotic adducts in animals and humans during the past three decades. In this perspective, we highlight the history of Alb as a target protein for adduction to environmental and dietary genotoxicants, pesticides, and herbicides, common classes of medicinal drugs, and endogenous electrophiles, and the emerging analytical mass spectrometry technologies to identify Alb-toxicant adducts in humans.
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Affiliation(s)
- Gabriele Sabbioni
- Institute of Environmental and Occupational Toxicology, CH-6780 Airolo, Switzerland
- Alpine Institute of Chemistry and Toxicology, CH-6718 Olivone, Switzerland
- Walther-Straub-Institut für Pharmakologie
und Toxikologie, Ludwig-Maximilians-Universität München, D-80336 München, Germany
| | - Robert J. Turesky
- Masonic Cancer Center and Department of
Medicinal Chemistry, College of Pharmacy, University of Minnesota, 2231 Sixth Street SE, Minneapolis, Minnesota 55455, United States
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7
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Esterases hydrolyze phenyl valerate activity as targets of organophosphorus compounds. Chem Biol Interact 2016; 259:358-367. [DOI: 10.1016/j.cbi.2016.04.024] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2016] [Revised: 03/30/2016] [Accepted: 04/12/2016] [Indexed: 12/24/2022]
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8
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Sun F, Ding J, Yu H, Gao R, Wang H, Pei C. Identification of new binding sites of human transferrin incubated with organophosphorus agents via Q Exactive LC–MS/MS. J Chromatogr B Analyt Technol Biomed Life Sci 2016; 1022:256-264. [DOI: 10.1016/j.jchromb.2016.04.028] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2015] [Revised: 03/29/2016] [Accepted: 04/15/2016] [Indexed: 01/23/2023]
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9
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Yang X, Bartlett MG. Identification of protein adduction using mass spectrometry: Protein adducts as biomarkers and predictors of toxicity mechanisms. RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2016; 30:652-664. [PMID: 26842586 DOI: 10.1002/rcm.7462] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/08/2015] [Revised: 11/12/2015] [Accepted: 11/13/2015] [Indexed: 06/05/2023]
Abstract
The determination of protein-xenobiotic adducts using mass spectrometry is an emerging area which allows detailed understanding of the underlying mechanisms involved in toxicity. These approaches can also be used to reveal potential biomarkers of exposure or toxic response. The following review covers studies of protein adducts resulting from exposure to a wide variety of xenobiotics including organophosphates, polycyclic aromatic hydrocarbons, acetaminophen, alkylating agents and other related compounds.
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Affiliation(s)
- Xiangkun Yang
- Department of Pharmaceutical and Biomedical Sciences, College of Pharmacy, The University of Georgia, Athens, GA, 30602-2352, USA
| | - Michael G Bartlett
- Department of Pharmaceutical and Biomedical Sciences, College of Pharmacy, The University of Georgia, Athens, GA, 30602-2352, USA
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10
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Belabassi Y, Chao CK, Holly R, George KM, Nagy JO, Thompson CM. Preparation and characterization of diethoxy- and monoethoxy phosphylated ('aged') serine haptens and use in the production of monoclonal antibodies. Chem Biol Interact 2014; 223:134-40. [PMID: 25261769 DOI: 10.1016/j.cbi.2014.09.010] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2014] [Revised: 08/17/2014] [Accepted: 09/12/2014] [Indexed: 11/27/2022]
Abstract
In this study, the first mechanism-based monoclonal antibodies have been produced that recognize and differentiate diethoxy- and monoethoxyphosphorylated serine residues. Haptens were synthesized as the stable phosphonate form of phosphoserine esters to improve the immunoresponse. Following condensation with a glutaric anhydride to link the phosphoserine moieties to carrier protein, the hapten densities attached to bovine serum albumin and keyhole limpet henocyanin were determined by partial trypsin digestion and MALDI mass spectrometry, and confirmed using a fluorescent assay (FITC) to quantify unmodified lysine residues. The conjugation reactions were pH optimized to improve hapten density. Screening of subclones led to the identification of two monoclonal antibodies: (a) N257/25.11 that specifically recognizes (EtO)2P(O)-Ser as the phosphylated or inhibited form, and (b) N262/16 that recognizes (EtO)(HO)P(O)-Ser as the 'aged' form. Analysis of blood samples treated with paraoxon (EtO)2P(O)-OPhNO2 showed a concentration dependent recognition of the phosphylated form.
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Affiliation(s)
- Yamina Belabassi
- ATERIS Technologies LLC, 901 N Orange Street, Missoula, MT 59802, USA
| | - Chih-Kai Chao
- ATERIS Technologies LLC, 901 N Orange Street, Missoula, MT 59802, USA
| | - Ryan Holly
- ATERIS Technologies LLC, 901 N Orange Street, Missoula, MT 59802, USA
| | - Kathleen M George
- Department of Biomedical and Pharmaceutical Sciences, The University of Montana, Missoula, MT 59812, USA
| | - Jon O Nagy
- ATERIS Technologies LLC, 901 N Orange Street, Missoula, MT 59802, USA
| | - Charles M Thompson
- ATERIS Technologies LLC, 901 N Orange Street, Missoula, MT 59802, USA; Department of Biomedical and Pharmaceutical Sciences, The University of Montana, Missoula, MT 59812, USA.
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Bui-Nguyen TM, Dennis WE, Jackson DA, Stallings JD, Lewis JA. Detection of Dichlorvos Adducts in a Hepatocyte Cell Line. J Proteome Res 2014; 13:3583-95. [DOI: 10.1021/pr5000076] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Affiliation(s)
- Tri M. Bui-Nguyen
- Oak Ridge Institute
for Science and Education (ORISE) Postdoctoral Researcher, U.S. Army
Center for Environmental Health Research, 568 Doughten Drive, Fort Detrick, Maryland 21702, United States
| | - William E. Dennis
- U.S. Army Center for Environmental Health Research, 568 Doughten Drive, Fort
Detrick, Maryland 21702, United States
| | - David A. Jackson
- U.S. Army Center for Environmental Health Research, 568 Doughten Drive, Fort
Detrick, Maryland 21702, United States
| | - Jonathan D. Stallings
- U.S. Army Center for Environmental Health Research, 568 Doughten Drive, Fort
Detrick, Maryland 21702, United States
| | - John A. Lewis
- U.S. Army Center for Environmental Health Research, 568 Doughten Drive, Fort
Detrick, Maryland 21702, United States
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Flaskos J. The Neuronal Cytoskeleton as a Potential Target in the Developmental Neurotoxicity of Organophosphorothionate Insecticides. Basic Clin Pharmacol Toxicol 2014; 115:201-8. [DOI: 10.1111/bcpt.12204] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2013] [Accepted: 01/14/2014] [Indexed: 12/26/2022]
Affiliation(s)
- John Flaskos
- School of Veterinary Medicine; Aristotle University of Thessaloniki; Thessaloniki Greece
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13
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Li B, Duysen EG, Froment MT, Masson P, Nachon F, Jiang W, Schopfer LM, Thiele GM, Klassen LW, Cashman J, Williams GR, Lockridge O. Polyclonal antibody to soman-tyrosine. Chem Res Toxicol 2013; 26:584-92. [PMID: 23469927 DOI: 10.1021/tx400027n] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Soman forms a stable, covalent bond with tyrosine 411 of human albumin, with tyrosines 257 and 593 in human transferrin, and with tyrosine in many other proteins. The pinacolyl group of soman is retained, suggesting that pinacolyl methylphosphonate bound to tyrosine could generate specific antibodies. Tyrosine in the pentapeptide RYGRK was covalently modified with soman simply by adding soman to the peptide. The phosphonylated-peptide was linked to keyhole limpet hemocyanin, and the conjugate was injected into rabbits. The polyclonal antiserum recognized soman-labeled human albumin, soman-mouse albumin, and soman human transferrin but not nonphosphonylated control proteins. The soman-labeled tyrosines in these proteins are surrounded by different amino acid sequences, suggesting that the polyclonal recognizes soman-tyrosine independent of the amino acid sequence. Antiserum obtained after 4 antigen injections over a period of 18 weeks was tested in a competition ELISA where it had an IC50 of 10(-11) M. The limit of detection on Western blots was 0.01 μg (15 picomoles) of soman-labeled albumin. In conclusion, a high-affinity, polyclonal antibody that specifically recognizes soman adducts on tyrosine in a variety of proteins has been produced. Such an antibody could be useful for identifying secondary targets of soman toxicity.
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Affiliation(s)
- Bin Li
- Eppley Institute, University of Nebraska Medical Center , Omaha, Nebraska 68198-5950, United States
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14
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Protein adducts as biomarkers of exposure to organophosphorus compounds. Toxicology 2012; 307:46-54. [PMID: 23261756 DOI: 10.1016/j.tox.2012.12.007] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2012] [Revised: 12/11/2012] [Accepted: 12/13/2012] [Indexed: 01/11/2023]
Abstract
Exposure to organophosphorus (OP) compounds can lead to serious neurological damage or death. Following bioactivation by the liver cytochromes P450, the OP metabolites produced are potent inhibitors of serine active-site enzymes including esterases, proteases and lipases. OPs may form adducts on other cellular proteins. Blood cholinesterases (ChEs) have long served as biomarkers of OP exposure in humans. However, the enzymatic assays used for biomonitoring OP exposures have several drawbacks. A more useful approach will focus on multiple biomarkers and avoid problems with the enzymatic activity assays. OP inhibitory effects result from a covalent bond with the active-site serine of the target enzymes. The serine OP adducts become irreversible following a process referred to as aging where one alkyl group dissociates over variable lengths of time depending on the OP adduct. The OP-adducted enzyme then remains in circulation until it is degraded, allowing for a longer window of detection compared with direct analysis of OPs or their metabolites. Mass spectrometry (MS) provides a very sensitive method for identification of post-translational protein modifications. MS analyses of the percentage adduction of the active-site serine of biomarker proteins such as ChEs will eliminate the need for basal activity levels of the individual and will provide for a more accurate determination of OP exposure. MS analysis of biomarker proteins also provides information about the OP that has caused inhibition. Other useful biomarker proteins include other serine hydrolases, albumin, tubulin and transferrin.
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15
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Acute poisoning with sarin causes alteration in oxidative homeostasis and biochemical markers in Wistar rats. J Appl Biomed 2012. [DOI: 10.2478/v10136-012-0010-2] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
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16
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Liyasova MS, Schopfer LM, Lockridge O. Cresyl saligenin phosphate, an organophosphorus toxicant, makes covalent adducts with histidine, lysine, and tyrosine residues of human serum albumin. Chem Res Toxicol 2012; 25:1752-61. [PMID: 22793878 DOI: 10.1021/tx300215g] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
CBDP [2-(2-cresyl)-4H-1-3-2-benzodioxaphosphorin-2-oxide] is a toxic organophosphorus compound. It is generated in vivo from tri-ortho-cresyl phosphate (TOCP), a component of jet engine oil and hydraulic fluids. Exposure to TOCP was proven to occur on board aircraft by finding CBDP-derived phospho-butyrylcholinesterase in the blood of passengers. Adducts on BChE, however, do not explain the toxicity of CBDP. Critical target proteins of CBDP are yet to be identified. Our goal was to facilitate the search for the critical targets of CBDP by determining the range of amino acid residues capable of reacting with CBDP and characterizing the types of adducts formed. We used human albumin as a model protein. Mass spectral analysis of the tryptic digest of CBDP-treated human albumin revealed adducts on His-67, His-146, His-242, His-247, His-338, Tyr-138, Tyr-140, Lys-199, Lys-351, Lys-414, Lys-432, and Lys-525. Adducts formed on tyrosine residues were different from those formed on histidines and lysines. Tyrosines were organophosphorylated by CBDP, while histidine and lysine residues were alkylated. This is the first report of an organophosphorus compound with both phosphorylating and alkylating properties. The o-hydroxybenzyl adduct on histidine is novel. The ability of CBDP to form stable adducts on histidine, tyrosine, and lysine allows one to consider new mechanisms of toxicity from TOCP exposure.
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Affiliation(s)
- Mariya S Liyasova
- Department of Environmental, Agricultural & Occupational Health, University of Nebraska Medical Center, Omaha, NE 68198-5950, USA
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Jiang W, Duysen EG, Lockridge O. Mice treated with a nontoxic dose of chlorpyrifos oxon have diethoxyphosphotyrosine labeled proteins in blood up to 4 days post exposure, detected by mass spectrometry. Toxicology 2012; 295:15-22. [PMID: 22406659 DOI: 10.1016/j.tox.2012.03.001] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2012] [Revised: 02/28/2012] [Accepted: 03/01/2012] [Indexed: 11/18/2022]
Abstract
Inhibition of acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) activity is an established biomarker of exposure to organophosphorus poisons (OP). Inhibition of activity is due to covalent binding of the OP to the active site serine. Mass spectrometry has made it possible to monitor OP exposure by analyzing OP adducts on tyrosine in proteins that have no active site serine. Our goal was to test the hypothesis that OP-tyrosine may serve as a biomarker of OP exposure in mice. A MALDI-TOF mass spectrometry strategy to analyze diethoxyphosphate-tyrosine of m/z 318 was developed. The adduct was synthesized by incubating l-tyrosine with chlorpyrifos oxon at pH 8.1. The adduct eluted from a reverse phase HPLC column with 22-23% acetonitrile. The fragmentation spectrum of the m/z 318 precursor ion confirmed its identity as diethoxyphosphate-tyrosine. Diethoxyphosphate-tyrosine was isolated from chlorpyrifos oxon treated mouse albumin after digesting the protein with pronase. Mice (n=3 per group) were treated with a nontoxic dose of chlorpyrifos oxon (3 mg/kg) and a toxic dose (10 mg/kg transdermally). The pronase digested plasma yielded diethoxyphosphate-tyrosine up to 120 h after treatment with 3 mg/kg chlorpyrifos oxon and up to 144 h after 10 mg/kg. In contrast plasma AChE activity returned to normal after 24-72 h. In conclusion MALDI-TOF mass spectrometry can be used to diagnose exposure to chlorpyrifos oxon days after AChE inhibition assays are uninformative.
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Affiliation(s)
- Wei Jiang
- Department of Environmental, Agricultural and Occupational Health, University of Nebraska Medical Center, Omaha, NE 68198-5950, United States.
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18
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Neurodegenerations Induced by Organophosphorous Compounds. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2012; 724:189-204. [DOI: 10.1007/978-1-4614-0653-2_15] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
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Lockridge O, Schopfer LM. Review of tyrosine and lysine as new motifs for organophosphate binding to proteins that have no active site serine. Chem Biol Interact 2010; 187:344-8. [PMID: 20211158 PMCID: PMC2905678 DOI: 10.1016/j.cbi.2010.03.002] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2009] [Revised: 02/27/2010] [Accepted: 03/02/2010] [Indexed: 10/19/2022]
Abstract
The accepted target for organophosphorus agent (OP) binding to enzymes is the active site serine in the consensus sequence Gly X Ser X Gly. New motifs have been identified by using mass spectrometry to fragment OP-labeled peptides. It has been found that OP can make covalent bonds with tyrosine and lysine in proteins that have no active site serine. The OP-tyrosine bond is stable, and does not undergo the decay seen with OP-serine. Information on OP binding to tyrosine has been applied to diagnosis of OP exposure, through the use of mass spectrometry to detect OP-labeled albumin in human and animal plasma. It is expected that the new OP binding motif will aid in the search for a mechanism of low dose OP toxicity. It is hypothesized that proteins involved in axonal transport, especially proteins whose function depends on reversible phosphorylation, are prime candidates for a role in OP-induced neurodegeneration. Treatment of neurodegenerative disorders could be developed by identifying methods to reverse OP binding to tyrosine.
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Affiliation(s)
- Oksana Lockridge
- Eppley Institute, 985950 University of Nebraska Medical Center, Omaha, NE 68198-5950, United States.
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20
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Schopfer LM, Grigoryan H, Li B, Nachon F, Masson P, Lockridge O. Mass spectral characterization of organophosphate-labeled, tyrosine-containing peptides: characteristic mass fragments and a new binding motif for organophosphates. J Chromatogr B Analyt Technol Biomed Life Sci 2010; 878:1297-311. [PMID: 19762289 PMCID: PMC2860652 DOI: 10.1016/j.jchromb.2009.07.026] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2009] [Revised: 07/11/2009] [Accepted: 07/17/2009] [Indexed: 10/20/2022]
Abstract
We have identified organophosphorus agent (OP)-tyrosine adducts on 12 different proteins labeled with six different OP. Labeling was achieved by treating pure proteins with up to 40-fold molar excess of OP at pH 8-8.6. OP-treated proteins were digested with trypsin, and peptides were separated by HPLC. Fragmentation patterns for 100 OP-peptides labeled on tyrosine were determined in the mass spectrometer. The goals of the present work were (1) to determine the common features of the OP-reactive tyrosines, and (2) to describe non-sequence MSMS fragments characteristic of OP-tyrosine peptides. Characteristic ions at 272 and 244 amu for tyrosine-OP immonium ions were nearly always present in the MSMS spectrum of peptides labeled on tyrosine by chlorpyrifos-oxon. Characteristic fragments also appeared from the parent ions that had been labeled with diisopropylfluorophosphate (216 amu), sarin (214 amu), soman (214 amu) or FP-biotin (227, 312, 329, 691 and 708 amu). In contrast to OP-reactive serines, which lie in the consensus sequence GXSXG, the OP-reactive tyrosines have no consensus sequence. Their common feature is the presence of nearby positively charged residues that activate the phenolic hydroxyl group. The significance of these findings is the recognition of a new binding motif for OP to proteins that have no active site serine. Modified peptides are difficult to find when the OP bears no radiolabel and no tag. The characteristic MSMS fragment ions are valuable because they are identifiers for OP-tyrosine, independent of the peptide.
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Affiliation(s)
| | - Hasmik Grigoryan
- Eppley Institute, University of Nebraska Medical Center, Omaha, NE, 68198
| | - Bin Li
- Eppley Institute, University of Nebraska Medical Center, Omaha, NE, 68198
| | - Florian Nachon
- Centre de Recherches du Service de Santé des Armées, Toxicology Dept, BP87, 38702 La Tronche Cedex, France
| | - Patrick Masson
- Centre de Recherches du Service de Santé des Armées, Toxicology Dept, BP87, 38702 La Tronche Cedex, France
| | - Oksana Lockridge
- Eppley Institute, University of Nebraska Medical Center, Omaha, NE, 68198
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21
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Jiang W, Duysen EG, Hansen H, Shlyakhtenko L, Schopfer LM, Lockridge O. Mice treated with chlorpyrifos or chlorpyrifos oxon have organophosphorylated tubulin in the brain and disrupted microtubule structures, suggesting a role for tubulin in neurotoxicity associated with exposure to organophosphorus agents. Toxicol Sci 2010; 115:183-93. [PMID: 20142434 DOI: 10.1093/toxsci/kfq032] [Citation(s) in RCA: 71] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
Exposure to organophosphorus (OP) agents can lead to learning and memory deficits. Disruption of axonal transport has been proposed as a possible explanation. Microtubules are an essential component of axonal transport. In vitro studies have demonstrated that OP agents react with tubulin and disrupt the structure of microtubules. Our goal was to determine whether in vivo exposure affects microtubule structure. One group of mice was treated daily for 14 days with a dose of chlorpyrifos that did not significantly inhibit acetylcholinesterase. Beta-tubulin from the brains of these mice was diethoxyphosphorylated on tyrosine 281 in peptide GSQQY(281)RALTVPELTQQMFDSK. A second group of mice was treated with a single sublethal dose of chlorpyrifos oxon (CPO). Microtubules and cosedimenting proteins from the brains of these mice were visualized by atomic force microscopy nanoimaging and by Coomassie blue staining of polyacrylamide gel electrophoresis bands. Proteins in gel slices were identified by mass spectrometry. Nanoimaging showed that microtubules from control mice were decorated with many proteins, whereas microtubules from CPO-treated mice had fewer associated proteins, a result confirmed by mass spectrometry of proteins extracted from gel slices. The dimensions of microtubules from CPO-treated mice (height 8.7 +/- 3.1 nm and width 36.5 +/- 15.5 nm) were about 60% of those from control mice (height 13.6 +/- 3.6 nm and width 64.8 +/- 15.9 nm). A third group of mice was treated with six sublethal doses of CPO over 50.15 h. Mass spectrometry identified diethoxyphosphorylated serine 338 in peptide NS(338)NFVEWIPNNVK of beta-tubulin. In conclusion, microtubules from mice exposed to chlorpyrifos or to CPO have covalently modified amino acids and abnormal structure, suggesting disruption of microtubule function. Covalent binding of CPO to tubulin and to tubulin-associated proteins is a potential mechanism of neurotoxicity.
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Affiliation(s)
- Wei Jiang
- Eppley Institute, University of Nebraska Medical Center, Omaha, Nebraska 68198-5950, USA
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Butyrylcholinesterase for protection from organophosphorus poisons: catalytic complexities and hysteretic behavior. Arch Biochem Biophys 2009; 494:107-20. [PMID: 20004171 DOI: 10.1016/j.abb.2009.12.005] [Citation(s) in RCA: 163] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2009] [Revised: 11/24/2009] [Accepted: 12/01/2009] [Indexed: 12/13/2022]
Abstract
Butyrylcholinesterase is a promiscuous enzyme that displays complex kinetic behavior. It is toxicologically important because it detoxifies organophosphorus poisons (OP) by making a covalent bond with the OP. The OP and the butyrylcholinesterase are both inactivated in the process. Inactivation of butyrylcholinesterase has no adverse effects. However, inactivation of acetylcholinesterase in nerve synapses can be lethal. OP-inhibited butyrylcholinesterase and acetylcholinesterase can be reactivated with oximes provided the OP has not aged. Strategies for preventing the toxicity of OP include (a) treatment with an OP scavenger, (b) reaction of non-aged enzyme with oximes, (c) reactivation of aged enzyme, (d) slowing down aging with peripheral site ligands, and (e) design of mutants that rapidly hydrolyze OP. Option (a) has progressed through phase I clinical trials with human butyrylcholinesterase. Option (b) is in routine clinical use. The others are at the basic research level. Butyrylcholinesterase displays complex kinetic behavior including activation by positively charged esters, ability to hydrolyze amides, and a lag time (hysteresis) preceding hydrolysis of benzoylcholine and N-methylindoxyl acetate. Mass spectrometry has identified new OP binding motifs on tyrosine and lysine in proteins that have no active site serine. It is proposed, but not yet proven, that low dose exposure involves OP modification of proteins that have no active site serine.
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Paradox findings may challenge orthodox reasoning in acute organophosphate poisoning. Chem Biol Interact 2009; 187:270-8. [PMID: 19883634 DOI: 10.1016/j.cbi.2009.10.014] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2009] [Revised: 10/17/2009] [Accepted: 10/20/2009] [Indexed: 12/15/2022]
Abstract
It is generally accepted that inhibition of acetylcholinesterase (AChE) is the most important acute toxic action of organophosphorus compounds, leading to accumulation of acetylcholine followed by a dysfunction of cholinergic signaling. However, the degree of AChE inhibition is not uniformly correlated with cholinergic dysfunction, probably because the excess of essential AChE varies among tissues. Moreover, the cholinergic system shows remarkable plasticity, allowing modulations to compensate for dysfunctions of the canonical pathway. A prominent example is the living (-/-) AChE knockout mouse. Clinical experience indicates that precipitous inhibition of AChE leads to more severe poisoning than more protracted yet finally complete inhibition. The former situation is seen in parathion, the latter in oxydemeton methyl poisoning. At first glance, this dichotomy is surprising since parathion is a pro-poison and has to be activated to the oxon, while the latter is still the ultimate inhibitor. Also oxime therapy in organophosphorus poisoning apparently gives perplexing results: Oximes are usually able to reactivate diethylphosphorylated AChE, but the efficiency may be occasionally markedly smaller than expected from kinetic data. Dimethylphosphorylated AChE is in general less amenable to oxime therapy, which largely fails in some cases of dimethoate poisoning where aging was much faster than expected from a dimethylphosphorylated enzyme. Similarly, poisoning by profenofos, an O,S-dialkyl phosphate, leads to a rapidly aged enzyme. Most surprisingly, these patients were usually well on admission, yet their erythrocyte AChE was completely inhibited. Analysis of the kinetic constants of the most important reaction pathways, determination of the reactant concentrations in vivo and comparison with computer simulations may reveal unexpected toxic reactions. Pertinent examples will be presented and the potentially underlying phenomena discussed.
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Grigoryan H, Li B, Xue W, Grigoryan M, Schopfer LM, Lockridge O. Mass spectral characterization of organophosphate-labeled lysine in peptides. Anal Biochem 2009; 394:92-100. [PMID: 19596251 DOI: 10.1016/j.ab.2009.07.008] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2009] [Revised: 07/01/2009] [Accepted: 07/02/2009] [Indexed: 12/13/2022]
Abstract
Organophosphate (OP) esters bind covalently to the active site serine of enzymes in the serine hydrolase family. Recently, mass spectrometry identified covalent binding of OPs to tyrosine in a wide variety of proteins when purified proteins were incubated with OPs. In the current work, manual inspection of tandem mass spectrometry (MS/MS) data led to the realization that lysines also make a covalent bond with OPs. OP-labeled lysine residues were found in seven proteins that had been treated with either chlorpyrifos oxon (CPO) or diisopropylfluorophosphate (DFP): human serum albumin (K212, K414, K199, and K351), human keratin 1 (K211 and K355), human keratin 10 (K163), bovine tubulin alpha (K60, K336, K163, K394, and K401), bovine tubulin beta (K58), bovine actin (K113, K291, K326, K315, and K328), and mouse transferrin (K296 and K626). These results suggest that OP binding to lysine is a general phenomenon. Characteristic fragments specific for CPO-labeled lysine appeared at 237.1, 220.0, 192.0, 163.9, 128.9, and 83.9amu. Characteristic fragments specific for DFP-labeled lysine appeared at 164.0, 181.2, and 83.8amu. This new OP-binding motif to lysine suggests new directions to search for mechanisms of long-term effects of OP exposure and in the search for biomarkers of OP exposure.
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Affiliation(s)
- Hasmik Grigoryan
- Eppley Institute, University of Nebraska Medical Center, Omaha, NE 68198, USA
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Grigoryan H, Li B, Anderson EK, Xue W, Nachon F, Lockridge O, Schopfer LM. Covalent binding of the organophosphorus agent FP-biotin to tyrosine in eight proteins that have no active site serine. Chem Biol Interact 2009; 180:492-8. [PMID: 19539807 DOI: 10.1016/j.cbi.2009.03.018] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2009] [Revised: 03/23/2009] [Accepted: 03/24/2009] [Indexed: 11/25/2022]
Abstract
Organophosphorus (OP) esters are known to bind covalently to the active site serine of enzymes in the serine hydrolase family. It was a surprise to find that proteins with no active site serine are also covalently modified by OP. The binding site in albumin, transferrin, and tubulin was identified as tyrosine. The goal of the present work was to determine whether binding to tyrosine is a general phenomenon. Fourteen proteins were treated with a biotin-tagged organophosphorus agent called FP-biotin. The proteins were digested with trypsin and the labeled peptides enriched by binding to monomeric avidin. Peptides were purified by HPLC and fragmented by collision induced dissociation in a tandem ion trap mass spectrometer. Eight proteins were labeled and six were not. Tyrosine was labeled in human alpha-2-glycoprotein 1 zinc-binding protein (Tyr 138, Tyr 174 and Tyr 181), human kinesin 3C motor domain (Tyr 145), human keratin 1 (Tyr 230), bovine actin (Tyr 55 and Tyr 200), murine ATP synthase beta (Tyr 431), murine adenine nucleotide translocase 1 (Tyr 81), bovine chymotrypsinogen (Tyr 201) and porcine pepsin (Tyr 310). Only 1-3 tyrosines per protein were modified, suggesting that the reactive tyrosine was activated by nearby residues that facilitated ionization of the hydroxyl group of tyrosine. These results suggest that OP binding to tyrosine is a general phenomenon. It is concluded that organophosphorus-reactive proteins include not only enzymes in the serine hydrolase family, but also proteins that have no active site serine. The recognition of a new OP-binding motif to tyrosine suggests new directions to search for mechanisms of long-term effects of OP exposure. Another application is in the search for biomarkers of organophosphorus agent exposure. Previous searches have been limited to serine hydrolases. Now proteins such as albumin and keratin can be considered.
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Affiliation(s)
- Hasmik Grigoryan
- Eppley Institute, University of Nebraska Medical Center, 986805 Nebraska Medical Center, Omaha, NE 68198-6805, United States.
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