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Santiago-Maldonado X, Rodríguez-Martínez JA, López L, Cunci L, Bayro M, Nicolau E. Selection, characterization, and biosensing applications of DNA aptamers targeting cyanotoxin BMAA. RSC Adv 2024; 14:13787-13800. [PMID: 38681844 PMCID: PMC11046380 DOI: 10.1039/d4ra02384f] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2024] [Accepted: 04/19/2024] [Indexed: 05/01/2024] Open
Abstract
Scientists have established a connection between environmental exposure to toxins like β-N-methylamino-l-alanine (BMAA) and a heightened risk of neurodegenerative disorders. BMAA is a byproduct from certain strains of cyanobacteria that are present in ecosystems worldwide and is renowned for its bioaccumulation and biomagnification in seafood. The sensitivity, selectivity, and reproducibility of the current analytical techniques are insufficient to support efforts regarding food safety and environment monitoring adequately. This work outlines the in vitro selection of BMAA-specific DNA aptamers via the systematic evolution of ligands through exponential enrichment (SELEX). Screening and characterization of the full-length aptamers was achieved using the SYBR Green (SG) fluorescence displacement assay. Aptamers BMAA_159 and BMAA_165 showed the highest binding affinities, with dissociation constants (Kd) of 2.2 ± 0.1 μM and 0.32 ± 0.02 μM, respectively. After truncation, the binding affinity was confirmed using a BMAA-conjugated fluorescence assay. The Kd values for BMAA_159_min and BMAA_165_min were 6 ± 1 μM and 0.63 ± 0.02 μM, respectively. Alterations in the amino proton region studied using solution nuclear magnetic resonance (NMR) provided further evidence of aptamer-target binding. Additionally, circular dichroism (CD) spectroscopy revealed that BMAA_165_min forms hybrid G-quadruplex (G4) structures. Finally, BMAA_165_min was used in the development of an electrochemical aptamer-based (EAB) sensor that accomplished sensitive and selective detection of BMAA with a limit of detection (LOD) of 1.13 ± 0.02 pM.
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Affiliation(s)
- Xaimara Santiago-Maldonado
- Department of Chemistry, University of Puerto Rico San Juan PR 00925-2437 USA +1-787-522-2150 +1-787-292-9820
| | | | - Luis López
- Department of Chemistry, University of Puerto Rico San Juan PR 00925-2437 USA +1-787-522-2150 +1-787-292-9820
| | - Lisandro Cunci
- Department of Chemistry, University of Puerto Rico San Juan PR 00925-2437 USA +1-787-522-2150 +1-787-292-9820
| | - Marvin Bayro
- Department of Chemistry, University of Puerto Rico San Juan PR 00925-2437 USA +1-787-522-2150 +1-787-292-9820
- Molecular Science Research Center, University of Puerto Rico San Juan 00931-3346 USA
| | - Eduardo Nicolau
- Department of Chemistry, University of Puerto Rico San Juan PR 00925-2437 USA +1-787-522-2150 +1-787-292-9820
- Molecular Science Research Center, University of Puerto Rico San Juan 00931-3346 USA
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Mohamed ZA, Elnour RO, Alamri S, Hashem M, Campos A, Vasconcelos V, Badawye H. Presence of the neurotoxin β-N-methylamino-L-alanine in irrigation water and accumulation in cereal grains with human exposure risk. ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2024:10.1007/s11356-024-33188-y. [PMID: 38635096 DOI: 10.1007/s11356-024-33188-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/03/2023] [Accepted: 03/29/2024] [Indexed: 04/19/2024]
Abstract
The present study demonstrates the presence of the neurotoxin β-N-methylamino-L-alanine and its cyanobacterial producers in irrigation water and grains of some cereal plants from farmlands irrigated with Nile River water in Egypt. BMAA detected by LC-MS/MS in phytoplankton samples was found at higher concentrations of free form (0.84-11.4 μg L-1) than of protein-bound form (0.16-1.6 μg L-1), in association with the dominance of cyanobacteria in irrigation water canals. Dominant cyanobacterial species isolated from these irrigation waters including Aphanocapsa planctonica, Chroococcus minutus, Dolichospermum lemmermanni, Nostoc commune, and Oscillatoria tenuis were found to produce different concentrations of free (4.8-71.1 µg g-1 dry weight) and protein-bound (0.1-11.4 µg g-1 dry weight) BMAA. In the meantime, BMAA was also detected in a protein-bound form only in grains of corn (3.87-4.51 µg g-1 fresh weight) and sorghum (5.1-7.1 µg g-1 fresh weight) plants, but not in wheat grains. The amounts of BMAA accumulated in these grains correlated with BMAA concentrations detected in relevant irrigation water canals. The presence of BMAA in cereal grains would constitute a risk to human and animal health upon consumption of contaminated grains. The study, therefore, suggests continuous monitoring of BMAA and other cyanotoxins in irrigation waters and edible plants to protect the public against exposure to such potent toxins.
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Affiliation(s)
- Zakaria A Mohamed
- Department of Botany and Microbiology, Faculty of Science, Sohag University, Sohag, 82524, Egypt.
| | - Rehab O Elnour
- Biology Department, Faculty of Sciences and Arts, Dahran Al-Janoub, King Khalid University, Abha, Saudi Arabia
| | - Saad Alamri
- Department of Biology, College of Science, King Khalid University, Abha, 61413, Saudi Arabia
| | - Mohamed Hashem
- Department of Biology, College of Science, King Khalid University, Abha, 61413, Saudi Arabia
| | - Alexandre Campos
- CIIMAR, Interdisciplinary Centre of Marine and Environmental Research, Terminal de Cruzeiros Do Porto de Leixões, Av. General Norton de Matos, S/N, 4450-208, Matosinhos, Portugal
| | - Vitor Vasconcelos
- CIIMAR, Interdisciplinary Centre of Marine and Environmental Research, Terminal de Cruzeiros Do Porto de Leixões, Av. General Norton de Matos, S/N, 4450-208, Matosinhos, Portugal
- Departament of Biology, Faculty of Sciences, University of Porto, Rua Do Campo Alegre, 4169-007, Porto, Portugal
| | - Hanan Badawye
- Department of Botany and Microbiology, Faculty of Science, Sohag University, Sohag, 82524, Egypt
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Bishop SL, Solonenka JT, Giebelhaus RT, Bakker DTR, Li ITS, Murch SJ. Microbial Diversity Impacts Non-Protein Amino Acid Production in Cyanobacterial Bloom Cultures Collected from Lake Winnipeg. Toxins (Basel) 2024; 16:169. [PMID: 38668594 PMCID: PMC11053616 DOI: 10.3390/toxins16040169] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2024] [Revised: 03/10/2024] [Accepted: 03/20/2024] [Indexed: 04/29/2024] Open
Abstract
Lake Winnipeg in Manitoba, Canada is heavily impacted by harmful algal blooms that contain non-protein amino acids (NPAAs) produced by cyanobacteria: N-(2-aminoethyl)glycine (AEG), β-aminomethyl-L-alanine (BAMA), β-N-methylamino-L-alanine (BMAA), and 2,4-diaminobutyric acid (DAB). Our objective was to investigate the impact of microbial diversity on NPAA production by cyanobacteria using semi-purified crude cyanobacterial cultures established from field samples collected by the Lake Winnipeg Research Consortium between 2016 and 2021. NPAAs were detected and quantified by ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) using validated analytical methods, while Shannon and Simpson alpha diversity scores were determined from 16S rRNA metagenomic sequences. Alpha diversity in isolate cultures was significantly decreased compared to crude cyanobacterial cultures (p < 0.001), indicating successful semi-purification. BMAA and AEG concentrations were higher in crude compared to isolate cultures (p < 0.0001), and AEG concentrations were correlated to the alpha diversity in cultures (r = 0.554; p < 0.0001). BAMA concentrations were increased in isolate cultures (p < 0.05), while DAB concentrations were similar in crude and isolate cultures. These results demonstrate that microbial community complexity impacts NPAA production by cyanobacteria and related organisms.
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Affiliation(s)
- Stephanie L. Bishop
- Department of Chemistry, University of British Columbia, Syilx Okanagan Nation Territory, Kelowna, BC V1V 1V7, Canada; (J.T.S.); (R.T.G.); (D.T.R.B.); (I.T.S.L.); (S.J.M.)
- Department of Biological Sciences, University of Calgary, Calgary, AB T2N 1N4, Canada
| | - Julia T. Solonenka
- Department of Chemistry, University of British Columbia, Syilx Okanagan Nation Territory, Kelowna, BC V1V 1V7, Canada; (J.T.S.); (R.T.G.); (D.T.R.B.); (I.T.S.L.); (S.J.M.)
| | - Ryland T. Giebelhaus
- Department of Chemistry, University of British Columbia, Syilx Okanagan Nation Territory, Kelowna, BC V1V 1V7, Canada; (J.T.S.); (R.T.G.); (D.T.R.B.); (I.T.S.L.); (S.J.M.)
- Department of Chemistry, University of Alberta, Edmonton, AB T6G 2N4, Canada
- The Metabolomics Innovation Centre, Edmonton, AB T6G 2N4, Canada
| | - David T. R. Bakker
- Department of Chemistry, University of British Columbia, Syilx Okanagan Nation Territory, Kelowna, BC V1V 1V7, Canada; (J.T.S.); (R.T.G.); (D.T.R.B.); (I.T.S.L.); (S.J.M.)
| | - Isaac T. S. Li
- Department of Chemistry, University of British Columbia, Syilx Okanagan Nation Territory, Kelowna, BC V1V 1V7, Canada; (J.T.S.); (R.T.G.); (D.T.R.B.); (I.T.S.L.); (S.J.M.)
| | - Susan J. Murch
- Department of Chemistry, University of British Columbia, Syilx Okanagan Nation Territory, Kelowna, BC V1V 1V7, Canada; (J.T.S.); (R.T.G.); (D.T.R.B.); (I.T.S.L.); (S.J.M.)
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Wang ZQ, Yang Y, Zhang JY, Zeng X, Zhang CC. Global translational control by the transcriptional repressor TrcR in the filamentous cyanobacterium Anabaena sp. PCC 7120. Commun Biol 2023; 6:643. [PMID: 37322092 PMCID: PMC10272220 DOI: 10.1038/s42003-023-05012-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2023] [Accepted: 06/02/2023] [Indexed: 06/17/2023] Open
Abstract
Transcriptional and translational regulations are important mechanisms for cell adaptation to environmental conditions. In addition to house-keeping tRNAs, the genome of the filamentous cyanobacterium Anabaena sp. strain PCC 7120 (Anabaena) has a long tRNA operon (trn operon) consisting of 26 genes present on a megaplasmid. The trn operon is repressed under standard culture conditions, but is activated under translational stress in the presence of antibiotics targeting translation. Using the toxic amino acid analog β-N-methylamino-L-alanine (BMAA) as a tool, we isolated and characterized several BMAA-resistance mutants from Anabaena, and identified one gene of unknown function, all0854, named as trcR, encoding a transcription factor belonging to the ribbon-helix-helix (RHH) family. We provide evidence that TrcR represses the expression of the trn operon and is thus the missing link between the trn operon and translational stress response. TrcR represses the expression of several other genes involved in translational control, and is required for maintaining translational fidelity. TrcR, as well as its binding sites, are highly conserved in cyanobacteria, and its functions represent an important mechanism for the coupling of the transcriptional and translational regulations in cyanobacteria.
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Affiliation(s)
- Zi-Qian Wang
- State Key Laboratory of Freshwater Ecology and Biotechnology and Key Laboratory of Algal Biology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, Hubei, 430072, People's Republic of China.
- University of Chinese Academy of Sciences, Beijing, 100049, People's Republic of China.
- State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China.
| | - Yiling Yang
- State Key Laboratory of Freshwater Ecology and Biotechnology and Key Laboratory of Algal Biology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, Hubei, 430072, People's Republic of China
| | - Ju-Yuan Zhang
- State Key Laboratory of Freshwater Ecology and Biotechnology and Key Laboratory of Algal Biology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, Hubei, 430072, People's Republic of China
| | - Xiaoli Zeng
- State Key Laboratory of Freshwater Ecology and Biotechnology and Key Laboratory of Algal Biology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, Hubei, 430072, People's Republic of China
| | - Cheng-Cai Zhang
- State Key Laboratory of Freshwater Ecology and Biotechnology and Key Laboratory of Algal Biology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, Hubei, 430072, People's Republic of China.
- Institute AMU-WUT, Aix-Marseille Université and Wuhan University of Technology, Wuhan, Hubei, People's Republic of China.
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Li A, Liu J, Qiu J, Wang G, Zheng X, Ji Y, Yan G, Zhao P, Wu X, Yan W, Zhang L, Li M, Fu Y. Cell cycle of microalga Isochrysis galbana arrested by neurotoxin β-N-methylamino-l-alanine and corresponding molecular mechanisms. THE SCIENCE OF THE TOTAL ENVIRONMENT 2023; 874:162445. [PMID: 36848993 DOI: 10.1016/j.scitotenv.2023.162445] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/13/2022] [Revised: 02/20/2023] [Accepted: 02/20/2023] [Indexed: 06/18/2023]
Abstract
The phycotoxin β-N-methylamino-l-alanine (BMAA) has attracted attention due to its risks to marine organisms and human health. In this study, approximately 85 % of synchronized cells of the marine microalga Isochrysis galbana were arrested at the cell cycle G1 phase by BMAA at 6.5 μM for a 24-h exposure. The concentration of chlorophyll a (Chl a) gradually decreased, while the maximum quantum yield of PSII (Fv/Fm), the maximum relative electron transport rate (rETRmax), light utilization efficiency (α) and half-saturated light irradiance (Ik) reduced early and recovered gradually in I. galbana exposed to BMAA in 96-h batch cultures. Transcriptional expression of I. galbana analyzed at 10, 12, and 16 h disclosed multiple mechanisms of BMAA to suppress the microalgal growth. Production of ammonia and glutamate was limited by the down-regulation of nitrate transporters, glutamate synthase, glutamine synthetase, cyanate hydrolase, and formamidase. Diverse extrinsic proteins related to PSII, PSI, cytochrome b6f complex, and ATPase were influenced by BMAA at transcriptional level. Suppression of the DNA replication and mismatch repair pathways increased the accumulation of misfolded proteins, which was reflected by the up-regulated expression of proteasome to accelerate proteolysis. This study improves our understanding of the chemical ecology impacts of BMAA in marine ecosystems.
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Affiliation(s)
- Aifeng Li
- College of Environmental Science and Engineering, Ocean University of China, Qingdao 266100, China; Key Laboratory of Marine Environment and Ecology, Ocean University of China, Ministry of Education, Qingdao 266100, China.
| | - Jianwei Liu
- College of Environmental Science and Engineering, Ocean University of China, Qingdao 266100, China
| | - Jiangbing Qiu
- College of Environmental Science and Engineering, Ocean University of China, Qingdao 266100, China; Key Laboratory of Marine Environment and Ecology, Ocean University of China, Ministry of Education, Qingdao 266100, China
| | - Guixiang Wang
- College of Environmental Science and Engineering, Ocean University of China, Qingdao 266100, China
| | - Xianyao Zheng
- College of Environmental Science and Engineering, Ocean University of China, Qingdao 266100, China
| | - Ying Ji
- College of Environmental Science and Engineering, Ocean University of China, Qingdao 266100, China
| | - Guowang Yan
- College of Environmental Science and Engineering, Ocean University of China, Qingdao 266100, China
| | - Peng Zhao
- College of Environmental Science and Engineering, Ocean University of China, Qingdao 266100, China
| | - Xizhen Wu
- College of Environmental Science and Engineering, Ocean University of China, Qingdao 266100, China
| | - Wenhui Yan
- College of Environmental Science and Engineering, Ocean University of China, Qingdao 266100, China
| | - Lei Zhang
- College of Environmental Science and Engineering, Ocean University of China, Qingdao 266100, China
| | - Min Li
- College of Environmental Science and Engineering, Ocean University of China, Qingdao 266100, China
| | - Yilei Fu
- College of Environmental Science and Engineering, Ocean University of China, Qingdao 266100, China
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Méresse S, Larrigaldie V, Oummadi A, de Concini V, Morisset-Lopez S, Reverchon F, Menuet A, Montécot-Dubourg C, Mortaud S. β-N-Methyl-Amino-L-Alanine cyanotoxin promotes modification of undifferentiated cells population and disrupts the inflammatory status in primary cultures of neural stem cells. Toxicology 2022; 482:153358. [DOI: 10.1016/j.tox.2022.153358] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2022] [Revised: 10/06/2022] [Accepted: 10/24/2022] [Indexed: 11/07/2022]
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Non-Proteinogenic Amino Acid β-N-Methylamino-L-Alanine (BMAA): Bioactivity and Ecological Significance. Toxins (Basel) 2022; 14:toxins14080539. [PMID: 36006201 PMCID: PMC9414260 DOI: 10.3390/toxins14080539] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2022] [Revised: 07/28/2022] [Accepted: 08/04/2022] [Indexed: 11/21/2022] Open
Abstract
Research interest in a non-protein amino acid β-N-methylamino-L-alanine (BMAA) arose due to the discovery of a connection between exposure to BMAA and the occurrence of neurodegenerative diseases. Previous reviews on this topic either considered BMAA as a risk factor for neurodegenerative diseases or focused on the problems of detecting BMAA in various environmental samples. Our review is devoted to a wide range of fundamental biological problems related to BMAA, including the molecular mechanisms of biological activity of BMAA and the complex relationships between producers of BMAA and the environment in various natural ecosystems. At the beginning, we briefly recall the most important facts about the producers of BMAA (cyanobacteria, microalgae, and bacteria), the pathways of BMAA biosynthesis, and reliable methods of identification of BMAA. The main distinctive feature of our review is a detailed examination of the molecular mechanisms underlying the toxicity of BMAA to living cells. A brand new aspect, not previously discussed in any reviews, is the effect of BMAA on cyanobacterial cells. These recent studies, conducted using transcriptomics and proteomics, revealed potent regulatory effects of BMAA on the basic metabolism and cell development of these ancient photoautotrophic prokaryotes. Exogenous BMAA strongly influences cell differentiation and primary metabolic processes in cyanobacteria, such as nitrogen fixation, photosynthesis, carbon fixation, and various biosynthetic processes involving 2-oxoglutarate and glutamate. Cyanobacteria were found to be more sensitive to exogenous BMAA under nitrogen-limited growth conditions. We suggest a hypothesis that this toxic diaminoacid can be used by phytoplankton organisms as a possible allelopathic tool for controlling the population of cyanobacterial cells during a period of intense competition for nitrogen and other resources in various ecosystems.
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Schwarze B, Korn A, Höfling C, Zeitschel U, Krueger M, Roßner S, Huster D. Peptide backbone modifications of amyloid β (1-40) impact fibrillation behavior and neuronal toxicity. Sci Rep 2021; 11:23767. [PMID: 34887476 PMCID: PMC8660793 DOI: 10.1038/s41598-021-03091-4] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2021] [Accepted: 11/25/2021] [Indexed: 11/23/2022] Open
Abstract
Fibril formation of amyloid β (Aβ) peptides is one of the key molecular events connected to Alzheimer's disease. The pathway of formation and mechanism of action of Aβ aggregates in biological systems is still object of very active research. To this end, systematic modifications of the Phe19-Leu34 hydrophobic contact, which has been reported in almost all structural studies of Aβ40 fibrils, helps understanding Aβ folding pathways and the underlying free energy landscape of the amyloid formation process. In our approach, a series of Aβ40 peptide variants with two types of backbone modifications, namely incorporation of (i) a methylene or an ethylene spacer group and (ii) a N-methylation at the amide functional group, of the amino acids at positions 19 or 34 was applied. These mutations are expected to challenge the inter-β-strand side chain contacts as well as intermolecular backbone β-sheet hydrogen bridges. Using a multitude of biophysical methods, it is shown that these backbone modifications lead, in most of the cases, to alterations in the fibril formation kinetics, a higher local structural heterogeneity, and a somewhat modified fibril morphology without generally impairing the fibril formation capacity of the peptides. The toxicological profile found for the variants depend on the type and extent of the modification.
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Affiliation(s)
- Benedikt Schwarze
- Institute for Medical Physics and Biophysics, Leipzig University, Härtelstr. 16/18, 04107, Leipzig, Germany
| | - Alexander Korn
- Institute for Medical Physics and Biophysics, Leipzig University, Härtelstr. 16/18, 04107, Leipzig, Germany
| | - Corinna Höfling
- Paul Flechsig Institute for Brain Research, Leipzig University, Liebigstr. 19, 04103, Leipzig, Germany
| | - Ulrike Zeitschel
- Paul Flechsig Institute for Brain Research, Leipzig University, Liebigstr. 19, 04103, Leipzig, Germany
| | - Martin Krueger
- Institute of Anatomy, Leipzig University, Liebigstr. 13, 04103, Leipzig, Germany
| | - Steffen Roßner
- Paul Flechsig Institute for Brain Research, Leipzig University, Liebigstr. 19, 04103, Leipzig, Germany
| | - Daniel Huster
- Institute for Medical Physics and Biophysics, Leipzig University, Härtelstr. 16/18, 04107, Leipzig, Germany.
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Probing the Influence of Single-Site Mutations in the Central Cross-β Region of Amyloid β (1-40) Peptides. Biomolecules 2021; 11:biom11121848. [PMID: 34944492 PMCID: PMC8699037 DOI: 10.3390/biom11121848] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2021] [Revised: 12/02/2021] [Accepted: 12/07/2021] [Indexed: 11/16/2022] Open
Abstract
Amyloid β (Aβ) is a peptide known to form amyloid fibrils in the brain of patients suffering from Alzheimer’s disease. A complete mechanistic understanding how Aβ peptides form neurotoxic assemblies and how they kill neurons has not yet been achieved. Previous analysis of various Aβ40 mutants could reveal the significant importance of the hydrophobic contact between the residues Phe19 and Leu34 for cell toxicity. For some mutations at Phe19, toxicity was completely abolished. In the current study, we assessed if perturbations introduced by mutations in the direct proximity of the Phe19/Leu34 contact would have similar relevance for the fibrillation kinetics, structure, dynamics and toxicity of the Aβ assemblies. To this end, we rationally modified positions Phe20 or Gly33. A small library of Aβ40 peptides with Phe20 mutated to Lys, Tyr or the non-proteinogenic cyclohexylalanine (Cha) or Gly33 mutated to Ala was synthesized. We used electron microscopy, circular dichroism, X-ray diffraction, solid-state NMR spectroscopy, ThT fluorescence and MTT cell toxicity assays to comprehensively investigate the physicochemical properties of the Aβ fibrils formed by the modified peptides as well as toxicity to a neuronal cell line. Single mutations of either Phe20 or Gly33 led to relatively drastic alterations in the Aβ fibrillation kinetics but left the global, as well as the local structure, of the fibrils largely unchanged. Furthermore, the introduced perturbations caused a severe decrease or loss of cell toxicity compared to wildtype Aβ40. We suggest that perturbations at position Phe20 and Gly33 affect the fibrillation pathway of Aβ40 and, thereby, influence the especially toxic oligomeric species manifesting so that the region around the Phe19/Leu34 hydrophobic contact provides a promising site for the design of small molecules interfering with the Aβ fibrillation pathway.
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Das A, Korn A, Carroll A, Carver JA, Maiti S. Application of the Double-Mutant Cycle Strategy to Protein Aggregation Reveals Transient Interactions in Amyloid-β Oligomers. J Phys Chem B 2021; 125:12426-12435. [PMID: 34748334 DOI: 10.1021/acs.jpcb.1c05829] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Transient oligomeric intermediates in the peptide or protein aggregation pathway are suspected to be the key toxic species in many amyloid diseases, but deciphering their molecular nature has remained a challenge. Here we show that the strategy of "double-mutant cycles", used effectively in probing protein-folding intermediates, can reveal transient interactions during protein aggregation. It does so by comparing the changes in thermodynamic parameters between the wild type, and single and double mutants. We demonstrate the strategy by probing the possible transient salt bridge partner of lysine 28 (K28) in the oligomeric states of amyloid β-40 (Aβ40), the putative toxic species in Alzheimer's disease. In mature fibrils, the binding partner is aspartate 23. This interaction differentiates Aβ40 from the more toxic Aβ42, where K28's binding partner is the C-terminal carboxylate. We selectively acetylated K28 and amidated the C-terminus of Aβ40, creating four distinct variants. Spectroscopic measurements of the kinetics and thermodynamics of aggregation show that K28 and the C-terminus interact transiently in the early phases of the Aβ40 aggregation pathway. Hydrogen-deuterium exchange mass spectrometry (using a simple analysis method that we introduce here that takes into account the isotopic mass distribution) supports this interpretation. It is also supported by cellular toxicity measurements, suggesting possible similarities in the mechanisms of toxicity of Aβ40 oligomers (which are more toxic than Aβ40 fibrils) and Aβ42. Our results show that double-mutant cycles can be a powerful tool for probing transient interactions during protein aggregation.
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Affiliation(s)
- Anirban Das
- Department of Chemical Sciences, Tata Institute of Fundamental Research, Homi Bhabha Road, Colaba, Mumbai 400005, India
| | - Alexander Korn
- Institute for Medical Physics and Biophysics, Leipzig University, Härtelstr. 16-18, D-04107 Leipzig, Germany
| | - Adam Carroll
- Research School of Chemistry, The Australian National University, Acton, Australian Capital Territory 2601, Australia
| | - John A Carver
- Research School of Chemistry, The Australian National University, Acton, Australian Capital Territory 2601, Australia
| | - Sudipta Maiti
- Department of Chemical Sciences, Tata Institute of Fundamental Research, Homi Bhabha Road, Colaba, Mumbai 400005, India
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Wang C, Yan C, Qiu J, Liu C, Yan Y, Ji Y, Wang G, Chen H, Li Y, Li A. Food web biomagnification of the neurotoxin β-N-methylamino-L-alanine in a diatom-dominated marine ecosystem in China. JOURNAL OF HAZARDOUS MATERIALS 2021; 404:124217. [PMID: 33129020 DOI: 10.1016/j.jhazmat.2020.124217] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/22/2020] [Revised: 09/25/2020] [Accepted: 10/05/2020] [Indexed: 06/11/2023]
Abstract
The neurotoxin β-N-methylamino-L-alanine (BMAA) reported in some cyanobacteria and eukaryote microalgae is a cause of concern due to its potential risk of human neurodegenerative diseases. Here, BMAA distribution in phytoplankton, zooplankton, and other marine organisms was investigated in Jiaozhou Bay, China, a diatom-dominated marine ecosystem, during four seasons in 2019. Results showed that BMAA was biomagnified in the food web from phytoplankton to higher trophic levels. Trophic magnification factors (TMFs) for zooplankton, bivalve mollusks, carnivorous crustaceans and carnivorous gastropod mollusks were ca. 4.58, 30.1, 42.5, and 74.4, respectively. Putative identification of β-amino-N-methylalanine (BAMA), an isomer of BMAA, was frequently detected in phytoplankton samples. A total of 56 diatom strains of the genera Pseudo-nitzschia, Thalassiosira, Chaetoceros, Planktoniella, and Minidiscus isolated from the Chinese coast were cultured in the laboratory, among which 21 strains contained BMAA mainly in precipitated bound form at toxin concentrations ranging from 0.11 to 3.95 µg/g dry weight. Only 2,4-diaminobutyric acid (DAB) but not BMAA or BAMA was detected in seven species of bacteria isolated from the gut of gastropod Neverita didyma, suggesting that this benthic vector of BMAA may have accumulated this compound via trophic transfer.
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Affiliation(s)
- Chao Wang
- College of Environmental Science and Engineering, Ocean University of China, Qingdao 266100, China; Key Laboratory of Marine Environment and Ecology, Ocean University of China, Ministry of Education, Qingdao 266100, China
| | - Chen Yan
- College of Environmental Science and Engineering, Ocean University of China, Qingdao 266100, China; Key Laboratory of Marine Environment and Ecology, Ocean University of China, Ministry of Education, Qingdao 266100, China
| | - Jiangbing Qiu
- College of Environmental Science and Engineering, Ocean University of China, Qingdao 266100, China; Key Laboratory of Marine Environment and Ecology, Ocean University of China, Ministry of Education, Qingdao 266100, China
| | - Chao Liu
- College of Environmental Science and Engineering, Ocean University of China, Qingdao 266100, China; Key Laboratory of Marine Environment and Ecology, Ocean University of China, Ministry of Education, Qingdao 266100, China
| | - Yeju Yan
- College of Environmental Science and Engineering, Ocean University of China, Qingdao 266100, China; Key Laboratory of Marine Environment and Ecology, Ocean University of China, Ministry of Education, Qingdao 266100, China
| | - Ying Ji
- College of Environmental Science and Engineering, Ocean University of China, Qingdao 266100, China; Key Laboratory of Marine Environment and Ecology, Ocean University of China, Ministry of Education, Qingdao 266100, China
| | - Guixiang Wang
- College of Environmental Science and Engineering, Ocean University of China, Qingdao 266100, China; Key Laboratory of Marine Environment and Ecology, Ocean University of China, Ministry of Education, Qingdao 266100, China
| | - Hongju Chen
- College of Environmental Science and Engineering, Ocean University of China, Qingdao 266100, China; Key Laboratory of Marine Environment and Ecology, Ocean University of China, Ministry of Education, Qingdao 266100, China
| | - Yang Li
- Guangdong Provincial Key Laboratory of Healthy and Safe Aquaculture, College of Life Science, South China Normal University, Guangzhou 510631, China
| | - Aifeng Li
- College of Environmental Science and Engineering, Ocean University of China, Qingdao 266100, China; Key Laboratory of Marine Environment and Ecology, Ocean University of China, Ministry of Education, Qingdao 266100, China.
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Ra D, Sa B, Sl B, Js M, Sj M, DA D, Ew S, O K, Eb B, Ad C, Vx T, Gg G, Pa C, Dc M, Wg B. Is Exposure to BMAA a Risk Factor for Neurodegenerative Diseases? A Response to a Critical Review of the BMAA Hypothesis. Neurotox Res 2021; 39:81-106. [PMID: 33547590 PMCID: PMC7904546 DOI: 10.1007/s12640-020-00302-0] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2020] [Revised: 10/19/2020] [Accepted: 10/20/2020] [Indexed: 12/15/2022]
Abstract
In a literature survey, Chernoff et al. (2017) dismissed the hypothesis that chronic exposure to β-N-methylamino-L-alanine (BMAA) may be a risk factor for progressive neurodegenerative disease. They question the growing scientific literature that suggests the following: (1) BMAA exposure causes ALS/PDC among the indigenous Chamorro people of Guam; (2) Guamanian ALS/PDC shares clinical and neuropathological features with Alzheimer’s disease, Parkinson’s disease, and ALS; (3) one possible mechanism for protein misfolds is misincorporation of BMAA into proteins as a substitute for L-serine; and (4) chronic exposure to BMAA through diet or environmental exposures to cyanobacterial blooms can cause neurodegenerative disease. We here identify multiple errors in their critique including the following: (1) their review selectively cites the published literature; (2) the authors reported favorably on HILIC methods of BMAA detection while the literature shows significant matrix effects and peak coelution in HILIC that may prevent detection and quantification of BMAA in cyanobacteria; (3) the authors build alternative arguments to the BMAA hypothesis, rather than explain the published literature which, to date, has been unable to refute the BMAA hypothesis; and (4) the authors erroneously attribute methods to incorrect studies, indicative of a failure to carefully consider all relevant publications. The lack of attention to BMAA research begins with the review’s title which incorrectly refers to BMAA as a “non-essential” amino acid. Research regarding chronic exposure to BMAA as a cause of human neurodegenerative diseases is emerging and requires additional resources, validation, and research. Here, we propose strategies for improvement in the execution and reporting of analytical methods and the need for additional and well-executed inter-lab comparisons for BMAA quantitation. We emphasize the need for optimization and validation of analytical methods to ensure that they are fit-for-purpose. Although there remain gaps in the literature, an increasingly large body of data from multiple independent labs using orthogonal methods provides increasing evidence that chronic exposure to BMAA may be a risk factor for neurological illness.
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Affiliation(s)
- Dunlop Ra
- Brain Chemistry Labs, Institute for Ethnomedicine, Jackson, WY, USA.
| | - Banack Sa
- Brain Chemistry Labs, Institute for Ethnomedicine, Jackson, WY, USA
| | - Bishop Sl
- Lewis Research Group, Faculty of Science, University of Calgary, Alberta, Canada
| | - Metcalf Js
- Brain Chemistry Labs, Institute for Ethnomedicine, Jackson, WY, USA
| | - Murch Sj
- Department of Chemistry, University of British Columbia, Kelowna, BC, Canada
| | - Davis DA
- Department of Neurology, Miller School of Medicine, University of Miami, Miami, FL, USA
| | - Stommel Ew
- Department of Neurology, Dartmouth-Hitchcock Medical Center, Lebanon, NH, USA
| | - Karlsson O
- Department of Environmental Science, Stockholm University, Stockholm, Sweden
| | - Brittebo Eb
- Department of Pharmaceutical Biosciences, Uppsala University, Uppsala, Sweden
| | | | - Tan Vx
- Department of Biological Sciences, Macquarie University Centre for Motor Neuron Disease Research, Macquarie University, Ryde, Australia
| | - Guillemin Gg
- Department of Biological Sciences, Macquarie University Centre for Motor Neuron Disease Research, Macquarie University, Ryde, Australia
| | - Cox Pa
- Brain Chemistry Labs, Institute for Ethnomedicine, Jackson, WY, USA
| | - Mash Dc
- Nova Southeastern University, Fort Lauderdale, FL, USA
| | - Bradley Wg
- Department of Neurology, Miller School of Medicine, University of Miami, Miami, FL, USA
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13
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Western Pacific ALS-PDC: Evidence implicating cycad genotoxins. J Neurol Sci 2020; 419:117185. [PMID: 33190068 DOI: 10.1016/j.jns.2020.117185] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2020] [Revised: 09/20/2020] [Accepted: 09/29/2020] [Indexed: 12/12/2022]
Abstract
Amyotrophic Lateral Sclerosis and Parkinsonism-Dementia Complex (ALS-PDC) is a disappearing neurodegenerative disorder of apparent environmental origin formerly hyperendemic among Chamorros of Guam-USA, Japanese residents of the Kii Peninsula, Honshu Island, Japan and Auyu-Jakai linguistic groups of Papua-Indonesia on the island of New Guinea. The most plausible etiology is exposure to genotoxins in seed of neurotoxic cycad plants formerly used for food and/or medicine. Primary suspicion falls on methylazoxymethanol (MAM), the aglycone of cycasin and on the non-protein amino acid β-N-methylamino-L-alanine, both of which are metabolized to formaldehyde. Human and animal studies suggest: (a) exposures occurred early in life and sometimes during late fetal brain development, (b) clinical expression of neurodegenerative disease appeared years or decades later, and (c) pathological changes in various tissues indicate the disease was not confined to the CNS. Experimental evidence points to toxic molecular mechanisms involving DNA damage, epigenetic changes, transcriptional mutagenesis, neuronal cell-cycle reactivation and perturbation of the ubiquitin-proteasome system that led to polyproteinopathy and culminated in neuronal degeneration. Lessons learned from research on ALS-PDC include: (a) familial disease may reflect common toxic exposures across generations, (b) primary disease prevention follows cessation of exposure to culpable environmental triggers; and (c) disease latency provides a prolonged period during which to intervene therapeutically. Exposure to genotoxic chemicals ("slow toxins") in the early stages of life should be considered in the search for the etiology of ALS-PDC-related neurodegenerative disorders, including sporadic forms of ALS, progressive supranuclear palsy and Alzheimer's disease.
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