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Van Den Berghe T, Babin D, Chen M, Callens M, Brack D, Maes H, Lievens J, Lammens M, Van Sumere M, Morbée L, Hautekeete S, Schatteman S, Jacobs T, Thooft WJ, Herregods N, Huysse W, Jaremko JL, Lambert R, Maksymowych W, Laloo F, Baraliakos X, De Craemer AS, Carron P, Van den Bosch F, Elewaut D, Jans L. Neural network algorithm for detection of erosions and ankylosis on CT of the sacroiliac joints: multicentre development and validation of diagnostic accuracy. Eur Radiol 2023; 33:8310-8323. [PMID: 37219619 DOI: 10.1007/s00330-023-09704-y] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2022] [Revised: 03/03/2023] [Accepted: 03/25/2023] [Indexed: 05/24/2023]
Abstract
OBJECTIVES To evaluate the feasibility and diagnostic accuracy of a deep learning network for detection of structural lesions of sacroiliitis on multicentre pelvic CT scans. METHODS Pelvic CT scans of 145 patients (81 female, 121 Ghent University/24 Alberta University, 18-87 years old, mean 40 ± 13 years, 2005-2021) with a clinical suspicion of sacroiliitis were retrospectively included. After manual sacroiliac joint (SIJ) segmentation and structural lesion annotation, a U-Net for SIJ segmentation and two separate convolutional neural networks (CNN) for erosion and ankylosis detection were trained. In-training validation and tenfold validation testing (U-Net-n = 10 × 58; CNN-n = 10 × 29) on a test dataset were performed to assess performance on a slice-by-slice and patient level (dice coefficient/accuracy/sensitivity/specificity/positive and negative predictive value/ROC AUC). Patient-level optimisation was applied to increase the performance regarding predefined statistical metrics. Gradient-weighted class activation mapping (Grad-CAM++) heatmap explainability analysis highlighted image parts with statistically important regions for algorithmic decisions. RESULTS Regarding SIJ segmentation, a dice coefficient of 0.75 was obtained in the test dataset. For slice-by-slice structural lesion detection, a sensitivity/specificity/ROC AUC of 95%/89%/0.92 and 93%/91%/0.91 were obtained in the test dataset for erosion and ankylosis detection, respectively. For patient-level lesion detection after pipeline optimisation for predefined statistical metrics, a sensitivity/specificity of 95%/85% and 82%/97% were obtained for erosion and ankylosis detection, respectively. Grad-CAM++ explainability analysis highlighted cortical edges as focus for pipeline decisions. CONCLUSIONS An optimised deep learning pipeline, including an explainability analysis, detects structural lesions of sacroiliitis on pelvic CT scans with excellent statistical performance on a slice-by-slice and patient level. CLINICAL RELEVANCE STATEMENT An optimised deep learning pipeline, including a robust explainability analysis, detects structural lesions of sacroiliitis on pelvic CT scans with excellent statistical metrics on a slice-by-slice and patient level. KEY POINTS • Structural lesions of sacroiliitis can be detected automatically in pelvic CT scans. • Both automatic segmentation and disease detection yield excellent statistical outcome metrics. • The algorithm takes decisions based on cortical edges, rendering an explainable solution.
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Affiliation(s)
- Thomas Van Den Berghe
- Department of Radiology and Medical Imaging, Ghent University Hospital, Corneel Heymanslaan 10, 9000, Ghent, Belgium.
| | - Danilo Babin
- Department of Telecommunication and Information Processing - Image Processing and Interpretation (TELIN-IPI), Faculty of Engineering and Architecture, Ghent University - IMEC, Sint-Pietersnieuwstraat 41, 9000, Ghent, Belgium
| | - Min Chen
- Department of Radiology, Peking University Shenzhen Hospital, Shenzhen, 518036, China
| | - Martijn Callens
- Department of Radiology and Medical Imaging, Ghent University Hospital, Corneel Heymanslaan 10, 9000, Ghent, Belgium
| | - Denim Brack
- Department of Radiology and Medical Imaging, Ghent University Hospital, Corneel Heymanslaan 10, 9000, Ghent, Belgium
| | - Helena Maes
- Department of Radiology and Medical Imaging, Ghent University Hospital, Corneel Heymanslaan 10, 9000, Ghent, Belgium
| | - Jan Lievens
- Department of Radiology and Medical Imaging, Ghent University Hospital, Corneel Heymanslaan 10, 9000, Ghent, Belgium
| | - Marie Lammens
- Department of Radiology and Medical Imaging, Ghent University Hospital, Corneel Heymanslaan 10, 9000, Ghent, Belgium
| | - Maxime Van Sumere
- Department of Radiology and Medical Imaging, Ghent University Hospital, Corneel Heymanslaan 10, 9000, Ghent, Belgium
| | - Lieve Morbée
- Department of Radiology and Medical Imaging, Ghent University Hospital, Corneel Heymanslaan 10, 9000, Ghent, Belgium
| | - Simon Hautekeete
- Department of Radiology and Medical Imaging, Ghent University Hospital, Corneel Heymanslaan 10, 9000, Ghent, Belgium
| | - Stijn Schatteman
- Department of Radiology and Medical Imaging, Ghent University Hospital, Corneel Heymanslaan 10, 9000, Ghent, Belgium
| | - Tom Jacobs
- Department of Radiology and Medical Imaging, Ghent University Hospital, Corneel Heymanslaan 10, 9000, Ghent, Belgium
| | - Willem-Jan Thooft
- Department of Radiology and Medical Imaging, Ghent University Hospital, Corneel Heymanslaan 10, 9000, Ghent, Belgium
| | - Nele Herregods
- Department of Radiology and Medical Imaging, Ghent University Hospital, Corneel Heymanslaan 10, 9000, Ghent, Belgium
| | - Wouter Huysse
- Department of Radiology and Medical Imaging, Ghent University Hospital, Corneel Heymanslaan 10, 9000, Ghent, Belgium
| | - Jacob L Jaremko
- Department of Radiology and Diagnostic Imaging and Rheumatology, University of Alberta, 8440 122 Street NW, Edmonton, Alberta, T6G 2B7, Canada
| | - Robert Lambert
- Department of Radiology and Diagnostic Imaging and Rheumatology, University of Alberta, 8440 122 Street NW, Edmonton, Alberta, T6G 2B7, Canada
| | - Walter Maksymowych
- Department of Radiology and Diagnostic Imaging and Rheumatology, University of Alberta, 8440 122 Street NW, Edmonton, Alberta, T6G 2B7, Canada
| | - Frederiek Laloo
- Department of Radiology and Medical Imaging, Ghent University Hospital, Corneel Heymanslaan 10, 9000, Ghent, Belgium
| | - Xenofon Baraliakos
- Rheumazentrum Ruhrgebiet Herne, Ruhr-University Bochum, Claudiusstraße 45, 44649, Herne, Germany
| | - Ann-Sophie De Craemer
- Department of Rheumatology, Ghent University Hospital, Corneel Heymanslaan 10, 9000, Ghent, Belgium
- Vlaams Instituut voor Biotechnologie (VIB) Centre for Inflammation Research (IRC), Ghent University, Technologiepark 927, 9052, Ghent, Belgium
| | - Philippe Carron
- Department of Rheumatology, Ghent University Hospital, Corneel Heymanslaan 10, 9000, Ghent, Belgium
- Vlaams Instituut voor Biotechnologie (VIB) Centre for Inflammation Research (IRC), Ghent University, Technologiepark 927, 9052, Ghent, Belgium
| | - Filip Van den Bosch
- Department of Rheumatology, Ghent University Hospital, Corneel Heymanslaan 10, 9000, Ghent, Belgium
- Vlaams Instituut voor Biotechnologie (VIB) Centre for Inflammation Research (IRC), Ghent University, Technologiepark 927, 9052, Ghent, Belgium
| | - Dirk Elewaut
- Department of Rheumatology, Ghent University Hospital, Corneel Heymanslaan 10, 9000, Ghent, Belgium
- Vlaams Instituut voor Biotechnologie (VIB) Centre for Inflammation Research (IRC), Ghent University, Technologiepark 927, 9052, Ghent, Belgium
| | - Lennart Jans
- Department of Radiology and Medical Imaging, Ghent University Hospital, Corneel Heymanslaan 10, 9000, Ghent, Belgium
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Houwenhuyse S, Callens M, Bulteel L, Decaestecker E. Comparison between the gut bacterial community of laboratory cultured and wild Daphnia. FEMS Microbiol Ecol 2023; 99:fiad116. [PMID: 37740575 DOI: 10.1093/femsec/fiad116] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2023] [Revised: 09/14/2023] [Accepted: 09/21/2023] [Indexed: 09/24/2023] Open
Abstract
The fitness of an organism is often impacted by the composition and biological activity of its associated bacterial community. Many factors, including host genetics, diet, and temperature can influence the bacterial community composition. Furthermore, these factors can differ strongly between natural and laboratory environments. Consequently, several studies have highlighted results from laboratory experiments investigating host-associated bacterial communities to be conflicting with those obtained under field conditions. Here, we compared the Daphnia magna gut bacterial communities in natural host populations with those of laboratory cultured hosts. We further analyzed changes in the gut bacterial communities after transferring hosts from natural populations to the laboratory on the short- and long-term. Results show that, in general, the gut bacterial communities from natural populations differ from those of laboratory cultures and that their composition and diversity changed one hour after being transferred to the laboratory. Over the following 14 days, the composition and diversity changed gradually. On the longer term (after two years of rearing hosts in the laboratory) the composition and diversity of the gut bacterial communities was strongly altered compared to the initial state. Our findings indicate that the gut bacterial communities of Daphnia magna in laboratory experiments is not representative for natural field conditions, and that caution should be taken when interpreting results from laboratory experiments for natural settings.
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Affiliation(s)
- Shira Houwenhuyse
- Laboratory of Aquatic Biology, Department of Biology, University of Leuven- KU Leuven, Campus KULAK, E. Sabbelaan 53, 8500 Kortrijk, Belgium
- Laboratory of Microbiology, Department of Biochemistry and Microbiology, Faculty of Sciences, Gent University, Karel Lodewijk Ledeganckstraat 35, 9000, Gent, Belgium
| | - Martijn Callens
- Laboratory of Aquatic Biology, Department of Biology, University of Leuven- KU Leuven, Campus KULAK, E. Sabbelaan 53, 8500 Kortrijk, Belgium
- Animal Sciences Unit - Aquatic Environment and Quality, Flanders Research Institute for Agriculture, Fisheries and Food, Oostende 8400, Belgium
| | - Lore Bulteel
- Laboratory of Aquatic Biology, Department of Biology, University of Leuven- KU Leuven, Campus KULAK, E. Sabbelaan 53, 8500 Kortrijk, Belgium
| | - Ellen Decaestecker
- Laboratory of Aquatic Biology, Department of Biology, University of Leuven- KU Leuven, Campus KULAK, E. Sabbelaan 53, 8500 Kortrijk, Belgium
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Callens M, Rose CJ, Finnegan M, Gatchitch F, Simon L, Hamet J, Pradier L, Dubois MP, Bedhomme S. Hypermutator emergence in experimental Escherichia coli populations is stress-type dependent. Evol Lett 2023; 7:252-261. [PMID: 37475751 PMCID: PMC10355175 DOI: 10.1093/evlett/qrad019] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2023] [Revised: 04/04/2023] [Accepted: 04/21/2023] [Indexed: 07/22/2023] Open
Abstract
Genotypes exhibiting an increased mutation rate, called hypermutators, can propagate in microbial populations because they can have an advantage due to the higher supply of beneficial mutations needed for adaptation. Although this is a frequently observed phenomenon in natural and laboratory populations, little is known about the influence of parameters such as the degree of maladaptation, stress intensity, and the genetic architecture for adaptation on the emergence of hypermutators. To address this knowledge gap, we measured the emergence of hypermutators over ~1,000 generations in experimental Escherichia coli populations exposed to different levels of osmotic or antibiotic stress. Our stress types were chosen based on the assumption that the genetic architecture for adaptation differs between them. Indeed, we show that the size of the genetic basis for adaptation is larger for osmotic stress compared to antibiotic stress. During our experiment, we observed an increased emergence of hypermutators in populations exposed to osmotic stress but not in those exposed to antibiotic stress, indicating that hypermutator emergence rates are stress type dependent. These results support our hypothesis that hypermutator emergence is linked to the size of the genetic basis for adaptation. In addition, we identified other parameters that covaried with stress type (stress level and IS transposition rates) that might have contributed to an increased hypermutator provision and selection. Our results provide a first comparison of hypermutator emergence rates under varying stress conditions and point towards complex interactions of multiple stress-related factors on the evolution of mutation rates.
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Affiliation(s)
- Martijn Callens
- CEFE, CNRS, University of Montpellier, EPHE, IRD, Montpellier, France
- Animal Sciences Unit—Aquatic Environment and Quality, Flanders Research Institute for Agriculture, Fisheries and Food, Oostende, Belgium
| | - Caroline J Rose
- CEFE, CNRS, University of Montpellier, EPHE, IRD, Montpellier, France
| | - Michael Finnegan
- CEFE, CNRS, University of Montpellier, EPHE, IRD, Montpellier, France
| | | | - Léna Simon
- CEFE, CNRS, University of Montpellier, EPHE, IRD, Montpellier, France
- Université Clermont Auvergne, VetAgro Sup, Lempdes, France
| | - Jeanne Hamet
- CEFE, CNRS, University of Montpellier, EPHE, IRD, Montpellier, France
| | - Léa Pradier
- CEFE, CNRS, University of Montpellier, EPHE, IRD, Montpellier, France
| | | | - Stéphanie Bedhomme
- Corresponding author: CEFE, 1919 route de Mende, 34293 Montpellier, France.
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Chernyuk D, Callens M, Polozova M, Gordeev A, Chigriai M, Rakovskaya A, Ilina A, Pchitskaya E, Van den Haute C, Vervliet T, Bultynck G, Bezprozvanny I. Neuroprotective properties of anti-apoptotic BCL-2 proteins in 5xFAD mouse model of Alzheimer's disease. IBRO Neurosci Rep 2023; 14:273-283. [PMID: 36926591 PMCID: PMC10011438 DOI: 10.1016/j.ibneur.2023.02.005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2022] [Revised: 01/31/2023] [Accepted: 02/21/2023] [Indexed: 02/25/2023] Open
Abstract
Alzheimer's disease (AD) is the most common cause of dementia. An early feature of the AD pathology is the dysregulation of intracellular Ca2+ signaling in neurons. In particular, increased Ca2+ release from endoplasmic reticulum-located Ca2+ channels, including inositol-1,4,5-trisphosphate type 1 receptors (IP3R1) and ryanodine receptors type 2 (RyR2), have been extensively reported. Known for its anti-apoptotic properties, Bcl-2 also has the ability to bind to and inhibit the Ca2+-flux properties of IP3Rs and RyRs. In this study, the hypothesis that the expression of Bcl-2 proteins can normalize dysregulated Ca2+ signaling in a mouse model of AD (5xFAD) and thereby prevent or slow the progression of AD was examined. Therefore, stereotactic injections of adeno-associated viral vectors expressing Bcl-2 proteins were performed in the CA1 region of the 5xFAD mouse hippocampus. In order to assess the importance of the association with IP3R1, the Bcl-2K17D mutant was also included in these experiments. This K17D mutation has been previously shown to decrease the association of Bcl-2 with IP3R1, thereby impairing its ability to inhibit IP3R1 while not affecting Bcl-2's ability to inhibit RyRs. Here, we demonstrate that Bcl-2 protein expression leads to synaptoprotective and amyloid-protective effects in the 5xFAD animal model. Several of these neuroprotective features are also observed by Bcl-2K17D protein expression, suggesting that these effects are not associated with Bcl-2-mediated inhibition of IP3R1. Potential mechanisms for this Bcl-2 synaptoprotective action may be related to its ability to inhibit RyR2 activity as Bcl-2 and Bcl-2K17D are equally potent in inhibiting RyR2-mediated Ca2+ fluxes. This work indicates that Bcl-2-based strategies hold neuroprotective potential in AD models, though the underlying mechanisms requires further investigation.
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Affiliation(s)
- D Chernyuk
- Laboratory of Molecular Neurodegeneration, Peter the Great St. Petersburg State Polytechnic University, Saint Petersburg, Russia
| | - M Callens
- KU Leuven, Laboratory of Molecular & Cellular Signaling, Department of Cellular & Molecular Medicine, Campus Gasthuisberg O/N-I bus 802, Herestraat 49, BE-3000 Leuven, Belgium
| | - M Polozova
- Laboratory of Molecular Neurodegeneration, Peter the Great St. Petersburg State Polytechnic University, Saint Petersburg, Russia
| | - A Gordeev
- Laboratory of Molecular Neurodegeneration, Peter the Great St. Petersburg State Polytechnic University, Saint Petersburg, Russia
| | - M Chigriai
- Laboratory of Molecular Neurodegeneration, Peter the Great St. Petersburg State Polytechnic University, Saint Petersburg, Russia
| | - A Rakovskaya
- Laboratory of Molecular Neurodegeneration, Peter the Great St. Petersburg State Polytechnic University, Saint Petersburg, Russia
| | - A Ilina
- Laboratory of Molecular Neurodegeneration, Peter the Great St. Petersburg State Polytechnic University, Saint Petersburg, Russia
| | - E Pchitskaya
- Laboratory of Molecular Neurodegeneration, Peter the Great St. Petersburg State Polytechnic University, Saint Petersburg, Russia
| | - C Van den Haute
- KU Leuven, Research Group for Neurobiology and Gene Therapy, Department of Neurosciences, Campus Gasthuisberg O/N-5 box 1023, Herestraat 49, BE-3000 Leuven, Belgium.,Leuven Viral Vector Core, BE-3000 Leuven, Belgium
| | - T Vervliet
- KU Leuven, Laboratory of Molecular & Cellular Signaling, Department of Cellular & Molecular Medicine, Campus Gasthuisberg O/N-I bus 802, Herestraat 49, BE-3000 Leuven, Belgium
| | - G Bultynck
- KU Leuven, Laboratory of Molecular & Cellular Signaling, Department of Cellular & Molecular Medicine, Campus Gasthuisberg O/N-I bus 802, Herestraat 49, BE-3000 Leuven, Belgium
| | - I Bezprozvanny
- Laboratory of Molecular Neurodegeneration, Peter the Great St. Petersburg State Polytechnic University, Saint Petersburg, Russia.,Department of Physiology, UT Southwestern Medical Center at Dallas, Dallas, TX, USA
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Tavelli R, Callens M, Grootaert C, Abdallah MF, Rajkovic A. Foodborne pathogens in the plastisphere: Can microplastics in the food chain threaten microbial food safety? Trends Food Sci Technol 2022. [DOI: 10.1016/j.tifs.2022.08.021] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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Callens M, Scornavacca C, Bedhomme S. Evolutionary responses to codon usage of horizontally transferred genes in Pseudomonas aeruginosa: gene retention, amelioration and compensatory evolution. Microb Genom 2021; 7:000587. [PMID: 34165421 PMCID: PMC8461475 DOI: 10.1099/mgen.0.000587] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2020] [Accepted: 04/19/2021] [Indexed: 12/18/2022] Open
Abstract
Prokaryote genome evolution is characterized by the frequent gain of genes through horizontal gene transfer (HGT). For a gene, being horizontally transferred can represent a strong change in its genomic and physiological context. If the codon usage of a transferred gene deviates from that of the receiving organism, the fitness benefits it provides can be reduced due to a mismatch with the expression machinery. Consequently, transferred genes with a deviating codon usage can be selected against or elicit evolutionary responses that enhance their integration, such as gene amelioration and compensatory evolution. Within bacterial species, the extent and relative importance of these different mechanisms has never been considered altogether. In this study, a phylogeny-based method was used to investigate the occurrence of these different evolutionary responses in Pseudomonas aeruginosa. Selection on codon usage of genes acquired through HGT was observed over evolutionary time, with the overall codon usage converging towards that of the core genome. Gene amelioration, through the accumulation of synonymous mutations after HGT, did not seem to systematically affect transferred genes. This pattern therefore seemed to be mainly driven by selective retention of transferred genes with an initial codon usage similar to that of the core genes. Additionally, variation in the copy number of tRNA genes was often associated with the acquisition of genes for which the observed variation could enhance their expression. This provides evidence that compensatory evolution might be an important mechanism for the integration of horizontally transferred genes.
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Affiliation(s)
- Martijn Callens
- CEFE, Univ Montpellier, CNRS, EPHE, IRD, Univ Paul Valéry Montpellier 3, Montpellier, France
| | - Celine Scornavacca
- Institut des Sciences de l’Evolution, Université Montpellier, CNRS, IRD, EPHE, Montpellier, France
| | - Stéphanie Bedhomme
- CEFE, Univ Montpellier, CNRS, EPHE, IRD, Univ Paul Valéry Montpellier 3, Montpellier, France
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Callens M, Pradier L, Finnegan M, Rose C, Bedhomme S. Read between the lines: Diversity of non-translational selection pressures on local codon usage. Genome Biol Evol 2021; 13:6263832. [PMID: 33944930 PMCID: PMC8410138 DOI: 10.1093/gbe/evab097] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/28/2021] [Indexed: 12/14/2022] Open
Abstract
Protein coding genes can contain specific motifs within their nucleotide sequence that function as a signal for various biological pathways. The presence of such sequence motifs within a gene can have beneficial or detrimental effects on the phenotype and fitness of an organism, and this can lead to the enrichment or avoidance of this sequence motif. The degeneracy of the genetic code allows for the existence of alternative synonymous sequences that exclude or include these motifs, while keeping the encoded amino acid sequence intact. This implies that locally, there can be a selective pressure for preferentially using a codon over its synonymous alternative in order to avoid or enrich a specific sequence motif. This selective pressure could -in addition to mutation, drift and selection for translation efficiency and accuracy- contribute to shape the codon usage bias. In this review, we discuss patterns of avoidance of (or enrichment for) the various biological signals contained in specific nucleotide sequence motifs: transcription and translation initiation and termination signals, mRNA maturation signals, and antiviral immune system targets. Experimental data on the phenotypic or fitness effects of synonymous mutations in these sequence motifs confirm that they can be targets of local selection pressures on codon usage. We also formulate the hypothesis that transposable elements could have a similar impact on codon usage through their preferred integration sequences. Overall, selection on codon usage appears to be a combination of a global selection pressure imposed by the translation machinery, and a patchwork of local selection pressures related to biological signals contained in specific sequence motifs.
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Affiliation(s)
- Martijn Callens
- Centre d'Ecologie Fonctionnelle et Evolutive, CNRS, Université de Montpellier, Université Paul Valéry Montpellier 3, Ecole Pratique des Hautes Etudes, Institut de Recherche pour le Développement, 34000 Montpellier, France
| | - Léa Pradier
- Centre d'Ecologie Fonctionnelle et Evolutive, CNRS, Université de Montpellier, Université Paul Valéry Montpellier 3, Ecole Pratique des Hautes Etudes, Institut de Recherche pour le Développement, 34000 Montpellier, France
| | - Michael Finnegan
- Centre d'Ecologie Fonctionnelle et Evolutive, CNRS, Université de Montpellier, Université Paul Valéry Montpellier 3, Ecole Pratique des Hautes Etudes, Institut de Recherche pour le Développement, 34000 Montpellier, France
| | - Caroline Rose
- Centre d'Ecologie Fonctionnelle et Evolutive, CNRS, Université de Montpellier, Université Paul Valéry Montpellier 3, Ecole Pratique des Hautes Etudes, Institut de Recherche pour le Développement, 34000 Montpellier, France
| | - Stéphanie Bedhomme
- Centre d'Ecologie Fonctionnelle et Evolutive, CNRS, Université de Montpellier, Université Paul Valéry Montpellier 3, Ecole Pratique des Hautes Etudes, Institut de Recherche pour le Développement, 34000 Montpellier, France
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Callens M, De Meester L, Muylaert K, Mukherjee S, Decaestecker E. The bacterioplankton community composition and a host genotype dependent occurrence of taxa shape the Daphnia magna gut bacterial community. FEMS Microbiol Ecol 2021; 96:5861314. [PMID: 32573725 PMCID: PMC7360484 DOI: 10.1093/femsec/fiaa128] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2020] [Accepted: 06/22/2020] [Indexed: 12/21/2022] Open
Abstract
The assembly of host-associated bacterial communities is influenced by a multitude of biotic and abiotic factors. It is essential to gain insight in the impact and relative strength of these factors if we want to be able to predict the effects of environmental change on the assembly of host-associated bacterial communities, or deliberately modify them. The environmental pool of bacteria, from which the host is colonized, and the genetic background of the host are both considered to be important in determining the composition of host-associated bacterial communities. We experimentally assessed the relative importance of these two factors and their interaction on the composition of Daphnia magna gut bacterial communities. Bacterioplankton originating from natural ponds or a laboratory culture were used to inoculate germ-free Daphnia of different genotypes. We found that the composition of the environmental bacterial community has a major influence on the Daphnia gut bacterial community, both reflected by the presence or absence of specific taxa as well as by a correlation between abundances in the environment and on the host. Our data also indicate a consistent effect of host genotype on the occurrence of specific bacterial taxa in the gut of Daphnia over different environments.
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Affiliation(s)
- Martijn Callens
- Laboratory of Aquatic Biology, Department of Biology, University of Leuven - Campus KULAK, E. Sabbelaan 53, B-8500 Kortrijk, Belgium.,CEFE, Univ Montpellier, CNRS, EPHE, IRD, Univ Paul Valéry Montpellier 3, Montpellier, France
| | - Luc De Meester
- Laboratory of Aquatic Ecology, Evolution and Conservation, University of Leuven, Charles Deberiotstraat 32, 3000 Leuven, Belgium.,Institute of Biology, Freie Universität Berlin, Köning-Luise-Strasse 1-3, 14195 Berlin, Germany.,Leibniz Institut für Gewasserökologie und Binnenfischerei (IGB), Müggelseedamm 310, 12587 Berlin, Germany
| | - Koenraad Muylaert
- Laboratory of Aquatic Biology, Department of Biology, University of Leuven - Campus KULAK, E. Sabbelaan 53, B-8500 Kortrijk, Belgium
| | - Shinjini Mukherjee
- Laboratory of Aquatic Ecology, Evolution and Conservation, University of Leuven, Charles Deberiotstraat 32, 3000 Leuven, Belgium
| | - Ellen Decaestecker
- Laboratory of Aquatic Biology, Department of Biology, University of Leuven - Campus KULAK, E. Sabbelaan 53, B-8500 Kortrijk, Belgium
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Massol F, Macke E, Callens M, Decaestecker E. A methodological framework to analyse determinants of host-microbiota networks, with an application to the relationships between Daphnia magna's gut microbiota and bacterioplankton. J Anim Ecol 2020; 90:102-119. [PMID: 32654135 DOI: 10.1111/1365-2656.13297] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2019] [Accepted: 06/25/2020] [Indexed: 01/04/2023]
Abstract
The past 30 years have seen both a surge of interest in assessing ecological interactions using tools borrowed from network theory and an explosion of data on the occurrence of microbial symbionts thanks to next-generation sequencing. Given that classic network methods cannot currently measure the respective effects of different environmental and biological drivers on network structure, we here present two methods to elucidate the determinants of bipartite interaction networks. The first method is based on classifications and compares communities within networks to the grouping of nodes by treatment or similar controlling groups. The second method assesses the link between multivariate explanatory variables and network structure using redundancy analyses after singular value decomposition. In both methods, the significance of effects can be gauged through two randomizations. Our methods were applied to experimental data on Daphnia magna and its interactions with gut microbiota and bacterioplankton. The whole network was affected by Daphnia's diet (algae and/or cyanobacteria) and sample type, but not by Daphnia genotype. At coarse grains, bacterioplankton and gut microbiota communities were different. At this scale, the structure of the gut microbiota-based network was not linked to any explanatory factors, while the bacterioplankton-based network was related to both Daphnia's diet and genotype. At finer grains, Daphnia's diet and genotype affected both microbial networks, but the effect of diet on gut microbiota network structure was mediated solely by differences in microbial richness. While no reciprocal effect between the microbial communities could be found, fine-grained analyses presented a more nuanced picture, with bacterioplankton likely affecting the composition of the gut microbiota. Our methods are widely applicable to bipartite networks, can elucidate both controlled and environmental effects in experimental setting using a large amount of sequencing data and can tease apart reciprocal effects of networks on one another. The twofold approach we propose has the advantage of being able to tease apart effects at different scales of network structure, thus allowing for detailed assessment of reciprocal effects of linked networks on one another. As such, our network methods can help ecologists understand huge datasets reporting microbial co-occurrences within different hosts.
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Affiliation(s)
- François Massol
- UMR 8198 Evo-Eco-Paleo, SPICI Group, University of Lille, Lille, France.,CNRS, CHU Lille, Institut Pasteur de Lille, U1019-UMR 8204-CIIL-Center for Infection and Immunity of Lille, University of Lille, Lille, France
| | - Emilie Macke
- Laboratory of Aquatic Biology, Department of Biology, KU Leuven (Kulak), Kortrijk, Belgium
| | - Martijn Callens
- Laboratory of Aquatic Biology, Department of Biology, KU Leuven (Kulak), Kortrijk, Belgium.,Centre d'Ecologie Fonctionnelle et Evolutive, UMR CNRS 5175, Montpellier, France
| | - Ellen Decaestecker
- Laboratory of Aquatic Biology, Department of Biology, KU Leuven (Kulak), Kortrijk, Belgium
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Macke E, Callens M, Massol F, Vanoverberghe I, De Meester L, Decaestecker E. Diet and Genotype of an Aquatic Invertebrate Affect the Composition of Free-Living Microbial Communities. Front Microbiol 2020; 11:380. [PMID: 32256467 PMCID: PMC7090131 DOI: 10.3389/fmicb.2020.00380] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2019] [Accepted: 02/20/2020] [Indexed: 12/04/2022] Open
Abstract
In spite of the growing interest in the role of the gut microbiome (GM) in host physiology and health, the mechanisms governing its assembly and its effects on the environment are poorly understood. In this article, we show that the host genotype and the GM of Daphnia influence the community structure of the surrounding bacterioplankton (BPK). When Daphnia genotypes were placed in an identical environment, both the GM and BPK showed a genotype and diet-dependent taxonomic composition. Overall, the GM strongly differed from the BPK in taxonomic composition and was characterized by a lower α-diversity, suggesting a selective rejecting of bacteria from the regional species pool. In a microbiome transplant experiment, the assembly of both the GM and BPK was strongly affected by the host genotype and the inoculum to which germ-free Daphnia were exposed. The combination of these results suggests a strong interaction between the host genotype, its GM and free-living microbial communities. Currently, it is generally assumed that an animal’s diet has a strong effect on the animal’s GM, but only a negligible (if any) effect on the surrounding environment. However, our results indicate that the diet/microbiome inocula have a small effect on the gut community and a large effect on the community in the surrounding environment. This structuring genotype × microbiome × environment effect is an essential prerequisite that could indicate that microbiomes play an important role in eco-evolutionary processes.
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Affiliation(s)
- Emilie Macke
- Aquatic Biology, IRF Life Sciences, KU Leuven, Kortrijk, Belgium
| | - Martijn Callens
- Aquatic Biology, IRF Life Sciences, KU Leuven, Kortrijk, Belgium.,Centre d'Ecologie Fonctionnelle et Evolutive, UMR CNRS 5175, Montpellier, France
| | - Francois Massol
- CNRS, Lille-Sciences et Technologies, UMR 8198 Evo-Eco-Paleo, SPICI Group, Villeneuve-d'Ascq, France.,University of Lille, CNRS, INSERM, CHU Lille, Institut Pasteur de Lille, U1019-UMR 8204-CIIL-Center for Infection and Immunity of Lille, Lille, France
| | | | - Luc De Meester
- Aquatic Ecology, Evolution and Conservation, KU Leuven, Leuven, Belgium
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Callens M, Watanabe H, Kato Y, Miura J, Decaestecker E. Microbiota inoculum composition affects holobiont assembly and host growth in Daphnia. Microbiome 2018; 6:56. [PMID: 29566771 PMCID: PMC5863831 DOI: 10.1186/s40168-018-0444-1] [Citation(s) in RCA: 31] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/27/2017] [Accepted: 03/13/2018] [Indexed: 05/24/2023]
Abstract
BACKGROUND Host-associated microbiota is often acquired by horizontal transmission of microbes present in the environment. It is hypothesized that differences in the environmental pool of colonizers can influence microbiota community assembly on the host and as such affect holobiont composition and host fitness. To investigate this hypothesis, the host-associated microbiota of the invertebrate eco(toxico)logical model Daphnia was experimentally disturbed using different concentrations of the antibiotic oxytetracycline. The community assembly and host-microbiota interactions when Daphnia were colonized by the disturbed microbiota were investigated by inoculating germ-free individuals with the microbiota. RESULTS Antibiotic-induced disturbance of the microbiota had a strong effect on the subsequent colonization of Daphnia by affecting ecological interactions between members of the microbiota. This resulted in differences in community assembly which, in turn, affected Daphnia growth. CONCLUSIONS These results show that the composition of the pool of colonizing microbiota can be an important structuring factor of the microbiota assembly on Daphnia, affecting holobiont composition and host growth. These findings contribute to a better understanding of how the microbial environment can shape the holobiont composition and affect host-microbiota interactions.
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Affiliation(s)
- Martijn Callens
- Aquatic Biology, Science and Technology, IRF Life Sciences, KU Leuven, Campus Kortrijk, E. Sabbelaan 53, 8500, Kortrijk, Belgium
- Centre d'Ecologie Fonctionelle Evolutive, CNRS Montpellier, UMR 5175, 1919 route de Mende, 34293, Montpellier CEDEX 5, France
| | - Hajime Watanabe
- Bioenvironmental Science, Osaka University, Yamadaoka, Suita, Osaka, 565 0871, Japan
| | - Yasuhiko Kato
- Bioenvironmental Science, Osaka University, Yamadaoka, Suita, Osaka, 565 0871, Japan
| | - Jun Miura
- Bioenvironmental Science, Osaka University, Yamadaoka, Suita, Osaka, 565 0871, Japan
| | - Ellen Decaestecker
- Aquatic Biology, Science and Technology, IRF Life Sciences, KU Leuven, Campus Kortrijk, E. Sabbelaan 53, 8500, Kortrijk, Belgium.
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Macke E, Callens M, De Meester L, Decaestecker E. Host-genotype dependent gut microbiota drives zooplankton tolerance to toxic cyanobacteria. Nat Commun 2017; 8:1608. [PMID: 29151571 PMCID: PMC5694789 DOI: 10.1038/s41467-017-01714-x] [Citation(s) in RCA: 82] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2016] [Accepted: 10/11/2017] [Indexed: 12/20/2022] Open
Abstract
The gut microbiota impacts many aspects of its host's biology, and is increasingly considered as a key factor mediating performance of host individuals in continuously changing environments. Here we use gut microbiota transplants to show that both host genotype and gut microbiota mediate tolerance to toxic cyanobacteria in the freshwater crustacean Daphnia magna. Interclonal variation in tolerance to cyanobacteria disappears when Daphnia are made germ-free and inoculated with an identical microbial inoculum. Instead, variation in tolerance among recipient Daphnia mirrors that of the microbiota donors. Metagenetic analyses point to host genotype and external microbial source as important determinants of gut microbiota assembly, and reveal strong differences in gut microbiota composition between tolerant and susceptible genotypes. Together, these results show that both environmentally and host genotype-induced variations in gut microbiota structure mediate Daphnia tolerance to toxic cyanobacteria, pointing to the gut microbiota as a driver of adaptation and acclimatization to cyanobacterial harmful algal blooms in zooplankton.
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Affiliation(s)
- Emilie Macke
- Laboratory of Aquatic Biology, Department of Biology, University of Leuven-Campus Kulak, E. Sabbelaan 53, B-8500, Kortrijk, Belgium.
| | - Martijn Callens
- Laboratory of Aquatic Biology, Department of Biology, University of Leuven-Campus Kulak, E. Sabbelaan 53, B-8500, Kortrijk, Belgium
| | - Luc De Meester
- Laboratory of Aquatic Ecology, Evolution and Conservation, University of Leuven, Charles Deberiotstraat 32, 3000, Leuven, Belgium
| | - Ellen Decaestecker
- Laboratory of Aquatic Biology, Department of Biology, University of Leuven-Campus Kulak, E. Sabbelaan 53, B-8500, Kortrijk, Belgium.
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Affiliation(s)
- Emilie Macke
- Laboratory Aquatic Biology, KU Leuven (Kulak), Dept of Biology; E. Sabbelaan 53, BE-8500 Kortrijk Belgium
| | | | - François Massol
- Univ. Lille; CNRS UMR 8198 Evo-Eco-Paleo SPICI group Lille France
| | - Martijn Callens
- Laboratory Aquatic Biology, KU Leuven (Kulak), Dept of Biology; E. Sabbelaan 53, BE-8500 Kortrijk Belgium
| | - Ellen Decaestecker
- Laboratory Aquatic Biology, KU Leuven (Kulak), Dept of Biology; E. Sabbelaan 53, BE-8500 Kortrijk Belgium
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Vanhaelst L, Vandepitte J, Snyers B, Callens M, Pipeleers D. Book-Review. Acta Clin Belg 2016. [DOI: 10.1080/17843286.1992.11718212] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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Callens M, Crijns W, Simons V, De Wolf I, Depuydt T, Maes F, Haustermans K, D'hooge J, D'Agostino E, Wevers M, Pfeiffer H, Van Den Abeele K. A spectroscopic study of the chromatic properties of GafChromic™EBT3 films. Med Phys 2016; 43:1156-66. [DOI: 10.1118/1.4941312] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Affiliation(s)
- M. Callens
- Wave Propagation and Signal Processing, KU Leuven–KULAK, Kortrijk 8500, Belgium
| | - W. Crijns
- Department of Radiation Oncology, University Hospitals Leuven, Leuven 3000, Belgium
| | - V. Simons
- imec, Kapeldreef 75, Leuven 3001, Belgium
| | - I. De Wolf
- imec, Kapeldreef 75, Leuven 3001, Belgium and Department of Materials Engineering, KU Leuven, Leuven 3001, Belgium
| | - T. Depuydt
- Department of Radiation Oncology, University Hospitals Leuven, Leuven 3000, Belgium
| | - F. Maes
- Department of Electrical Engineering, ESAT/PSI, KU Leuven, Leuven 3001, Belgium
| | - K. Haustermans
- Department of Radiation Oncology, University Hospitals Leuven, Leuven 3000, Belgium
| | - J. D'hooge
- Department of Cardiovascular Sciences, KU Leuven, Leuven 3000, Belgium
| | | | - M. Wevers
- Department of Materials Engineering, KU Leuven, Leuven 3001, Belgium
| | - H. Pfeiffer
- Department of Materials Engineering, KU Leuven, Leuven 3001, Belgium
| | - K. Van Den Abeele
- Wave Propagation and Signal Processing, KU Leuven–KULAK, Kortrijk 8500, Belgium
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Aelvoet W, Terryn N, Blommaert A, Molenberghs G, Hens N, De Smet F, Callens M, Beutels P. Community-acquired pneumonia (CAP) hospitalizations and deaths: is there a role for quality improvement through inter-hospital comparisons? Int J Qual Health Care 2015; 28:22-32. [PMID: 26590376 DOI: 10.1093/intqhc/mzv092] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/12/2015] [Indexed: 01/12/2023] Open
Abstract
OBJECTIVE To assess between-hospital variations in standardized in-hospital mortality ratios of community-acquired pneumonia (CAP), and identify possible leads for quality improvement. DESIGN We used an administrative database to estimate standardized in-hospital mortality ratios for 111 Belgian hospitals, by carrying out a set of hierarchical logistic regression models, intended to disentangle therapeutic attitudes and biases. To facilitate the detection of false-negative/positive results, we added an inconclusive zone to the funnel plots, derived from the results of the study. Data quality was validated by comparison with (i) alternative data from the largest Belgian Sickness Fund, (ii) published German hospital data and (iii) the results of an on-site audit. SETTING All Belgian hospital discharge records from 2004 to 2007. STUDY PARTICIPANTS A total of 111 776 adult patients were admitted for CAP. MAIN OUTCOME MEASURE Risk-adjusted standardized in-hospital mortality ratios. RESULTS Out of the 111 hospitals, we identified five and six outlying hospitals, with standardized mortality ratios of CAP consistently on the extremes of the distribution, as providing possibly better or worse care, respectively, and 18 other hospitals as having possible quality weaknesses/strengths. At the individuals' level of the analysis, adjusted odds ratios showed the paramount importance of old age, comorbidity and mechanical ventilation. The data compared well with the different validation sources. CONCLUSIONS Despite the limitations inherent to administrative data, it seemed possible to establish inter-hospital differences in standardized in-hospital mortality ratios of CAP and to identify leads for quality improvement. Monitoring is needed to assess progress in quality.
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Affiliation(s)
- W Aelvoet
- Federal Public Service (FPS) Health, Food Chain Safety and Environment, Eurostation Bloc II-First Floor-01D327, Place Victor Horta 40 bte 10, B-1060 Brussels, Belgium Vrije Universiteit Brussel, Faculteit Geneeskunde en Farmacie, Brussels, Belgium
| | - N Terryn
- Federal Public Service (FPS) Health, Food Chain Safety and Environment, Eurostation Bloc II-First Floor-01D327, Place Victor Horta 40 bte 10, B-1060 Brussels, Belgium
| | - A Blommaert
- Centre for Health Economics Research and Modeling Infectious Diseases (CHERMID), Vaccine and Infectious Disease Institute (WHO Collaborating Centre), University of Antwerp, Antwerp, Belgium
| | - G Molenberghs
- Interuniversity Institute for Biostatistics and Statistical Bioinformatics (I-BioStat), Universiteit Hasselt and KU Leuven, Belgium
| | - N Hens
- Centre for Health Economics Research and Modeling Infectious Diseases (CHERMID), Vaccine and Infectious Disease Institute (WHO Collaborating Centre), University of Antwerp, Antwerp, Belgium Interuniversity Institute for Biostatistics and statistical Bioinformatics (I-BIOSTAT), Hasselt University
| | - F De Smet
- National Alliance of Christian Mutualities, Brussels, Belgium Department of Public Health and Primary Care, Occupational, Environmental and Insurance Medicine, KU Leuven, Louvain, Belgium
| | - M Callens
- National Alliance of Christian Mutualities, Brussels, Belgium
| | - P Beutels
- Centre for Health Economics Research and Modeling Infectious Diseases (CHERMID), Vaccine and Infectious Disease Institute (WHO Collaborating Centre), University of Antwerp, Antwerp, Belgium School of Public Health and Community Medicine, The University of New South Wales, Sydney, Australia
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Callens M, de Dooy J, van Hal G. Resource use data from sickness funds: their story about alcohol intoxication in minors in Belgium. Eur J Public Health 2015. [DOI: 10.1093/eurpub/ckv170.086] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
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Callens M, Macke E, Muylaert K, Bossier P, Lievens B, Waud M, Decaestecker E. Food availability affects the strength of mutualistic host-microbiota interactions in Daphnia magna. ISME J 2015; 10:911-20. [PMID: 26405832 DOI: 10.1038/ismej.2015.166] [Citation(s) in RCA: 56] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/26/2015] [Revised: 07/14/2015] [Accepted: 08/10/2015] [Indexed: 01/15/2023]
Abstract
The symbiotic gut microbial community is generally known to have a strong impact on the fitness of its host. Nevertheless, it is less clear how the impact of symbiotic interactions on the hosts' fitness varies according to environmental circumstances such as changes in the diet. This study aims to get a better understanding of host-microbiota interactions under different levels of food availability. We conducted experiments with the invertebrate, experimental model organism Daphnia magna and compared growth, survival and reproduction of conventionalized symbiotic Daphnia with germ-free individuals given varying quantities of food. Our experiments revealed that the relative importance of the microbiota for the hosts' fitness varied according to dietary conditions. The presence of the microbiota had strong positive effects on Daphnia when food was sufficient or abundant, but had weaker effects under food limitation. Our results indicate that the microbiota can be a potentially important factor in determining host responses to changes in dietary conditions. Characterization of the host-associated microbiota further showed that Aeromonas sp. was the most prevalent taxon in the digestive tract of Daphnia.
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Affiliation(s)
- Martijn Callens
- Laboratory of Aquatic Biology, Science & Technology, KULeuven Campus Kulak, Kortrijk, Belgium
| | - Emilie Macke
- Laboratory of Aquatic Biology, Science & Technology, KULeuven Campus Kulak, Kortrijk, Belgium
| | - Koenraad Muylaert
- Laboratory of Aquatic Biology, Science & Technology, KULeuven Campus Kulak, Kortrijk, Belgium
| | - Peter Bossier
- Laboratory of Aquaculture & Artemia Reference Center, Department of Animal Production, UGent, Ghent, Belgium
| | - Bart Lievens
- Laboratory for Process Microbial Ecology and Bioinspirational Management, Department of Microbial and Molecular Systems, KULeuven Campus De Nayer, Sint-Katelijne-Waver, Belgium
| | - Michael Waud
- Laboratory for Process Microbial Ecology and Bioinspirational Management, Department of Microbial and Molecular Systems, KULeuven Campus De Nayer, Sint-Katelijne-Waver, Belgium
| | - Ellen Decaestecker
- Laboratory of Aquatic Biology, Science & Technology, KULeuven Campus Kulak, Kortrijk, Belgium
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Callens M, Crijns W, Simons V, De Wolf I, Depuydt T, Maes F, Haustermans K, D'hooge J, D'Agostino E, Pfeiffer H, Van Den Abeele K. SU-E-T-44: A Micro-Raman Spectroscopy Study of the Dose-Dependence of EBT3 GafChromicTM Films for Quantifying the Degree of Molecular Polymerization. Med Phys 2015. [DOI: 10.1118/1.4924405] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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20
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Callens M, Verboven E, D'Agostino E, Pfeiffer H, D'hooge J, Van Den Abeele K. WE-D-210-04: Radiation-Induced Polymerization of Ultrasound Contrast Agents in View of Non-Invasive Dosimetry in External Beam Radiation Therapy. Med Phys 2015. [DOI: 10.1118/1.4925961] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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22
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Puech J, Callens M, Willson M. Analysis of the kinetics of reversible enzyme inhibition by a general algebraic method. Application to multisite inhibition of the phosphoglycerate kinase from Trypanosoma brucei. J Enzyme Inhib 1999; 14:27-47. [PMID: 10520758 DOI: 10.3109/14756369809036544] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
The action of an inhibitor on a stationary enzyme reaction is described by a simple equation, which reflects how the progressive binding of inhibitor molecules influences the existence and the productivity of the enzyme forms. This allows deduction of the structure of the enzyme system from the experimental results, using new type of plots (1/[I], 1/[I](a)v) where a = 0,1,2,... in complement to the usual graphs. A reaction scheme is thereby logically built. This method may be used without any theoretical calculation. It is valid whatever the inhibitor, when the association reactions of the substrates and the inhibitor to the enzyme are in rapid equilibrium, and with dead end inhibitors, more generally for steady state enzyme reactions. This method may be adapted to enzyme activation. An original inhibition mode is described with particular bifunctional molecules: cooperative binding of the inhibitor to the enzyme, outside the active site, by direct mutual interaction of two inhibitor molecules, and locking of the conformational changes that normally precede the release of the products.
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Affiliation(s)
- J Puech
- Laboratoire de Microscopie et Structure des Matériaux, Université Paul Sabatier, Toulouse, France
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Abstract
A highly sensitive detection of swine vesicular disease virus (SVDV) based on a single tube RT-PCR system and digoxigenin (DIG)-PCR-ELISA detection was developed. Using a one tube RT-PCR system, optimisation of the PCR conditions and optimisation of the microwell hybridisation and colourimetric detection of the amplicons resulted in a method that could detect viral RNA in infected tissue culture fluid with a titre as low as 0.1 TCID50/100 microl. The same sensitivity was obtained with SVDV-spiked faeces, if the samples were pre-treated with 1,1,2-trichlorotrifluoroethane/chloroform and subsequently concentrated using an ultrafiltration system and RNA extracted with the Purescript kit. The specificity of the test was validated on 27 SVDV strains belonging to four different groups. No cross-reactivity with genetically and symptomatically related viruses was detected using RNA of foot-and-mouth disease virus (FMDV), porcine enterovirus (PEV), vesicular stomatitis virus (VSV), Coxsackie B5 virus (CV-B5) and encephalomyocarditis virus (EMCV). The test was validated successfully on clinical samples, being slightly more sensitive and much faster than virus isolation on cell cultures. Moreover the possibility of automating the procedure will allow the processing of large numbers of clinical samples.
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Affiliation(s)
- M Callens
- Veterinary and Agrochemical Research Centre, Brussels (Ukkel), Belgium
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Ernest I, Callens M, Uttaro AD, Chevalier N, Opperdoes FR, Muirhead H, Michels PA. Pyruvate kinase of Trypanosoma brucei: overexpression, purification, and functional characterization of wild-type and mutated enzyme. Protein Expr Purif 1998; 13:373-82. [PMID: 9693062 DOI: 10.1006/prep.1998.0918] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
A procedure was developed for overexpression of Trypanosoma brucei pyruvate kinase in Escherichia coli. The enzyme was purified to near-homogeneity from the bacterial lysate by first removing nucleic acids and contaminating proteins by protamine sulfate precipitation and subsequent passage over a phosphocellulose column. The purified protein is essentially indistinguishable in its physicochemical and kinetic properties from the enzyme purified from trypanosomes. Furthermore, experiments were undertaken to locate the binding site of the allosteric effector fructose 2,6-bisphosphate. Regulation of pyruvate kinase by this effector is unique to trypanosomes and related protozoan organisms. Therefore, a three-dimensional structure model of the enzyme was made, and a putative effector-binding site could be identified in an interdomain cleft. Four residues in this cleft were mutated, and the mutant proteins were produced and purified, using the same methodology as for the wild-type pyruvate kinase. Some mutants showed only minor changes in the activation by the effector. However, substitution of Arg22 by Gly resulted in a 9.2-fold higher S(0.5) for phosphoenolpyruvate and a significantly smaller kcat than the wild-type enzyme. Furthermore, the apparent affinity of this mutant for the allosteric effectors fructose 1,6-bisphosphate and fructose 2,6-bisphosphate was 8.2- and 5.2-fold lower than that of its wild-type counterpart. Effector binding was also affected, although to a lesser extent, in a mutant Phe463Val. These data indicate that particularly residue Arg22, but also Phe463, are somehow involved in the binding of the allosteric effectors.
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Affiliation(s)
- I Ernest
- Research Unit for Tropical Diseases, Christian de Duve Institute of Cellular Pathology and Laboratory of Biochemistry, Brussels, Belgium
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Zomer AW, Allert S, Chevalier N, Callens M, Opperdoes FR, Michels PA. Purification and characterisation of the phosphoglycerate kinase isoenzymes of Trypanosoma brucei expressed in Escherichia coli. Biochim Biophys Acta 1998; 1386:179-88. [PMID: 9675273 DOI: 10.1016/s0167-4838(98)00095-8] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
The Trypanosoma brucei phosphoglycerate kinase (PGK) glycosomal and cytosolic isoenzymes have been overexpressed in Escherichia coli and purified to near-homogeneity. Both enzymes were similar to the corresponding natural proteins with respect to their physicochemical and kinetic properties. In addition, a mutant of the glycosomal PGK lacking the 20 amino acid long C-terminal extension was overexpressed and purified. Various properties of this truncated glycosomal PGK were examined and it was found that in some aspects the protein behaved quite differently when compared with its natural counterpart. This was notably the case for the apparent Km for 3-phosphoglyceric acid, its sensitivity to inhibitors and its response to salts and guanidine HCl. However, its Vmax was found to be similar to that of the natural glycosomal PGK. These results suggest that the changes in the C-terminus caused a conformational change effecting the 3-phosphoglyceric acid binding site located at the N-terminal domain of the protein.
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Affiliation(s)
- A W Zomer
- Research Unit for Tropical Diseases, Christian de Duve Institute of Cellular Pathology and Laboratory of Biochemistry, Catholic University of Louvain, Brussels, Belgium
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Callens M, De Clercq K, Gruia M, Danes M. Detection of foot-and-mouth disease by reverse transcription polymerase chain reaction and virus isolation in contact sheep without clinical signs of foot-and-mouth disease. Vet Q 1998; 20 Suppl 2:S37-40. [PMID: 9652065] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
Two non-vaccinated sheep were experimentally infected with FMDV and one day later 4 other sheep were brought in contact. Although the contact sheep showed no clinical signs, serology indicated that all sheep became infected. Various secretion samples, taken over a period of at least one month, and various tissue samples were examined for the presence of FMDV by RT-PCR and by virus isolation. FMDV was most often found in saliva (mouth swabs), followed by nasal secretion and sera. Faecal material, wool and milk were less suitable. The period of detection with the highest frequency of positive isolations was between 2 to 4 days pi for the infected sheep and between 5 to 10 days pc for the contact animals. It was established that in subclinically infected sheep, with a very low amount of virus present, FMD viral RNA could be detected by a sensitive RT-PCR-ELISA although virus isolation and standard RT-PCR remained negative. Moreover there was some evidence of active spreading of FMDV from the contact sheep to two sentinel pigs. This indicates that serologically positive contact sheep without clinical signs may be considered as a danger for the transmission of FMDV.
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Affiliation(s)
- M Callens
- Veterinary and Agricultural Research Centre (VAR), Brussels, Ukkel, Belgium.
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Callens M, De Clercq K, Gruia M, Danes M. Detection of foot‐and‐mouth disease by reverse transcription polymerase chain reaction and virus isolation in contact sheep without clinical signs of foot‐and‐mouth disease. Vet Q 1998. [DOI: 10.1080/01652176.1998.9694964] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/15/2022] Open
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Abstract
A strategy for reverse transcriptase polymerase chain reaction (RT-PCR) using multiple primers was developed to detect and to differentiate the seven serotypes of foot-and-mouth disease virus (FMDV) simultaneously, quickly and accurately. The development of the test was carried out on virus isolates grown in tissue culture prior to cDNA synthesis and PCR using various sets of primers. Primers P33 and P32 were used for the consensus PCR to detect FMDV regardless of the serotype. Positive cDNA was assayed in two multi-primer PCR mixes containing type-specific primers capable of distinguishing between the seven serotypes. The serotype-specific primers were selected to correspond to regions of the genome coding for parts of the VP1 polypeptide that is responsible for the antigenic diversity of the virus group. Multi-primer mix P33-P(A-C-O-ASIA 1) gave products of 732, 596, 402, 292 bp for the A,C,O and ASIA 1 serotypes, respectively, and no target products for South African Territories serotypes (SAT 1, SAT 2 and SAT 3). The multi-primer mix P33-P(A-C-O-ASIA 1) was also capable of detecting a mixture of two different serotypes. Multi-primer mix P1-P(SAT 1-3-2) gave products of 246, 201 and 75 bp for the SAT 1, SAT 3 and SAT 2 serotypes, respectively, and no specific products for serotypes A, C, O and ASIA 1. This is the first PCR assay to be described that differentiates between the SAT serotypes of FMDV. The method has been applied to 25 cell-culture-derived isolates of the SAT serotypes of FMDV and the results were totally compatible with the standard techniques for FMDV detection and serotyping.
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Affiliation(s)
- M Callens
- National Institute for Veterinary Research, Brussels (Ukkel), Belgium.
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Van Ginckel R, Janssens B, Callens M, Goeminne N, Wouters L, De Coster R. Effects of combined and sequential treatment with tamoxifen and the aromatase inhibitor vorozole on 7,12-dimethylbenz(a) anthracene-induced mammary carcinoma in the rat. Cancer Chemother Pharmacol 1996; 38:21-8. [PMID: 8603447 DOI: 10.1007/s002800050442] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The aromatase inhibitor vorozole dose-dependently inhibited the growth of dimethylbenz(a) anthracene (DMBA)-induced mammary carcinoma in the rat. An oral dose of 5 mg/kg per day brought about growth inhibition and reduction of tumor multiplicity similar to that produced by ovariectomy. Tamoxifen (8 mg/kg per day) also reduced tumor growth, albeit to a lesser extent than did ovariectomy. Concomitant administration of varying doses of tamoxifen with the fully effective dose of vorozole (5 mg/kg per day) tended to be less effective than ovariectomy of vorozole alone. This is likely to be due to the estrogen-agonistic effects of tamoxifen. Combination of tamoxifen with the partially effective dose of vorozole (1 mg/kg per day) gave results comparable with those obtained for either of the compounds used in monotherapy. Combining tamoxifen with a marginally active low dose of vorozole (0.2 mg/kg per day) resulted in a minor additional growth inhibition as compared with that obtained with this dose of vorozole alone. Sequential treatment with tamoxifen (8 mg/kg per day) for 42 days and vorozole (5 mg/kg per day) for 42 days, and vice-versa, was performed with a drug-free interval of 14 days between treatments. Tumors regressing under vorozole therapy relapsed when subsequently treated with tamoxifen. In contrast, vorozole further reduced tumor volumes in rats previously treated with tamoxifen. Furthermore, monotherapy with tamoxifen as well as the two sequential tamoxifen-vorozole treatment schedules were in most cases less effective than vorozole monotherapy in inhibiting both tumor growth and tumor multiplicity. Although extrapolation of these findings in cycling animals to the clinical situation, involving postmenopausal women, is not straightforward, these results warrant further studies in preclinical models. Moreover, clinical trials comparing the most effective aromatase inhibitors with tamoxifen in previously untreated postmenopausal patients with breast cancer may also be warranted.
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Kohl L, Drmota T, Thi CD, Callens M, Van Beeumen J, Opperdoes FR, Michels PA. Cloning and characterization of the NAD-linked glycerol-3-phosphate dehydrogenases of Trypanosoma brucei brucei and Leishmania mexicana mexicana and expression of the trypanosome enzyme in Escherichia coli. Mol Biochem Parasitol 1996; 76:159-73. [PMID: 8920004 DOI: 10.1016/0166-6851(95)02556-1] [Citation(s) in RCA: 26] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
A polyclonal antiserum raised against the purified glycosomal glycerol-3-phosphate dehydrogenase of Trypanosoma brucei brucei has been used to identify the corresponding cDNA clone in a T.b. brucei expression library. This cDNA was subsequently used to obtain genomic clones containing glycerol-3-phosphate dehydrogenase genes. Two tandemly arranged genes were detected in these clones. Characterization of one of the genes showed that it codes for a polypeptide of 353 amino acids, with a molecular mass of 37,651 Da and a calculated net charge of +8. Using the T.b. brucei gene as a probe, a corresponding glycerol-3-phosphate dehydrogenase gene was also identified in a genomic library of Leishmania mexicana mexicana. The L.m. mexicana gene codes for a polypeptide of 365 amino acids, with a molecular mass of 39,140 Da and a calculated net charge of +8. The amino-acid sequences of both polypeptides are 63% identical and carry a type-1 peroxisomal targeting signal (PTS1) SKM and -SKL at their respective C-termini. Moreover, the L.m. mexicana polypeptide also carries a short N-terminal extension reminiscent of a mitochondrial transit sequence. Subcellular localisation analysis showed that in L.m. mexicana the glycerol-3-phosphate dehydrogenase activity co-fractionated both with mitochondria and with glycosomes. This is not the case in T. brucei, where the enzyme is predominantly glycosomal. The two trypanosomatid sequences resemble their prokaryotic homologues (32-36%) more than their eukaryotic counterparts (25-31%) and carry typical prokaryotic signatures. The possible reason for this prokaryotic nature of a trypanosomatid glycerol-3-phosphate dehydrogenase is discussed.
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Affiliation(s)
- L Kohl
- Research Unit for Tropical Diseases, Catholic University of Louvain, Brussels, Belgium
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Callens M, Hannaert V. The rational design of trypanocidal drugs: selective inhibition of the glyceraldehyde-3-phosphate dehydrogenase in Trypanosomatidae. Ann Trop Med Parasitol 1995; 89 Suppl 1:23-30. [PMID: 8745924 DOI: 10.1080/00034983.1995.11813011] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Within the framework of a project aimed at the structure-based design of drugs for use against sleeping sickness, selective inhibitors were designed, synthesised and tested. The target protein was glycosomal glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and the adenosine part of the NAD cofactor was chosen as lead. After one design cycle and exploiting the selectivity cleft in trypanosomal GAPDH near the C2 of the adenosine ribose, a selective inhibitor, 2'-deoxy-2'-(3-methoxybenzamido)adenosine, was obtained. This compound inhibits human GAPDH only marginally, whereas the enzymes from Trypanosoma brucei and Leishmania mexicana are inhibited by 50% at 2.2 and 0.3 mM, respectively. Moreover, the inhibition of the parasite enzyme is 45-fold (T. brucei) or 170-fold (L. mexicana) greater with this substituted analogue than that produced with adenosine.
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Affiliation(s)
- M Callens
- Research Unit for Tropical Diseases, International Institute of Cellular and Molecular Pathology, Brussels, Belgium
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Affiliation(s)
- M Trinquier
- Groupe de Chimie Organique Biologique-URA 470, Université Paul Sabatier, Toulouse, France
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33
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Van Calenbergh S, Verlinde CL, Soenens J, De Bruyn A, Callens M, Blaton NM, Peeters OM, Rozenski J, Hol WG, Herdewijn P. Synthesis and structure-activity relationships of analogs of 2'-deoxy-2'-(3-methoxybenzamido)adenosine, a selective inhibitor of trypanosomal glycosomal glyceraldehyde-3-phosphate dehydrogenase. J Med Chem 1995; 38:3838-49. [PMID: 7562915 DOI: 10.1021/jm00019a014] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
In continuation of a project aimed at the structure-based design of drugs against sleeping sickness, analogs of 2'-deoxy-2'-(3-methoxybenzamido)adenosine (1) were synthesized and tested to establish structure-activity relationships for inhibiting glycosomal glyceraldehyde-3-phosphate dehydrogenase (GAPDH). Compound 1 was recently designed using the NAD:GAPDH complexes of the human enzyme and that of Trypanosoma brucei, the causative agent of sleeping sickness. In an effort to exploit an extra hydrophobic domain due to Val 207 of the parasite enzyme, several new 2'-amido-2'-deoxyadenosines were synthesized. Some of them displayed an interesting improvement in inhibitory activity compared to 1. Carbocyclic or acyclic analogs showed marked loss of activity, illustrating the importance of the typical (C-2'-endo) puckering of the ribose moiety. We also describe the synthesis of a pair of compounds that combine the beneficial effects of a 2- and 8-substituted adenine moiety on potency with the beneficial effect of a 2'-amido moiety on selectivity. Unfortunately, in both cases, IC50 values demonstrate the incompatibility of these combined modifications. Finally, introduction of a hydrophobic 5'-amido group on 5'-deoxyadenosine enhances the inhibition of the protozoan enzyme significantly, although the gain in selectivity is mediocre.
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Affiliation(s)
- S Van Calenbergh
- Laboratory for Medicinal Chemistry, FFW, University of Ghent, Belgium
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34
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Borchert TV, Zeelen JP, Schliebs W, Callens M, Minke W, Jaenicke R, Wierenga RK. An interface point-mutation variant of triosephosphate isomerase is compactly folded and monomeric at low protein concentrations. FEBS Lett 1995; 367:315-8. [PMID: 7607330 DOI: 10.1016/0014-5793(95)00586-x] [Citation(s) in RCA: 27] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Wild-type trypanosomal triosephosphate isomerase (wtTIM) is a very tight dimer. The interface residue His-47 of wtTIM has been mutated into an asparagine. Ultracentrifugation data show that this variant (H47N) only dimerises at protein concentrations above 3 mg/ml. H47N has been characterised at a protein concentration where it is predominantly a monomer. Circular dichroism measurements in the near-UV and far-UV show that this monomer is a compactly folded protein with secondary structure similar as in wtTIM. The thermal stability of the monomeric H47N is decreased compared to wtTIM: temperature gradient gel electrophoresis (TGGE) measurements give Tm-values of 41 degrees C for wtTIM, whereas the Tm-value for the monomeric form of H47N is approximately 7 degrees C lower.
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Chevalier N, Callens M, Michels PA. High-level expression of Trypanosoma brucei fructose-1,6-bisphosphate aldolase in Escherichia coli and purification of the enzyme. Protein Expr Purif 1995; 6:39-44. [PMID: 7756837 DOI: 10.1006/prep.1995.1006] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
A procedure has been developed for high-level expression of Trypanosoma brucei fructose-bisphosphate aldolase in Escherichia coli. Therefore, a specific restriction site was introduced by mutagenesis at the front of the gene, enabling its ligation in an expression plasmid, immediately downstream of the regulatory sequences. Growth conditions were established for production of high amounts of soluble and active enzyme. Aldolase was purified to near-homogeneity from the soluble fraction of the bacterial lysate by nuclease treatment, differential precipitation steps, and passage over a CM-Sepharose column. From a 1-liter culture of E. coli cells, 60-120 mg of purified protein that is essentially indistinguishable in physicochemical and kinetic properties and in stability from the enzyme purified from trypanosomes grown in infected laboratory animals was reproducibly obtained.
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Affiliation(s)
- N Chevalier
- Research Unit for Tropical Diseases, International Institute of Cellular and Molecular Pathology, Brussels, Belgium
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36
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Verlinde CL, Callens M, Van Calenbergh S, Van Aerschot A, Herdewijn P, Hannaert V, Michels PA, Opperdoes FR, Hol WG. Selective inhibition of trypanosomal glyceraldehyde-3-phosphate dehydrogenase by protein structure-based design: toward new drugs for the treatment of sleeping sickness. J Med Chem 1994; 37:3605-13. [PMID: 7932587 DOI: 10.1021/jm00047a017] [Citation(s) in RCA: 50] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Within the framework of a project aimed at rational design of drugs against diseases caused by trypanosomes and related hemoflagellate parasites, selective inhibitors of trypanosomal glycolysis were designed, synthesized, and tested. The design was based upon the crystallographically determined structures of the NAD:glyceraldehyde-3-phosphate dehydrogenase complexes of humans and Trypanosoma brucei, the causative agent of sleeping sickness. After one design cycle, using the adenosine part of the NAD cofactor as a lead, the following encouraging results were obtained: (1) a 2-methyl substitution, targeted at a small pocket near Val 36, improves inhibition of the parasite enzyme 12.5-fold; (2) an 8-(thien-2-yl) substitution, aimed at Leu 112 of the parasite enzyme, where the equivalent residue in the mammalian enzyme is Val 100, results in a 167-fold better inhibition of the trypanosomal enzyme, while the inhibition of the human enzyme is improved only 13-fold; (3) exploitation of a "selectivity cleft" created by a unique backbone conformation in the trypanosomal enzyme near the adenosine ribose yields a considerable improvement in selectivity: 2'-deoxy-2'-(3-methoxybenzamido)adenosine inhibits the human enzyme only marginally but enhances inhibition of the parasite enzyme 45-fold when compared with adenosine. The designed inhibitors are not only better inhibitors of T. brucei GAPDH but also of the enzyme from Leishmania mexicana.
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Affiliation(s)
- C L Verlinde
- Department of Biological Structure, SM-20, School of Medicine, University of Washington, Seattle 98195
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Hannaert V, Callens M, Opperdoes FR, Michels PA. Purification and characterization of the native and the recombinant Leishmania mexicana glycosomal glyceraldehyde-3-phosphate dehydrogenase. Eur J Biochem 1994; 225:143-9. [PMID: 7925431 DOI: 10.1111/j.1432-1033.1994.00143.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
The gene coding for the glycosomal glyceraldehyde-3-phosphate dehydrogenase from Leishmania mexicana has been cloned into vector pET3A and expressed as a soluble and active protein in Escherichia coli BL21(DE3) in which the endogenous gene has been inactivated by mutation. The recombinant enzyme was purified to near homogeneity by ammonium sulphate precipitation, followed by hydrophobic and cation-exchange chromatography. From a 1-L culture of E. coli cells, 25 mg purified protein was obtained with a specific activity of 125 units/mg. The recombinant protein restores the natural E. coli phenotype when expressed at low level. The enzyme has also been partially purified from glycosomes of cultured L. mexicana promastigotes. The recombinant and the native proteins show identical mobilities on SDS/PAGE, and have the same isoelectric point and similar pH-activity profiles. The kinetics of both enzymes are very similar, the most important aspect being their lower apparent affinity for the cofactor NAD when compared to all other homologous enzymes studied, with the exception of glycosomal glyceraldehyde-3-phosphate dehydrogenase from Trypanosoma brucei.
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Affiliation(s)
- V Hannaert
- Research Unit for Tropical Diseases, International Institute of Cellular and Molecular Pathology, Brussels, Belgium
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Ernest I, Callens M, Opperdoes FR, Michels PA. Pyruvate kinase of Leishmania mexicana mexicana. Cloning and analysis of the gene, overexpression in Escherichia coli and characterization of the enzyme. Mol Biochem Parasitol 1994; 64:43-54. [PMID: 8078522 DOI: 10.1016/0166-6851(94)90133-3] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Leishmania mexicana mexicana contains two tandemly arranged genes for pyruvate kinase (PYK). The 5' located gene codes for a polypeptide with a molecular mass of 54,370. The calculated net charge and isoelectric point of the polypeptide are -6 and 6.5, respectively. Its amino-acid sequence is 73.7% identical to that of the Trypanosoma brucei PYK and 46.4-49.8% to the enzyme of mammalian cells. The second gene appears not to be functional, because its 5' and 3' extremities have undergone recombinations. L. m. mexicana PYK has been overexpressed in Escherichia coli, using a T7 expression system. Approximately 30% of the protein was detected in the soluble cell fraction. It has been highly purified by chromatography over DEAE-Sephacel and Affigel Blue. From a 1-1 culture 6 mg enzyme was obtained with a specific activity of 224 units mg-1. The protein has a subunit molecular mass of 59,000, as determined by SDS/PAGE, and an isoelectric point of 5.9. Some kinetic properties of the enzyme have been measured and compared with those reported for the T. brucei enzyme. The kinetics of both enzymes are very similar, the most important aspect being their activation by fructose 2,6-bisphosphate. Nevertheless, some differences were observed; the T. brucei enzyme is activated by the effector in a cooperative manner, whereas the activation of the L. m. mexicana enzyme is not cooperative.
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Affiliation(s)
- I Ernest
- International Institute of Cellular and Molecular Pathology, Research Unit for Tropical Diseases, Brussels, Belgium
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Kohl L, Callens M, Wierenga RK, Opperdoes FR, Michels PA. Triose-phosphate isomerase of Leishmania mexicana mexicana. Cloning and characterization of the gene, overexpression in Escherichia coli and analysis of the protein. Eur J Biochem 1994; 220:331-8. [PMID: 8125090 DOI: 10.1111/j.1432-1033.1994.tb18629.x] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
The gene of triose-phosphate isomerase in Leishmania mexicana has been cloned and characterized. The gene encodes a polypeptide of 251 amino acids, with a calculated molecular mass of 27,561 Da and a net charge of +2. Only one gene could be detected, although the enzyme is present in two different compartments of the cell, in microbody-like organelles called glycosomes and in the cytosol. The primary structure of the enzyme has many features in common with that of triose-phosphate isomerase in the related organism Trypanosoma brucei. Their sequences are 68% identical. The residues constituting the subunit interface are highly conserved between the enzyme of L. mexicana and T. brucei, but are mostly different from those in the enzyme of other organisms. One major substitution was detected in the interface region of the L. mexicana protein: a glutamate was found at position 66, instead of glutamine in all other available 20 sequences. The glutamine is thought to be important for the stability of the dimeric enzyme. L. mexicana triose-phosphate isomerase has been overexpressed in Escherichia coli. Growth conditions were established to obtain high levels of soluble and active protein. The enzyme has been purified to near homogeneity. It appears a stable dimeric protein with a specific activity of 5500 units/mg protein, a subunit mass of 28 kDa and an isoelectric point of 9.0. The enzyme has also been partially purified from glycosomes of cultured L. mexicana promastigotes. Some kinetic properties of the recombinant protein have been compared with those of the promastigote enzyme and with the values previously reported for the T. brucei enzyme. The kinetics of the different enzyme preparations were very similar. For the recombinant enzyme the following values were measured: with glyceraldehyde 3-phosphate as substrate Km = 0.30 +/- 0.05 mM and kcat = 2.5 x 10(5) min-1; with dihydroxyacetone phosphate as substrate Km = 1.3 +/- 0.3 mM and kcat = 2.8 x 10(4) min-1.
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Affiliation(s)
- L Kohl
- Research Unit for Tropical Diseases, International Institute of Cellular and Molecular Pathology, Brussels, Belgium
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Willson M, Lauth N, Perie J, Callens M, Opperdoes FR. Inhibition of glyceraldehyde-3-phosphate dehydrogenase by phosphorylated epoxides and alpha-enones. Biochemistry 1994; 33:214-20. [PMID: 8286343 DOI: 10.1021/bi00167a028] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Pentalenolactone and koningic acid are antibiotics known for their potent inhibition of the glycolytic enzyme glyceraldehyde-3-phosphate dehydrogenase. The reactive groups present in these antibiotics are, respectively, an epoxide and an alpha-enone, which form covalent bonds with an active-site cysteine residue of the enzyme. This information was used for the design of two series of glyceraldehyde 3-phosphate analogues with similar reactive groups that could function as potential irreversible inhibitors of glyceraldehyde-3-phosphate dehydrogenase. Inactivation kinetics, NMR analysis, protection experiments, and titration of free cysteine residues together indicate that the inhibitors bind to the active site of the enzyme and form a covalent bond with the active-site cysteine residue of the enzyme. Binding probably takes place at the inorganic phosphate site of the enzyme and may lead to a conformational change. Comparison of the reactivities of the inhibitors for the glycosomal enzyme from the protozoan parasite Trypanosoma brucei and the rabbit muscle enzyme revealed that some of them had a preference for the trypanosome enzyme. When their effect was measured on the multiplication of trypanosome in vitro cultures, one inhibitor appeared to exhibit an inhibitory effect at a concentration significantly lower than the trypanocidal drugs, pentamidin and (difluoromethyl)ornithine, that are routinely used in the treatment of African sleeping sickness.
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Affiliation(s)
- M Willson
- Laboratoire de Chimie Organique Biologique, URA CNRS 470, Université Paul Sabatier, Toulouse, France
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41
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Perie J, Riviere-Alric I, Blonski C, Gefflaut T, Lauth de Viguerie N, Trinquier M, Willson M, Opperdoes FR, Callens M. Inhibition of the glycolytic enzymes in the trypanosome: an approach in the development of new leads in the therapy of parasitic diseases. Pharmacol Ther 1993; 60:347-65. [PMID: 8022865 DOI: 10.1016/0163-7258(93)90016-7] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Glycolysis in the trypanosome represents an important target for the development of new therapeutic agents due to the fact that this metabolism is essential for the parasite, glucose being its sole source of energy. In addition, different features of this metabolism and those associated with glycolytic enzymes offer opportunities for the development of efficient and selective compounds. Examples are given in this work of inhibitors directed to the enzymes aldolase and glyceraldehyde-phosphate-dehydrogenase and also of molecules acting specifically on the clusters of basic amino-acids present at the surfaces of the glycolytic enzymes in the parasite.
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Affiliation(s)
- J Perie
- Groupe de Chimie Organique Biologique, URA au CNRS 470, Université Paul Sabatier, Toulouse, France
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42
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Callens M, Van Roy J, Zeelen JP, Borchert TV, Nalis D, Wierenga RK, Opperdoes FR. Selective interaction of glycosomal enzymes from Trypanosoma brucei with hydrophobic cyclic hexapeptides. Biochem Biophys Res Commun 1993; 195:667-72. [PMID: 8373406 DOI: 10.1006/bbrc.1993.2097] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Hydrophobic cyclic hexapeptides have been reported to selectively inhibit glycosomal triosephosphate isomerase from Trypanosoma brucei (Kuntz et al, 1992, Eur. J. Biochem., 207, 441-447). Here it is shown that this inhibition is not due to a specific interaction between the enzyme and soluble hydrophobic cyclic hexapeptides, but that it is the result of a coprecipitation of trypanosome triosephosphate isomerase with cyclic hexapeptides when the solubilities of the latter are exceeded. A study of the interaction of these hexapeptides with other glycosomal enzymes revealed that several of them, such as phosphoglycerate kinase and hexokinase, also coprecipitated with these peptides, whereas most of the homologous enzymes from other organisms did not coprecipitate, nor were they inactivated.
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Affiliation(s)
- M Callens
- Research Unit for Tropical Diseases, International Institute of Cellular and Molecular Pathology, Brussels, Belgium
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43
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Willson M, Callens M, Kuntz DA, Perié J, Opperdoes FR. Synthesis and activity of inhibitors highly specific for the glycolytic enzymes from Trypanosoma brucei. Mol Biochem Parasitol 1993; 59:201-10. [PMID: 8341319 DOI: 10.1016/0166-6851(93)90218-m] [Citation(s) in RCA: 54] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Most glycosomal enzymes of Trypanosoma brucei carry a relatively high number of positive charges. In at least 3 of the enzymes some of the charges unique to these enzymes are concentrated in 2 distinct areas on the enzymes' surface, about 4 nm apart [4] and these positively charged structural elements have been suggested to be the site of interaction with the trypanocidal drug Suramin. We have synthesized a series of symmetrical long chain molecules with negative charges or strong dipoles at each end. Several of these compounds inhibited the glycosomal enzymes more strongly than Suramin. They also exhibited a specificity for the trypanosome enzymes, when compared with homologous enzymes from other organisms. By varying the chain length of the active compounds, a 4-nm distance between the molecules' extremes proved optimal for inhibition. Tetra-substituted compounds were better than di-substituted. Modifications introduced at the two ends indicated that a planar orientation, with an amide bond linking a phenyl ring to the chain, is preferred. Inhibition kinetics for some of the enzymes indicated the existence of multi-site interactions with the inhibitors.
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Affiliation(s)
- M Willson
- Groupe de Chimie Organique Biologique (URA au CNRS 470), Université Paul Sabatier, Toulouse, France
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Borchert TV, Pratt K, Zeelen JP, Callens M, Noble ME, Opperdoes FR, Michels PA, Wierenga RK. Overexpression of trypanosomal triosephosphate isomerase in Escherichia coli and characterisation of a dimer-interface mutant. Eur J Biochem 1993; 211:703-10. [PMID: 8436128 DOI: 10.1111/j.1432-1033.1993.tb17599.x] [Citation(s) in RCA: 60] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
In this paper, the successful expression of trypanosomal triosephosphate isomerase (TIM) from Trypanosoma brucei brucei to high yield in Escherichia coli, using a T7-polymerase-based expression system, is described. Overexpressed trypanosomal TIM is fully active. The measured physicochemical properties of this recombinant TIM and TIM purified from trypanosomes are indistinguishable. Crystals of recombinant TIM have been grown in the presence of 2.4 M ammonium sulphate under the same conditions as for trypanosomally expressed TIM. The recombinant TIM crystal structure has been refined at 0.23 nm resolution; no differences were detected between this structure and the original crystal structure. A TIM mutant was made in which a unique dimer-interface histidine residue (His47) was changed into an asparagine. This variant ([H47N]TIM) could be expressed and purified to homogeneity by a procedure which was somewhat different from the purification of recombinant wild-type TIM. It is shown that the [H47N]TIM dimer is considerably less stable than wild-type trypanosomal TIM. The catalytic activity of [H47N]TIM is concentration dependent. The dilution-dependent inactivation is reversible. His47 is involved in a water-mediated hydrogen bond with Asp385 of the other subunit. The lower stability of the [H47N]TIM dimer implies that this water-mediated hydrogen bond is important for the stability of the TIM dimer.
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Affiliation(s)
- T V Borchert
- European Molecular Biology Laboratory, Heidelberg, Federal Republic of Germany
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Verlinde CL, Witmans CJ, Pijning T, Kalk KH, Hol WG, Callens M, Opperdoes FR. Structure of the complex between trypanosomal triosephosphate isomerase and N-hydroxy-4-phosphono-butanamide: binding at the active site despite an "open" flexible loop conformation. Protein Sci 1992; 1:1578-84. [PMID: 1304889 PMCID: PMC2142129 DOI: 10.1002/pro.5560011205] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
The structure of triosephosphate isomerase from Trypanosoma brucei complexed with the competitive inhibitor N-hydroxy-4-phosphono-butanamide was determined by X-ray crystallography to a resolution of 2.84 A. Full occupancy binding of the inhibitor is observed only at one of the active sites of the homodimeric enzyme where the flexible loop is locked in a completely open conformation by crystal contacts. There is evidence that the inhibitor also binds to the second active site of the enzyme, but with low occupancy. The hydroxamyl group of the inhibitor forms hydrogen bonds to the side chains of Asn 11, Lys 13, and His 95, whereas each of its three methylene units is involved in nonpolar interactions with the side chain of the flexible loop residue Ile 172. Interactions between the hydroxamyl and the catalytic base Glu 167 are absent. The binding of this phosphonate inhibitor exhibits three unusual features: (1) the flexible loop is open, in contrast with the binding mode observed in eight other complexes between triosephosphate isomerase and various phosphate and phosphonate compounds; (2) compared with these complexes the present structure reveals a 1.5-A shift of the anion-binding site; (3) this is the first phosphonate inhibitor that is not forced by the enzyme into an eclipsed conformation about the P-CH2 bond. The results are discussed with respect to an ongoing drug design project aimed at the selective inhibition of glycolytic enzymes of T. brucei.
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Affiliation(s)
- C L Verlinde
- BIOSON Research Institute, University of Groningen, The Netherlands
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Willson M, Périé JJ, Malecaze F, Opperdoes F, Callens M. Biological properties of amidinium sulfinic and sulfonic acid derivatives: inhibition of glycolytic enzymes of Trypanosoma brucei and protective effect on cell growth. Eur J Med Chem 1992. [DOI: 10.1016/0223-5234(92)90114-g] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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Van Bastelaere PB, Callens M, Vangrysperre WA, Kersters-Hilderson HL. Binding characteristics of Mn2+, Co2+ and Mg2+ ions with several D-xylose isomerases. Biochem J 1992; 286 ( Pt 3):729-35. [PMID: 1417732 PMCID: PMC1132964] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
D-Xylose isomerases are metal-ion (Mn2+, Co2+, Mg2+)-requiring tetrameric enzymes. Both the stoichiometry and the binding constants have been determined by titrating the metal-ion-free enzymes from five organisms (Actinomycetaceae and more divergent bacteria) with the respective metal ions using the enzyme activity as indicator of active complex-formation. The following characteristics have been observed for each specific isomerase: (i) two essential metal ion sites (one structural and one catalytic) exist per subunit; (ii) the metal ion binding at one site does not affect the binding at the other site; (iii) of the four possible configurations E, aE, Eb and aEb, only the double-occupied enzyme is active; (iv) the metal ion activation is a time-dependent process; (v) the dissociation constants for both the structural and catalytic sites may be identical or may differ by one or higher orders of magnitude; (vi) metal ion binding is stronger in the order Mn2+ greater than Co2+ much greater than Mg2+; (vii) pronounced increases in Km values concomitant with decreasing equivalents of metal ion added are only observed in the presence of Mg2+ ions.
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Van Ginckel R, Distelmans W, De Brabander M, Callens M, Janssens B, Jagers E, Wouters L, De Coster R, Janssen PA. Levamisole plus 5-fluorouracil inhibits the growth of human colorectal xenografts in nude mice. Eur J Cancer 1992; 28A:1137-9. [PMID: 1627384 DOI: 10.1016/0959-8049(92)90473-f] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Fragments of human colorectal adenocarcinomas were inserted under the renal capsule of nude mice. The growth of these tumour grafts was significantly inhibited by the combination of 5-fluorouracil (5-FU) and levamisole. An alternating regimen of levamisole 2.5 mg/kg and 5-FU 20 mg/kg decreased the size of tumour implants by 33-59% and/or increased the number of macroscopically disappeared fragments in the combined group compared with ineffective monotherapy with saline, levamisole or 5-FU. This model could be valuable for investigating the mechanism of action of levamisole and to evaluate the effects of this adjuvant therapy in other oncological settings.
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Krekels MD, Wouters W, Van Ginckel R, Janssens B, Callens M, De Coster R. Aromatase inhibition by R 83 842, the dextro isomer of R 76 713, in JEG-3 choriocarcinoma grown in ovariectomized nude mice. J Steroid Biochem Mol Biol 1992; 41:761-4. [PMID: 1562551 DOI: 10.1016/0960-0760(92)90419-j] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The effects of repeated (5 days) dosing with the non-steroidal aromatase inhibitor R 83 842 (the dextro isomer of R 76 713) on tumor aromatase and uterus weight in ovariectomized nude mice bearing JEG-3 tumors were examined. In animals bearing an androstenedione implant the presence of a JEG-3 tumor significantly increased uterus weight, proving that tumor aromatase indeed converted androgens to estrogens. Oral administration of R 76 713 (10 mg/kg) for 5 days reduced the increase in uterus weight by 84% in tumor bearing mice revealing true in vivo aromatase inhibition by R 76 713. Experiments performed in the absence of exogenously added androgens gave similar results. Uterus weights in tumor bearing mice were significantly higher than in control mice. Oral administration of R 83 842 (5 mg/kg) for 5 days reduced uterus weight in the tumor bearing animals. Ex vivo aromatase measurements performed in JEG-3 tumors from these animals showed an aromatase inhibition of 93.9% in treated mice as compared to untreated mice. Five days oral treatment with R 83 842 dose-dependently lowered both aromatase activity and uterus weight. Doses of 5 and 0.5 mg/kg inhibited tumor aromatase by 94.1 and 74.7%, respectively, and reduced uterus weight. After a dose of 0.05 mg/kg aromatase activity and uterus weight were similar to those in the control group.
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Affiliation(s)
- M D Krekels
- Department of Endocrinology and Oncology, Janssen Research Foundation, Beerse, Belgium
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Abstract
We have studied the kinetics of the allosteric interactions of pyruvate kinase from Trypanosoma brucei. The kinetics for phosphoenolpyruvate depended strongly on the nature of the bivalent metal ions. Pyruvate kinase activated by Mg2+ had the highest catalytic activity, but also the highest S0.5 for phosphoenolpyruvate, while the opposite was true for pyruvate kinase activated by Mn2+. The reaction rates of Mg(2+)-pyruvate kinase and Mn(2+)-pyruvate kinase were clearly allosteric with respect to phosphoenolpyruvate, while the kinetics with Co(2+)-pyruvate kinase were hyperbolic. However, Co(2+)-pyruvate kinase was still sensitive to heterotropic activation. Trypanosomal pyruvate kinase is unique in that the best activator was fructose 2,6-bisphosphate. Ribulose 1,5-bisphosphate and 5-phosphorylribose 1-pyrophosphate were also strong heterotropic activators, which were much more effective than fructose 1,6-bisphosphate and glucose 1,6-bisphosphate. In the presence of the heterotropic activators, the sigmoidal kinetics with respect to phosphoenolpyruvate and the bivalent metal ions were modified as were the concentrations of phosphoenolpyruvate and the bivalent metal ions needed to attain the maximal activity. Maximal activities were not significantly changed with Mg2+ and Mn2+ as the activating metal ions. Moreover, with Co2+ and fructose 2,6-bisphosphate or ribulose 1,5-bisphosphate or 5-phosphorylribose 1-pyrophosphate, the maximal activity was significantly reduced. Ribulose 1,5-bisphosphate and 5-phosphorylribose 1-pyrophosphate resembled fructose 2,6-bisphosphate rather than fructose 1,6-bisphosphate and glucose 1,6-bisphosphate in their action in that the K0.5 values for the former 3 compounds increased when Mg2+ was replaced by Co2+, while the K0.5 for fructose 1,6-bisphosphate and glucose 1,6-bisphosphate increased.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- M Callens
- International Institute of Cellular and Molecular Pathology, Research Unit for Tropical Diseases, Brussels, Belgium
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