Jan Tytgat

Universitair Psychiatrisch Centrum KU Leuven, Cortenberg, Flanders, Belgium

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Publications (231)846.98 Total impact

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    ABSTRACT: We present a structural and functional study of a sodium channel activation inhibitor from crab spider venom. Hm-3 is an insecticidal peptide toxin consisting of 35 amino acid residues from the spider Heriaeus melloteei (Thomisidae). We produced Hm-3 recombinantly in Escherichia coli and determined its structure by NMR spectroscopy. Typical for spider toxins, Hm-3 was found to adopt the so-called ″inhibitor cystine knot″ (ICK) or ″knottin″ fold stabilized by three disulfide bonds. Its molecule is amphiphilic with a hydrophobic ridge on the surface enriched in aromatic residues and surrounded by positive charges. Correspondingly, Hm-3 binds to both neutral and negatively charged lipid vesicles. Electrophysiological studies showed that at a concentration of 1 μM Hm-3 effectively inhibited a number of mammalian and insect sodium channels. Importantly, Hm-3 shifted the dependence of channel activation to more positive voltages. Moreover, the inhibition was voltage-dependent, and strong depolarizing prepulses attenuated Hm-3 activity. The toxin is therefore concluded to represent the first sodium channel gating modifier from an araneomorph spider and feature a ″membrane-access″ mechanism of action. Its amino acid sequence and position of the hydrophobic cluster are notably different from other known gating modifiers from spider venom, all of which are described from mygalomorph species. We hypothesize parallel evolution of ICK toxins from Araneomorphae and Mygalomorphae suborders.
    The Journal of biological chemistry. 10/2014;
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    ABSTRACT: Cone snails (Conus sp.) are poisonous animals that can be found in all oceans where they developed a venomous strategy to prey or to defend. The venom of these species contains an undeniable source of unique and potent pharmacologically active compounds. Their peptide compounds, called conotoxins, are not only interesting for the development of new pharmaceutical ligands, but they are also useful for studying their broad spectrum of targets. One conotoxin family in particular, the α-conotoxins, acts on nicotinic acetylcholine receptors (nAChRs) which dysfunctions play important roles in pathologies such as epilepsy, myasthenic syndromes, schizophrenia, Parkinson's disease and Alzheimer's disease. Here we define a new subclass of the α-conotoxin family. We purified the venom of a yet unexplored cone snail species, i.e. Conus australis, and we isolated a 16-amino acid peptide named α-conotoxin AusIA. The peptide has the typical α-conotoxin CC-Xm-C-Xn-C framework, but both loops (m/n) contain 5 amino acids, which has never been described before. Using conventional electrophysiology we investigated the response of synthetically made globular (I-III, II-IV) and ribbon (I-IV, II-III) AusIA to different nicotinic acetylcholine receptors. The α7 nAChR was the only receptor found to be blocked with a similar potency by both peptide-configurations. This suggests that both α5/5 conotoxin isomers might be present in the venom gland of C. australis. NMR spectroscopy showed that no secondary structures define the peptides' three-dimensional topology. Moreover, the ribbon configuration, which is generally considered to be non-native, is more stable than the globular isoform. Accordingly, our findings show relevancy concerning the α-conotoxin classification which might be helpful in the design of novel therapeutic compounds.
    Toxicon : official journal of the International Society on Toxinology. 09/2014;
  • Alternative Sampling Strategies in Toxicology and Therapeutic Drug Monitoring, Ghent, Belgium; 09/2014
  • Alternative Sampling Strategies in Toxicology and Therapeutic Drug Monitoring; 09/2014
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    ABSTRACT: Today, forensic hair analysis is considered to be a standard method for identifying chronic drug users since information about drug use stored and located in hair can cover several months to even years. When interpreting these results, one should be aware of all kind of pitfalls. External factors such as bleaching might influence the analytical result. Although the effect of hydrogen peroxide on cocaine in a solution was described before, it was never investigated whether the described reaction products (ecgonine methylester, benzoylecgonine, hydroxynorcocaine and dihydroxycocaine) are indeed found on contaminated or user hair. Since it is of great importance in forensic hair analysis to know whether cocaine and/or reaction products are detectable in hair after bleaching, matrix-assisted laser desorption/ionization mass spectrometric imaging (MALDI-MSI) was used to study the effect of hydrogen peroxide treatment on incorporated cocaine in hairs. Cocaine oxidation products were identified in a solution based on MS/MS spectra and spatial distribution of these products in hair was explored using MALDI TOF-MS. All images were accomplished by spraying α-Cyano-4-hydroxycinnamic acid (CHCA) as a MALDI-matrix. Images revealed a loss of detectability of cocaine and its reaction products in hairs already after a short bleaching period. Since all compounds of interest are found in the hydrogen peroxide and wash solution, these findings indicate that all evidence of cocaine use might be lost after a hair bleaching treatment. Therefore, forensic toxicologists should take into consideration whether hair samples were bleached before making any conclusions from hair analysis results.
    Forensic Science International 07/2014; 242C:103-110. · 2.31 Impact Factor
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    ABSTRACT: Transcriptome approaches have revealed a diversity of venom compounds from a number of venomous species. Mesobuthus gibbosus scorpion showed a medical importance for the toxic effect of its sting. Previously, our group reported the first three transcripts that encode toxin genes in M. gibbosus. However, no additional toxin genes or venom components have been described for this species. Furthermore, only a very small number of reports on the genomic organization of toxin genes of scorpion species have been published. Up to this moment, no information on the gene characterization of M. gibbosus is available. This study provides the first insight into gene expression in venom glands from M. gibbosus scorpion. A cDNA library was generated from the venom glands and subsequently analyzed (301 clones). Sequences from 177 high-quality ESTs were grouped as 48 Mgib sequences, of those 48 sequences, 40 (29 "singletons" and 11 "contigs") correspond with one or more ESTs. We identified putative precursor sequences and were grouped them in different categories (39 unique transcripts, one with alternative reading frames), resulting in the identification of 12 new toxin-like and 5 antimicrobial precursors (transcripts). The analysis of the gene families revealed several new components categorized among various toxin families with effect on ion channels. Sequence analysis of a new KTx precursor provides evidence to validate a new KTx subfamily (alpha-KTx 27.x). A second part of this work involves the genomic organization of three Meg-chlorotoxin-like genes (ClTxs). Genomic DNA sequence reveals close similarities (presence of one same-phase intron) with the sole genomic organization of chlorotoxins ever reported (from M. martensii). Transcriptome analysis is a powerful strategy that provides complete information of the gene expression and molecular diversity of the venom glands (telson). In this work, we generated the first catalogue of the gene expression and genomic organization of toxins from M. gibbosus. Our result represents a relevant contribution to the knowledge of toxin transcripts and complementary information related with other cell function proteins and venom peptide transcripts. The genomic organization of the chlorotoxin genes may help to understand the diversity of this gene family.
    BMC Genomics 04/2014; 15(1):295. · 4.40 Impact Factor
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    ABSTRACT: In this paper we present the spatial structure of the wheat antimicrobial peptide (AMP) Tk-AMP-X2 studied using NMR spectroscopy. This peptide is found to adopt a disulfide-stabilized α-helical hairpin fold and therefore belongs to the α-hairpinin family of plant defense peptides. Based on Tk-AMP-X2 structural similarity to cone snail and scorpion potassium channel blockers, a mutant molecule Tk-hefu and was engineered by incorporating the functionally important residues from κ-hefutoxin 1 onto Tk-AMP-X2 scaffold. The designed peptide contained the so-called essential dyad of amino acid residues significant for channel-blocking activity. Electrophysiological studies showed that while the parent peptide Tk-AMP-X2 did not present any activity against potassium channels, Tk-hefu blocked Kv1.3 channels with similar potency (IC50 ≈35 μM) to κ-hefutoxin 1 (IC50 ≈40 μM). We conclude that α-hairpinins are attractive in their simplicity structural templates, which may be used for functional engineering and drug design.
    Journal of Biological Chemistry 03/2014; · 4.65 Impact Factor
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    ABSTRACT: Differentiation between human and animal remains by means of analysis of volatile compounds released during decomposition is impossible since no volatile marker(s) specific for human decomposition has been established today. Hence, the identification of such a marker for human decomposition would represent great progression for the discovery of buried cadavers by analytical techniques. Cadaver dogs can be trained more efficiently, the understanding of forensic entomology can be enhanced, and the development of a portable detection device may be within reach. This study describes the development and validation of a new analytical method that can be applied in the search of such (a) specific marker(s). Sampling of the volatile compounds released by decomposing animal and human remains was performed both in a laboratory environment and outdoors by adsorption on sorbent tubes. Different coatings and several sampling parameters were investigated. Next, the volatile compounds were analyzed and identified by a thermal desorber combined with gas chromatography coupled to mass spectrometry (TD-GC/MS). Different GC columns were tested. Finally, the analytical method was validated using a standard mixture of nine representative compounds.
    Analytical and Bioanalytical Chemistry 03/2014; 406:3611-3619. · 3.66 Impact Factor
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    ABSTRACT: Sea anemones produce ion channels peptide toxins of pharmacological and biomedical interest. However, peptides acting on ligand-gated ion channels, including acid-sensing ion channel (ASIC) toxins, remain poorly explored. PhcrTx1 is the first compound characterized from the sea anemone Phymanthus crucifer, and it constitutes a novel ASIC inhibitor. This peptide was purified by gel filtration, ion-exchange and reversed-phase chromatography followed by biological evaluation on ion channels of isolated rat dorsal root ganglia (DRG) neurons using patch clamp techniques. PhcrTx1 partially inhibited ASIC currents (IC50∼100 nM), and also voltage-gated K+ currents but the effects on the peak and on the steady state currents were lower than 20% in DRG neurons, at concentrations in the micromolar range. No significant effect was observed on Na+ voltage-gated currents in DRG neurons. The N-terminal sequencing yielded 32 amino acid residues, with a molecular mass of 3477 Da by mass spectrometry. No sequence identity to other sea anemone peptides was found. Interestingly, the bioinformatic analysis of Cys-pattern and secondary structure arrangement suggested that this peptide presents an Inhibitor Cystine Knot (ICK) scaffold, which has been found in other venomous organisms such as spider, scorpions and cone snails. Our results show that PhcrTx1 represents the first member of a new structural group of sea anemones toxins acting on ASIC and, with much lower potency, on Kv channels. Moreover, this is the first report of an ICK peptide in cnidarians, suggesting that the occurrence of this motif in venomous animals is more ancient than expected.
    Peptides 03/2014; 53:3-12. · 2.52 Impact Factor
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    ABSTRACT: α-Conotoxins are peptide toxins found in the venom of marine Cone snails and potent antagonists of various subtypes of nicotinic acetylcholine receptors (nAChRs). nAChRs are cholinergic receptors forming ligand-gated ion channels in the plasma membranes of certain neurons and the neuromuscular junction. As nAChRs have an important role in regulating transmitter release, cell excitability, and neuronal integration, nAChR dysfunctions have been implicated in a variety of severe pathologies such as epilepsy, myasthenic syndromes, schizophrenia, Parkinson's and Alzheimer's diseases. In order to expand the knowledge concerning Cone snail toxins, we examined the venom of Conus longurionis. We isolated an 18-amino acid peptide named α-conotoxin Lo1a, which is active on nAChRs. To the best of our knowledge, this is the first characterization of a conotoxin from this species. The peptide was characterized by electrophysiological screening against several types of cloned nAChRs expressed in Xenopus laevis oocytes. The three-dimensional solution structure of the α-conotoxin Lo1a was determined by NMR spectroscopy. Lo1a, member of the α4/7 family, blocks the response to acetylcholine in oocytes expressing α7 nAChRs with an IC50 of 3.24 ± 0.7 μM. Furthermore, Lo1a shows a high selectivity for neuronal versus muscle subtype nAChRs. As Lo1a has an unusual C-terminus, we designed two mutants, Lo1a-ΔD and Lo1a-RRR, in order to investigate the influence of the C-terminal residue. Lo1a-ΔD has a C-terminal Asp-deletion whereas in Lo1a-RRR, a triple Arg-tail replaces the Asp. They block the neuronal nAChR α7 with a lower IC50 value, but remarkably, both adopted affinity for the muscle subtype α1β1δε.
    Journal of Biological Chemistry 02/2014; · 4.65 Impact Factor
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    ABSTRACT: Scorpion K(+) channel toxins and insect defensins share a conserved three-dimensional structure and related biological activities (defense against competitors or invasive microbes by disrupting their membrane functions), which provides an ideal system to study how functional evolution occurs in a conserved structural scaffold. Using an experimental approach, we show that the deletion of a small loop of a parasitoid venom defensin possessing the "scorpion toxin signature" (STS) can remove steric hindrance of peptide-channel interactions and result in a neurotoxin selectively inhibiting K(+) channels with high affinities. This insect defensin-derived toxin adopts a hallmark scorpion toxin fold with a common cysteine-stabilized α-helical and β-sheet motif, as determined by nuclear magnetic resonance (NMR) analysis. Mutations of two key residues located in STS completely diminish or significantly decrease the affinity of the toxin on the channels, demonstrating that this toxin binds to K(+) channels in the same manner as scorpion toxins. Taken together, these results provide new structural and functional evidence supporting the predictability of toxin evolution. The experimental strategy is the first employed to establish an evolutionary relationship of two distantly related protein families.
    Molecular Biology and Evolution 01/2014; · 14.31 Impact Factor
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    ABSTRACT: In Brazil, Tityus serrulatus (Ts) is the species responsible for most of the scorpion related accidents. Among the Ts toxins, the neurotoxins with action on potassium channels (α-KTx) present high interest, due to their effect in the envenoming process and the ion channel specificity they display. The α-KTx toxins family is the most relevant because its toxins can be used as therapeutic tools for specific target cells. The improved isolation method provided toxins with high resolution, obtaining pure Ts6 and Ts7 in two chromatographic steps. The effects of Ts6 and Ts7 toxins were evaluated in 14 different types of potassium channels using the voltage-clamp technique with two-microelectrodes. Ts6 toxin shows high affinity for Kv1.2, Kv1.3 and Shaker IR, blocking these channels in low concentrations. Moreover, Ts6 blocks the Kv1.3 channel in picomolar concentrations with an IC50 of 0.55 nM and therefore could be of valuable assistance to further designing immunosuppressive therapeutics. Ts7 toxin blocks multiple subtypes channels, showing low selectivity among the channels analyzed. This work also stands out in its attempt to elucidate the residues important for interacting with each channel and, in the near future, to model a desired drug.
    Toxins 01/2014; 6(3):892-913. · 2.13 Impact Factor
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    ABSTRACT: Since it is an apocrine secretion, scorpion venom is a complex mixture that contains a variety of low-molecular-weight basic proteins (neurotoxins), mucus, salts, as well as a large number of other constituents. Diversity of scorpion venom peptides exists also at the transcript level. Two kinds of venom peptides are typically considered: the neurotoxins and the antimicrobial peptides. We constructed a cDNA library and carried an EST (Expressed Sequence Tag) approach to overview the different peptides in the transcriptome of the telson from Parabuthus stridulus. P. stridulus are psammophilous and highly venomous scorpions endemic to Namibia (Prendini 2004) with medical relevance because of important human envenomation occurrence. We obtained 111 ESTs, 20% of them corresponding to cellular process transcripts, 7% to hypothetical proteins and 17% were sequences without good matches, but the majority of ESTs, 56%, corresponds to transcripts encoding for different venom components, including voltage-gated sodium, potassium and calcium channel toxins, antimicrobial peptides and other venom and cell proteins. To the best of our knowledge this report contains the first transcriptome analysis of genes transcribed by the venomous gland of the scorpion species P. stridulus, belonging to the family of medically important Buthidae scorpions. One hundred and eleven ESTs were analyzed, showing an important number of genes that encode for products similar to known scorpion venom components. In total, 17 unique and novel sequences were indentified. The identification and characterization of these compounds will be a good source of novel pharmacological tools for studying ion channels and the understanding of the physiological effects of toxins in P.stridulus envenomations at a molecular level.
    Toxicon 01/2014; · 2.92 Impact Factor
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    ABSTRACT: Clathrodin is a marine alkaloid and believed to be a modulator of voltage-gated sodium (NaV) channels. Since there is an urgent need for small molecule NaV channel ligands as novel therapeutics, clathrodin could represent an interesting lead compound. Therefore, clathrodin was reinvestigated for its potency and NaV channel subtype selectivity. Clathrodin and its synthetic analogues were subjected to screening on a broad range of NaV channel isoforms, both in voltage clamp and patch clamp conditions. Even though clathrodin was not found to exert any activity, some analogues were capable of modulating the NaV channels, hereby validating the pyrrole-2-aminoimidazole alkaloid structure as a core structure for future small molecule-based NaV channel modulators.
    Marine Drugs 01/2014; 12(4):2132-43. · 3.98 Impact Factor
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    ABSTRACT: Voltage-gated sodium channels play an integral part in neurotransmission and their dysfunction is frequently a cause of various neurological disorders. On the basis of the structure of marine alkaloid clathrodin, twenty eight new analogs were designed, synthesized and tested for their ability to block human NaV1.3, NaV1.4 and NaV1.7 channels, as well as for their selectivity against human cardiac isoform NaV1.5, using automated patch clamp electrophysiological assay. Several compounds exhibited promising activities on different NaV channel isoforms in the medium micromolar range and some of the compounds showed also moderate isoform selectivities. The most promising results were obtained for the NaV1.3 channel, for which four compounds were found to possess IC50 values lower than 15 μM. All of the active compounds bind to the open-inactivated states of the channels and therefore act as state-dependent modulators. The obtained results validate the approach of using natural products driven chemistry for drug discovery starting points and represent a good foundation for future design of selective NaV modulators.
    European Journal of Medicinal Chemistry 01/2014; 74:23 - 30. · 3.43 Impact Factor
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    ABSTRACT: We study the effect of all Tityus discrepans venom components on macrophage alterations. Only seven toxins called “Inflammatory Toxin” (InfTx1-7) induced cell changes. Incubation with InfTx1 through InfTx5 rose macrophage NO level at 2 h toxin exposure. Cells rose NO release by 4 h exposure with InfTx2 and InfTx5, the NO levels reached concentrations similar or higher than the induced by lipopolysaccharides (LPS) incubation. InfTx2, -6 and -7 increased cell TNF-α release. InfTx2 as LPS roses cell TNF-α secretion gradually in time. Macrophages were loaded with fluorescent dyes, exposed to all toxins and observed with a 3D wide field deconvolution setup. Cells exposed to whole venom or InfTx4 through InfTx7 developed pseudopodia, cytoplasm prolongations, blebs, and loss their rounded form. The molecular masses and N-terminal sequences of InfTx4 through InfTx7 were analyzed by MALDI-TOF mass spectrometry and Edman degradation. InfTx4-7 induced a remarkably rose of of intracellular Ca2+ levels ([Ca2+]i), measured as a rise of normalized cell green fluorescence intensity (FI) ×2.7, ×2.6, ×95 and ×2.9 the controls, respectively. InfTx6-7 action mechanisms were studied under different conditions. Results suggested that InfTx6 interact with a membrane sodium channel inducing cell depolarization with a consequently increase on intracellular [Na+], this would activate Na+/Ca2+ exchanger 3 (NCX) in the reverse mode and the phospholipase C inositol 1,4,5-trisphosphate (PLC-IP3) signaling pathway inducing [Ca2+]i overload. Inftx7 should activate the NCX in the reverse mode and/or should activate the Na+/H+ exchanger, increasing intracellular [Na+] which indirectly induce the activation of NCX3rv and the PLC-IP3 signaling pathway. All these mechanisms would cooperate with the [Ca2+]i overload. A rise of [Ca2+]i activates the synthesis and secretion of inflammatory molecules like TNF-α, which in turn, increases the gene transcription for inducible nitric oxide synthase, resulting on NO production.
    Toxicon 01/2014; · 2.92 Impact Factor
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    ABSTRACT: Marine snails of the genus Conus are a large family of predatory gastropods with an unparalleled molecular diversity of pharmacologically active compounds in their venom. Cone snail venom comprises of a rich and diverse cocktail of peptide toxins which act on a wide variety of ion channels such as voltage-gated sodium- (NaV), potassium- (KV), and calcium- (CaV) channels as well as nicotinic acetylcholine receptors (nAChRs) which are classified as ligand-gated ion channels. The mode of action of several conotoxins has been the subject of investigation, while for many others this remains unknown. This review aims to give an overview of the knowledge we have today on the molecular pharmacology of conotoxins specifically interacting with nAChRs along with the structure-function relationship data.
    Marine Drugs 01/2014; 12(5):2970-3004. · 3.98 Impact Factor
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    ABSTRACT: Voltage-gated sodium channels (VGSC) are attractive targets for drug discovery because of the broad therapeutic potential of their modulators. Based on the structure of marine alkaloid clathrodin, we have recently discovered novel subtype-selective VGSC modulators I and II that were used as starting points for two different ligand-based virtual screening approaches for discovery of novel VGSC modulators. Similarity searching in ZINC database of drug-like compounds based on compound I, resulted in five state-dependent Nav1.3 and Nav1.7 modulators with improved activity compared to I (IC50 < 20 µM). Compounds 2 and 16 that blocked sodium permeation in Nav1.7 with IC50 values of 7 µM and 9 µM, respectively, are among the most potent clathrodin analogs discovered so far. In the case of compound II, 3D similarity searching in the same database was followed by docking of an enriched compound library into our human Nav1.4 open-pore homology model. Although some of the selected compounds, e.g. 31 and 32 displayed 21% and 22% inactivated state Ipeak block of Nav1.4 at 10 µM, none showed better Nav1.4 modulatory activity than compound II. Taken together, virtual screening yielded compounds 2 and 16, which represent novel scaffolds for the discovery of human Nav1.7 modulators.
    Journal of Chemical Information and Modeling 11/2013; · 4.30 Impact Factor
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    ABSTRACT: Immunoassays are widely used to perform an initial toxicological screening of biological samples. However, LC-MS/MS is described as a promising technique that can overcome the limitations of immunoassays (such as their lack of selectivity). The objective of this project was to implement a LC-MS/MS method for screening of forensic ante-and post-mortem urine and whole blood samples that can replace the immunoassays. Easy and rapid sample preparation techniqueswere evaluated. Protein precipitation with acetonitrile combined with aqueous dilution (dilution factor 5 for urine and 10 for blood) proved to be an effective procedure. On the LC-MS/MS, 1 scheduled multiple reaction monitoring transition for each of 414 compounds was analyzed in positive mode, followed by an enhanced product ion scan if the peak height exceeded a specified threshold. In negative ionization mode, 38 compounds were measured with a scheduled multiple reaction monitoring method. For analysis of THC and two metabolites, a separate positive multiple reaction monitoring method was used to enhance sensitivity. 162 forensic urine samples and 146 blood samples were analyzed with both LC-MS/MS and immunoassay screening. LC-MS/MS screening was superior and can be considered as a trustworthy alternative to immunoassays in forensic toxicology.
    Journal of Forensic Toxicology & Pharmacology. 10/2013; 2:1-8.

Publication Stats

4k Citations
846.98 Total Impact Points

Institutions

  • 2013–2014
    • Universitair Psychiatrisch Centrum KU Leuven
      Cortenberg, Flanders, Belgium
    • University of São Paulo
      San Paulo, São Paulo, Brazil
  • 1994–2014
    • KU Leuven
      • • Laboratory for Toxicology and Food Chemistry
      • • Department of Pharmaceutical and Pharmacological Sciences
      • • Faculty of Pharmaceutical Sciences
      Louvain, Flanders, Belgium
    • Catholic University of Louvain
      Walloon Region, Belgium
  • 2009–2013
    • University of Antwerp
      • Department of Biomedical sciences
      Antwerpen, VLG, Belgium
  • 2003–2013
    • Northeast Institute of Geography and Agroecology
      • • Institute of Zoology
      • • Center for Structural and Molecular Biology
      • • Institute of Biophysics
      Beijing, Beijing Shi, China
    • University of Debrecen
      • Department of Biophysics and Cell Biology
      Debrecen, Hajdu-Bihar, Hungary
  • 2007
    • Lyon Neuroscience Research Center
      Lyons, Rhône-Alpes, France
  • 2006
    • French National Centre for Scientific Research
      • Institute of Molecular and Cellular Pharmacology
      Lutetia Parisorum, Île-de-France, France
  • 2005
    • Shahid Beheshti University of Medical Sciences
      • Department of Toxicology and Pharmacology
      Tehrān, Ostan-e Tehran, Iran
    • Hunan University
      • College of Chemistry and Chemical Engineering
      Ch’ang-sha-shih, Hunan, China
  • 1999–2005
    • Universidad Nacional Autónoma de México
      • • Institute of Biotechnology
      • • Department of Molecular Medicine and Bioprocesses
      Mexico City, The Federal District, Mexico
  • 1992–2005
    • Harvard Medical School
      • Department of Neurobiology
      Boston, MA, United States
  • 2004
    • Peking University
      • School of Life Sciences
      Beijing, Beijing Shi, China
  • 1992–1993
    • Harvard University
      • Department of Molecular and Cell Biology
      Boston, MA, United States