Jan Tytgat

Universitair Psychiatrisch Centrum KU Leuven, Cortenberg, Flemish, Belgium

Are you Jan Tytgat?

Claim your profile

Publications (272)934.07 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: Four analogs of HelaTx1, a 25-mer peptide from scorpion venom, were synthesized by deleting its C-terminal hexapeptide fragment and N-terminal Ser residue and by inserting an amino acid in the middle part of the molecule. CD spectrum of HelaTx1(1-19) was almost superimposable to that of native HelaTx1. Functional characterization showed that HelaTx1(1-19) retained its inhibitory activity on Kv1.1 channel although 3 times less potent than HelaTx1, indicating that C-terminal part of HelaTx1 was not essential for its conformation and activity. Further deletion of N-terminal Ser residue and insertion of Ala in the middle part of the molecule affected the CD spectra and resulted in the decrease of activity.
    No preview · Article · Dec 2015 · Toxicon
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The toxin PnTx4(5-5) from the spider Phoneutria nigriventer is extremely toxic/lethal to insects but has no macroscopic behavioral effects observed in mice after intracerebral injection. Nevertheless, it was demonstrated that it inhibits the N-methyl-D-aspartate (NMDA) - subtype of glutamate receptors of cultured rat hippocampal neurons. PnTx4(5-5) has 63% identity to PnTx4(6-1), another insecticidal toxin from P. nigriventer, which can slow down the sodium current inactivation in insect central nervous system, but has no effect on Nav1.2 and Nav1.4 rat sodium channels. Here, we have cloned and heterologous expressed the toxin PnTx4(5-5) in E. coli. The recombinant toxin rPnTx4(5-5) was tested on the sodium channel NavBg from the cockroach Blatella germanica and on mammalian sodium channels Nav1.2-1.6, all expressed in Xenopus leavis oocytes. We showed that the toxin has different affinity and mode of action on insect and mammalian sodium channels. The most remarkable effect was on NavBg, where rPnTx4(5-5) strongly slowed down channel inactivation (EC50=212.5 nM), and at 1 μM caused an increase on current peak amplitude of 105.2 ± 3,1%. Interestingly, the toxin also inhibited sodium current on all the mammalian channels tested, with the higher current inhibition on Nav1.3 (38.43 ± 8.04%, IC50= 1.5 μM). Analysis of activation curves on Nav1.3 and Nav1.5 showed that the toxin shifts channel activation to more depolarized potentials, which can explain the sodium current inhibition. Furthermore, the toxin also slightly slowed down sodium inactivation on Nav1.3 and Nav1.6 channels. As far as we know, this is the first araneomorph toxin described which can shift the sodium channel activation to more depolarized potentials and also slows down channel inactivation.
    Full-text · Article · Dec 2015 · Biochimie
  • [Show abstract] [Hide abstract]
    ABSTRACT: The Kv1.3 channel is a novel target for immunomodulation of autoreactive effector memory T cells, which play a major role in the pathogenesis of autoimmune diseases. In this study, the Ts6 and Ts15 toxins isolated from Tityus serrulatus (Ts) were investigated for their immunosuppressant roles on CD4(+) cell subsets: naive, effector - TEF , central memory - TCM and effector memory - TEM . The electrophysiological assays confirmed that both toxins were able to block Kv1.3 channels. Interestingly, an extended Kv channel screening shows that Ts15 blocks Kv2.1 channels. Ts6 and Ts15 significantly inhibit the TEM proliferation and INF-γ production; however, Ts15 also inhibits other CD4(+) cell subsets (naive, TEF and TCM ). Based on the Ts15 inhibitory effect of proliferation of all CD4(+) cell subsets, and based on its blocking effect on Kv2.1, we investigated the Kv2.1 expression in T cells. The assays showed that CD4(+) and CD8(+) cells express the Kv2.1 channels mainly extracellular with TCM expressing the highest number of Kv2.1 channels. In vivo, we also provide experimental evidence to the protective effect of Ts6 and Ts15 on delayed-type hypersensitivity (DTH) reaction. Altogether, this study presents the immunosuppressive behavior of Ts6 and Ts15 toxins, indicating that these toxins could be promising candidates for autoimmune disease therapy. Moreover, this is the first report illustrating the involvement of a novel K(+) channel subtype, Kv2.1, and its distribution in T cell subsets. This article is protected by copyright. All rights reserved.
    No preview · Article · Nov 2015 · Immunology
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Scorpion toxins are important pharmacological tools for probing the physiological roles of ion channels which are involved in many physiological processes and as such have significant therapeutic potential. The discovery of new scorpion toxins with different specificities and affinities is needed to further characterize the physiology of ion channels. In this regard, a new short polypeptide called Kbot21 has been purified to homogeneity from the venom of Buthus occitanus tunetanus scorpion. Kbot21 is structurally related to BmBKTx1 from the venom of the Asian scorpion Buthus martensii Karsch. These two toxins differ by only two residues at position 13 (R /V) and 24 (D/N).Despite their very similar sequences, Kbot21 and BmBKTx1 differ in their electrophysiological activities. Kbot21 targets KV channel subtypes whereas BmBKTx1 is active on both big conductance (BK) and small conductance (SK) Ca2+-activated K+ channel subtypes, but has no effects on Kv channel subtypes. The docking model of Kbot21 with the Kv1.2 channel shows that the D24 and R13 side-chain of Kbot21 are critical for its interaction with KV channels.
    Full-text · Article · Sep 2015 · PLoS ONE
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: In this study, a validated method using a thermal desorber combined with a gas chromatograph coupled to mass spectrometry was used to identify the volatile organic compounds released during decomposition of 6 human and 26 animal remains in a laboratory environment during a period of 6 months. 452 compounds were identified. Among them a human specific marker was sought using principle component analysis. We found a combination of 8 compounds (ethyl propionate, propyl propionate, propyl butyrate, ethyl pentanoate, pyridine, diethyl disulfide, methyl(methylthio)ethyl disulfide and 3-methylthio-1-propanol) that led to the distinction of human and pig remains from other animal remains. Furthermore, it was possible to separate the pig remains from human remains based on 5 esters (3-methylbutyl pentanoate, 3-methylbutyl 3-methylbutyrate, 3-methylbutyl 2-methylbutyrate, butyl pentanoate and propyl hexanoate). Further research in the field with full bodies has to corroborate these results and search for one or more human specific markers. These markers would allow a more efficiently training of cadaver dogs or portable detection devices could be developed.
    Full-text · Article · Sep 2015 · PLoS ONE
  • E Cuypers · A-J Bonneure · J Tytgat

    No preview · Article · Sep 2015 · Drug Testing and Analysis

  • No preview · Conference Paper · Aug 2015
  • Source

    Full-text · Dataset · Jul 2015
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The toxin, previously described as a "non-toxic" toxin, was isolated from the scorpion venom of Tityus serrulatus (Ts), responsible for the most severe and the highest number of accidents in Brazil. In this study, the subtype specificity and selectivity of Ts4 was investigated using six mammalian Nav channels (Nav1.2→Nav1.6 and Nav1.8) and two insect Nav channels (DmNav1 and BgNav). The electrophysiological assays showed that Ts4 specifically inhibited the fast inactivation of Nav1.6 channels, the most abundant sodium channel expressed in the adult central nervous system, and can no longer be classified as a "non-toxic peptide". Based on the results, we could classify the Ts4 as a classical α-toxin. The Ts4 3D-structural model was built based on the solved X-ray Ts1 3D-structure, the major toxin from Ts venom with which it shares high sequence identity (65.57%). The Ts4 model revealed a flattened triangular shape constituted by three-stranded antiparallel β-sheet and one α-helix stabilized by four disulfide bonds. The absence of a Lys in the first amino acid residue of the N-terminal of Ts4 is probably the main responsible for its low toxicity. Other key amino acid residues important to the toxicity of α- and β-toxins are discussed here.
    Full-text · Article · Jul 2015 · Toxins
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: We designed a peptide, PnPP-19, comprising the potential active core of Phoneutria nigriventer native toxin PnTx2-6, and investigated its role on EF, its toxicity and immunogenicity. EF was evaluated through ICP/MAP ratio during EFS on rat pelvic ganglion. Corpus cavernous strips were PE-contracted and relaxation was induced by EFS with or without PnPP-19 (10(-8)M). The activity on sodium channels was evaluated by electrophysiological screening of transfected channels on Xenopus oocytes and DRG cells. Antibodies were detected by indirect ELISA in mice previously treated with the peptide. Histopathological studies were performed with mice organs receiving different doses of PnPP-19. PnPP-19 was able to potentiate erection at 4 and 8 Hz, in vivo and ex vivo. It showed no toxicity and low immunogenicity to mice and did not affect sodium channels or rat hearts. PnPP-19 increased cGMP levels at 8 Hz and this effect was inhibited by L-NAME (10(-4)M). EF was partially inhibited by 7-nitroindazole (7-NI, 10(-5)M), a selective inhibitor of nNOS. PnPP-19 potentiates erection, in vivo and ex vivo, via NO/cGMP pathway, does not affect sodium channels or rat heart, and shows no toxicity and low immunogenicity, what makes it a very promising candidate as a novel drug in the therapy of erectile dysfunction. Copyright © 2015 American Urological Association Education and Research, Inc. Published by Elsevier Inc. All rights reserved.
    Full-text · Article · Jun 2015 · The Journal of urology
  • [Show abstract] [Hide abstract]
    ABSTRACT: Ts19 Fragment II (Ts19 Frag-II) was first isolated from the venom of the scorpion Tityus serrulatus (Ts). It is a protein presenting 49 amino acid residues, three disulfide bridges, Mr 5,534Da and was classified as a new member of class (subfamily) 2 of the β-KTxs, the second one described for Ts scorpion. The β-KTx family is composed by two-domain peptides: N-terminal helical domain (NHD), with cytolytic activity, and a C-terminal CSαβ domain (CCD), with Kv blocking activity. The extensive electrophysiological screening (16 Kv channels and 5 Nav channels) showed that Ts19 Frag-II presents a specific and significant blocking effect on Kv1.2 (IC50 value of 544±32nM). However, no cytolytic activity was observed with this toxin. We conclude that the absence of 9 amino acid residues from the N-terminal sequence (compared to Ts19 Frag-I) is responsible for the absence of cytolytic activity. In order to prove this hypothesis, we synthesized the peptide with these 9 amino acid residues, called Ts19 Frag-III. As expected, Ts19 Frag-III showed to be cytolytic and did not block the Kv1.2 channel. The post-translational modifications of Ts19 and its fragments (I-III) are also discussed here. A mechanism of post-translational processing (post-splitting) is suggested to explain Ts19 fragments production. In addition to the discovery of this new toxin, this report provides further evidence for the existence of several compounds in the scorpion venom contributing to the diversity of the venom arsenal. Copyright © 2015. Published by Elsevier Inc.
    No preview · Article · Jun 2015 · Peptides
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Kbot55 is a 39 amino acid peptide isolated from the venom of the Tunisian scorpion Buthus occitanus tunetanus. This peptide is cross-linked by 3 disulfide bridges and has a molecular mass of 4128.65Da. Kbot55 is very low represented in the venom and thus represents a challenge for biochemical characterization. In this study, Kbot55 has been subjected to a screening on ion channels expressed in Xenopus laevis oocytes. It was found that Kbot55 targets voltage-gated potassium channels with high affinity. Kbot55 shows very low amino acid identity with other scorpion potassium toxins and therefore was considered a bona fide novel type of scorpion toxin. Sequence alignment analysis indicated that Kbot55 is the first representative of the new α-Ktx31 subfamily and therefore was classified as α-Ktx31.1. Copyright © 2015. Published by Elsevier Inc.
    Full-text · Article · Jun 2015 · Peptides
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Sponges of the genus Agelas produce compounds that modulate the activity of voltage-gated sodium ion channels and contribute novel scaffolds for the development of compounds with activity against a plethora of biological targets. In particular, clathrodin and dibromosceptrin were reported to decrease the average maximum amplitude of inward sodium currents in isolated chick embryo sympathetic ganglia cells; we envisaged these compounds as a starting point to design novel Nav channel modulators. This endeavor was part of our long-term goal of designing a comprehensive library of Agelas alkaloid analogs that would cover a broader chemical space and allow us to examine the activity of such compounds on Nav channels. Our series of compounds was designed by maintaining the terminal structural features found in clathrodin while rigidizing the central part of the molecule and replacing the 3-aminopropene linker with a 4-methylenepiperazine moiety. Synthesised compounds were screened for inhibitory action against the human voltage-gated sodium channel isoforms Nav 1.3, Nav 1.4, cardiac Nav 1.5, and Nav 1.7 using an automated patch clamp electrophysiology technique. The results demonstrate that we have obtained a series of compounds with a modest but selective inhibitory activity against the Nav 1.3 channel isoform. The most potent compound showed selective activity against the Nav 1.3 channel isoform with an IC50 of 19 μM and is a suitable starting point for further development of selective Nav 1.3 channel modulators. Such compounds could prove to be beneficial as a pharmacological tool towards the development of novel therapeutically useful compounds in the treatment of pain.
    Full-text · Article · Jun 2015 · Medicinal Chemistry Research
  • [Show abstract] [Hide abstract]
    ABSTRACT: As a cornerstone of quality management in the laboratory, External Quality Assessment (EQA) schemes are used to assess laboratory and analytical method performance. The characteristic function is used to describe the relation between the target concentration and the EQA standard deviation, which is an essential part of the evaluation process. The characteristic function is also used to compare the variability of different analytical methods. We fitted the characteristic function to data from the Belgian External Quality Assessment program for serum ethanol. Data included results from headspace gas chromatography and the enzymatic methods of Abbott, Roche, Siemens, and Ortho-Clinical Diagnostics. We estimated the characteristic function with weighted nonlinear regression. By introducing dummy variables, we rewrote the original formula of the characteristic function to assess statistical inference for comparing the variability of the different analytical methods. The characteristic function fitted the data precisely. Comparison between methods showed that there was little difference between the estimated variability for low concentrations, and that the increase in SD with increasing target concentration was slower for Abbott and Roche than for the other methods. The characteristic function can successfully be introduced in clinical schemes, although its applicability to fit the data should always be assessed. Because of its easy parameterization, it can be used to assess differences in performance between analytical methods and to assess laboratory performance. The characteristic function also offers an alternative framework for coefficients of variation to describe variability of analytical methods. © 2015 American Association for Clinical Chemistry.
    No preview · Article · May 2015 · Clinical Chemistry
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Tityus serrulatus (Ts) venom is composed of mainly neurotoxins specific for voltage-gated K(+) and Na(+) channels, which are expressed in many cells such as macrophages. Macrophages are the first line of defense invasion and they participate in the inflammatory response of Ts envenoming. However, little is known about the effect of Ts toxins on macrophage activation. This study investigated the effect of Ts5 toxin on different sodium channels as well as its role on the macrophage immunomodulation. The electrophysiological assays showed that Ts5 inhibits the rapid inactivation of the mammalian sodium channels Nav1.2, Nav1.3, Nav1.4, Nav1.5, Nav1.6 and Nav1.7. Interestingly, Ts5 also inhibits the inactivation of the insect Drosophila melanogaster sodium channel (DmNav1), and is therefore classified as the first Ts α-like toxin. The immunological experiments on macrophages reveal that Ts5 is a pro-inflammatory toxin inducing the cytokine production of tumor necrosis factor (TNF)-α and interleukin (IL)-6. On the basis of recent literature, our study also stresses a possible mechanism responsible for venom-associated molecular patterns (VAMPs) internalization and macrophage activation and moreover we suggest two main pathways of VAMPs signaling: direct and indirect. This work provides useful insights for a better understanding of the involvement of VAMPs in macrophage modulation. Copyright © 2015. Published by Elsevier B.V.
    Full-text · Article · Apr 2015 · Biochimie
  • [Show abstract] [Hide abstract]
    ABSTRACT: Matrix-assisted laser desorption/ionization-mass spectrometry imaging (MALDI-MSI) for the analysis of intact hair is a powerful tool for the detection of drugs of abuse in toxicology and forensic applications. Here we present a quick, easy, and reproducible method of preparing longitudinal sections of single hairs. This method improves the accessibility of chemicals embedded in the hair matrix for molecular imaging with mass spectrometry. The images obtained from a single, sectioned hair sample show molecular distributions in the exposed medulla, cortex, and a portion of the cuticle observed as a narrow layer surrounding the cortex. Using MALDI-MS/MS imaging, the distribution of cocaine was observed throughout five longitudinally sectioned drug-user hair samples. The images showed the distribution of the product ion at m/z 182, derived from the precursor ion of cocaine at m/z 304. MetA-SIMS images of longitudinally sectioned hair samples showed a more detailed distribution of cocaine at m/z 304, benzoylecgonine the major metabolite of cocaine at m/z 290 and other drugs such as methadone which was observed at m/z 310. Chronological information of drug intake can be obtained more sensitively. The chronological detail is in hours rather than months, which is of great interest in clinical as well as forensic applications. Copyright © 2015 John Wiley & Sons, Ltd. Copyright © 2015 John Wiley & Sons, Ltd.
    No preview · Article · Apr 2015 · Drug Testing and Analysis
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: In the last decades, Ts1 has not only been the subject of many studies, it has also been considered as a very useful tool to investigate NaV channels and to explore the exact role of NaV channels in channelopathies. Ts1 is believed to modulate the activation process of NaV upon interaction at the neurotoxin binding site 4. Our aim was to carry out an in depth functional characterization of Ts1 on a wide array of Nav channels, in order to investigate its mechanism of action and to verify if Ts1 can indeed be considered as a prototype site 4 selective toxin, valid for all the Nav isoforms we know currently. Ts1 has been subjected to an in-depth functional investigation on 9 NaV isoforms expressed in Xenopus laevis oocytes. Ts1 does not only interfere with the activation process but also modulates the inactivation in a bell-shaped voltage-dependent matter. Furthermore, Ts1 altered the ion selectivity through insect NaV. without influencing the tetrodotoxin selectivity of the channels. Finally, Ts1 was also found to inhibit the sodium current through the cardiac Nav1.5 isoform. On the basis of the totally unexpected plethora of Nav modulations as induced by Ts1, we demonstrate that caution is required in interpretation the in vivo experiments when using Ts1. The electrophysiological characterization of Ts1 indeed shows that the general accepted contours of NaV binding sites are much more obscure than believed and that interpretation of NaV pharmacology upon toxin binding is more complex than believed thus far. Copyright © 2015 Elsevier Ltd. All rights reserved.
    Full-text · Article · Apr 2015 · Neuropharmacology
  • [Show abstract] [Hide abstract]
    ABSTRACT: Scorpion venom consists of a complex mixture of molecules including biologically active compounds. Because of their high potency and selectivity, toxins have medical applicability. In the last decades, scorpion toxins have thus gained considerable interest among scientist in the fields of pharmacology, biophysics and neurobiology. Identification of scorpion venom peptides and toxins can be achieved based on transcriptome approaches. We constructed the first cDNA library and Expressed Sequence Tag (EST) study to explore the transcriptomic composition of the telson from the southern African scorpion Hottentotta conspersus, belonging to the family Buthidae. We obtained 21 new venom-related sequences (8 contigs and 16 singlets) from a total of 98 ESTs analyzed, including putative neurotoxins (chloride, potassium, sodium and calcium channel toxins), bradykinin-potentiating peptides and other venom peptides without established function. These novel toxin-related sequences might serve as basis for further research both of pharmaceutical and phylogenetic nature. Copyright © 2015. Published by Elsevier Ltd.
    No preview · Article · Mar 2015 · Toxicon
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The lesser Asian scorpion Mesobuthus eupeus (Buthidae) is one of the most widely spread and dispersed species of the Mesobuthus genus and its venom is actively studied. Nevertheless, a considerable amount of active compounds is still under-investigated due to the high complexity of this venom. Here we report a comprehensive analysis of putative potassium channel toxins (KTxs) from the cDNA library of M. eupeus venom glands and compare the deduced KTx structures with peptides purified from the venom. For the transcriptome analysis we used conventional tools as well as a search for structural motifs characteristic of scorpion venom components in the form of regular expressions. We found 59 candidate KTxs distributed in 30 subfamilies and presenting the cysteine-stabilized α/β (CSα/β) and inhibitor cystine knot (ICK) types of fold. M. eupeus venom was then separated to individual components by multi-stage chromatography. A facile fluorescent system based on the expression of the KcsA-Kv1.1 hybrid channels in Escherichia coli and utilization of a labeled scorpion toxin was elaborated and applied to follow Kv1.1 pore-binding activity during venom separation. As a result, eight high-affinity Kv1.1 channel blockers were identified including five novel peptides, which extend the panel of potential pharmacologically important Kv1 ligands. Activity of the new peptides against rat Kv1.1 channel was confirmed (IC50 in the range of 1-750 nM) by the two-electrode voltage-clamp technique using a standard Xenopus oocyte system. Our integrated approach is of general utility and efficiency to mine natural venoms for KTxs. Copyright © 2015, The American Society for Biochemistry and Molecular Biology.
    Full-text · Article · Mar 2015 · Journal of Biological Chemistry
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Cyclic nucleotide-sensitive ion channels are molecular pores that open in response to cAMP or cGMP, which are universal second messengers. Binding of a cyclic nucleotide to the carboxyterminal cyclic nucleotide binding domain (CNBD) of these channels is thought to cause a conformational change that promotes channel opening. The C-linker domain, which connects the channel pore to this CNBD, plays an important role in coupling ligand binding to channel opening. Current structural insight into this mechanism mainly derives from X-ray crystal structures of the C-linker/CNBD from hyperpolarization-activated cyclic nucleotide-modulated (HCN) channels. However, these structures reveal little to no conformational changes upon comparison of the ligand-bound and unbound form. In this study, we take advantage of a recently identified prokaryote ion channel, SthK, which has functional properties that strongly resemble cyclic nucleotide-gated (CNG) channels and is activated by cAMP, but not by cGMP. We determined X-ray crystal structures of the C-linker/CNBD of SthK in the presence of cAMP or cGMP. We observe that the structure in complex with cGMP, which is an antagonist, is similar to previously determined HCN channel structures. In contrast, the structure in complex with cAMP, which is an agonist, is in a more open conformation. We observe that the CNBD makes an outward swinging movement, which is accompanied by an opening of the C-linker. This conformation mirrors the open gate structures of the Kv1.2 channel or MthK channel, which suggests that the cAMP-bound C-linker/CNBD from SthK represents an activated conformation. These results provide a structural framework for better understanding cyclic nucleotide modulation of ion channels, including HCN and CNG channels.
    Full-text · Article · Jan 2015 · PLoS ONE

Publication Stats

7k Citations
934.07 Total Impact Points


  • 1996-2015
    • Universitair Psychiatrisch Centrum KU Leuven
      Cortenberg, Flemish, Belgium
  • 1994-2015
    • University of Leuven
      • • Laboratory for Toxicology and Food Chemistry
      • • Center for Molecular and Vascular Biology
      • • Faculty of Pharmaceutical Sciences
      • • Department of Biology
      Louvain, Flanders, Belgium
  • 2014
    • The Catholic University of America
      Washington, Washington, D.C., United States
  • 2011
    • Nanyang Technological University
      Tumasik, Singapore
    • University of Wisconsin–Madison
      Madison, Wisconsin, United States
  • 2004
    • Universität Ulm
      Ulm, Baden-Württemberg, Germany
    • Shanghai Jiao Tong University
      Shanghai, Shanghai Shi, China
  • 2003
    • Architecture et Fonction des Macromolécules Biologiques
      Marsiglia, Provence-Alpes-Côte d'Azur, France
  • 1992
    • Harvard Medical School
      Boston, Massachusetts, United States
  • 1990
    • Martin Luther University Halle-Wittenberg
      • Julius Bernstein Institute for Physiology
      Halle-on-the-Saale, Saxony-Anhalt, Germany