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Biomedical subjects

E Habermann

Publications and source records attributed to E Habermann.

At least 19 recordsLinked to original sources
PubMed1992

Reductive cleavage of tetanus toxin and botulinum neurotoxin A by the thioredoxin system from brain. Evidence for two redox isomers of tetanus toxin.

Inhibition of neurotransmitter release by tetanus toxin and botulinum neurotoxin A can be mimicked by intracellular application of the corresponding toxin light chains. The aim of this study was to determine whether the two-chain toxins are reduced by brain preparations to yield free light chains which would represent the ultimate toxins. The interchain disulfide of two-chain tetanus toxin was cleaved by rat cortex homogenate fortified with NADPH. Reduction was promoted further by addition of thioredoxin. Thioredoxin reductase was demonstrated in and purified from porcine brain cortex. The thioredoxin system which consisted of purified enzyme, thioredoxin and NADPH reduced both toxins. The resulting light chains appeared homogeneous in SDS gel electrophoresis. The complementary heavy chain of tetanus but not of botulinum toxin migrated in two bands, the faster one with the velocity of heavy chain obtained by chemical reduction. The major, slower form was converted into the faster by chemical but not by enzymatic reduction. Tetanus toxin, whether in its single-chain or two-chain version also occurred in two forms which differed by their electrophoretic mobility. The two forms of single-chain toxin were interconverted by chemical reduction or oxidation but not by the thioredoxin system. It is concluded that a) a thioredoxin system in brain tissue reduces the interchain disulfide of two-chain tetanus toxin and botulinum neurotoxin A, b) tetanus toxin but not botulinum neurotoxin A consists of two electrophoretically distinct forms which differ by the thiol-disulfide status of their heavy chains, c) the disulfide loop within the heavy chain of tetanus toxin is resistant to the thioredoxin system.

Animals↗
PubMed1992

Evidence for a link between specific proteolysis and inhibition of [3H]-noradrenaline release by the light chain of tetanus toxin.

The light chain of tetanus toxin is known to inhibit the Ca(2+)-evoked release of [3H]-noradrenaline from digitonin-permeabilized bovine adrenomedullary cells in culture but does not change the basal outflow or the total cellular radioactivity. Evidence for the involvement of proteolysis in this effect was obtained by three approaches. First, the permeabilized cells were exposed to a series of enzymes. The endoproteinase Glu-C mimicked the inhibition produced by the light chain. Second, protease inhibitors of different specificities were assessed for blockade of the action of light chain on [3H]-noradrenaline release from permeabilized cells. Blockade was complete with EDTA (2.5 mmol/l) or 1,10-o-phenanthroline (1 mmol/l), and absent with the highest concentrations tested of diisopropylfluorophosphate, phenylmethylsulfonyl fluoride, pepstatin, leupeptin, bestatin, phosphoramidon, thiorphan or trans-epoxysuccinic acid (E64) which is regarded as an inhibitor of thiol proteases. This inhibitor spectrum suggested that light chain might be a metalloprotease. Finally a sequence-His-Glu-Leu-X-His-occurring in the light chains of tetanus toxin and of the botulinum neurotoxins A, C, D, E was also found in many endoproteinases and an aminopeptidase. The motif is known to constitute their active site and to bind Zn2+. In fact Zn2+ (0.6-0.9 mol/mol) was found in thoroughly dialysed two-chain tetanus toxin. The three approaches jointly support the hypothesis that the light chain of tetanus toxin, and probably of all clostridial neurotoxins, inhibits [3H]-noradrenaline release from adrenomedullary cells by degradation of (a) specific, still unknown protein(s) involved in exocytosis.

Adrenal Medulla↗
PubMed1992

Increase of permeability of synaptosomes and liposomes by the heavy chain of tetanus toxin.

In search of a role for the heavy chain of tetanus toxin in poisoning, its actions on natural and artificial membranes have been assessed. The heavy chain increases the permeability of synaptosomes to lactate dehydrogenase and potassium ions, and promotes the outward shift of the lipophilic cation tetraphenylphosphonium which is a particularly sensitive indicator for depolarization. Independent of the assay system the potency of the heavy chain is high, i.e. in the range of about 1 nM, whereas its efficacy is low. Its potency is decreased by the addition of the light chain and by treatment of the synaptosomes with the C-terminal fragment C of the heavy chain, but not with its N-terminal fragment beta 2. Single- or two-chain toxin itself is inactive, and so are the light chain or the two heavy chain fragments beta 2 and C. Liposomes were made from phosphatidylcholine and phosphatidylserine or gangliosides and loaded with calcein. At pH 6 the outflow of calcein is promoted in the order heavy chain greater than toxin much greater than fragment beta 2, and the action of toxin is promoted by ganglioside. At pH 5, fragment beta 2 is nearly as active as the heavy chain and more potent than the toxin. The heavy chain, but neither of the fragments, is strongly adsorbed in hydrophobic interaction chromatography and caused aggregation of polystyrene-divinylbenzene beads. Evidence for polymerization of heavy chains is lacking in zonal centrifugation. It is concluded that both domains of the heavy chain co-operate to exert the membranal events described, and that the heavy chain is partially hidden by the light chain in the complete toxin molecule.

Animals↗
PubMed1992

Morphological and biochemical study of cytoskeletal changes in cultured cells after extracellular application of Clostridium novyi alpha-toxin.

Clostridium novyi alpha-toxin caused retraction and rounding of cultured endothelial cells from porcine pulmonary arteries; nevertheless, the endothelial cells firmly adhered to their supports. F-actin stained with fluorescein-labeled phalloidin was condensed around the nucleus, whereas intermediate filaments and microtubules appeared unchanged. The content of F-actin and myosin was decreased, but that of G-actin or vimentin was not. A predominant role of the microfilament system in C. novyi alpha-toxin cytopathic action is suggested.

Actins↗
PubMed1992

Morphological changes of cultured endothelial cells after microinjection of toxins that act on the cytoskeleton.

Clostridium novyi alpha-toxin and C. difficile toxins A and B (all 200 to 300 kDa) and C. botulinum C2-I toxin (50 kDa) caused a delayed and persistent retraction and rounding of microinjected cells. Microinjected phalloidin acted fast and reversibly. Unlike C2-I toxin, phalloidin passed through the intercellular junctions. Specific antitoxin applied to the medium did not prevent the action of microinjected C. novyi or C. difficile toxin B. Microinjected antitoxin protected against the toxins applied with the medium or injected into the same cells.

Bacterial Proteins↗
PubMed1991

Limited proteolysis of tetanus toxin. Relation to activity and identification of cleavage sites.

Tetanus toxin is synthesized by Clostridium tetani as a 151-kDa peptide chain. The primary gene product is processed post-translationally by removal of the initiating methionine residue, formation of disulfide bridges and limited proteolysis by bacterial or exogenous proteinases. The mature toxins consist of a 52-kDa light chain and a 98-kDa heavy chain, linked together by a disulfide bond. Proteolytic nicking is accompanied by increased pharmacological potency. To identify the structural alterations involved, single-chain toxin has been subjected to limited proteolysis with various enzymes. The new N-termini have been determined by Edman degradation and the C-termini by isolation of short C-terminal peptide fragments and subsequent analysis of the sequence and composition. All two-chain toxins result from proteolytic nicking within the 17-residue segment of residues 445-461. Thus, the protease(s) of the culture broth cleave on the C-terminal side of Glu449 and partially Ala456, giving rise to two heavy chain N-termini. Trypsin and clostripain first attack the C-terminal of Arg454 and later Arg448, whereas endoproteinase Arg-C cleaves the former bond only. Chymotrypsin and endoproteinase Glu-C each split a single peptide bond, i.e. that located after Tyr452 and Glu449, respectively. Papain gives rise to a large number of cleavages within the 17-residue segment, the new C-terminus being Thr445 or Asn446 and the new N-terminus being Asp460 or Leu461. Further papain digestion leads to an additional cleavage within the heavy chain between Ser863 and Lys864. The original N-terminal Pro1 and C-terminal Asp1314, predicted from the nucleotide sequence, are conserved in all proteolytic digests. The pharmacological activity of the various two-chain toxins was 5-11 times that of the single-chain toxin, as estimated from the inhibition of [3H]noradrenaline release from rat-brain homogenate. The present data on the processing and activation by limited proteolysis prove the existence of several active tetanus isotoxins. These data, together with our previous data on the localization of disulfide bridges and sulfhydryl groups (Krieglstein, K., Henschen, A., Weller, U. & Habermann, E. (1990) Eur. J. Biochem. 188, 39-45), provide the detailed protein chemical characterization of the tetanus isotoxins.

Amino Acid Sequence↗
PubMed1991

Heterologous combinations of heavy and light chains from botulinum neurotoxin A and tetanus toxin inhibit neurotransmitter release in Aplysia.

The neuroparalytic activities of botulinum neurotoxin type A (BoNT A), tetanus toxin (TeTx), or homologous and heterologous combinations of their constituent polypeptides were examined at cholinergic and non-cholinergic synapses of Aplysia californica. When applied extracellularly, BoNT A or a mixture of its heavy (HC) and light (LC) chains were far more potent in blocking transmitter release at cholinergic than non-cholinergic synapses. The reverse was true for TeTx or a mixture its constituent chains. Such selectivity was assigned to differences in neuronal targetting and uptake of the neurotoxins since both exhibited similar potencies when injected directly into the cell body of either cell type. When bath-applied, heterologous combinations of the toxins' HC and LC appeared as effective as the parent neurotoxins from whence each HC was derived. Moreover, targetting/internalization was attributable to the analogous N-terminal moieties, H2 and beta 2, of the HC from BoNT A and TeTx. Thus, it may be postulated that the latter regions possess two functional domains, one being distinct and responsible for the divergent neuronal specificity, whereas the other serves a common role in translocating the LC of either toxin. Also, it was shown that the C-terminal portion of the HC of TeTx is unable to play the intracellular role of its counterpart in BoNT A.

Animals↗
PubMed1991

Limited proteolysis of single-chain tetanus toxin by tissue enzymes, in cultured brain tissue and during retrograde axonal to the spinal cord.

Single-chain toxin was investigated in vitro and in vivo for limited proteolysis into the fully active two-chain toxin. Plasmin from serum, elastase and gelatinase from leucocytes, as well as clostripain from C. histolyticum cleaved single-chain toxin and increased by that way its ability to inhibit [3H]noradrenaline release in vitro. Cultured mouse brain generated fragments from 125I-single-chain toxin which were cell-associated. Some of them comigrated in electrophoresis with light and heavy chain after mercaptolysis. When injected i.v. into rats, 125I-single-chain-toxin disappeared from the blood with a half-life of about 11 h without signs of nicking. However, after its injection into the triceps surae muscle both single- and two-chain toxin were found in the ipsilateral ventral horn of the spinal cord. Thus single-chain toxin is subjected to limited proteolysis by enzymes involved in tissue damage, by cultured brain tissue, and during or after its retrograde axonal transport to the spinal cord. Limited proteolysis is necessary for the release of the light chain known to mediate the action of toxin on several systems.

Animals↗
PubMed1991

A comparative biochemical, pharmacological and immunological study of Clostridium novyi alpha-toxin, C. difficile toxin B and C. sordellii lethal toxin.

The three clostridial cytotoxins, i.e. alpha-toxin of C. novyi (Tox alpha-nov), toxin B of C. difficile (ToxB-dif) and lethal toxin of C. sordellii (LT-sor) consist of single peptide chains of about 200,000 (Tox alpha-nov), 250,000 (LT-sor) and 275,000 (ToxB-dif) mol. wts. ToxB-dif and LT-sor but not Tox alpha-nov cross-reacted with rabbit polyclonal antibodies. Toxicity upon i.v. injection in mice was similar (LD50, 100 hr, 50-200 ng/kg) and was characterized by a slowly developing fluid loss into the interstitial space. When injected into the rat paw the toxins caused a delayed local edema lasting for days. In vitro the three toxins provoked a persistent retraction of endothelial cells cultured from pig pulmonary artery. ToxB-dif and Tox alpha-nov triggered the accumulation of F-actin in the perinuclear region at the expense of the tight peripheral bands whereas LT-sor led to a random loss of microfilament structure. The toxins inhibited uridine incorporation into endothelial or chicken embryonic cells whereas T 84 cells responded by an about 10-fold increase of uridine incorporation. Neither toxin ADP-ribosylated actin. The similarities between the three cytotoxins warrant their arrangement into a common group which perturbs the microfilament system.

Adenosine Diphosphate Ribose↗
PubMed1990

Arrangement of disulfide bridges and positions of sulfhydryl groups in tetanus toxin.

Tetanus toxin is a 151-kDa protein. The complete amino acid sequence is known. The mature toxin is made up of two peptide chains and contains 10 half-cystine residues. Treatment with 4-vinylpyridine in the presence of 6 M guanidine converted six of them into S-pyridylethyl cysteine residues as determined by amino acid analysis. When alkylation was preceded by mercaptolysis, all 10 half-cystine residues were recovered in the S-pyridylethylated form. It was therefore concluded that the toxin contains six sulfhydryl groups and two disulfide bonds. The positions of the residues carrying sulfhydryl groups and of those involved in disulfide bridges were determined by labelling of the toxin alternatively with 4-vinylpyridine or with 4-dimethylaminoazobenzene-4'-iodoacetamide (DABIA), directly or after mercaptolysis. The toxin derivatives were cleaved with cyanogen bromide and the elution patterns in reversed-phase HPLC compared. The chromatography components were identified by N-terminal amino acid sequence and amino acid composition. In the chromatography of the non-mercaptolysed, DABIA-treated sample four chromophore-carrying components were detected which could be demonstrated by N-terminal sequence analysis to correspond to six half-cystine-containing cyanogen bromide fragments. In the mercaptolysed, DABIA-treated sample three additional chromophore-carrying components were present, corresponding to two previously disulfide-linked cyanogen bromide fragments and one fragment which had contained an internal disulfide bridge. The HPLC patterns showed characteristic differences as the DABIA-labelled fragments were considerably more hydrophobic than the corresponding vinylpyridine-labelled fragments. It was established that the half-cystine residues in positions 26, 185, 198, 311, 868, and 1300 are present in the sulfhydryl form, that those in positions 438 and 466 are disulfide-bridged, thereby connecting the light and heavy chains of the toxin, and that those in positions 1076 and 1092 are disulfide-bridged, thereby giving rise to a loop in the heavy chain. During the progress of the investigations about 20% of the amino acid sequence previously predicted from DNA analysis was confirmed by protein-chemical methods.

Amino Acid Sequence↗
PubMed1990

Role of omega-conotoxin-sensitive calcium channels in inositolphosphate production and noradrenaline release due to potassium depolarization or stimulation with carbachol.

omega-Conotoxin GVIA (CTX) has been used to assess the role of voltage-sensitive Ca2+ channels involved in inositolphosphate (InsP) production and in noradrenaline (NA) release from washed brain homogenates. Stimulation was performed by depolarization with high [K+] and by the M-cholinergic agonist carbachol. In chicken brain CTX (1 mumol/l and less) nearly completely inhibited both InsP production and NA release due to high [K+]. The peptide depressed InsP production moderately but NA release largely when evoked with carbachol. In rat brain inhibition by CTX of InsP production or NA release was weak or even absent independent of the mode of stimulation. Independent of species or test system, the dihydropyridine derivative nitrendipine (1 mumol/l and above) was inactive. Because of its preferential CTX sensitivity chicken brain is particularly suitable to study the role of voltage-sensitive Ca2+ channels in presynaptic events. Here InsP production, like NA release, depends on entry of extracellular Ca2+ nearly completely when evoked by depolarization. When evoked by way of cholinergic M-receptor stimulation, InsP production is triggered by a second pathway in addition to the CTX-sensitive Ca2+ entry.

Animals↗
PubMed1990

Microinjection of alpha-toxin from Clostridium novyi type A promotes meiotic maturation in Xenopus laevis oocytes.

Microinjection of purified alpha-toxin into Xenopus laevis oocytes induced meiotic maturation provided insulin was present in the medium. Induction of maturation as indicated by breakdown of the germinal vesicle depended on the amount of intracellular alpha-toxin (with a detection limit of 2 ng/oocyte) and on the concentration of insulin. The hormone concentrations used were inactive when given alone and so was alpha-toxin (1 micrograms/ml) applied from the outside. The results demonstrate an intracellular target for alpha-toxin whereas an extracellular target is apparently lacking in oocytes.

Animals↗
PubMed1990

Inhibition of neurotransmitter release by botulinum neurotoxins and tetanus toxin at Aplysia synapses: role of the constituent chains.

1. The effects on the release of transmitter by botulinum neurotoxins (BoNT; types A, B, E), tetanus toxin (TeTx), constituent chains or fragments were studied on identified cholinergic and non-cholinergic synapses in Aplysia. 2. Cholinergic synapses in the buccal ganglion were found to be greater than 100 fold more sensitive to extracellular application of BoNT than to TeTx whereas in non-cholinergic synapses of the cerebral ganglion the potencies of the toxins were reversed. When intracellularly applied TeTx and BoNT were found nearly equipotent. This disparity in the susceptibilities of BoNT and TeTx to inhibit transmission was attributed to differences in the toxin's acceptors or uptake systems in the two neurone types. 3. Micro-injection into cholinergic neurones of the isolated renatured toxins' chains showed that both light and heavy chains of BoNT are intracellularly required whereas the light chain of TeTx alone is sufficient. 4. The heavy chain of BoNT as well as that of TeTx were found to mediate internalization of active moieties via its amino-terminal half. Furthermore the heavy chain of one toxin could internalize the light chain of the other.

Animals↗
PubMed1990

Chains and fragments of tetanus toxin, and their contribution to toxicity.

1. Single-chain toxin is enzymatically converted into two-chain isotoxins which differ from the precursor by their higher pharmacological activity, acidity and hydrophilicity. The interchain disulfide bridge and the disulfide loop within fragment C have been located at the amino acid level. 2. Independent of the enzymes used, the nicking sites are positioned within a region spanning no more than 17 amino acids. The N- and C-termini of the primary gene product are preserved in the two-chain toxin. The chains have been separated by isoelectric focussing and can be reconstituted to functionally intact toxin. 3. Light chain inhibits neurotransmitter release on different systems. First, permeabilized bovine adrenal chromaffin cells and rat pheochromocytoma (PC 12) cells release catecholamines when exposed to micromolar [Ca2+]. Inhibition is achieved with light chain or reduced two-chain toxin, but not with single-chain toxin or heavy chain. Washing away the light chain does not restitute the Ca2(+)-evoked release. The light chains of tetanus and botulinum A toxin act in a apparently similar, however not identical manner. Second, light but not heavy chain inhibits the release of acetylcholine when injected into Aplysia neurones. 4. The pharmacology of heavy chain is quite different. Ganglioside binding is mediated by its fragment C moiety, and modulated by the adjoining beta 2 piece and by light chain. Heavy chain and to a lesser degree its N-terminal beta 2-fragment promote the loss of calcein from liposomes indicating pore formation. Its C-terminal fragment C is inactive in this respect.(ABSTRACT TRUNCATED AT 250 WORDS)

Protein Processing, Post-Translational↗
PubMed1989

The light chain but not the heavy chain of botulinum A toxin inhibits exocytosis from permeabilized adrenal chromaffin cells.

The heavy and light chains of botulinum A toxin were separated by anion exchange chromatography. Their intracellular actions were studied using bovine adrenal chromaffin cells permeabilized with streptolysin O. Purified light chain inhibited the Ca2+-stimulated [3H]noradrenaline release with a half-maximal effect at about 1.8 nM. The inhibition was incomplete. Heavy chain up to 28 nM was neither effective by itself nor did it enhance the inhibitory effect of light chain. It is concluded that the light chain of botulinum A toxin contains the functional domain responsible for the inhibition of exocytosis.

Adrenal Medulla↗
PubMed1989

Light chain of tetanus toxin intracellularly inhibits acetylcholine release at neuro-neuronal synapses, and its internalization is mediated by heavy chain.

The ability of the two-chain form of tetanus toxin (TeTx), its constituent light (LC) or heavy (HC) chains, and papain fragment to block evoked acetylcholine (ACh) release in the buccal ganglia of Aplysia californica was studied electrophysiologically. Extracellularly applied, TeTx or its B fragment (consisting of LC and beta 2, the amino-terminal portion of HC) blocked ACh release, whereas LC, HC, or the beta 2 fragment did not affect it. Toxicity was restored when LC was bath applied together with HC or the beta 2 fragment. When injected into the presynaptic neuron, TeTx, the B fragment or LC, but not HC, induced inhibition of ACh release. These results indicate that the blockade of ACh release by TeTx is mimicked by intracellular action of LC, the internalization of which is mediated by the HC via its amino-terminal moiety.

Acetylcholine↗
PubMed1989

Chains and fragments of tetanus toxin. Separation, reassociation and pharmacological properties.

Tetanus toxin, as obtained from bacterial culture filtrates, consists of two chains. Since their roles in poisoning are unknown, we have made a detailed study of their preparation, reassociation and pharmacological activity. 1. Two-chain tetanus toxin (pI 6.0) was subjected to isoelectric focussing under reducing conditions in 2M urea. Both light (pI 4.8) and heavy (pI 7.2) chains separated as nearly homogeneous proteins of low toxicities. Upon removal of urea and reoxidation, partial homodimerization by formation of disulfide bonds took place in the purified fractions. The toxin was reconstituted nearly quantitatively by covalent heterodimerization of the complementary chains, as shown by SDS/gel electrophoresis, toxicity studies, inhibition of evoked [3H]noradrenaline release and binding to rat brain membranes. 2. Accordingly, fragment B (pI 5.6) resulting from papain hydrolysis, was separated into a light chain and the N-terminal moiety of the heavy chain, called fragment beta 2 (pI 7.1 and 6.8, two maxima). Removal of urea and reoxidation led to reconstitution of fragment B. Covalent linkage did not occur between the two parts of the heavy chain, or between the light chain and the C-terminal part of the heavy chain. 3. The heavy chain alone inhibited K+-evoked [3H]noradrenaline release from a rat brain homogenate. However, the concentration-response ratio was flat and 10-100-fold higher concentrations were required than with native or reconstituted two-chain toxin. The light chain was inactive. Purified heavy chain but not light chain decreased the [3H]noradrenaline content, whereas the two-chain toxin increased it. Binding to rat brain membranes was assessed by competition with 125I-labelled two-chain toxin. In hypotonic buffer, the heavy chain, the papain fragment C and native and reconstituted two-chain toxin had comparable affinities to membranes. In isotonic buffer the heavy chain displayed an about 1000-fold lower affinity than native or reconstituted two-chain toxin. The light chain did not bind to membranes in either test. Our data indicate that (a) the light chain and the N-terminal part of the heavy chain are held together not only by one disulfide bond but also by hydrogen bonds and ionic forces to yield a two-chain toxin or fragment B and (b) both chains contribute to the actions of the toxin in vivo and in vitro, and to its binding.

Animals↗