Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.4.24.69 (botulinum neurotoxin)
 1,901 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Rat pinealocytes receive noradrenergic innervation that stimulates melatonin synthesis. Besides melatonin, we showed previously that pinealocytes accumulate L-glutamate in microvesicles and secrete it through an exocytic mechanism. The secreted glutamate binds to the class II metabotropic glutamate receptor and inhibits norepinephrine-stimulated melatonin synthesis in neighboring pinealocytes through an inhibitory cyclic AMP cascade. In this study, it was found that, in addition to metabotropic receptors, pinealocytes express functional ionotropic receptors. RT-PCR and northern analyses indicated the expression of mRNA for GluR1, KA2, and NR2C in pineal gland. The presence of GluR1 protein was confirmed by immunological techniques, but neither KA2 nor NR2C was detected. Consistent with this observation, the presence of (RS)-alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid or kainate, non-N-methyl-D-aspartate receptor agonists, transiently stimulated increased the intracellular Ca(2+) concentration of cultured pinealocytes, whereas N-methyl-D-aspartate did not. These responses were prevented by 6-cyano-7-nitroquinoxaline-2,3-dione, a selective antagonist for non-N-methyl-D-aspartate receptors, by L-type Ca(2+) channel blockers such as nifedipine, or by omitting Ca(2+) or Na(+) in the medium. In the presence of Ca(2+) and Na(+), (RS)-alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid or kainate evoked glutamate secretion from the cultured cells, which was prevented by 6-cyano-7-nitroquinoxaline-2,3-dione, L-type Ca(2+) channel blockers, type E or B botulinum neurotoxin, or incubation at <20 degrees C. These results strongly suggest that GluR1 is functionally expressed in pinealocytes and triggers microvesicle-mediated exocytosis of L-glutamate via activation of L-type Ca(2+) channels. It is possible that GluR1 participates in a signaling cascade that enhances and expands the L-glutamate signal throughout the pineal gland.
 ...
PMID:Ionotropic glutamate receptors trigger microvesicle-mediated exocytosis of L-glutamate in rat pinealocytes. 1085 73

Erythropoietin (EPO) reduced Ca(2+)-induced glutamate (Glu) release from cultured cerebellar granule neurons. Inhibition was also produced by EPO mimetic peptide 1 (EMP1), a small synthetic peptide agonist of EPO receptor (EPO-R), but not by iEMP1, an inactive analogue of EMP1. EPO and EMP1 induced autophosphorylation of Janus kinase 2 (JAK2), a tyrosine kinase that associates with EPO-R. Furthermore, genistein, but not genistin, antagonized both the phosphorylation of JAK2 and the suppression of Glu release induced by EPO and EMP1. During chemical ischemia, substantial amounts of Glu were released from cultured cerebellar and hippocampal neurons by at least two distinct mechanisms. In the early phase, Glu release occurred by exocytosis of synaptic vesicle contents, because it was abolished by botulinum type B neurotoxin (BoNT/B). In contrast, the later phase of Glu release mainly involved a BoNT/B-insensitive non-exocytotic pathway. EMP1 inhibited Glu release only during the early exocytotic phase. A 20-min exposure of hippocampal slices to chemical ischemia induced neuronal cell death, especially in the CA1 region and the dentate gyrus, which was suppressed by EMP1 but not iEMP1. However, EMP1 did not attenuate neuronal cell death induced by exogenously applied Glu. These results suggest that activation of EPO-R suppresses ischemic cell death by inhibiting the exocytosis of Glu.
 ...
PMID:Erythropoietin receptor-mediated inhibition of exocytotic glutamate release confers neuroprotection during chemical ischemia. 1150 31

Considerable data support the idea that intracellular membrane fusion involves a conserved machinery containing the SNARE proteins. SNAREs assembled in vitro form a stable 4-helix bundle and it has been suggested that formation of this complex provides the driving force for bilayer fusion. We have tested this possibility in assays of exocytosis in cells expressing a botulinum neurotoxin E (BoNT/E)-resistant mutant of SNAP-25 in which additional disruptive mutations have been introduced. Single or double mutations of glutamine to glutamate or to arginine in the central zero layer residues of SNAP-25 did not impair the extent, time course or Ca2+-dependency of exocytosis in PC12 cells. Using adrenal chromaffin cells, we found that exocytosis could be reconstituted in cells transfected to express BoNT/E. A double Q-->E mutation did not prevent reconstitution and the kinetics of single granule release events were indistinguishable from control cells. This shows a high level of tolerance of changes in the zero layer indicating that the conservation of these residues is not due to an essential requirement in vesicle docking or fusion and suggests that formation of a fully stable SNARE complex may not be required to drive membrane fusion.
 ...
PMID:SNAP-25 with mutations in the zero layer supports normal membrane fusion kinetics. 1179 5

Many neurons release a variety of amino acids in response to depolarizing stimuli. Although some of these amino acids, namely, glutamate, aspartate, and gamma-aminobutyric acid (GABA), have been qualified as neurotransmitters, functional roles of the other amino acids including alanine remain obscure. We investigated the mechanism and the origin of alanine release from cultured rat cerebellar cells. High-K(+)-induced depolarization produced a considerable amount (139+/-8 pmol/2 min/dish) of alanine release, comparable to that of glutamate (103+/-7 pmol/2 min/dish). Other depolarizing agents including veratridine or 4-aminopyridine also induced alanine release, suggesting that the major source is excitable neurons, rather than non-excitable glial cells. Depolarization-evoked alanine release was suppressed in the absence of extracellular Ca(2+), and was almost abolished by treating the cells with botulinum type B neurotoxin (BoNT/B), indicating that alanine is released by Ca(2+)-dependent exocytosis of vesicle-associated membrane protein-2 (VAMP-2)-containing vesicles. The properties of alanine release were different from those of glutamate and GABA in several aspects: (a) Depolarization-dependent alanine release appeared as early as 7 days in vitro, much earlier than that of GABA. (b) Fifty microM kainate, which causes selective cell death of GABAergic neurons in the culture, only partially reduced alanine release, whereas it had no effect on glutamate release. (c) Alanine release was not affected by phorbol ester, which enhanced glutamate and GABA release in a kinase-dependent manner. We therefore conclude that alanine release occurs via exocytosis of a pool of synaptic vesicles distinct from those containing glutamate or GABA.
 ...
PMID:Exocytotic release of alanine from cultured cerebellar neurons. 1237 90

Nitric oxide (NO; 1 microM) or an NO donor (500 microM diethylenetriamine-nitric oxide, DETA-NONOate) caused rapid glutamate and ATP release from cultured rat cortical astrocytes. NO-induced glutamate release was prevented by calcium chelators (EGTA or BAPTA-AM) and an inhibitor of vesicular exocytosis (botulinum neurotoxin C, BoTx-C), but not by a glutamate transport inhibitor, L-trans-pyrrolidine-2,4-dicarboxylate (t-PDC), a cyclooxygenase inhibitor (indomethacin), or an inhibitor of soluble guanylate cyclase 1H-[1,2,4]oxadiazolo-[4,3-a]quinoxalin-1-one (ODQ), and was not induced by mitochondrial respiratory inhibitors (myxothiazol or azide). Similarly to glutamate, NO-induced ATP release was also completely blocked by BAPTA-AM and BoTx-C, suggesting again a vesicular, calcium-dependent mechanism of release. Addition of DETA-NONOate (500 microM) to fura-2-loaded astrocytes induced a rapid, transient increase in intracellular calcium levels followed by a lower, sustained level of calcium entry. The latter was blocked by gadolinium (1 microM), an inhibitor of capacitative Ca(2+) entry. Thus, NO appears to cause rapid exocytosis of vesicular glutamate and ATP from astrocytes by raising intracellular calcium levels. Astrocytes activated by lipopolysaccharide/endotoxin and interferon-gamma to express inducible NO synthase (iNOS) maintained substantially higher extracellular glutamate levels than nonactivated cells or activated cells treated with an iNOS inhibitor (1400W), but the rate of glutamate uptake by these cells was similar. This suggests that NO from inflammatory-activated astrocytes causes release of astrocytic glutamate. NO-induced release of astrocytic glutamate and ATP may be important in physiological or pathological communication between astrocytes and neurons.
 ...
PMID:Nitric oxide induces rapid, calcium-dependent release of vesicular glutamate and ATP from cultured rat astrocytes. 1242 Mar 11

Botulinum neurotoxin serotypes A and E (BoNT/A and BoNT/E) block neurotransmitter release by cleaving the 206-amino-acid SNARE protein, SNAP-25. For each BoNT serotype, cleavage of SNAP-25 results in the loss of intact protein, the production of an N-terminal truncated protein, and the generation of a small C-terminal peptide. Peptides that mimic the C-terminal fragments of SNAP-25 following BoNT/A or BoNT/E cleavage were shown to depress transmitter release in bovine chromaffin cells and in Aplysia buccal ganglion cells. Similarly, the N-terminal-truncated SNAP-25 resulting from BoNT/A or BoNT/E cleavage has been found to inhibit transmitter exocytosis in various systems. With one exception, however, the inhibitory action of truncated SNAP-25 has not been demonstrated at a well-defined cholinergic synapse. The goal of the current study was to determine the level of inhibition of neurotransmitter release by N-terminal BoNT/A- or BoNT/E-truncated SNAP-25 in two different neuronal systems: cholinergically coupled Aplysia neurons and rat hippocampal cell cultures. Both truncated SNAP-25 products inhibited depolarization-dependent glutamate release from hippocampal cultures and depressed synaptic transmission in Aplysia buccal ganglion cells. These results suggest that truncated SNAP-25 can compete with endogenous SNAP-25 for binding with other SNARE proteins involved in transmitter release, thus inhibiting neurotransmitter exocytosis.
 ...
PMID:Inhibition of neurotransmitter release by peptides that mimic the N-terminal domain of SNAP-25. 1276 Apr 19

Phorbol esters, activators of protein kinase C (PKC), have been shown to enhance synaptic transmission. One potential downstream target of PKC in the presynaptic terminal is the soluble N-ethylmaleimide sensitive factor (NSF) attachment protein receptor (SNARE) SNAP-25, which has a PKC phosphorylation site in its C-terminal coil centered at serine 187 (S187/Ser187). We examined the role of S187 in hippocampal synaptic transmission. After proteolytic cleavage of native SNAP-25 by botulinum neurotoxin E (BoNT/E), synaptic transmission was restored in a subset of transfected CA3 pyramidal cells with a toxin-resistant form of SNAP-25 containing unaltered S187 (Swt), S187 mutated to alanine (SA) or S187 mutated to glutamate (SE). We observed that phorbol-12,13-diacetate (PDAc, 10 microM) induced potentiation of neurotransmission to a similar degree for both Swt and SA (2.4-fold and 3.1-fold increase, respectively). Furthermore, basal levels of transmission mediated by SE were reduced relative to that of Swt (failure rates of 72% and 41%, respectively). Together, these data suggest that phosphorylation of SNAP-25 S187 does not mediate the observed enhancement of neurotransmission by phorbol esters at hippocampal synapses.
 ...
PMID:SNAP-25 Ser187 does not mediate phorbol ester enhancement of hippocampal synaptic transmission. 1452 23

Botulinum toxin type A (BoNT-A) produced by the bacterium Clostridium botulinum is a potent inhibitor of acetylcholine release in the neuromuscular junction and has been used to treat many disorders related to excessive muscle contraction. However, BoNT-A has recently been used in pain therapy to treat myofascial pain, low back pain and various types of headaches, including migraine. The purpose of this study is to investigate the antinociceptive effect of BoNT-A and its underlying mechanism in the rat formalin inflammatory pain model. BoNT-A (3.5, 7, 15 and 30 U/kg) or vehicle was administered to the plantar surface of the right hindpaw of male Sprague-Dawley rats. BoNT-A dose-dependently (P<0.05) inhibited formalin-induced nociceptive behavior during phase 2 but not during phase 1 when administered 5 h to 12 days before formalin challenge. The onset of the antinociceptive effect started at 5 h after pre-treatment and this effect lasted for at least 12 days. BoNT-A (7 U/kg) also reduced edema. Consistent with the lack of effect in the formalin phase 1, BoNT-A, at 15 U/kg, had no effect on acute thermal nociception; no local muscle weakness was observed at this dose. Pre-treatment of rats with BoNT-A (3.5, 7 or 15 U/kg) all significantly reduced formalin-evoked glutamate (Glu) release. These results demonstrate that local peripheral injection of BoNT-A significantly reduces formalin-induced nociceptive behaviors with the absence of obvious muscle weakness. Such an antinociceptive effect of BoNT-A is associated with the inhibition of formalin-induced release of Glu (and/or neuropeptides) from primary afferent terminals.
 ...
PMID:Subcutaneous administration of botulinum toxin A reduces formalin-induced pain. 1471 98

Experimental studies suggest that the delivery of antiepileptic agents into the seizure focus might be of potential utility for the treatment of focal-onset epilepsies. Botulinum neurotoxin E (BoNT/E) causes a prolonged inhibition of neurotransmitter release after its specific cleavage of the synaptic protein synaptosomal-associated protein of 25 kDa (SNAP-25). Here, we show that BoNT/E injected into the rat hippocampus inhibits glutamate release and blocks spike activity of pyramidal neurons. BoNT/E effects persist for at least 3 weeks, as determined by immunodetection of cleaved SNAP-25 and loss of intact SNAP-25. The delivery of BoNT/E to the rat hippocampus dramatically reduces both focal and generalized kainic acid-induced seizures as documented by behavioral and electrographic analysis. BoNT/E treatment also prevents neuronal loss and long-term cognitive deficits associated with kainic acid seizures. Moreover, BoNT/E-injected rats require 50% more electrical stimulations to reach stage 5 of kindling, thus indicating a delayed epileptogenesis. We conclude that BoNT/E delivery to the hippocampus is both antiictal and antiepileptogenic in experimental models of epilepsy.
 ...
PMID:Antiepileptic effects of botulinum neurotoxin E. 1572 34

Clostridium botulinum neurotoxins (BoNTs) act on nerve endings to block acetylcholine release. Their potency is due to their enzymatic activity and selective high affinity binding to neurons. Although there are many pieces of data available on the receptor for BoNT, little attempt has been made to characterize the receptors for BoNT/C and BoNT/D. For this purpose, we prepared the recombinant carboxyl-terminal domain of the heavy chain (H(C)) and then examined its binding capability to rat brain synaptosomes treated with enzymes and heating. Synaptosomes treated with proteinase K or heating retained binding capability to both H(C)/C and H(C)/D, suggesting that a proteinaceous substance does not constitute the receptor component. We next performed a thin layer chromatography overlay assay of H(C) with a lipid extract of synaptosomes. Under physiological or higher ionic strengths, H(C)/C bound to gangliosides GD1b and GT1b. These data are in accord with results showing that neuraminidase and endoglycoceramidase treatment decreased H(C)/C binding to synaptosomes. On the other hand, H(C)/D interacted with phosphatidylethanolamine but not with any ganglioside. Using cerebellar granule cells obtained from GM3 synthase knock-out mice, we found that BoNT/C did not elicit a toxic effect but that BoNT/D still inhibited glutamate release to the same extent as in granule cells from wild type mice. These observations suggested that BoNT/C recognized GD1b and GT1b as functional receptors, whereas BoNT/D induced toxicity in a ganglioside-independent manner, possibly through binding to phosphatidylethanolamine. Our results provide novel insights into the receptor for clostridial neurotoxin.
 ...
PMID:Binding of Clostridium botulinum type C and D neurotoxins to ganglioside and phospholipid. Novel insights into the receptor for clostridial neurotoxins. 1611 73


<< Previous 1 2 3 4 5 Next >>