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)

1. A 50-kDa fragment representing the NH2-terminus of the heavy subunit of botulinum type A neurotoxin was found, at low pH, to evoke the release of K+ from lipid vesicles loaded with potassium phosphate. Similar K+ release was also observed with the intact neurotoxin, its heavy chain and a fragment consisting of the light subunit linked the 50-kDa NH2-terminal heavy chain fragment. The light subunit alone, however, was inactive. 2. In addition to K+, the channels formed in lipid bilayers by botulinum neurotoxin type A or the NH2-terminal heavy chain fragment were found to be large enough to permit the release of NAD (Mr 665). 3. The optimum pH for the release of K+ was found to be 4.5. Above this value K+ release rapidly decreased and was undetectable above pH 6.0. 4. The binding of radiolabelled botulinum toxin to a variety of phospholipids was assessed. High levels of toxin binding were only observed to lipid vesicles with an overall negative charge; much weaker binding occurred to lipid vesicles composed of electrically neutral phospholipids. 5. A positive correlation between the efficiency of toxin-binding and the efficiency of K+ release from lipid vesicles was not observed. Whereas lipid vesicles containing the lipids cardiolipin or dicetyl phosphate bound the highest levels of neurotoxin, the toxin-evoked release of K+ was low compared to vesicles containing either phosphatidyl glycerol, phosphatidyl serine or phosphatidyl inositol. 6. The implications of these observations to the mechanism by which the toxin molecule is translocated into the nerve ending are discussed.
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PMID:A 50-kDa fragment from the NH2-terminus of the heavy subunit of Clostridium botulinum type A neurotoxin forms channels in lipid vesicles. 244 87

Rat pinealocytes accumulate glutamate in microvesicles and secrete it through exocytosis so as to transmit signals intercellularly. Glutamate is involved in the negative regulation of norepinephrine-stimulated melatonin production. In this study, we found that aspartate is also released from cultured rat pinealocytes during the exocytosis of glutamate. The release of aspartate was triggered by addition of KCI or A23187 (a Ca2+ ionophore) in the presence of Ca2+ and was proportional to the amount of L-glutamate released. Furthermore, the release of aspartate was inhibited by both botulinum neurotoxin type E and L- or N-type voltage-gated Ca2+ channel blockers. Bay K 8644, an agonist for the L-type Ca2+ channel, stimulated the release of aspartate 2.1-fold. Immunohistochemical analyses with antibodies against aspartate and synaptophysin revealed that aspartate is colocalized with synaptophysin in a cultured pinealocyte. HPLC with fluorometric detection indicated that the released aspartate is of the L form, although pinealocytes also contain the D form in their cytoplasm, corresponding to approximately 30% of the total free aspartate. Radiolabeled L-aspartate was taken up by the microsomal fraction from bovine pineal glands in a Na+-dependent manner. The Na+-dependent uptake of L-aspartate was strongly inhibited by L-cysteine sulfinate, beta-hydroxyaspartate, and L-serine-O-sulfate, inhibitors for the Na+-dependent glutamate/aspartate transporter on the plasma membrane. Na+-dependent sequestration of L-aspartate was also observed in cultured rat pinealocytes, which was inhibited similarly by these transporter inhibitors. These results strongly suggest that L-aspartate is released through microvesicle-mediated exocytosis from pinealocytes and is taken up again through the Na+-dependent transporter at the plasma membrane. The possible role of L-aspartate as an intercellular chemical transmitter in the pineal gland is discussed.
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PMID:L-aspartate but not the D form is secreted through microvesicle-mediated exocytosis and is sequestered through Na+-dependent transporter in rat pinealocytes. 920 28

Serine-, cysteine-, and metalloproteases are widely spread in many pathogenic bacteria, where they play critical functions related to colonization and evasion of host immune defenses, acquisition of nutrients for growth and proliferation, facilitation of dissemination, or tissue damage during infection. Since all the antibiotics used clinically at the moment share a common mechanism of action, acting as inhibitors of the bacterial cell wall biosynthesis or affecting protein synthesis on ribosomes, resistance to these pharmacological agents represents a serious medical problem, which might be resolved by using new generation of antibiotics, possessing a different mechanism of action. Bacterial protease inhibitors constitute an interesting such possibility, due to the fact that many specific as well as ubiquitous proteases have recently been characterized in some detail in both gram-positive as well as gram-negative pathogens. Few potent, specific inhibitors for such bacterial proteases have been reported at this moment except for some signal peptidase, clostripain, Clostridium histolyticum collagenase, botulinum neurotoxin, and tetanus neurotoxin inhibitors. No inhibitors of the critically important and ubiquitous AAA proteases, degP or sortase have been reported, although such compounds would presumably constitute a new class of highly effective antibiotics. This review presents the state of the art in the design of such enzyme inhibitors with potential therapeutic applications, as well as recent advances in the use of some of these proteases in therapy.
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PMID:Bacterial protease inhibitors. 1211 49

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.
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PMID:SNAP-25 Ser187 does not mediate phorbol ester enhancement of hippocampal synaptic transmission. 1452 23

Protein kinase C (PKC) enhances NMDA receptor (NMDAR)-mediated currents and promotes NMDAR delivery to the cell surface via SNARE-dependent exocytosis. Although the mechanisms of PKC potentiation are established, the molecular target of PKC is unclear. Here we show that synaptosomal-associated protein of 25 kDa (SNAP-25), a SNARE protein, is functionally relevant to PKC-dependent NMDAR insertion, and identify serine residue-187 as the molecular target of PKC phosphorylation. Constitutively active PKC delivered via the patch pipette potentiated NMDA (but not AMPA) whole-cell currents in hippocampal neurons. Expression of RNAi targeting SNAP-25 or mutant SNAP-25(S187A) and/or acute disruption of the SNARE complex by treatment with BoNT A, BoNT B or SNAP-25 C-terminal blocking peptide abolished NMDAR potentiation. A SNAP-25 peptide and function-blocking antibody suppressed PKC potentiation of NMDA EPSCs at mossy fiber-CA3 synapses. These findings identify SNAP-25 as the target of PKC phosphorylation critical to PKC-dependent incorporation of synaptic NMDARs and document a postsynaptic action of this major SNARE protein relevant to synaptic plasticity.
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PMID:SNAP-25 is a target of protein kinase C phosphorylation critical to NMDA receptor trafficking. 2005 6