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At least 253 records · Page 14Linked to original sources
PubMed1993

A complex of rab3A, SNAP-25, VAMP/synaptobrevin-2 and syntaxins in brain presynaptic terminals.

Two monoclonal antibodies (SPM-1 and SPM-2) immunoprecipitate brain N-type calcium channels. On immunoaffinity chromatography of digitonin extracts of bovine brain membranes on SPM-1- and SPM-2-Sepharose, proteins of 36 (syntaxins A and B), 28 and 19 kDa are specifically retained by both columns. Here we show that the 19 and 28 kDa bands contain VAMP/synaptobrevin-2, and rab3A/smg25A and SNAP-25, respectively. Since SPM-1 and SPM-2 recognize only syntaxins and the 28 kDa band (rab3A/sm25A and SNAP-25), respectively, the results indicate that all these proteins form a complex. Our results suggest tight linkage between the components involved in neurotransmitter release.

Amino Acid Sequence↗
PubMed1993

Expression of synaptotagmin and syntaxin associated with N-type calcium channels in small cell lung cancer.

The presence of synaptic proteins involved in excitation/secretion coupling was examined in ten small cell lung cancer lines. N-Type calcium channels (omega-conotoxin receptors), synaptotagmin (p65) and syntaxin (HPC-1) were detected in eight. Co-immunoprecipitation experiments indicated that syntaxin can form a complex with synaptotagmin and calcium channels. The expression of synaptotagmin in small cell lung cancer may elicit an autoimmune response that reduces transmitter release at the nerve terminal.

Animals↗
PubMed1993

On the structure of the 'synaptosecretosome'. Evidence for a neurexin/synaptotagmin/syntaxin/Ca2+ channel complex.

Recent experiments have identified interactions between presynaptic and synaptic vesicle membrane proteins, that might be important in organizing the components of the fast neurotransmitter release mechanism to ensure that the process follows a rapid time course. Here we extend previous investigations to show that in addition to the alpha-latrotoxin receptor (neurexin) and synaptotagmin another presynaptic protein, syntaxin, co-purifies on a alpha-latrotoxin affinity column. This implies that syntaxin is associated with these two molecules in a complex; a conclusion supported by the immunoprecipitation of [125I]latrotoxin binding by syntaxin antibodies. In addition, antibodies against syntaxin and the alpha-latrotoxin receptor immunoprecipitate [125I]omega-conotoxin binding sites, indicating that calcium channels are associated with this complex. Thus, neurexin, synaptotagmin, syntaxin, and calcium channels can be found in a structure we propose to call the 'synaptosecretosome'. The components of the synaptosecretosome, in association with additional proteins, are postulated to organize the process of neurotransmitter release.

Animals↗
PubMed1994

Fusion complex formation protects synaptobrevin against proteolysis by tetanus toxin light chain.

The clostridial neurotoxin, tetanus toxin, is a Zn(2+)-dependent protease which inhibits neurotransmitter exocytosis by selective cleavage of the synaptic vesicle protein, synaptobrevin. Synaptobrevin is thought to serve as a receptor for two neuronal plasma membrane proteins, syntaxin and SNAP-25, which in the presence of non-hydrolyzable ATP analogs form a 20 S fusion complex with the soluble fusion proteins NSF and alpha-SNAP. Here we show that synaptobrevin, when in this 20 S complex, or its 7 S precursor, is protected against proteolysis by the enzymatically active tetanus toxin light chain. Our data define distinct pools of synaptobrevin, which provide markers of different steps of vesicle/plasma membrane interaction.

Animals↗
PubMed1993

A protein assembly-disassembly pathway in vitro that may correspond to sequential steps of synaptic vesicle docking, activation, and fusion.

The SNARE hypothesis holds that a transport vesicle chooses its target for fusion when a soluble NSF attachment protein (SNAP) receptor on the vesicle (v-SNARE) pairs with its cognate t-SNARE at the target membrane. Three synaptosomal membrane proteins have previously been identified: syntaxin, SNAP-25 (t-SNAREs), and vesicle-associated membrane protein (VAMP) (v-SNARE); all assemble with SNAPs and NSF into 20S fusion particles. We now report that in the absence of SNAP and NSF, these three SNAREs form a stable complex that can also bind synaptotagmin. Synaptotagmin is displaced by alpha-SNAP, suggesting that these two proteins share binding sites on the SNARE complex and implying that synaptotagmin operates as a "clamp" to prevent fusion from proceeding in the absence of a signal. The alpha-SNAP-SNARE complex can bind NSF, and NSF-dependent hydrolysis of ATP dissociates the complex, separating syntaxin, SNAP-25, and VAMP. ATP hydrolysis by NSF may provide motion to initiate bilayer fusion.

Adenosine Triphosphatases↗
PubMed1993

The syntaxin family of vesicular transport receptors.

Syntaxins A and B are nervous system-specific proteins implicated in the docking of synaptic vesicles with the presynaptic plasma membrane. A family of syntaxin-related proteins from rat has been identified that shares 23%-84% amino acid identity. Each of the six syntaxins terminate with a carboxy-terminal hydrophobic domain that anchors the protein on the cytoplasmic surface of cellular membranes. The syntaxins display a broad tissue distribution and, when expressed in COS cells, are targeted to different subcellular compartments. Microinjection studies suggest that the nervous system-specific syntaxin 1A is important for calcium-regulated secretion from neuro-endocrine PC12 cells. These results indicate that the syntaxins are a family of receptors for intracellular transport vesicles and that each target membrane may be identified by a specific member of the syntaxin family.

Amino Acid Sequence↗
PubMed1995

Genetic and electrophysiological studies of Drosophila syntaxin-1A demonstrate its role in nonneuronal secretion and neurotransmission.

Cloning and characterization of the Drosophila syntaxin-1A gene, syx-1A, reveal that it is present in several tissues but is predominantly expressed in the nervous system, where it is localized to axons and synapses. We have generated an allelic series of loss-of-function mutations that result in embryonic lethality with associated morphological and secretory defects dependent on the severity of the mutant allele. Electrophysiological recordings from partial loss-of-function mutants indicate absence of endogenous synaptic transmission at the neuromuscular junction and an 80% reduction of evoked transmission. Complete absence of syx-1A causes subtle morphological defects in the peripheral and central nervous systems, affects nonneural secretory events, and entirely abolishes neurotransmitter release. These data demonstrate that syntaxin plays a key role in nonneuronal secretion and is absolutely required for evoked neurotransmission.

Alleles↗
PubMed1995

The neuron-specific kinesin superfamily protein KIF1A is a unique monomeric motor for anterograde axonal transport of synaptic vesicle precursors.

Axonal transport has been intensively examined as a good model for studying the mechanism of organelle transport in cells, but it is still unclear how different types of membrane organelles are transported through the nerve axon. To elucidate the function of this mechanism, we have cloned KIF1A, a novel neuron-specific kinesin superfamily motor that was discovered to be a monomeric, globular molecule and that had the fastest reported anterograde motor activity (1.2 microns/s). To identify its cargo, membranous organelles were isolated from the axon. KIF1A was associated with organelles that contained synaptic vesicle proteins such as synaptotagmin, synaptophysin, and Rab3A. However, this organelle did not contain SV2, another synaptic vesicle protein, nor did it contain presynaptic membrane proteins, such as syntaxin 1A or SNAP-25, or other known anterograde motor proteins, such as kinesin and KIF3. Thus, we suggest that the membrane proteins are sorted into different classes of transport organelles in the cell body and are transported by their specific motor proteins through the axon.

Amino Acid Sequence↗
PubMed1994

Exocytosis relating proteins in the nervous system.

Hypothetical models of the molecular mechanism underlying presynaptic exocytosis were reviewed and the exocytosis relating proteins were categorized into four groups: docking, anchoring, fusion and inhibiting proteins. HPC-1/syntaxin, an axonal membrane protein, was classified as an anchoring protein, not as the vesicle docking protein, because electron microscopic study using cryoimmunogold technique revealed that HPC-1 distributed over the entire axonal membrane, where the synaptic vesicles were not 'docked' to the membrane. Since selective toxin or antibody against HPC-1 affected exocytosis, HPC-1 might be a necessary component for the exocytosis, but HPC-1 by itself seemed to have no ability to bind synaptic vesicles to the membrane in vivo. The molecular mechanism for Ca-dependent, rapid exocytosis and possible roles of the exocytosis relating proteins in the neurite morphogenesis are discussed.

Amino Acid Sequence↗
PubMed1993

Neuron specific expression of a membrane protein, HPC-1: tissue distribution, and cellular and subcellular localization of immunoreactivity and mRNA.

The monoclonal antibody HPC-1 recognizes a protein antigen in the hippocampus, and its specific reactivity to the plasma membrane of the amacrine cell somas and the inner plexiform layer in rat retina has been reported. Sequencing the cDNA indicated in our previous study that the HPC-1 antigen was a membrane protein. By means of immunoblotting, an antiserum against the fusion protein of Escherichia coli beta-galactosidase and the HPC-1 antigen detected several proteins of about 35 kDa in the nervous tissues including retina, cerebral cortex, hippocampus, cerebellum and spinal cord, but no signal was obtained in the non-neuronal tissues. Immunofluorescent histochemistry of the various rat tissues revealed that the HPC-1 antigen was confined to the nervous system, including the matrices of the cerebral cortex and hippocampus, the molecular layer, membranes of granular cell somas and glomeruli in the cerebellum and gray matter of spinal cord. However, little staining was seen in the white matter of the central nervous tissues. Thus, the HPC-1 antigen was accumulated in the synapse-rich regions of neuronal cells. In situ hybridization revealed that the HPC-1 mRNA was present in most, if not all, neurons in the central and peripheral nervous systems except for the retina. In the retina, mRNA signals were detected in amacrine and ganglion cells in which HPC-1 immunoreactivity was absent in their soma, suggesting polarized localization of the HPC-1 mRNA on the ganglion cell axon terminal.

Animals↗
PubMed1993

Immunohistochemical demonstration of neuron specific antigen, HPC-1 in the enteric nervous system of the guinea-pig distal colon.

The HPC-1 antigen is a newly identified neuron specific membrane protein in the central nervous system. The HPC-1 antigen was revealed similarity to epimorphin. The presence of HPC-1 antigen in the enteric nervous system of guinea-pig distal colon was immunohistochemically demonstrated using the antibody against the HPC-1. Immunohistochemical study clearly revealed the topography and structure of the enteric nervous system of the guinea-pig distal colon. HPC-1 was present only in the nervous system and entirely distributed. HPC-1 antigen is present at the surfaces of ganglion cells, but not in the cytoplasm.

Animals↗
PubMed2003

Interaction of taxilin with syntaxin which does not form the SNARE complex.

Taxilin is novel binding partner of the syntaxin family, which is implicated in intracellular vesicle traffic. However, precise binding properties of taxilin to the syntaxin family remain to be clarified. Then, we here further investigated the interaction of taxilin with the syntaxin family by use of recombinant taxilins. Syntaxin-1a, -3, and -4 bound to taxilin in a dose-dependent and saturable manners. The concentrations of syntaxin-1a, -3, and -4 giving a half-maximal binding to taxilin were about 1.5, 3.0, and 1.0microM, respectively. The interaction of taxilin with syntaxin-1a was inhibited by SNAP-25 or Munc18 in a dose-dependent manner. When recombinant taxilin was incubated with the extract from the rat brain crude membrane fraction, recombinant taxilin bound to syntaxin-1s free of at least VAMP2, SNAP-25, and Munc18. These results suggest that taxilin interacts with the syntaxin family which does not form at least the SNARE complex.

Animals↗
PubMed2004

Identification and characterization of taxilin isoforms.

The syntaxin family is implicated in intracellular vesicle traffic. We have recently identified taxilin, a novel syntaxin-binding protein, which has a long coiled-coil region in its C-terminal half. A database search has revealed the presence of two other molecules having a long coiled-coil region homologous to that of taxilin in mammals. Then, we here attempted to isolate and characterize the two molecules. Both the two molecules stoichiometrically interacted with several syntaxin family members. Then, we renamed original taxilin alpha-taxilin and named the two molecules beta- and gamma-taxilins, respectively. Beta-taxilin was a human homologue of chicken MDP77. Gamma-taxilin was an uncharacterized protein and Northern blot analysis revealed that gamma-taxilin was ubiquitously expressed. Beta- and gamma-taxilins preferentially interacted with syntaxin-1a and -4, respectively. The taxilin family members mutually interacted with the syntaxin family members. These results indicate that there is the taxilin family composed of at least three members in mammals.

Animals↗
PubMed2006

Epithelial sodium channel is regulated by SNAP-23/syntaxin 1A interplay.

Sodium-selective amiloride-sensitive epithelial channel (ENaC) located in the apical membrane is involved in the reabsorption of sodium in tight epithelia. The soluble N-ethylmaleimide-sensitive attachment receptors (SNAREs) mediate vesicle trafficking in a variety of cell systems. Syntaxin (a t-SNARE) has been shown to interact with and functionally regulate a number of ion channels including ENaC. In this study, we investigated the role of SNAP-23, another SNARE protein, on ENaC activity in the HT-29 colonic epithelial cell system and Xenopus oocytes. Recording of amiloride-sensitive currents in both systems suggest that SNAP-23 modulates channel function, though a much higher concentration is required to inhibit ENaC in Xenopus oocytes. The introduction of Botulinum toxin A (a neurotoxin which cleaves SNAP-23), but not Botulinum toxin B or heat-inactivated Botulinum toxin A, reversed the inhibitory effect of SNAP-23 on amiloride-sensitive currents. However, syntaxin 1A and SNAP-23 combined portray a complex scenario that suggests that this channel interacts within a quaternary complex. Synaptotagmin expression neither interacts with, nor showed any effect on amiloride-sensitive currents when co-expressed with ENaC. Pull down assays suggest mild interaction between ENaC and SNAP-23, which gets stronger in the presence of syntaxin 1A. Data further suggest that SNAP-23 possibly interacts with the N-terminal alphaENaC. These functional and biochemical approaches provide evidence for a complex relationship between ENaC and the exocytotic machinery. Our data suggest that SNARE protein interplay defines the fine regulation of sodium channel function.

Amiloride↗