SEARCH · PubMed Health

Results for “synaptic vesicles”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 703 records · Page 39Linked to original sources

PubMed1998

Synaptic vesicle protein SV2B, but not SV2A, is predominantly expressed and associated with microvesicles in rat pinealocytes.

Microvesicles are endocrine counterparts of neuronal synaptic vesicles, and accumulate and secrete classic neurotransmitters. In mammalian pinealocytes, microvesicles accumulate L-glutamate through a vesicular glutamate transporter and secrete it through exocytosis. To characterize the molecular organization of microvesicles in more detail, we investigated in this study the expression and localization of synaptic vesicle protein 2 (SV2) in rat pinealocytes. RT-PCR analysis indicated that transcripts specific for two isoforms, SV2A, a ubiquitous form present in neuronal and endocrine cells, and SV2B, a neuron-specific form, are amplified in pineal RNAs. Northern blotting with specific transcripts indicated that the mRNA for SV2B is predominantly expressed, whereas that for SV2A is below the detection limit. Site-specific antibodies against SV2B recognized a single 72-kDa polypeptide in the pineal membrane fraction, whereas anti-SV2A antibodies did not recognize any polypeptides. Immunohistochemical analysis of cultured cells indicated that SV2B is expressed in pinealocytes but not in other types of cells. SV2B is present in somata and is especially rich in processes, which are filled with microvesicles. SV2B is colocalized with synaptophysin and synaptotagmin, markers for microvesicles. Immunoelectron microscopy indicated that SV2B is associated with microvesicles. These results indicated that SV2B, but not SV2A, is expressed in rat pinealocytes and associated with microvesicles. As SV2B is also expressed in cultured alphaTC6 clonal pancreatic a cells, SV2B is not a protein specific for neurons.

Animals↗

PubMed1983

Photoaffinity labeling of a synaptic vesicle specific nucleotide transport system from Torpedo marmorata.

We have employed azido derivatives of ATP and AMP to identify the ATP translocase of synaptic vesicles. Azido-AMP inhibits transport of both ATP and AMP in vitro. The affinity of the translocase for the azido derivatives is similar to that of the native ligands. Upon UV irradiation of vesicles incubated with radiolabeled azido-AMP or -ATP, a molecular weight (Mr) 34000 polypeptide is selectively modified. On two-dimensional gel electrophoresis, the single radiolabeled polypeptide has a pI of approximately 7.7. Analysis of the fractions obtained when vesicles were purified on linear sucrose density gradients reveals that the Mr 34000 polypeptide is highly enriched in the vesicle-containing fractions. The findings support the notion that this polypeptide is identical with a previously described vesicle-specific component of the same molecular size [Stadler, H., & Tashiro, T. (1979) Eur. J. Biochem. 101, 171-178], and we conclude on the basis of uptake inhibition and photoaffinity labeling results that this protein is directly involved in ATP translocation of synaptic vesicles.

Adenine Nucleotides↗

PubMed1987

Changes induced by diazepam in the synaptic vesicle size of rat phrenic nerve terminals.

The effect of diazepam (Valium), administered by i.p. injection on the cross-sectional area of synaptic vesicle profiles of the endplate-rich area of the rate diaphragm was studied by electron microscopy at 15-180 min after treatment. In the dose range of 0.25-10 mg/kg, diazepam induced a significant increase of the size of the synaptic vesicles. This increase was dose-related within a certain margin, dependent on the treatment time, while the effect of each dose increased significantly with the period after treatment. At 2.5-10 mg/kg a maximum seemed to be reached at 90 min.

Animals↗

PubMed1970

An electron microscopic characterization of classes of synaptic vesicles by means of controlled aldehyde fixation.

Examination of variables of aldehyde fixation that may affect the shape of agranular synaptic vesicles has revealed that even brief storage of aldehyde-perfused nervous tissue pieces in cacodylate buffer, prior to hardening in osmium tetroxide, has an unusually severe flattening effect on agranular vesicles of a particular type. These are the vesicles of peripheral cholinergic axon endings, and of certain central synaptic bulbs. Types of synaptic bulbs can now be further defined on the basis of shape of agranular synaptic vesicles under controlled conditions of aldehyde fixation. Previously described "S" bulbs in the spinal cord contain uniformly spheroid vesicles, which are wholly resistant to flattening. Previously described "F" bulbs contain somewhat smaller agranular vesicles that are flattened after aldehyde fixation, even when this is followed by prompt hardening in osmium tetroxide solution. A third type, previously characterized as having irregularly round agranular vesicles after the above treatment, contains only severely flattened vesicles when the osmium tetroxide hardening is preceded by even a brief wash with sodium cacodylate buffer containing sucrose. Moreover, the "third" type is characteristic of all cholinergic peripheral axon endings examined, as well as the large axosomatic ("L") synaptic bulbs of the spinal cord.

Adrenal Glands↗

PubMed1977

The effects of different methods of fixation on central nervous system synaptic pinocytotic vesicles.

Synaptic pinocytotic vesicles (invaginating from the surface membrane) and coated vesicles inside rat mossy fiber endings were counted after the use of different kinds of fixatives. Significantly greater numbers of pinocytotic vesicles and coated pinocytotic vesicles per unit length of membrane were found when osmium was used as the first fixative. A high positive correlation was found between these values and the number of coated vesicles per unit area of mossy fiber ending profiles. The results emphasize the need for caution when considering the theory that in vivo synaptic vesicle recycling involves a coated vesicle invagination of the surface membrane followed by internalisation and loss of coat of the vesicle.

Animals↗

PubMed1994

GTP cleavage by the small GTP-binding protein Rab3A is associated with exocytosis of synaptic vesicles induced by alpha-latrotoxin.

Neurotransmitter release from presynaptic nerve terminals is a highly regulated form of exocytosis. Small GTP-binding proteins of the Rab family have been proposed to act as central regulators in this process that cycle between a GTP- and GDP-bound form. Previous work has shown that the synaptic vesicle protein Rab3A undergoes a membrane association-dissociation cycle that is associated with neurotransmitter release. Using isolated nerve terminals as our model system, we have now analyzed the GDP/GTP status of Rab3A. Synaptic vesicle-bound Rab3A was almost exclusively in the GTP form whereas cytosolic Rab3A contained only GDP. Approximately equal amounts of GTP and GDP were found in the pool of Rab3A localized to a membrane fraction containing plasma membrane-synaptic vesicle complexes. In contrast to Rab3A, Rab5 (an endosomal G-protein) was predominantly GDP-bound in all analyzed compartments. To analyze whether Rab3A-bound GTP is cleaved during exocytosis, synaptosomes were stimulated with alpha-latrotoxin, the active component of black widow spider venom. This resulted in massive exocytosis. A significant increase of the GDP/GTP ratio of Rab3A was observed under these conditions that was not due to a nonspecific loss of high energy nucleotides. Our findings suggest that cleavage of Rab3A-bound GTP is a crucial step in regulated exocytosis of synaptic vesicles.

Animals↗

PubMed1990

GABAergic growth cones: release of endogenous gamma-aminobutyric acid precedes the expression of synaptic vesicle antigens.

Growth cone fractions isolated from neonatal [postnatal day 3 (P3)] rat forebrain contain GABAergic growth cones as demonstrated by immunofluorescence staining with monospecific antibodies to gamma-aminobutyric acid (GABA). HPLC analysis shows that GABAergic growth cones release this endogenous GABA when stimulated with high K+. Endogenous GABA release is Ca2(+)-independent and, in this respect, similar to that seen previously with [3H]GABA. Isolated growth cone fractions also exhibit a K(+)-stimulated, Ca2(+)-independent release of endogenous taurine. None of the other amino acids shown to be present in isolated growth cone fractions were released, including glutamate, aspartate, and glycine. A population of dissociated cerebral cortical neurones prepared from P1 rat forebrain were GABA-immunoreactive after 1 day in culture. The cell body, neurites, and growth cones of these neurones were all stained with GABA antibodies. At this time in culture, neurones did not stain with either of two antibodies to synaptic vesicle antigens, i.e., p65 and synaptophysin. Growth cones isolated from P3 rat forebrain were also not immunoreactive with these antibodies. After about 8 days in culture, when neurones had established extensive networks of long, varicose axons and elaborately branched dendrites, many neurones and their neurites were immunoreactive for GABA antibodies. At this time in culture, p65 and synaptophysin antibodies did stain neuronal cell bodies and particularly their varicose axons. Dendrites were not stained with synaptic vesicle antibodies. These results suggest that GABAergic neurones synthesize GABA during neurite outgrowth and that GABA is present in, and can be released from, the growth cones of these neurones. The presence of GABA in GABAergic growth cones is not associated with synaptic vesicles, which explains the Ca2+ independency of both endogenous and [3H]GABA release from these growth cones.

Animals↗

PubMed2006

[The intracellular calcium and mechanisms of endocytosis of synaptic vesicles at the frog nerve ending].

In the experiments on frog motor nerve endings of cutaneous pectoris muscle, made by extracellular recording of synaptic signals, it has been shown that the increase in intracellular calcium ion concentration in the nerve ending (by enhance of extracellular potassium ion concentration, or by addition of caffeine) leads to an increase in the miniature end-plate potential frequency, which is preserved over the whole period (about 10 min) of action of these substrates. The rhythmic stimulation of motor nerve (20 or 100 imp/s) quickly leads to a decrease in the end plate potentials amplitude. It has been shown by fluorescent microscopy with the use of endocytotic marker FM 1-43 that in the course of a short time exposition (5 min) in a high potassium solution (40 mM) or caffeine (5 mM), light spots appeared in the nerve ending. This shows that synaptic vesicles undergo intensive processes of endocytosis. During a longer exposition (30 min) no light spots were revealed, whereas the nerve ending width increased. This data allowed to propose that the process of endocytosis was blocked. In the presence of even lower concentrations of potassium ions and caffeine, and during a long rhythmic stimulation (20 or 100 imp/s) no blocking of endocytosis was revealed. It is concluded that high concentrations of intracellular calcium in the frog motor nerve ending leads to a reversible block of endocytosis, while exocytosis in synaptic vesicles is proceeding.

Animals↗

PubMed1990

Axonal transport of synaptic vesicles and muscarinic receptors: effect of protein synthesis inhibitors.

The effect of cycloheximide, a protein synthesis inhibitor, was studied on the axonal transport of noradrenergic synaptic vesicles and presynaptic muscarinic receptors, identified by in vitro binding of [3H]dihydrotetrabenazine and [3H]quinuclidinylbenzilate, respectively, in rat sciatic nerve. Cycloheximide (1.5 mg/kg) administered subcutaneously 2 h before ligation decreased by approximately 50% the accumulation of vesicles and receptors in the proximal segment above the ligature placed on the nerve; its action was detectable after a lag period of 10 h and disappeared 96 h after administration. Double ligatures were placed on the nerve at various time intervals between the first (distal) and the second (proximal) ligature, and the accumulation of vesicles and receptors proximal to the second ligature was measured; the first ligature diminished the accumulation above the second ligature. At an interval of 96 h between the first and the second ligature, cycloheximide completely prevented the accumulation of vesicles and receptors proximal to the second ligature. The effects of double ligatures and the response to cycloheximide treatment can best be explained on the assumption that an important proportion of synaptic vesicles and presynaptic receptors is being recycled in the nerve cell bodies after retrograde transport.

Animals↗

PubMed2005

Synaptic vesicle pools.

Communication between cells reaches its highest degree of specialization at chemical synapses. Some synapses talk in a 'whisper'; others 'shout'. The 'louder' the synapse, the more synaptic vesicles are needed to maintain effective transmission, ranging from a few hundred (whisperers) to nearly a million (shouters). These vesicles reside in different 'pools', which have been given a bewildering array of names. In this review, we focus on five tissue preparations in which synaptic vesicle pools have been identified and thoroughly characterized. We argue that, in each preparation, each vesicle can be assigned to one of three distinct pools.

Animals↗

PubMed1999

Endophilin/SH3p4 is required for the transition from early to late stages in clathrin-mediated synaptic vesicle endocytosis.

Endophilin/SH3p4 is a protein highly enriched in nerve terminals that binds the GTPase dynamin and the polyphosphoinositide phosphatase synaptojanin, two proteins implicated in synaptic vesicle endocytosis. We show here that antibody-mediated disruption of endophilin function in a tonically stimulated synapse leads to a block in the invagination of clathrin-coated pits adjacent to the active zone and therefore to a block of synaptic vesicle recycling. We also show that in a cell-free system, endophilin is not associated with clathrin coats and is a functional partner of dynamin. Our findings suggest that endophilin is part of a biochemical machinery that acts in trans to the clathrin coat from early stages to vesicle fission.

Adaptor Proteins, Signal Transducing↗

PubMed1996

Interaction of Rabphilin3 with synaptic vesicles through multiple regions.

Rabphilin3 is a downstream target protein of Rab3A small G protein, implicated in neurotransmitter release. We have previously reported that about 4 molecules of Rabphilin3 are associated with one synaptic vesicle through a vesicle anchoring protein(s). We have shown here that Rabphilin3 interacts with rat synaptic vesicles through at least three regions: the N-terminal region (1-280 amino acids (aa)), the C-terminal region containing the two C2 domains (440-704 aa), and an unidentified region. A model for the interaction of Rabphilin3 with the vesicles is discussed.

Adaptor Proteins, Signal Transducing↗

PubMed1993

Photoaffinity labeling of the vesamicol receptor of cholinergic synaptic vesicles.

On the basis of the high-affinity vesamicol analog 4-aminobenzovesamicol (ABV), a tritiated, arylazido ligand (azidoABV) of the vesamicol receptor (VR) in cholinergic synaptic vesicles was synthesized. azidoABV is an inhibitor of acetylcholine (AcCh) active transport, and it binds to the VR with higher affinity than vesamicol. The rate of dissociation of azidoABV from synaptic vesicles is 0.058 +/- 0.003 min-1 at 20 degrees C (about 3-fold slower than that of vesamicol), and the equilibrium dissociation constant is 2 nM (about 4-fold lower than that of vesamicol). Photolysis of [3H]azidoABV in the presence of a stoichiometric excess of the VR led to incorporation of 28% of the radiolabel, of which 57% was blocked by 50 microM vesamicol. Sodium dodecyl sulfate polyacrylamide gel electrophoretic analysis of the labeled vesicles revealed, after autofluorography, specific labeling over a broad molecular weight range that extended from about 50 to 200 kDa. This labeling pattern was essentially the same as that obtained with an azido analog of AcCh that was used to label the AcCh transporter (Rogers, G.A., & Parsons, S. M. (1992) Biochemistry 31, 5770-5777). In addition, about 6% of the radioligand that was specifically incorporated into proteins with M(r) greater than 12 kDa labeled four polypeptides that corresponded to bands in the Coomassie image at M(r) = 23, 33, 35, and 38 kDa. The results suggest that the VR exists as part of a complex system of subunits.

Acetylcholine↗

PubMed1999

Endophilin I mediates synaptic vesicle formation by transfer of arachidonate to lysophosphatidic acid.

Endophilin I is a presynaptic protein of unknown function that binds to dynamin, a GTPase that is implicated in endocytosis and recycling of synaptic vesicles. Here we show that endophilin I is essential for the formation of synaptic-like microvesicles (SLMVs) from the plasma membrane. Endophilin I exhibits lysophosphatidic acid acyl transferase (LPAAT) activity, and endophilin-I-mediated SLMV formation requires the transfer of the unsaturated fatty acid arachidonate to lysophosphatidic acid, converting it to phosphatidic acid. A deletion mutant lacking the SH3 domain through which endophilin I interacts with dynamin still exhibits LPAAT activity but no longer mediates SLMV formation. These results indicate that endophilin I may induce negative membrane curvature by converting an inverted-cone-shaped lipid to a cone-shaped lipid in the cytoplasmic leaflet of the bilayer. We propose that, through this action, endophilin I works with dynamin to mediate synaptic vesicle invagination from the plasma membrane and fission.

Acyl Coenzyme A↗

PubMed1987

Lead-dependent deposits in diverse synaptic vesicles: suggestive evidence for the presence of anionic binding sites.

We have observed electron dense deposits dependent on incubation of aldehyde-fixed tissues with lead ions within synaptic vesicles of several types of neurons that differ in the neurotransmitters utilized and in the secretory granules of the adrenal medulla. Evidently, vesicle components that can interact with lead ions are widespread. A plausible explanation for the occurrence of the deposits is the presence of anionic binding sites within the vesicles. This would agree well with other biochemical, cytochemical, and immunocytochemical evidence, such as that indicating the presence of sulfated macromolecules in certain synaptic vesicles. Anionic binding sites could play significant roles by participating in processes such as Ca2+ storage, stabilization of pH gradients, or the control of osmotic phenomena.

Adrenal Medulla↗

PubMed2000

The t-SNARE syntaxin is sufficient for spontaneous fusion of synaptic vesicles to planar membranes.

Vesicular trafficking and exocytosis are directed by the complementary interaction of membrane proteins that together form the SNARE complex. This complex is composed of proteins in the vesicle membrane (v-SNAREs) that intertwine with proteins of the target membrane (t-SNAREs). Here we show that modified synaptic vesicles (mSV), containing v-SNAREs, spontaneously fuse to planar membranes containing the t-SNARE, syntaxin 1A. Fusion was Ca(2+)-independent and did not occur with vesicles lacking v-SNAREs. Therefore, syntaxin alone forms a functional fusion complex with v-SNAREs. Our functional fusion assay uses synaptic vesicles that are modified, so each fusion event results in an observable transient current. The mSV do not fuse with protein-free membranes. Additionally, artificial vesicles lacking v-SNAREs do not fuse with membranes containing syntaxin. This technique can be adapted to measure fusion in other SNARE systems and should enable the identification of proteins critical to vesicle-membrane fusion. This will further our understanding of exocytosis and may improve targeting and delivery of therapeutic agents packaged in vesicles.

Animals↗

PubMed1990

Sorting during transport to the surface of PC12 cells: divergence of synaptic vesicle and secretory granule proteins.

PC12 cells, a cell line derived from a rat pheochromocytoma, have both regulated and constitutive secretory pathways. Regulated secretion occurs via large dense core granules, which are related to chromaffin granules and are abundant in these cells. In addition, PC12 cells also contain small electron-lucent vesicles, whose numbers increase in response to nerve growth factor and which may be related to cholinergic synaptic vesicles. These could characterize a second regulated secretory pathway. We have investigated the trafficking of protein markers for both these organelles. We have purified and characterized the large dense core granules from these cells using sequential velocity and equilibrium gradients. We demonstrate the copurification of the major PC12 soluble regulated secretory protein (secretogranin II) with this organelle. As a marker for the synaptic vesicle-like organelles in this system, we have used the integral membrane glycoprotein p38 or synaptophysin. We show that the p38-enriched fraction of PC12 cells comigrates with rat brain synaptic vesicles on an equilibrium gradient. We also demonstrate that p38 purifies away from the dense core granules; less than 5% of this protein is found in our dense granule fraction. Finally we show that p38 does not pass through the dense granule fraction in pulse-chase experiments. These results rule out the possibility of p38 reaching the small clear vesicles via mature dense granules and imply that these cells may have two independently derived regulated pathways.

Adrenal Gland Neoplasms↗

PubMed1990

Svp25, a synaptic vesicle membrane glycoprotein from Torpedo electric organ that binds calcium and forms a homo-oligomeric complex.

Svp25 is a major glycoprotein of cholinergic synaptic vesicles isolated from the Torpedo electric organ. On SDS-PAGE svp25 migrates as a protein of Mr 25,000 and on two dimensional gel electrophoresis separates into several isoforms around a pI of 6.0. It binds concanavalin A and on phase separation with Triton X-114 behaves as an integral membrane protein. Svp25 represents a major vesicular 45Ca2(+)-binding protein. Under non-reducing conditions svp25 forms complexes of higher molecular weight which are multiples of 25,000. Svp25 is contained in the dense web of nerve terminal ramifications at the ventral side of the electroplaque cells. Colloidal gold labelling using a monospecific antibody confirms the selective association of the protein with synaptic vesicles. Although the function of the vesicular svp25 glycoprotein is not known, its ability to bind Ca2+ suggests that it is regulated by activation of the nerve terminal.

Animals↗