Cholinergic nerve terminals contain ascorbic acid which induces Ca<sup>2+</sup>‐dependent release of acetylcholine and ATP from isolated <i>Torpedo</i> synaptic vesicles

Pinchasi, Irit; Michaelson, Daniel M.; Sokolovsky, Mordechai

doi:10.1016/0014-5793(79)81207-7

Cited by 13 publications

(5 citation statements)

References 17 publications

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“…There are two other possible mechanisms of ATP abundance at the presynapse: 1) many clear core synaptic vesicles are themselves known to package ATP in their lumen [ 48 ] and 2) a number of synaptic vesicle proteins and active zone-associated proteins are known to bind ATP without any evidence of ATP hydrolysis. It has been shown that synaptic vesicle 2 (SV2) and the SV2- related protein homolog (SVOP) are both capable of binding ATP [ 49 , 50 ].…”

Section: Discussionmentioning

confidence: 99%

Central Presynaptic Terminals Are Enriched in ATP but the Majority Lack Mitochondria

et al. 2015

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Synaptic neurotransmission is known to be an energy demanding process. At the presynapse, ATP is required for loading neurotransmitters into synaptic vesicles, for priming synaptic vesicles before release, and as a substrate for various kinases and ATPases. Although it is assumed that presynaptic sites usually harbor local mitochondria, which may serve as energy powerhouse to generate ATP as well as a presynaptic calcium depot, a clear role of presynaptic mitochondria in biochemical functioning of the presynapse is not well-defined. Besides a few synaptic subtypes like the mossy fibers and the Calyx of Held, most central presynaptic sites are either en passant or tiny axonal terminals that have little space to accommodate a large mitochondrion. Here, we have used imaging studies to demonstrate that mitochondrial antigens poorly co-localize with the synaptic vesicle clusters and active zone marker in the cerebral cortex, hippocampus and the cerebellum. Confocal imaging analysis on neuronal cultures revealed that most neuronal mitochondria are either somatic or distributed in the proximal part of major dendrites. A large number of synapses in culture are devoid of any mitochondria. Electron micrographs from neuronal cultures further confirm our finding that the majority of presynapses may not harbor resident mitochondria. We corroborated our ultrastructural findings using serial block face scanning electron microscopy (SBFSEM) and found that more than 60% of the presynaptic terminals lacked discernible mitochondria in the wild-type mice hippocampus. Biochemical fractionation of crude synaptosomes into mitochondria and pure synaptosomes also revealed a sparse presence of mitochondrial antigen at the presynaptic boutons. Despite a low abundance of mitochondria, the synaptosomal membranes were found to be highly enriched in ATP suggesting that the presynapse may possess alternative mechanism/s for concentrating ATP for its function. The potential mechanisms including local glycolysis and the possible roles of ATP-binding synaptic proteins such as synapsins, are discussed.

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Section: Discussionmentioning

confidence: 99%

Central Presynaptic Terminals Are Enriched in ATP but the Majority Lack Mitochondria

et al. 2015

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“…We have not identified the ion. There are numerous reports describing a similar calcium-induced lysis of secretory vesicles (Pinchasi et al, 1979;Kuo et al, 1979;Konings and DePotter, 1982). In these studies, vesicle lysis was observed in the presence of M free calcium (buffered with EGTA).…”

Section: Discussionmentioning

confidence: 84%

Fe²⁺‐Induced Lysis and Lipid Peroxidation of Chromaffin Granules

Spears

Holz

1985

Journal of Neurochemistry

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Chromaffin granules, the catecholaminergic storage granules from adrenal chromaffin cells, lysed in 10(-9)-10(-7) M Fe2+. Lysis was accompanied by the production of malondialdehyde which results from lipid peroxidation. Both chromaffin granule lysis and malondialdehyde production were inhibited by the free radical trapping agent butylated hydroxytoluene but not by catalase and/or superoxide dismutase. The results suggest that lysis resulted from a direct transfer of electrons from Fe2+ to a component of the chromaffin granule membrane without the participation of either superoxide or hydrogen peroxide and may have resulted from lipid peroxidation. In some experiments, ascorbate alone induced chromaffin granule lysis which was inhibited by EDTA, EGTA, or deferoxamine. The lysis was probably caused by trace amounts of reducible polyvalent cation. Lysis sometimes occurred when Ca2+ was added with EGTA (10 microM free Ca2+ concentration) and was consistently observed together with malondialdehyde production in the presence of Ca2+, EGTA, and 10 microM Fe2+ (total concentration). The apparent Ca2+ dependency for chromaffin granule lysis and malondialdehyde production was probably caused by a trace reducible polyvalent ion displaced by Ca2+ from EGTA and not by a Ca2+-dependent reaction involving the chromaffin granule.

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“…A second issue is that the widely reported preferential release of newly synthesized ACh (e.g., in electric organ, Dunant et al, 1972) becomes a prediction of the existence of active zone vesicles when their position is considered in conjunction with biochemical data on the presence of vesicular Ca pumps (Israel et al, 1980;Michaelson et al, 1980, Rephaeli andParsons, 1982) and Ca-induced release of vesicular ACh Pinchasi et al, 1978;Diebler, 1982). The argument is as follows.…”

Section: Significance Of a Defined Vesicle Subpopulationmentioning

confidence: 99%

Liquid nitrogen‐based quick freezing: Experiences with bounce‐free delivery of cholinergic nerve terminals to a metal surface

Phillips

Boyne

1984

J. Elec. Microsc. Tech.

100

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The limitations of chemical fixation in permitting the 1:1 quantitative correlations required for convincing ultrastructural explanations of cell biological processes are noted. We describe techniques for obtaining highly reproducible direct quick freezing on the polished surface of pure copper bars dipping into a static dewar of liquid Nz. The importance and the ease of testing and obtaining bounce suppression with commercially available equipment is emphasized. Artefacts caused by tissue damage and bad freezing are illustrated, and a hitherto unrecognized population of presynaptic membrane attached vesicles is described in Torpedine electric organ. Between 15 and 20% of the synaptic vesicles are attached to ca. 30% of the cytoplasmic face of the presynaptic terminal membrane. There is a close correlation between the occurrence of such attachments and the application of electrocyte basal lamina to the external face. We suggest that these vesicles are the 'membrane operators,' 'vesigates,' and 'highly active subpopulation' of vesicles whose existence has been invoked to explain biochemical data in other laboratories. We further speculate that relatively selective Ca pumping by this immediately submembranous population leads to displacement of acetylcholine (ACh) and reloading with newly synthesized ACh. The preferential release of the latter would then be expected.

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Cholinergic nerve terminals contain ascorbic acid which induces Ca²⁺‐dependent release of acetylcholine and ATP from isolated Torpedo synaptic vesicles

Cited by 13 publications

References 17 publications

Central Presynaptic Terminals Are Enriched in ATP but the Majority Lack Mitochondria

Central Presynaptic Terminals Are Enriched in ATP but the Majority Lack Mitochondria

Fe²⁺‐Induced Lysis and Lipid Peroxidation of Chromaffin Granules

Liquid nitrogen‐based quick freezing: Experiences with bounce‐free delivery of cholinergic nerve terminals to a metal surface

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Cholinergic nerve terminals contain ascorbic acid which induces Ca2+‐dependent release of acetylcholine and ATP from isolated Torpedo synaptic vesicles

Cited by 13 publications

References 17 publications

Central Presynaptic Terminals Are Enriched in ATP but the Majority Lack Mitochondria

Central Presynaptic Terminals Are Enriched in ATP but the Majority Lack Mitochondria

Fe2+‐Induced Lysis and Lipid Peroxidation of Chromaffin Granules

Liquid nitrogen‐based quick freezing: Experiences with bounce‐free delivery of cholinergic nerve terminals to a metal surface

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Cholinergic nerve terminals contain ascorbic acid which induces Ca²⁺‐dependent release of acetylcholine and ATP from isolated Torpedo synaptic vesicles

Fe²⁺‐Induced Lysis and Lipid Peroxidation of Chromaffin Granules