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PubMed1993

Temperature effect on immunostaining of microtubule-associated protein 2 and synaptophysin after 30 minutes of forebrain ischemia in rat.

The regional distribution of the postsynaptic microtubule-associated protein 2 (MAP2) and the presynaptic marker protein synaptophysin was investigated by immunohistochemistry in brains of rats submitted to 30-min forebrain ischemia by four-vessel occlusion. The following brain temperature profiles during ischemia were compared: (1) constant brain temperature of 36 degrees C (normothermia; n = 5); (2) spontaneous temperature decline from 36 degrees to 31 degrees C (spontaneous hypothermia; n = 5) and (3) constant temperature of 30 degrees C (induced hypothermia; n = 5). Normothermia was produced by exposing the ischemic head to an external heat source, and induced hypothermia by cooling the head with liquid nitrogen vapours. Sham-operated animals were either kept at ambient temperature or exposed to the same heat source, as required for maintaining normothermia during ischemia. Seven days after sham operation or ischemia, brains were fixed by perfusion and processed for immunohistochemistry using monoclonal antibodies against MAP2 and synaptic vesicle-specific protein (synaptophysin). Normothermic ischemia resulted in complete loss of MAP2 immunostaining in the whole hippocampus, spontaneous hypothermic ischemia in complete loss of MAP2 in CA1 sector, and induced hypothermic ischemia only in variable loss of MAP2 in CA1 sector. Post-ischemic immunostaining of synaptophysin revealed a temperature-dependent increase in stratum lacunosum-moleculare of CA1 sector, the density of which correlated inversely with MAP2 staining. Comparison with morphological alterations showed a close relationship between loss of MAP2 staining and histological injury. The post-ischemic activation of synaptophysin may reflect regenerative processes associated with synaptic remodelling and, therefore, is an indirect marker of the severity of ischemic injury.

Animals↗
PubMed1987

Synaptophysin: a reliable marker for medulloblastomas.

Synaptophysin is an acidic, integral membrane glycoprotein (Mr 38,000) of presynaptic vesicles in various neurons and neuroendocrine cells, and in tumours derived from such cells. By indirect immunofluorescence microscopy of cryostat sections, using the monoclonal antibody SY 38 to synaptophysin, a consistent positive immunoreactivity was observed in all medulloblastomas (n = 6) and neuroblastomas (n = 3) as well as a ganglioneuroma and a glioneuronal hamartoma. The presence of synaptophysin in medulloblastomas was confirmed biochemically by immunoblotting experiments. For purpose of comparison, the expression of intermediate-sized filament (IF) proteins was also examined. While neurofilament proteins were consistently expressed in the neuroblastomas (3/3), the ganglioneuroma and the glioneuronal hamartoma, IF distribution in medulloblastomas was variable. A neurofilament-positive type of tumour (1/6) could be distinguished from vimentin-expressing neoplasms (4/6) by immunocytochemistry. These data indicate that synaptophysin is a reliable marker for medulloblastomas as well as other differentiated and undifferentiated neuronal tumours and in this respect is superior to the more heterogeneous expression patterns of IF proteins in these tumours.

Adult↗
PubMed1993

Synaptophysin-containing microvesicles transport heat-shock protein hsp60 in insulin-secreting beta cells.

58-62 kDa heat-shock proteins (hsp60) are molecular chaperonins involved in the process of protein folding, transmembrane translocation and assembly of oligomeric protein complexes. In eukaryotic cells hsp60 proteins have been found in mitochondria and chloroplasts. However, we have recently documented that, in addition to mitochondria, a hsp60-like protein is present in secretory granules of insulin-secreting beta cells. The pathway by which hsp60 is targeted to secretory granules was unknown. Here we report the existence of microvesicles involved in the transport of hsp60 protein. Immunoelectron microscopy of serial thin-sections of beta cells directly visualized stages associated with hsp60 delivery: attachment of microvesicles to a secretory granule, fusion with the secretory granule membrane and release of hsp60 molecules. Further biochemical and immunological analysis of microvesicles revealed the presence in their membrane of synaptophysin, a major component of synaptic-like microvesicles (SLMV) of neuroendocrine cells. Double immunogold labelling with antibodies to synaptophysin and hsp60 demonstrated co-localization of both proteins in the same microvesicles. Moreover, fusion of synaptophysin-positive microvesicles leaves synaptophysin incorporated, at least transiently, to secretory granule membranes. These findings suggest that, in beta cells, synaptic-like vesicles are involved in the transport and delivery of hsp60 and represent a novel pathway for protein transport and secretion.

Animals↗
PubMed1990

Characterization of synaptophysin and G proteins in synaptic vesicles and plasma membrane of Aplysia californica.

Two components of synaptic terminals that may be involved in transmitter release are synaptophysin (p38) and G proteins. In order to study release mechanisms in Aplysia californica we have prepared subcellular fractions from nervous tissue to characterize and localize these components. We identify Aplysia synaptophysin by Western blot analysis with monoclonal antibody SY38, find that it is enriched in synaptic vesicles, and, using immunocytochemistry, show that it is localized to neuropil. These characteristics indicate that Aplysia synaptophysin is closely related to mammalian synaptophysin; it appears to be much smaller, however, having a mass of 28 kDa instead of 38 kDa. We previously determined that G protein subunits in Aplysia are enriched in neuropil and synaptosomes. We now show that within the synaptic terminal the pertussis toxin-sensitive alpha-subunit as well as the beta-subunit are associated with plasma membrane using [32P]ADP-ribosylation and Western blotting with G protein-specific antibodies.

Animals↗
PubMed1991

Synaptophysin and chromogranin A immunoreactivities in senile plaques of Alzheimer's disease.

Immunolabelling for synaptophysin and chromogranin A, two polypeptides associated with small clear and large dense core synaptic vesicles respectively, has been performed on tissue sections of the temporal cortex in Alzheimer's disease in combination with anti-A4 amyloid labelling. The dystrophic neurites in many senile plaques were observed to be labelled by the anti-synaptophysin or anti-chromogranin A antibodies. Some diffuse amyloid deposits, demonstrated by antibodies against synthetic amyloid A4 peptides, were associated with a punctuate increase in synaptophysin or chromogranin A immunoreactivity. The labelling of dystrophic plaque neurites may reflect the accumulation in these processes of synaptic vesicles or material derived from them. We suggest also that the punctuate increase in synaptophysin and chromogranin A immunoreactivities associated with some A4 amyloid deposits may be an early event reflecting neuronal dysfunction.

Alzheimer Disease↗
PubMed1993

Changes of immunoreactivity for synaptophysin ('protein p38') following a transient cerebral ischemia in the rat striatum.

We assessed the chronological change of the expression of synaptophysin, an integral glycoprotein on the presynaptic vesicles, after a transient cerebral ischemic insult in the rat. The ischemic lesion was consistently localized in the dorsolateral part of the striatum, which was clearly visualized by a depletion of calcineurin immunostaining or increases of immunoreactivities for glial fibrillary acidic protein and tyrosine hydroxylase. Immunoreactivity for synaptophysin was transiently increased in the ischemic lesions from 3 to 7 days after cerebral ischemia. Thereafter, synaptophysin immunostaining in the damaged areas gradually decreased and finally almost disappeared one month after surgery. Because synaptophysin is located in the presynaptic vesicle, and thought to be involved in presynaptic functions such as vesicle-membrane fusion and release of neurotransmitters, present findings suggest that loss of the postsynaptic site after ischemic insult induces a transient increase of the presynaptic functions, followed by a decrease of functional presynaptic activity or trans-synaptic retrograde degeneration of axon terminals.

Animals↗
PubMed1988

Fractionation of synaptophysin-containing vesicles from rat brain and cultured PC12 pheochromocytoma cells.

Synaptophysin is a transmembrane glycoprotein of neuroendocrine vesicles. Its content and distribution in subcellular fractions from cultured PC12 cells, rat brain and bovine adrenal medulla were determined by a sensitive dot immunoassay. Synaptophysin-containing fractions appeared as monodispersed populations similar to synaptic vesicles in density and size distribution. Membranes from synaptic vesicles contained approximately 100-times more synaptophysin than chromaffin granules. In conclusion, synaptophysin is located almost exclusively in vesicles of brain and PC12 cells which are distinct from dense core granules.

Adrenal Medulla↗
PubMed1988

Identification of gastroenteropancreatic neuroendocrine cells in normal and neoplastic human tissue with antibodies against synaptophysin, chromogranin A, secretogranin I (chromogranin B), and secretogranin II.

Gastroenteropancreatic human neuroendocrine (NE) cells (normal and neoplastic) were investigated for the expression of the neuroendocrine-specific polypeptides synaptophysin, chromogranin A, secretogranin I (chromogranin B), and secretogranin II, using immunohistochemistry and immunoblotting. Monoclonal antibody against synaptophysin stained most, and possibly all, of the neuroendocrine cells in both normal and neoplastic tissue. Monoclonal antibody against chromogranin A also stained a high proportion of normal and neoplastic neuroendocrine cells. Immunostaining with polyclonal antisecretogranin I and antisecretogranin II antibodies was detectable in almost all of the normal and neoplastic tissue sections that were analyzed, and it was confined to a smaller population of neuroendocrine cells than that observed for synaptophysin and chromogranin A. Consistent with the immunohistochemical observations, immunoblotting revealed the presence of all four antigens in various tumors. The data show that synaptophysin and chromogranin A, for which monoclonal antibodies are commercially available, may be used as diagnostic markers for human gastroenteropancreatic tumors. Our results also suggest that the development of monoclonal antibodies against human secretogranins I and II will provide additional tools for a refined diagnosis of such tumors.

Antibodies, Neoplasm↗
PubMed1994

The expression of GAP-43 and synaptophysin in the developing rat retina.

We have undertaken a detailed study of the expression of GAP-43 and synaptophysin immunoreactivity in the developing postnatal rat retina. We found that these two 'presynaptic' proteins have quite different expression patterns. GAP-43 was first expressed in the optic nerve and the optic fiber layer of the retina, where it disappeared between the 8th and 16th postnatal day. From the 5th postnatal day on, GAP-43 also appeared in the inner plexiform layer, where it was present in three distinct bands. This expression changed little in postnatal development and persisted in the adult retina. GAP-43 was not detected in the outer plexiform layer of the retina. Synaptophysin was absent from the optic nerve and optic fibers at all postnatal stages. It was first expressed in the developing outer plexiform and, with reduced intensity, in the outer nuclear layer between postnatal days 2 and 5. In the inner plexiform layer, synaptophysin could be first detected between postnatal days 8 and 12. The intensity of staining increased during postnatal development in both plexiform layers. The developmental sequence of synaptophysin expression can be correlated with the maturation of presynaptic terminals of photoreceptors and bipolar cells. The rather complex pattern of GAP-43 expression is not easily compatible with a single model of GAP-43 function, and suggests diverse functions of this molecule in the retina.

Animals↗
PubMed1996

Synaptophysin-like immunoreactivity in the rat olfactory bulb during postnatal development and after restricted early olfactory experience.

Synaptophysin is a synaptic vesicle protein that provides a marker of synaptic distribution in the brain. We used synaptophysin immunohistochemistry to detect changes in synaptic distribution in the main olfactory bulb during normal early postnatal development and following early olfactory restriction. Synaptophysin-like immunoreactivity appears early in the postnatal development of most bulbar laminae. In the first postnatal week, the entire glomerular neuropil is stained intensely, but by PND 19, the glomerular perimeter becomes more intensely stained than its core. This immunoreactivity is especially dense along that aspect of the perimeter facing the olfactory nerve layer. To determine if this developmental pattern could be affected by early olfactory experience, unilateral naris closure was performed on PND 1. In deprived bulbs at PND 19, the difference in staining between the glomerular border and the glomerular core is significantly less than in either contralateral glomeruli or glomeruli from unoperated animals. The difference between the glomerular border and the glomerular core is greater in bulbs contralateral to a closed naris than in bulbs from unoperated animals. Staining intensity measured over entire glomeruli is not altered by naris closure, nor is staining of other laminae. The changes detected after naris closure indicate that the glomerular distribution of synaptophysin may be particularly sensitive to early olfactory experience.

Aging↗
PubMed1992

Molecular cloning of a cDNA encoding a novel protein related to the neuronal vesicle protein synaptophysin.

The structure of synaptophysin, an integral membrane protein present in synaptic vesicles, is highly conserved. We report the sequence analysis of a clone, HL-5, isolated from a human erythroleukemia cell cDNA library, that is similar to synaptophysin in DNA and amino acid sequence. The predicted protein product derived from this clone is truncated, and the tissue distribution of HL-5 is different from that of synaptophysin. Thus, HL-5 appears to be a member of a previously undescribed family of synaptophysin-like genes.

Amino Acid Sequence↗
PubMed1990

Chronic osmotic stimulation reduces vasopressin but not synaptophysin content in rat neurohypophysis.

The content of synaptophysin, a vesicular integral membrane protein of neurons and endocrine cells, and that of vasopressin was measured in neurohypophyses of rats during chronic osmotic stimulation. The animals received 2% NaCl in their drinking water for up to 4 days. Synaptophysin content of neurohypophyses was determined using quantitative immunoblotting, vasopressin content was measured by radioimmunoassay. Salt loading caused a decrease in the content of vasopressin to about 15% of that of control animals, whether expressed per neurohypophysis or relative to the total tissue protein. In contrast, no change was found in the synaptophysin content. Taken together with published evidence of changes in the relative numbers of the hormone-containing neurosecretory granules (NSGs) and the microvesicles (MVs) under the conditions of chronic osmotic stimulation, these results strongly indicate the surface density of synaptophysin on NSGs to be significantly lower than its surface density on MVs.

Animals↗
PubMed1992

Increase in synaptophysin immunoreactivity following cortical infarction.

Plasticity in the central nervous system has been demonstrated using lesions of the hippocampus and rhinal cortex but has not been well studied after cerebral ischemia. Focal cerebral ischemia creates an area of infarction that is surrounded by neuronal tissue that may respond to nearby damage by creating new synapses. To determine if synaptogenesis occurs, antibodies to synaptophysin, a calcium-binding protein found on synaptic vesicles, were used with immunohistochemical techniques to assess the level of synaptophysin immunoreactivity as a measure of changes in the number of synapses. Cerebral ischemia was induced in hypertensive rats by permanently occluding the distal middle cerebral artery and ipsilateral common carotid artery. After 2 months recovery, the animals were perfused and the brains removed for immunohistochemical processing and evaluation. When comparing the cortex surrounding the infarcted area to similar areas on the contralateral side of the brain, the infarcted side had increased levels of anti-synaptophysin like activity that are statistically significant. We hypothesize that this increase in synaptophysin immunoreactivity is due to an increase in synapses in the cortex surrounding an area of infarction and supports the hypothesis of plasticity in the cortex following cerebral infarction.

Animals↗
PubMed1995

Decreased synaptophysin in the medial temporal lobe in schizophrenia demonstrated using immunoautoradiography.

Synaptic alterations have been suggested, largely on theoretical grounds, to occur in the brain in schizophrenia. The messenger RNA encoding synaptophysin, a presynaptic terminal protein, is reduced in the medial temporal lobe in the disease, but immunocytochemical and immunoblotting data have not produced clear evidence for a loss of the encoded protein. Here we have used immunoautoradiography with an antisynaptophysin monoclonal antibody and a 35S-labelled secondary antibody in medial temporal lobe sections from 11 schizophrenics and 14 matched controls. In the schizophrenic cases there was an overall loss of synaptophysin (P < 0.02). Analysis by subfield showed significant reductions in the right dentate gyrus molecular layer, subiculum and parahippocampal gyrus, with similar trends in most other subfields. These data confirm that synaptophysin expression is decreased within the medial temporal lobe in schizophrenia. In the respect that synaptophysin is a marker of synaptic density, our findings suggest that reduced synaptic density may be a feature of the molecular neuropathology of the disease.

Autoradiography↗
PubMed2004

Synaptic lesions and synaptophysin distribution change in spinal motoneurons at early stages following sciatic nerve transection in neonatal rats.

The purpose of this investigation was to evaluate the rate of synaptic stripping, changes in the synaptophysin distribution, and synapses ultrastructure of spinal motoneurons at early stages of sciatic nerve axotomy in newborn rats. Seven groups were used in the experiment, which were sacrificed after 1, 3, 6, 12, 24, 48 and 72 h. L4-L6 spinal segments from the animals of the above groups were prepared and processed for indirect immunoperoxidase. Accordingly, tissue samples were prepared from similar groups for routine electron microscopy. Synaptophysin-labeled motoneurons were classified into intact, partial, cytoplasmic and negative patterns. Synaptophysin immunoreactivity in both the axotomized and non-axotomized sides showed no negative pattern at the first three time points, while this pattern significantly increased in the 12, 24, 48 and 72 h groups at the axotomized side, moreover, there was a progressive reduction in the percentage of the intact pattern at the axotomized side. The percentages of the cytoplasmic and partial patterns also increased during the time course. The rate of synaptic stripping was five time higher in the axotomized side than that of non-axotomized side. The results of the ultrastructural study showed synaptic membranes irregularity, synaptic vesicles displacement, synaptic membrane detachment and ensheathment of degenerated synapses. The conclusion of the study was that early synaptophysin immunoreactivity changes were seen in both the axotomized and non-axotomized sides, but the rate of change in the axotomized side was more rapid than that of the non-axotomized side.

Animals↗
PubMed2005

Altered expression of MAP-2, GAP-43, and synaptophysin in the hippocampus of rats with chronic cerebral hypoperfusion correlates with cognitive impairment.

Chronic cerebral hypoperfusion causes cognitive impairment, but the underlying molecular mechanism is not well understood. We used permanent occlusion of bilateral common carotid arteries (2-VO) to induce chronic cerebral hypoperfusion in male Wistar rats. Cognitive impairment and the expression patterns of MAP-2, GAP-43, and synaptophysin were examined. We found that both learning capacity and memory were gradually impaired in the rats with chronic cerebral hypoperfusion concomitant with increased duration of 2-VO treatment. Four weeks of 2-VO treatment resulted in down-regulation of synaptophysin expression at the protein levels, and a further decrease was observed at 10-20 weeks, although mRNA levels remained the same. Ten weeks of 2-VO treatment lead to down-regulation of MAP-2 expression at both the mRNA and protein levels with a further decrease at 20 weeks. Interestingly, GAP-43 mRNA was significantly up-regulated by 2-VO treatment, although the protein levels were not altered. Therefore, the cognitive impairment caused by chronic cerebral hypoperfusion may be partially explained by reduced expression of synaptophysin and MAP-2 at the protein level. The reduction in MAP-2 expression may be attributed to the inhibition of transcription, while the reduction in synaptophysin expression might be due to the inhibition of translation. Up-regulation of GAP-43 mRNA in the rat hippocampus with 2-VO treatment suggests that a compensatory mechanism may antagonize ischemic challenges.

Animals↗
PubMed2005

Synaptophysin enhances the neuroprotection of VMAT2 in MPP+-induced toxicity in MN9D cells.

The use of the potent neurotoxin MPTP in producing a model for Parkinson's disease (PD) has allowed us to dissect the cellular processes responsible for both selective neuronal vulnerability and neuroprotection in idiopathic PD. It has been suggested that vesicular monoamine transporters (VMATs) play a critical neuroprotective role in MPP+ toxicity. However, little is known about how this detoxificative sequestration in dopaminergic (DAergic) neurons is regulated at the molecular and cellular levels. Using the DAergic cell line MN9D as an in vitro model, we found that overexpression of VMAT2 (a neuronal isoform of VMATs) protects the transformants from MPP+-induced toxicity, consistent with the previous work on fibroblastic CHO cells. We further found that the MN9D cells displayed lower expression levels of secretory vesicle proteins such as synaptophysin. Overexpression of synaptophysin in MN9D cells can significantly increase the resistance of the transformants to MPP+ toxicity. The co-expression of VMAT2 and synaptophysin has shown synergistic protection for the transformants, suggesting a role of synaptophysin in the biogenesis of secretory vesicles and in influencing the targeting of VMAT2 to these vesicles. Our work indicates that both the expression level of VMAT2 and capacity of vesicular packaging of DA are important in protecting DAergic cells from MPP+ toxicity.

1-Methyl-4-phenylpyridinium↗
PubMed2005

Sex-differences in age-related cognitive decline in C57BL/6J mice associated with increased brain microtubule-associated protein 2 and synaptophysin immunoreactivity.

Understanding cognitive aging is becoming more important as the elderly population grows. Here, the effects of age and sex on learning and memory performance were compared in female and male young (3-4 months old) middle-aged (10-12 months old) and old (18-20 months old) wild-type C57BL/6J mice. Old males and females performed worse than young or middle-aged mice in novel location, but not novel object recognition tasks. Old mice, of both sexes, also showed impaired spatial water maze performance during training compared with young or middle-aged mice, however only old females failed to show robust spatial bias during probe trials. While there was no age-difference in passive avoidance performance for males, females showed an age-related decline. There was no difference in cognitive performance between young and middle-age mice of either sex on any task. Cognitive performance was associated with alterations in immunoreactivity of microtubule-associated protein 2-positive dendrites and synaptophysin-positive pre-synaptic terminals in hippocampal CA1, CA3, and dentate, entorhinal cortex, and central nucleus of amygdala. Overall, microtubule-associated protein 2 immunoreactivity was increased in old females compared with both young and middle-age females with no significant difference in males. In contrast, synaptophysin immunoreactivity increased from young to middle-age in females, and from middle-age to old in males; females had higher levels of synaptophysin immunoreactivity than males in middle-age only. Elevated levels of microtubule-associated protein 2 and synaptophysin may constitute a compensatory response to age-related functional decline in mice.

Adaptation, Physiological↗