Overexpression of Synaptophysin Enhances Neurotransmitter Secretion at Xenopus Neuromuscular Synapses

Janet Alder, Hiroaki Kanki, Flavia Valtorta, Paul Greengard, Mu Ming Poo

Research output: Contribution to journalArticle

Abstract

Previous studies have suggested the importance of synaptophysin (p38), a major integral membrane protein of the synaptic vesicle, in transmitter secretion, but few have directly addressed its functional role at intact synapses. In the present study, injection of synthetic mRNA for synaptophysin into one of the early blastomeres of a Xenopus embryo resulted in elevated synaptophysin expression in 1 and 2 d embryos and in cultured spinal neurons derived from the injected blastomere, as shown by immunocytochemistry. At neuromuscular synapses made by neurons overexpressing synaptophysin [p38(+)] in 1 d cell cultures, the spontaneous synaptic currents (SSCs) showed a markedly higher frequency, as compared to control synapses. This increase in frequency was not accompanied by a change in the mean amplitude or the amplitude distribution of the SSCs, suggesting that synaptophysin is not involved in determining the size of transmitter quanta. The impulse-evoked synaptic currents (ESCs) of synapses made by p38(+) neurons showed increased amplitude as well as reduced fluctuation and delay of onset of ESCs. Under high-frequency tetanic stimulation at 5 Hz, the rate of tetanus-induced depression was faster for p38(+) neurons. Taken together, these results suggest a role for synaptophysin in the late steps of transmitter secretion, affecting the probability of vesicular exocytosis and/or the number of synaptic vesicles initially docked at the active zone.

Original languageEnglish
Pages (from-to)511-519
Number of pages9
JournalJournal of Neuroscience
Volume15
Issue number1 I
Publication statusPublished - Jan 1995

Fingerprint

Synaptophysin
Xenopus
Synapses
Neurotransmitter Agents
Neurons
Blastomeres
Synaptic Vesicles
Embryonic Structures
Exocytosis
Tetanus
Membrane Proteins
Cell Culture Techniques
Immunohistochemistry
Messenger RNA
Injections

Keywords

  • Embryonic neurons
  • Neuromuscular synapse
  • Overexpression
  • Synaptic vesicle
  • Synaptophysin
  • Transmitter secretion

ASJC Scopus subject areas

  • Neuroscience(all)

Cite this

Overexpression of Synaptophysin Enhances Neurotransmitter Secretion at Xenopus Neuromuscular Synapses. / Alder, Janet; Kanki, Hiroaki; Valtorta, Flavia; Greengard, Paul; Poo, Mu Ming.

In: Journal of Neuroscience, Vol. 15, No. 1 I, 01.1995, p. 511-519.

Research output: Contribution to journalArticle

Alder, Janet ; Kanki, Hiroaki ; Valtorta, Flavia ; Greengard, Paul ; Poo, Mu Ming. / Overexpression of Synaptophysin Enhances Neurotransmitter Secretion at Xenopus Neuromuscular Synapses. In: Journal of Neuroscience. 1995 ; Vol. 15, No. 1 I. pp. 511-519.
@article{465e4e07667946bdbfdf0ad8511dbc2e,
title = "Overexpression of Synaptophysin Enhances Neurotransmitter Secretion at Xenopus Neuromuscular Synapses",
abstract = "Previous studies have suggested the importance of synaptophysin (p38), a major integral membrane protein of the synaptic vesicle, in transmitter secretion, but few have directly addressed its functional role at intact synapses. In the present study, injection of synthetic mRNA for synaptophysin into one of the early blastomeres of a Xenopus embryo resulted in elevated synaptophysin expression in 1 and 2 d embryos and in cultured spinal neurons derived from the injected blastomere, as shown by immunocytochemistry. At neuromuscular synapses made by neurons overexpressing synaptophysin [p38(+)] in 1 d cell cultures, the spontaneous synaptic currents (SSCs) showed a markedly higher frequency, as compared to control synapses. This increase in frequency was not accompanied by a change in the mean amplitude or the amplitude distribution of the SSCs, suggesting that synaptophysin is not involved in determining the size of transmitter quanta. The impulse-evoked synaptic currents (ESCs) of synapses made by p38(+) neurons showed increased amplitude as well as reduced fluctuation and delay of onset of ESCs. Under high-frequency tetanic stimulation at 5 Hz, the rate of tetanus-induced depression was faster for p38(+) neurons. Taken together, these results suggest a role for synaptophysin in the late steps of transmitter secretion, affecting the probability of vesicular exocytosis and/or the number of synaptic vesicles initially docked at the active zone.",
keywords = "Embryonic neurons, Neuromuscular synapse, Overexpression, Synaptic vesicle, Synaptophysin, Transmitter secretion",
author = "Janet Alder and Hiroaki Kanki and Flavia Valtorta and Paul Greengard and Poo, {Mu Ming}",
year = "1995",
month = "1",
language = "English",
volume = "15",
pages = "511--519",
journal = "Journal of Neuroscience",
issn = "0270-6474",
publisher = "Society for Neuroscience",
number = "1 I",

}

TY - JOUR

T1 - Overexpression of Synaptophysin Enhances Neurotransmitter Secretion at Xenopus Neuromuscular Synapses

AU - Alder, Janet

AU - Kanki, Hiroaki

AU - Valtorta, Flavia

AU - Greengard, Paul

AU - Poo, Mu Ming

PY - 1995/1

Y1 - 1995/1

N2 - Previous studies have suggested the importance of synaptophysin (p38), a major integral membrane protein of the synaptic vesicle, in transmitter secretion, but few have directly addressed its functional role at intact synapses. In the present study, injection of synthetic mRNA for synaptophysin into one of the early blastomeres of a Xenopus embryo resulted in elevated synaptophysin expression in 1 and 2 d embryos and in cultured spinal neurons derived from the injected blastomere, as shown by immunocytochemistry. At neuromuscular synapses made by neurons overexpressing synaptophysin [p38(+)] in 1 d cell cultures, the spontaneous synaptic currents (SSCs) showed a markedly higher frequency, as compared to control synapses. This increase in frequency was not accompanied by a change in the mean amplitude or the amplitude distribution of the SSCs, suggesting that synaptophysin is not involved in determining the size of transmitter quanta. The impulse-evoked synaptic currents (ESCs) of synapses made by p38(+) neurons showed increased amplitude as well as reduced fluctuation and delay of onset of ESCs. Under high-frequency tetanic stimulation at 5 Hz, the rate of tetanus-induced depression was faster for p38(+) neurons. Taken together, these results suggest a role for synaptophysin in the late steps of transmitter secretion, affecting the probability of vesicular exocytosis and/or the number of synaptic vesicles initially docked at the active zone.

AB - Previous studies have suggested the importance of synaptophysin (p38), a major integral membrane protein of the synaptic vesicle, in transmitter secretion, but few have directly addressed its functional role at intact synapses. In the present study, injection of synthetic mRNA for synaptophysin into one of the early blastomeres of a Xenopus embryo resulted in elevated synaptophysin expression in 1 and 2 d embryos and in cultured spinal neurons derived from the injected blastomere, as shown by immunocytochemistry. At neuromuscular synapses made by neurons overexpressing synaptophysin [p38(+)] in 1 d cell cultures, the spontaneous synaptic currents (SSCs) showed a markedly higher frequency, as compared to control synapses. This increase in frequency was not accompanied by a change in the mean amplitude or the amplitude distribution of the SSCs, suggesting that synaptophysin is not involved in determining the size of transmitter quanta. The impulse-evoked synaptic currents (ESCs) of synapses made by p38(+) neurons showed increased amplitude as well as reduced fluctuation and delay of onset of ESCs. Under high-frequency tetanic stimulation at 5 Hz, the rate of tetanus-induced depression was faster for p38(+) neurons. Taken together, these results suggest a role for synaptophysin in the late steps of transmitter secretion, affecting the probability of vesicular exocytosis and/or the number of synaptic vesicles initially docked at the active zone.

KW - Embryonic neurons

KW - Neuromuscular synapse

KW - Overexpression

KW - Synaptic vesicle

KW - Synaptophysin

KW - Transmitter secretion

UR - http://www.scopus.com/inward/record.url?scp=0028800496&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0028800496&partnerID=8YFLogxK

M3 - Article

C2 - 7823159

AN - SCOPUS:0028800496

VL - 15

SP - 511

EP - 519

JO - Journal of Neuroscience

JF - Journal of Neuroscience

SN - 0270-6474

IS - 1 I

ER -