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A postsynaptic spectrin scaffold defines active zone size, spacing, and efficacy at the Drosophila neuromuscular junction.

ABSTRACT: Synaptic connections are established with characteristic, cell type-specific size and spacing. In this study, we document a role for the postsynaptic Spectrin skeleton in this process. We use transgenic double-stranded RNA to selectively eliminate alpha-Spectrin, beta-Spectrin, or Ankyrin. In the absence of postsynaptic alpha- or beta-Spectrin, active zone size is increased and spacing is perturbed. In addition, subsynaptic muscle membranes are significantly altered. However, despite these changes, the subdivision of the synapse into active zone and periactive zone domains remains intact, both pre- and postsynaptically. Functionally, altered active zone dimensions correlate with an increase in quantal size without a change in presynaptic vesicle size. Mechanistically, beta-Spectrin is required for the localization of alpha-Spectrin and Ankyrin to the postsynaptic membrane. Although Ankyrin is not required for the localization of the Spectrin skeleton to the neuromuscular junction, it contributes to Spectrin-mediated synapse development. We propose a model in which a postsynaptic Spectrin-actin lattice acts as an organizing scaffold upon which pre- and postsynaptic development are arranged.

SUBMITTER: Pielage J

PROVIDER: S-EPMC2064525 | biostudies-literature | 2006 Nov

REPOSITORIES: biostudies-literature

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A postsynaptic spectrin scaffold defines active zone size, spacing, and efficacy at the Drosophila neuromuscular junction.

Pielage Jan J Fetter Richard D RD Davis Graeme W GW

The Journal of cell biology 20061101 3

Synaptic connections are established with characteristic, cell type-specific size and spacing. In this study, we document a role for the postsynaptic Spectrin skeleton in this process. We use transgenic double-stranded RNA to selectively eliminate alpha-Spectrin, beta-Spectrin, or Ankyrin. In the absence of postsynaptic alpha- or beta-Spectrin, active zone size is increased and spacing is perturbed. In addition, subsynaptic muscle membranes are significantly altered. However, despite these chang ...[more]

PMID: 17088429

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Project description:Neurotransmission is shaped by extracellular pH. Alkalization enhances pH-sensitive transmitter release and receptor activation, whereas acidification inhibits these processes and can activate acid-sensitive conductances in the synaptic cleft. Previous work has shown that the synaptic cleft can either acidify because of synaptic vesicular release and/or alkalize because of Ca2+ extrusion by the plasma membrane ATPase (PMCA). The direction of change differs across synapse types. At the mammalian neuromuscular junction (NMJ), the direction and magnitude of pH transients in the synaptic cleft during transmission remain ambiguous. We set out to elucidate the extracellular pH transients that occur at this cholinergic synapse under near-physiological conditions and identify their sources. We monitored pH-dependent changes in the synaptic cleft of the mouse levator auris longus using viral expression of the pseudoratiometric probe pHusion-Ex in the muscle. Using mice from both sexes, a significant and prolonged alkalization occurred when stimulating the connected nerve for 5 s at 50 Hz, which was dependent on postsynaptic intracellular Ca2+ release. Sustained stimulation for a longer duration (20 s at 50 Hz) caused additional prolonged net acidification at the cleft. To investigate the mechanism underlying cleft alkalization, we used muscle-expressed GCaMP3 to monitor the contribution of postsynaptic Ca2+ Activity-induced liberation of intracellular Ca2+ in muscle positively correlated with alkalization of the synaptic cleft, whereas inhibiting PMCA significantly decreased the extent of cleft alkalization. Thus, cholinergic synapses of the mouse NMJ typically alkalize because of cytosolic Ca2+ liberated in muscle during activity, unless under highly strenuous conditions where acidification predominates.SIGNIFICANCE STATEMENT Changes in synaptic cleft pH alter neurotransmission, acting on receptors and channels on both sides of the synapse. Synaptic acidification has been associated with a myriad of diseases in the central and peripheral nervous system. Here, we report that in near-physiological recording conditions the cholinergic neuromuscular junction shows use-dependent bidirectional changes in synaptic cleft pH-immediate alkalinization and a long-lasting acidification under prolonged stimulation. These results provide further insight into physiologically relevant changes at cholinergic synapses that have not been defined previously. Understanding and identifying synaptic pH transients during and after neuronal activity provides insight into short-term synaptic plasticity synapses and may identify therapeutic targets for diseases.

Dataset Information

A postsynaptic spectrin scaffold defines active zone size, spacing, and efficacy at the Drosophila neuromuscular junction.

Publications

A postsynaptic spectrin scaffold defines active zone size, spacing, and efficacy at the Drosophila neuromuscular junction.

Similar Datasets

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