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Postsynaptic actin filaments at the giant mossy fiber‐unipolar brush cell synapse
Author(s) -
Diño Maria R.,
Mugnaini Enrico
Publication year - 2000
Publication title -
synapse
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.809
H-Index - 106
eISSN - 1098-2396
pISSN - 0887-4476
DOI - 10.1002/1098-2396(20001215)38:4<499::aid-syn16>3.0.co;2-h
Subject(s) - postsynaptic potential , synapse , postsynaptic density , actin cytoskeleton , microbiology and biotechnology , biology , cytoskeleton , actin , biophysics , chemistry , neuroscience , biochemistry , receptor , cell
The unipolar brush cell (UBC), a small interneuron occurring at high density in the granular layer of the mammalian vestibulocerebellum, receives a giant glutamatergic synapse from a single mossy fiber (MF) rosette, usually on a brush of dendritic branchlets. MF stimulation produces a current in the UBC several orders of magnitude greater in duration than at other glutamatergic synapses. We assumed that the cytoskeleton would have a special role in plasticity of the MF‐UBC synapse. Neurofilaments and microtubules are enriched in the UBC somatodendritic compartment but are conspicuously absent in close proximity to the giant synapse, where standard electron microscopy reveals a granulo‐flocculent material. Because osmium tetroxide fixation during sample preparation for standard electron microscopy destabilizes actin filaments, we hypothesized that this subsynaptic granulo‐flocculent material is actin‐based. After actin stabilization, we observed prominent, but loosely organized, bundles of microfilaments at the subsynaptic region of the MF‐UBC synapse that linked the postsynaptic density with the cytoskeletal core of the dendritic branchlets. Confocal fluorescence microscopy and pre‐ and postembedding immunogold labeling with phalloidin and actin antibodies showed that these microfilaments consist of f‐actin and contain little β‐actin. This extraordinary postsynaptic actin apparatus is ideally situated to form a dynamic framework for glutamate receptors and other postsynaptic molecules, and to mediate activity‐dependent plastic rearrangements of the giant synapse. Synapse 38:499–510, 2000. © 2000 Wiley‐Liss, Inc.