Drebrin a knockout eliminates the rapid form of homeostatic synaptic plasticity at excitatory synapses of intact adult cerebral cortex.
Homeostatic synaptic plasticity (HSP) is important for maintaining neurons' excitability within the dynamic range and for protecting neurons from unconstrained long-term potentiation that can cause breakdown of synapse specificity (Turrigiano [2008] Cell 135:422-435). Knowledge of the molecular mechanism underlying this phenomenon remains incomplete, especially for the rapid form of HSP. To test whether HSP in adulthood depends on an F-actin binding protein, drebrin A, mice deleted of the adult isoform of drebrin (DAKO) but retaining the embryonic isoform (drebrin E) were generated. HSP was assayed by determining whether the NR2A subunit of N-methyl-D-aspartate receptors (NMDARs) can rise rapidly within spines following the application of an NMDAR antagonist, D-APV, onto the cortical surface. Electron microscopic immunocytochemistry revealed that, as expected, the D-APV treatment of wild-type (WT) mouse cortex increased the proportion of NR2A-immunolabeled spines within 30 minutes relative to basal levels in hemispheres treated with an inactive enantiomer, L-APV. This difference was significant at the postsynaptic membrane and postsynaptic density (i.e., synaptic junction) as well as at nonsynaptic sites within spines and was not accompanied by spine size changes. In contrast, the D-APV treatment of DAKO brains did not augment NR2A labeling within the spine cytoplasm or at the synaptic junction, even though basal levels of NR2A were not significantly different from those of WT cortices. These findings indicate that drebrin A is required for the rapid (<30 minutes) form of HSP at excitatory synapses of adult cortices, whereas drebrin E is sufficient for maintaining basal NR2A levels within spines.
Aoki
Chiye
C
Center for Neural Science, New York University, New York, New York 10003, USA. ca3@nyu.edu
Kojima
Nobuhiko
N
Sabaliauskas
Nicole
N
Shah
Lokesh
L
Ahmed
Tunazzina H
TH
Oakford
John
J
Ahmed
Tahir
T
Yamazaki
Hiroyuki
H
Hanamura
Kenji
K
Shirao
Tomoaki
T
D015763:2-Amino-5-phosphonovalerate / Q000494:pharmacology; D000818:Animals; D002540:Cerebral Cortex / Q000187:drug effects / Q000502:physiology* / Q000648:ultrastructure; D003593:Cytoplasm / Q000378:metabolism; D049229:Dendritic Spines / Q000187:drug effects / Q000502:physiology / Q000648:ultrastructure; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009473:Neuronal Plasticity / Q000187:drug effects / Q000502:physiology*; D009474:Neurons / Q000187:drug effects / Q000502:physiology* / Q000648:ultrastructure; D009479:Neuropeptides / Q000235:genetics / Q000378:metabolism*; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D016194:Receptors, N-Methyl-D-Aspartate / Q000037:antagonists & inhibitors / Q000378:metabolism; D013569:Synapses / Q000187:drug effects / Q000502:physiology* / Q000648:ultrastructure; D013997:Time Factors
D018691:Excitatory Amino Acid Antagonists; C120997:NR2A NMDA receptor; D009479:Neuropeptides; D020033:Protein Isoforms; D016194:Receptors, N-Methyl-D-Aspartate; C083795:drebrin E; C053386:drebrins; D015763:2-Amino-5-phosphonovalerate