A role for the ubiquitin-proteasome system in activity-dependent presynaptic silencing.
Chronic changes in electrical excitability profoundly affect synaptic transmission throughout the lifetime of a neuron. We have previously explored persistent presynaptic silencing, a form of synaptic depression at glutamate synapses produced by ongoing neuronal activity and by strong depolarization. Here we investigate the involvement of the ubiquitin-proteasome system (UPS) in the modulation of presynaptic function. We found that proteasome inhibition prevented the induction of persistent presynaptic silencing. Specifically, application of the proteasome inhibitor MG-132 (carbobenzoxy-L-leucyl-L-leucyl-L-leucinal) prevented decreases in the size of the readily releasable pool of vesicles and in the percentage of active synapses. Presynaptic silencing was accompanied by decreases in levels of the priming proteins Munc13-1 and Rim1. Importantly, overexpression of Rim1alpha prevented the induction of persistent presynaptic silencing. Furthermore, strong depolarization itself increased proteasome enzymatic activity measured in cell lysates. These results suggest that modulation of the UPS by electrical activity contributes to persistent presynaptic silencing by promoting the degradation of key presynaptic proteins.
Department of Psychiatry, Washington University School of Medicine, St. Louis, Missouri 63110, USA.
Xiaoping
X
Jiang
Patricia E
PE
Litkowski
Amanda A
AA
Taylor
Ying
Y
Lin
B Joy
BJ
Snider
Krista L
KL
Moulder
D000818:Animals; D002478:Cells, Cultured; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D019204:GTP-Binding Proteins / Q000378:metabolism*; D006624:Hippocampus / Q000201:enzymology*; D007976:Leupeptins / Q000494:pharmacology; D009419:Nerve Tissue Proteins / Q000378:metabolism*; D009433:Neural Inhibition / Q000187:drug effects / Q000502:physiology*; D009474:Neurons / Q000201:enzymology; D017729:Presynaptic Terminals / Q000378:metabolism*; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism*; D061988:Proteasome Inhibitors; D051381:Rats; D009435:Synaptic Transmission / Q000502:physiology; D025801:Ubiquitin / Q000378:metabolism*
D015853:Cysteine Proteinase Inhibitors; D007976:Leupeptins; D009419:Nerve Tissue Proteins; D061988:Proteasome Inhibitors; C491489:Rims1 protein, rat; D025801:Ubiquitin; C103912:Unc13a protein, rat; D046988:Proteasome Endopeptidase Complex; D019204:GTP-Binding Proteins; C072553:benzyloxycarbonylleucyl-leucyl-leucine aldehyde