Continual remodeling of postsynaptic density and its regulation by synaptic activity

A postsynaptic density (PSD) protein, PSD-95, was tagged with green fluores cent protein (GFP-PSD-95) and expressed in cultured hippocampal neurons usi ng recombinant adenoviruses. CFP-PSD-95 was selectively localized to excita tory postsynaptic sites. Time-lapse fluorescence imaging of hippocampal neu rons revealed that >20% of GFP-PSD-95 clusters turned over within 24 hours. The appearance rate of clusters was higher than the disappearance rate, an d this difference accounted for the gradual increase of the cluster density observed in culture. Dynamics of PSD-95 clusters were also inhibited by bl ockers of excitatory synaptic transmission. Continual PSD turnover and its regulation by synaptic activity may be important in activity-dependent remo deling of neuronal connections.