Continual remodeling of postsynaptic density and its regulation by synaptic activity

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