Activation of N-methyl-D-aspartate receptor induces a shift of drebrin distribution: disappearance from dendritic spines and appearance in dendritic shafts.

Drebrin is a major actin-filament-binding protein localized in mature dendritic spines. A recent in vivo immunoelectron microscopic study suggests that drebrin content at each dendritic spine is regulated by some unknown mechanisms. In the present in vitro study, we examined whether glutamate stimulation alters drebrin content in dendritic spines. Glutamate stimulation induced disappearance of drebrin immunostaining from dendritic spines but led to appearance of drebrin immunostaining in dendritic shafts and somata. The glutamate-induced shift of drebrin immunostaining was blocked by an NMDA receptor antagonist. Immunoblot analyses showed that both the total and the cytosolic drebrin remained unchanged and revealed that the drebrin shift was not due to drebrin degradation. These findings indicate that NMDA receptor activation induces a shift in subcellular distribution of drebrin associated with actin filaments, and that the shift might be a molecular basis for actin reorganization accompanied with synaptic plasticity.