Effects of proteasome inhibitors on the synaptic localization of Vesl-1S/Homer-1a proteins

The Vesl-1S/Homer-1a proteins are upregulated during seizure and long-term potentiation, but are rapidly degraded by ubiquitin-proteasome systems under normal conditions. We examined the distribution of Vesl-1S proteins in cultured hippocampal neurons. Application of proteasome inhibitors caused accumulation of Vesl-1S immunoreactivity in the neurons which showed a punctate distribution in the cortical regions of the cells, and these puncta were found to be juxtaposed with synaptophysin, a presynaptic, synapse-specific protein. These results suggest that Vesl-1S protein is synaptically targeted.