Activity-dependent dynamics and sequestration of proteasomes in dendritic spines

The importance of proteasomes in cellular metabolism was recognized by the award of a Nobel prize in 2004 for work on the ubiquitin-proteasome system. Remarkable time-lapse images now provide a glimpse of proteasomes in action in one of their important roles, as modulators of synaptic action in neurons. Significantly the proteasomes are seen to move into the dendritic spines upon depolarization and to become sequestered there. The trafficking of individual synaptic proteins has been seen before, but the observation that a major cell biological machine traffics into spines to change synapses is new, and perhaps counterintuitive. Here the proteasomes seem to be providing specific on-site degradation of proteins in the synapse, rather than routine garbage disposal at a remote site.