Activity produces waste, so it makes sense to position waste disposal facilities close to sites of activity. Baris Bingol and Erin Schuman (California Institute of Technology, Pasadena, CA) have discovered that neurons do just that, recruiting proteasomes to active dendritic spines.
Dendritic spines must construct and destroy many proteins as they respond to synaptic excitation. Protein synthesis machinery has been shown to sit locally in spines to make protein when needed. Indication that the degradation machinery (proteasomes) might also serve its function locally came from Bingol's discovery that adjacent synapses in the same neuron contained different amounts of proteasome.
Investigating the dynamics of this varied distribution, the team observed that excitation of neurons drove proteasomes from the shafts to the spines within minutes. Proteasome levels then remained high in the spines for up to an hour. Ubiquitinated proteins, targeted for destruction, also initially increased, but...
