Past events

Recent studies suggest that central nervous system (CNS) synapses persist for many weeks, months and even lifetimes, yet little is known on the mechanisms that allow these structures to persist for so long despite the many deconstructive processes acting at biological systems and neurons in particular. As a step toward a better understanding of synaptic maintenance we set out to examine some of the deconstructive and reconstructive forces acting at individual CNS synapses. To that end we studied the molecular dynamics of several presynaptic and postsynaptic cytomatrix molecules. Fluorescence recovery after photobleaching (FRAP) and photoactivation experiments revealed that these molecules are continuously incorporated into and lost from individual synaptic structures within tens of minutes. Moreover, these dynamics can be accelerated by synaptic activity. Finally, we find that synaptic molecules are continuously exchanged between nearby synaptic structures at similar rates and that these rates greatly exceed the rates at which synapses are replenished with molecules arriving from somatic sources. Our findings indicate that the dynamics of key synaptic matrix molecules may be dominated by local protein exchange and redistribution, whereas protein synthesis and degradation serve to maintain and regulate the sizes of local, shared pools of these proteins. The nature of these dynamics raises intriguing questions as to how synapses manage to maintain their individual, use-dependent structural and functional characteristics over long durations.