Fig. 8.

Diagram outlining the possible relationship between regulation of synaptic vesicle protein expression and the formation of synaptic vesicles. Synaptotagmin I, vamp 2, and synapsin I mRNAs are translated at relatively high rates at early times in culture, but these proteins are unstable. In contrast, synaptophysin mRNA is translated inefficiently at early times in culture. As the neurons develop, the rate of synaptophysin translation increases. In parallel with the increase in synaptophysin expression, the neurons acquire the ability to form SVs more efficiently. Because of the increase in efficiency of SV formation, a higher percentage of the synaptotagmin I and vamp 2 synthesized can be incorporated into SVs, possibly resulting in stabilization of these proteins. The increase in SV number may also cause an increase in synapsin I stability by allowing a greater percentage of the synapsin I synthesized to associate with SVs. The model is described in detail in the Discussion.