Differential turnover of syntaxin and SNAP-25 during synaptogenesis in cultured cerebellar granule neurons.

In order to investigate the molecular mechanism underlying synaptogenesis, we examined the dynamics and stability of syntaxin 1A and SNAP-25 in cultured cerebellar granule cells. In neurons cultured for less than 5 days in vitro (DIV), syntaxin was highly expressed with a half-life of >48 hours. SNAP-25 was also expressed at 5 DIV, but at a lower level and with a much shorter half-life of 16 hours. As the neurons matured and established synpatic connections, the expression of both proteins increased steadily, with the more rapid increase between 5 DIV and 8 DIV associated with SNAP-25. The half-life of syntaxin was slightly increased in the mature neurons. SNAP-25, however, showed an increased half-life of about 35 hours. These results suggested that the dynamics and stability of the t-SNAREs are differentially modulated during synaptogenesis, which may be important in establishing and maintaining synaptic connections.