SNAP25 and neuroblastoma: With the rapid turnover of endogenous SNAP-25 (∼16 h in cells actively forming synaptic contacts [42], and assuming a linear relationship between the intracellular concentration of the wt LC and the degree of the SNAP-25 cleavage, it would appear that at day 8 (192 h) of chase, the absolute amount of wt LC in neuroblastoma cells is likely to have declined by approximately 50%, which is similar to the persistence of the LC ad as determined in our experiments.