Truncation of SNAP-25 reduces the stimulatory action of cAMP on rapid exocytosis in insulin-secreting cells.

Synaptosomal protein of 25 kDa (SNAP-25) is important for Ca(2+)-dependent fusion of large dense core vesicles (LDCVs) in insulin-secreting cells. Exocytosis is further enhanced by cAMP-increasing agents such as glucagon-like peptide-1 (GLP-1), and this augmentation includes interaction with both PKA and cAMP-GEFII. To investigate the coupling between SNAP-25- and cAMP-dependent stimulation of insulin exocytosis, we have used capacitance measurements, protein-binding assays, and Western blot analysis.