Isoproterenol stimulates transient SNAP23-VAMP2 interaction in rat parotid glands.

The exocytosis of salivary proteins is mainly regulated by cAMP, although soluble N-ethylmaleimide-sensitive factor attachment protein receptors (SNAREs), which mediate cAMP-dependent exocytic membrane fusion, have remained unidentified. Here we examined the effect of isoproterenol (ISO) and cytochalasin D (CyD) on the level of SNARE complexes in rat parotid glands. When SNARE complexes were immunoprecipitated by anti-SNAP23, the coprecipitation of VAMP2 was significantly increased in response to ISO and/or CyD, although the coprecipitation of VAMP8 or syntaxin 4 was scarcely augmented. These results suggest that the SNAP23-VAMP2 interaction plays a key role in cAMP-mediated exocytosis from parotid glands.