Isoproterenol stimulates transient SNAP23–VAMP2 interaction in rat parotid glands

The exocytosisof 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 complexesin rat parotid glands. When SNARE complexeswere immunoprecipitatedby anti- SNAP23, the coprecipitationof VAMP2was significantly increased in response to ISO and/or CyD, although the coprecipitationof VAMP8 or syntaxin4 was scarcely augmented. These results suggest that the SNAP23– VAMP2interaction plays a key role in cAMP-mediated exocytosisfrom parotid glands.