Rat submandibular and parotid protein phosphorylation and exocytosis: effect of site-selective cAMP analogs

A series of cAMP analogs that have different specificities for the two different binding sites on the regulatory subunit of type I and type II cAMP-dependent protein kinase (PKA) were used to determine whether selective activation of type I or type II PKA could link either or both isozyme forms of PKA with exocytosis and specific protein phosphorylation in salivary gland cells. Using dispersed rat submandibular or parotid cells, selective activation of either type I or type II resulted in a synergistic response for both rat submandibular mucin and parotid amylase secretion and the phosphorylation of a 26-kDa integral membrane phosphoprotein. These data suggest that the activation of either isozyme of PKA can elicit cellular exocytosis and specific protein phosphorylation in both of these cell types.