A REGULATORY ROLE FOR CAMP-DEPENDENT PROTEIN-KINASE IN PROTEIN TRAFFIC ALONG THE EXOCYTIC ROUTE

The influence of protein kinase A activity on transport of newly synth esized vesicular stomatitis virus G glycoprotein along the exocytic pa thway was examined. Transport of vesicular stomatitis virus G glycopro tein to the cell surface was inhibited by romocinnamylamino)ethyl]-5-i soquinolinesulfonamide (H-89), a selective inhibitor of protein kinase A. This block occurred at the exit of the Golgi complex, whereas tran sport through the Golgi compartments or from the endoplasmic reticulum to the Golgi was decreased in the presence of H-89. As judged by immu nofluorescence endoplasmic reticulum to Golgi transport was accelerate d in cells incubated with activators of protein kinase A such as isobu tylmethylxanthine (IBMX) or forskolin (FK). Treatment with IBMX and FR also increased transport from the trans-Golgi network to the cell sur face. During incubation with IBMX and Fh, the organization of the Golg i complex was altered showing intercisternae fusion and miscompartment alization of resident proteins. These structural changes affected both the kinetics of acquisition of endoglycosidase H resistance and trans port activities. These data support a differential regulatory role for protein kinase A in different transport steps along the exocytic path way. In particular, transport from the trans-Golgi network to the cell surface was dependent on protein kinase A activity. In addition, the results suggest the involvement of this enzyme on the maintenance of t he Golgi complex organization.