REGULATION OF APICAL TRANSPORT IN EPITHELIAL-CELLS BY A G(S) CLASS OF HETEROTRIMERIC G-PROTEIN

THE role of heterotrimeric GTP-binding proteins in signal transduction is well established1. They might also be involved in vesicular transport2-6. Here we show that in the epithelial cell line Madin-Darby Canine Kidney, transport of influenza haemagglutinin protein to the apical surface is stimulated and that of vesicular stomatitis virus glycoprotein to the basolateral surface is retarded by AlF(3-5) treatment. Treatment of cells with the reagents known to influence the G(i) class of G proteins affected only the basolateral pathway whereas reagents acting on the G(s) class of G proteins specifically affected the apical pathway. In permeabilized cells, antibodies raised against the N-terminal domain of the alpha-subunit of G(s) inhibited the transport of haemagglutinin from the trans-Golgi network to apical surface but not between the endoplasmic reticulum and Golgi complex. These observations demonstrate involvement of a G(s) class of heterotrimeric G proteins, besides that of the G(i), in vesicular transport2. Moreover, the apical and the basolateral pathways in epithelial cells seem to be regulated by G(s) and G(i) proteins, respectively, in the trans-Golgi network.