Protein kinase D regulates vesicular transport by phosphorylating and activating phosphatidylinositol-4 kinase IIIβ at the Golgi complex

Protein kinase D ( PKD) regulates the fission of vesicles originating from the trans- Golgi network(1,2). We show that phosphatidylinositol 4- kinase III beta ( PI4KIII beta) - a key player in the structure and function of the Golgi complex(3) - is a physiological substrate of PKD. Of the three PKD isoforms, only PKD1 and PKD2 phosphorylated PI4KIII beta at a motif that is highly conserved from yeast to humans. PKD- mediated phosphorylation stimulated lipid kinase activity of PI4KIII beta and enhanced vesicular stomatitis virus G- protein transport to the plasma membrane. The identification of PI4KIII beta as one of the PKD substrates should help to reveal the molecular events that enable transport- carrier formation.