ASSOCIATION OF A PHOSPHATIDYLINOSITOL-SPECIFIC 3-KINASE WITH A HUMAN TRANS-GOLGI NETWORK RESIDENT PROTEIN

The eukaryotic trans-(Golgi network (TGN) is a key site for the format ion of transport vesicles destined for different intracellular compart ments [1], A key marker for the mammalian TGN is TGN38/46 [2], This in tegral membrane glycoprotein cycles between the TGN and the cell surfa ce and is implicated in recruitment of cytosolic factors and regulatio n of at least one type of vesicle formation at the mammalian TGN [2,3] , In this study, we have identified a phosphatidylinositol (Ptdlns)-sp ecific 3-kinase activity associated with the human orthologue (TGN46), which is sensitive to lipid kinase inhibitors, Treatment of HeLa cell s with low levels of these inhibitors reveals subtle morphological cha nges in TGN46-positive compartments, Our findings suggest a role for P tdlns 3-kinases and presumably for the product, Ptdlns 3 phosphate (Pt dlns3P), in the formation of secretory transport vesicles by mechanism s conserved in yeast and mammals.