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 formation of transport vesicles destined for different intracellular compartments [1]. A key marker for the mammalian TGN is TGN38/46 [2]. This integral membrane glycoprotein cycles between the TGN and the cell surface and is implicated in recruitment of cytosolic factors and regulation of at least one type of vesicle formation at the mammalian TGN [2] [3]. In this study, we have identified a phosphatidylinositol (PtdIns)-specific 3-kinase activity associated with the human orthologue (TGN46), which is sensitive to lipid kinase inhibitors. Treatment of HeLa cells with low levels of these inhibitors reveals subtle morphological changes in TGN46-positive compartments. Our findings suggest a role for PtdIns 3-kinases and presumably for the product, PtdIns 3-phosphate (PtdIns3P), in the formation of secretory transport vesicles by mechanisms conserved in yeast and mammals

Association of a phosphatidylinositol-specific 3-kinase with a human trans-Golgi network resident protein

AbstractThe eukaryotic trans-Golgi network (TGN) is a key site for the formation of transport vesicles destined for different intracellular compartments [1]. A key marker for the mammalian TGN is TGN38/46 [2]. This integral membrane glycoprotein cycles between the TGN and the cell surface and is implicated in recruitment of cytosolic factors and regulation of at least one type of vesicle formation at the mammalian TGN [2,3]. In this study, we have identified a phosphatidylinositol (PtdIns)-specific 3-kinase activity associated with the human orthologue (TGN46), which is sensitive to lipid kinase inhibitors. Treatment of HeLa cells with low levels of these inhibitors reveals subtle morphological changes in TGN46-positive compartments. Our findings suggest a role for PtdIns 3-kinases and presumably for the product, PtdIns 3-phosphate (PtdIns3P), in the formation of secretory transport vesicles by mechanisms conserved in yeast and mammals

The trans Golgi network is lost from cells infected with African Swine Fever

The cellular secretory pathway is important during the assembly and envelopment of viruses and also controls the transport of host proteins, such as cytokines and major histocompatibility proteins, that function during the elimination of viruses by the immune system. African swine fever virus (ASFV) encodes at least 26 proteins with stretches of hydrophobic amino acids suggesting entry into the secretory pathway (R. J. Yanez, J. M. Rodriguez, M. L. Nogal, L. Yuste, C. Enriquez, J. F. Rodriguez, and E. Vinuela, Virology 208:249-278, 1995). To predict how and where these potential membrane proteins function, we have studied the integrity of the secretory pathway in cells infected with ASFV. Remarkably, ASFV caused complete loss of immunofluorescence signal for the trans Golgi network (TGN) marker protein TGN46 and dispersed the AP1 TGN adapter complex. Loss of TGN46 signal was not due to degradation of TGN46, suggesting redistribution of TGN46 to other membrane compartments. ASFV markedly slowed transport of cathepsin D to lysosomes, demonstrating that loss of TGN structure correlated with loss of TGN function. ASFV shows a tropism for macrophages, and it is possible that ASFV compromises TGN function to augment the activity of viral membrane proteins or to suppress the function of host immunoregulatory proteins