Beta (1-4) galactosyltransferase enzyme (GT) is localized in the trans Golgi where glycoproteins get galactosylated. This enzyme has also been gound at the cell surface where it acts as cell-adhesion molecule, mediating intercellular adhesion by binding to terminal N-acetylglucosamine residues on lactosaminoglycans substrates, there by bridging cells together, and as a high affinity receptor for the laminin long arm. The cell surface and Golgi transferase seem to be differentially regulated, the former is induced by beta-adrenergic agonist like isoproterenol without effecting the Golgi transferase while as upon differentiation of certain cell types it is the Golgi transferase that increases without effecting the cell surface transferase. The cell surface GT is possibly involved in growth since its effector molecule alpha-lactalbumin blocks the growth of cells induced by beta-adrenergic agonists isoproterenol. In the current studies we are investigating the expression of GT in several cell lines and the distribution of this enzyme in Golgi and cell surface, hormones involved in the regulation of expression of the two forms of the enzyme and the time when they are expressed during cell-cycle. Our results indicate that in Swiss mouse 3T3 cells GT is expressed prior to DNA replication and then down-regulated.
