Carbohydrate sulfotransferase 2
trans-Golgi network
Golgi localization of carbohydrate sulfotransferases is a determinant of L-selectin ligand biosynthesis.
Sulfation of endothelial glycoproteins by the sulfotransferase GlcNAc6ST-2 is a regulatory modification that promotes binding of the leukocyte adhesion molecule L-selectin. GlcNAc6ST-2 is a member of a family of related enzymes that act on similar carbohydrate substrates in vitro but discrete glycoproteins in vivo. We demonstrate that GlcNAc6ST-1, -2, and -3 have distinct Golgi distributions, with GlcNAc6ST-1 confined to the trans-Golgi network, GlcNAc6ST-3 confined to the early secretory pathway, and GlcNAc6ST-2 distributed throughout the Golgi. Their localization was correlated with preferred activity on either N-linked or O-linked glycoproteins. A chimera comprising the localization domain of GlcNAc6ST-1 fused to the catalytic domain of GlcNAc6ST-2 was confined to the trans-Golgi network and adopted the substrate preference of GlcNAc6ST-1. We propose a model in which Golgi enzyme localization and competition orchestrate the biosynthesis of L-selectin ligands.