Identification and characterization of human Golgi nucleotide sugar transporter SLC35D2, a novel member of the SLC35 nucleotide sugar transporter family

We report the molecular cloning of SLC35D2, a novel member of the SLC35 nucleotide sugar transporter family. The gene SLC35D2 maps to chromosome 9q22.33. SLC35D2 cDNA codes for a hydrophobic protein consisting of 337 amino acid residues with 10 putative transmembrane helices. Northern blot analysis revealed the SLC35D2 mRNA as a single major band corresponding to 2.0 kb in length. SLC35D2 was localized in the Golgi membrane and exhibited around 50% similarity with three nucleotide sugar transporters: human SLC35D1 (UDP-glucuronic acid/UDP-N-acetylgalactosamine transporter), fruitfly fringe connection (frc) transporter, and nematode SQV-7 transporter, the latter two being involved in developmental and organogenetic processes. Heterologous expression of SLC35D2 protein in yeast indicated that UDP-N-acetylglucosamine is a candidate for the substrate(s) of the transporter. The sequence similarity, subcellular localization, and transporting substrate suggest that SLC35D2 is a good candidate for the ortholog of frc transporter, which is involved in the Notch signaling system by providing the fringe N-acetylglucosaminyltransferase with the substrate. We also describe the identification and categorization of the human SLC35 gene family.