Complementation cloning identifies CDG-IIc, a new type of congenital disorders of glycosylation, as a GDP-fucose transporter deficiency

Abstract

Congenital disorders of glycosylation (CDG) comprise a rapidly growing group of inherited disorders in which glycosylation of glycoproteins is defective due to mutations in genes required for the assembly of lipid-linked oligosaccharides, their transfer to nascent glycoproteins (CDG-I) or the processing of protein-bound glycans (CDG-II). Previously' a defect in the GDP-fucose import into the lumen of the Golgi was identified in a person with CDG (A.C.) with a general deficiency of fucosyl residues in glycoproteins. This patient presents the clinical features of leukocyte adhesion deficiency type II (LAD II) including mental retardation, short stature, facial stigmata, and recurrent bacterial peripheral infections with persistently elevated peripheral leukocytes. Using a fucose-specific, lectin-staining procedure for detection of fucosylated glycoproteins and a retroviral cDNA library, we isolated a cDNA complementing the fucosylation defect in the patient's fibroblasts. The cDNA encodes a highly hydrophobic protein of 364 amino acids with multiple putative transmembrane domains. Restoration of GDP-fucose import activity in Golgi-enriched vesicles from the patient's fibroblasts verified the GDP-fucose transporter activity of this protein. We identified two missense mutations in the GDP-fucose transporter cDNA of patient A.C. and of two other people with LAD II. Thus complementation cloning allowed us to identify the human GDP-fucose transporter cDNA and GDP-fucose transporter deficiency as a cause for a new type of CDG. Following the recent recommendations for the nomenclature for CDG, this new type is classified as CDG-IIc (formerly LAD II).

Analysis of the Plastidic phosphate translocator Gene Family in Arabidopsis and Identification of New phosphate translocator-Homologous Transporters, Classified by Their Putative Substrate-Binding Site

“…Thus, we propose the common motif T[X] 7(8) K that is similar to motifs identified in GDPMan and UDP-sugar transporters (Gao et al, 2001). In the case of the GDP-Fuc transporter from human, a mutation in that region leads to a defect in GDP-Fuc transport into the lumen of the Golgi (Lü bke et al, 2001).…”

“…This comparison shows that these proteins can be split into different families of transport proteins. Only some of them have been functionally characterized, yet one family consists of pPTs, and the other families consist of NSTs of endoplasmatic reticulum (ER) and Golgi membranes that transport UDP-glucuronic acid, GDPMan, and other nucleotide sugars from the cytosol into the lumen of the ER and the Golgi apparatus (Baldwin et al, 2001;Lü bke et al, 2001;Lü hn et al, 2001). The family that is most similar to the pPT family consists of some uncharacterized proteins from animals and fungi (KR family).…”

Independent and simultaneous translocation of two substrates by a nucleotide sugar transporter

“…Mutants of nucleotide sugar transporters have developmental phenotypes and have been described in Caenorhabditis elegans (7,8), yeast (9), Leishmania donovani (10), Drosophila melanogaster (11,12), cattle (13), and humans (14)(15)(16). Mutations in the transporters of UDP-N-acetylglucosamine (UDP-GlcNAc) in Holstein cows and GDP-fucose in humans give rise to complex vertebral malformation and leukocyte adhesion deficiency syndrome II, respectively.…”

Congenital disorders of glycosylation: a concise chart of glycocalyx dysfunction

“…Mutations in the SLC35C1 gene encoding a Golgi GDP-Fuc transporter impairs terminal fucosylation, which yields epitopes such as ABO and Lewis blood group antigens [39]. Some of these fucosylated epitopes function as ligands for selectins [40] and thereby participate to leukocyte adhesion and extravasation reactions [41].…”