guanosine-diphosphate-mannose and Leukocyte-Adhesion-Deficiency-Syndrome

Leukocyte adhesion deficiency type II (LAD II) is a rare disorder characterized by recurrent infections, persistent leukocytosis, and severe mental and growth retardation. LAD II neutrophils are deficient in expression of selectin ligand activity, and exhibit a correspondingly diminished ability to roll on endothelium and to traffic to inflammatory sites in vivo. LAD II patients exhibit a deficiency in the expression of cell surface fucosylated glycan structures that include the H and Lewis blood group determinants and the sialyl Lewis x epitope, yet the corresponding fucosyltransferase activities responsible for synthesis of these structures are expressed at normal levels. The molecular defect in LAD II has been localized to the pathway that synthesizes GDP-fucose from GDP-mannose. However, the two known component enzymes in this GDP-fucose biosynthetic pathway are normal in sequence and in expression levels in LAD II cells. The genetic lesion in LAD II that accounts for the generalized fucosylation defect in LAD II patients remains to be determined.

Topics: ABO Blood-Group System; Animals; Cell Adhesion Molecules; Cell Line; Cell Movement; Fucose; Fucosyltransferases; Guanosine Diphosphate Fucose; Guanosine Diphosphate Mannose; Humans; Hydro-Lyases; Leukocyte-Adhesion Deficiency Syndrome; Leukocytes; Lewis Blood Group Antigens; Lymphocytes; Neutrophils; Phenotype; Selectins

Leukocyte adhesion deficiency type II (LAD II) is caused by a disorder in the metabolism of GDP-L-fucose, which causes hypofucosylation of glycoconjugates. This study analyzes a newly identified LAD II patient who shows the same severe hypofucosylation of glycoconjugates as the other described patients. However, in vitro assays of cytosolic extracts from leukocytes and fibroblasts of the patient demonstrated a normal GDP-L-fucose biosynthesis from GDP-D-mannose. Analysis of the two enzymes involved in the pathway, GDP-D-mannose 4,6-dehydratase and FX protein, revealed normal numbers of transcripts without any detectable mutations within the coding regions of either gene. In contrast to previously published observations [Sturla et al. (1998) FEBS Lett. 429, 274-278], the major pathway of GDP-L-fucose synthesis can be normal in LAD II.

Topics: Carbohydrate Epimerases; Carbon Radioisotopes; Carrier Proteins; Cell Extracts; Cytosol; DNA, Complementary; Guanosine Diphosphate Fucose; Guanosine Diphosphate Mannose; Humans; Hydro-Lyases; Ketone Oxidoreductases; Leukocyte-Adhesion Deficiency Syndrome

Leukocyte adhesion deficiency type II (LAD II) is a rare genetic disease characterized by severe immunodeficiency which is related to defective expression in leukocytes of sialyl-Lewis X (SLeX), a fucosylated ligand for endothelial selectins. The molecular basis of LAD II is still unknown, but has been tentatively localized in the de novo pathway of GDP-L-fucose biosynthesis from GDP-D-mannose. Here, we demonstrate that in cell lysates from a LAD II patient, GDP-D-mannose-4,6-dehydratase (GMD), the first of the two enzymes of the pathway has a defective activity compared to control subjects. GMD in cell lysates from both parents showed intermediate activity levels. Cloning of GMD from patient and control lymphocytes ruled out any mutation affecting the amino acid GMD sequence and the purified recombinant proteins from both controls and the patient showed identical specific activities. Since the levels of immunoreactive GMD in cell lysates were comparable in the patient and in controls, the biochemical deficiency of intracellular GMD activity in LAD II seems to be due to mutation(s) affecting some still unidentified GMD-regulating protein.

Topics: Cloning, Molecular; Guanosine Diphosphate Fucose; Guanosine Diphosphate Mannose; Humans; Hydro-Lyases; Leukocyte-Adhesion Deficiency Syndrome; Male; Oligosaccharides; Recombinant Proteins; RNA, Messenger; Sequence Analysis, DNA; Sialyl Lewis X Antigen