alpha-Neup5Ac-(2--3)-beta-D-Galp-(1--4)-[alpha-L-Fucp-(1--3)]-D-GlcpNAc and Leukocyte-Adhesion-Deficiency-Syndrome

Leukocyte trafficking from the blood stream to tissues is essential for continuous surveillance of foreign antigens. This dynamic process, designated as the leukocyte adhesion cascade, involves distinct steps. In leukocyte adhesion deficiency (LAD) I the firm adhesion of leukocyte to the endothelium is defective, due to mutations in the beta 2 integrin gene. LAD II is caused by mutations in the fucose transporter specific to the Golgi apparatus, leading to the absence of Sialyl Lewis X-the fucosylated ligand for the selectins-thus affecting the rolling phase, the first phase of the cascade. In LAD III, a primary activation defect occurs in beta integrins 1, 2, and 3. Recently, the genetic basis for LAD III has been revealed to involve mutations in kindlin-3, a newly recognized essential component of integrin activation-the second phase of the adhesion cascade. Until now, no human or animal models of defect in transmigration-the fourth and last phase of the cascade-has been described.

Topics: Animals; Carrier Proteins; Cell Adhesion; Endothelium; Golgi Apparatus; Humans; Integrin beta Chains; Leukocyte Rolling; Leukocyte-Adhesion Deficiency Syndrome; Leukocytes; Lewis X Antigen; Membrane Proteins; Neoplasm Proteins; Sialyl Lewis X Antigen

Topics: Animals; Cell Adhesion; Diagnosis, Differential; Fucose; Humans; Leukocyte-Adhesion Deficiency Syndrome; Leukocytes; Ligands; Oligosaccharides; Prognosis; Secretin; Sialyl Lewis X Antigen

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