Fucosylated oligosaccharides occur throughout nature and many of them play a variety of roles in biology, especially in a number of recognition processes. As reviewed here, much of the recent emphasis in the study of the oligosaccharides in mammals has been on their potential medical importance, particularly in inflammation and cancer. Indeed, changes in fucosylation patterns due to different levels of expression of various fucosyltransferases can be used for diagnoses of some diseases and monitoring the success of therapies. In contrast, there are generally at present only limited data on fucosylation in non-mammalian organisms. Here, the state of current knowledge on the fucosylation abilities of plants, insects, snails, lower eukaryotes and prokaryotes will be summarised. (+info)
Correction of leukocyte adhesion deficiency type II with oral fucose.
(18/1136)
We describe a simple, noninvasive, and effective therapy for leukocyte adhesion deficiency type II (LAD II), a rare inherited disorder of fucose metabolism. This disorder leads to an immunodeficiency caused by the absence of carbohydrate-based selectin ligands on the surface of neutrophils as well as to severe psychomotor and mental retardation. The fucosylation defect in LAD II fibroblasts can be corrected by addition of L-fucose to the culture medium. This prompted us to initiate dietary fucose therapy on a patient with LAD II. Oral supplementation of fucose in this patient induced the expression of fucosylated selectin ligands on neutrophils and core fucosylation of serum glycoproteins. During 9 months of treatment, infections and fever disappeared, elevated neutrophil counts returned to normal, and psychomotor capabilities improved. (+info)
A cyclic AMP receptor protein mutant that constitutively activates an Escherichia coli promoter disrupted by an IS5 insertion.
(19/1136)
Previously an Escherichia coli mutant that had acquired the ability to grow on propanediol as the sole carbon and energy source was isolated. This phenotype is the result of the constitutive expression of the fucO gene (in the fucAO operon), which encodes one of the enzymes in the fucose metabolic pathway. The mutant was found to bear an IS5 insertion in the intergenic regulatory region between the divergently oriented fucAO and fucPIK operons. Though expression of the fucAO operon was constitutive, the fucPIK operon became noninducible such that the mutant could no longer grow on fucose. A fucose-positive revertant which was found to contain a suppressor mutation in the crp gene was selected. Here we identify this crp mutation, which results in a single amino acid substitution (K52N) that has been proposed previously to uncover a cryptic activating region in the cyclic AMP receptor protein (CRP). We show that the mutant CRP constitutively activates transcription from both the IS5-disrupted and the wild-type fucPIK promoters, and we identify the CRP-binding site that is required for this activity. Our results show that the fucPIK promoter, a complex promoter which ordinarily depends on both CRP and the fucose-specific regulator FucR for its activation, can be activated in the absence of FucR by a mutant CRP that uses three, rather than two, activating regions to contact RNA polymerase. For the IS5-disrupted promoter, which retains a single CRP-binding site, the additional activating region of the mutant CRP evidently compensates for the lack of upstream regulatory sequences. (+info)
Core alpha1-->3-fucose is a common modification of N-glycans in parasitic helminths and constitutes an important epitope for IgE from Haemonchus contortus infected sheep.
(20/1136)
Synthesis of parasite specific IgE plays a critical role in the defence against helminth infections. We report here that IgE from serum from Schistosoma mansoni infected mice and Haemonchus contortus infected sheep recognizes complex-type N-glycans from Arabidopsis thaliana, which contain R-GlcNAcbeta1-->4(Fucalpha1-->3)GlcNAcbeta1-Asn (core alpha1-->3-Fuc) and Xylbeta1-->2Manbeta1-->4GlcNAcbeta1-R (core beta1-->2-Xyl) modifications, and honeybee phospholipase A2, which carries N-glycans that contain the core alpha1-->3-Fuc epitope. Evidence is presented that core alpha1-->3-fucosylated N-glycans bind a substantial part of the parasite specific IgE in serum of H. contortus infected sheep. These results suggest that the core alpha1-->3-Fuc antigen may contribute to induction of a Th2 response leading to the production of IgE. In addition we show here that N-glycans carrying core alpha1-->3-Fuc and beta1-->2-Xyl antigens are synthesized by many parasitic helminths and also by the free living nematode Caenorhabditis elegans. Since N-glycans containing the core alpha1-->3-Fuc have also been implicated in honeybee and plant induced allergies, this conserved glycan might represent an important common IgE epitope. (+info)
A fucose-deficient glycoprotein precursor to Rauscher leukemia virus gp69/71.
(21/1136)
Rauscher leukemia virus glycoprotein gp69/71 is synthesized in virus-infected cells by way of a 90,000 dalton glycoprotein precursor, termed Pr2a+b. This precursor could be labeled with radioactive glucosamine and methionine but not with fucose; whereas gp69/71 could be detected by labeling with radioactive glucosamine, fucose, or a mixture of amino acids but seemed to be deficient in methionine relative to Pr2a+b. Pr2a+b and gp69/71, were specifically precipitated by an antiserum prepared against phosphocellulose purified Rauscher gp69/71. Other virus-specific precursors, in addition to Pr2a+b, could be precipitated by antiserum prepared against detergent disrupted virus. Neither Pr2a+b nor gp69/71 was precipitated from cell extracts by antisera to Rauscher p30. Tryptic maps of Pr2a+b and gp69/71 showed that these glycoproteins share many tryptic peptides. Pulse-chase experiments with 14C-labeled amino acids indicated that gp69/71 was not radio-labeled during the pulse-labeling period but slowly appeared during the chase incubations. Pr2a+b, however, was rapidly labeled and tended to disappear during long chases. Furthermore, two nonglycosylated viral proteins, termed p15E and p12E, are structurally related to Pr2a+b. Viral p15E and p12E contained the same methionine-containing tryptic peptide fraction as Pr2a+b as determined by ion-exchange chromatography. These results provide evidence that Pr2a+b is a precursor to gp69/71 and establish a structural and possible precursor-product relationship between Pr2a+b, p15E, and p12E. (+info)
Two critical periods of protein and glycoprotein synthesis in memory consolidation for visual categorization learning in chicks.
(22/1136)
A protein synthesis inhibitor, anisomycin (ANI), and an inhibitor of glycoprotein synthesis, 2-deoxygalactose (2-D-gal), were used to investigate memory consolidation following visual categorization training in 2-day-old chicks. ANI (0.6 micromole/chick) and 2-D-gal (40 micromoles/chick) were injected intracerebrally at different time intervals from 1 hr before to 23 hr after the training. Retention was tested 24 hr post-training. Both ANI and 2-D-gal injections revealed two periods of memory sensitivity to pharmacological intervention. ANI impaired retention when injected from 5 min before to 30 min after the training or from 4 hr to 5 hr post-training, thus demonstrating that consolidation of long-term memory in this task requires two periods of protein synthesis. 2-D-Gal first produced an amnesia when it was injected in the interval from 5 min before to 5 min after the training. Injections made between 5 min and 5 hr post-training were without effect on the retention. The second period of memory impairment by 2-D-gal started at 5 hr post-training and lasted until 21 hr after the training. Administration of 2-D-gal made 23 hr after the training did not influence retention in the test at either 24 hr or 26 hr. These results are consistent with the hypothesis that two waves of protein and glycoprotein synthesis are necessary for the formation of long-term memory. The prolonged duration of performance impairment by 2-D-gal in the present task might reflect an extended memory consolidation period for a categorization form of learning. (+info)
New aspects of siglec binding specificities, including the significance of fucosylation and of the sialyl-Tn epitope. Sialic acid-binding immunoglobulin superfamily lectins.
(23/1136)
The siglecs (sialic acid-binding immunoglobulin superfamily lectins) are immunoglobulin superfamily members recognizing sialylated ligands. Most prior studies of siglec specificities focused on alpha2-3- and alpha2-6-sialyllactos(amin)es and on one or two of the siglecs at a time. Here, we explore several new aspects of specificities of the first six reported siglecs, using sialylated glycans presented in multivalent form, on synthetic polyacrylamide backbones, or on mucin polypeptides. First, we report that binding of siglec-1 (sialoadhesin), siglec-3 (CD33), siglec-4a (myelin-associated glycoprotein), and siglec-5 to alpha2-3 sialyllactosamine is affected markedly by the presence of an alpha1-3-linked fucose. Thus, while siglecs may not interfere with selectin-mediated recognition, fucosylation could negatively regulate siglec binding. Second, in contrast to earlier studies, we find that siglec-3 prefers alpha2-6-sialyllactose. Third, siglec-5 binds alpha2-8-linked sialic acid, making it the siglec least specific for linkage recognition. Fourth, siglecs-2 (CD22), -3, -5, and -6 (obesity-binding protein 1) showed significant binding to sialyl-Tn (Neu5Acalpha2-6-GalNAc), a tumor marker associated with poor prognosis. Fifth, siglec-6 is an exception among siglecs in not requiring the glycerol side chain of sialic acid for recognition. Sixth, all siglecs require the carboxyl group of sialic acid for binding. Finally, the presentation of the sialyl-Tn epitope and/or more extended structures that include this motif may be important for optimal recognition by the siglecs. This was concluded from studies using ovine, bovine, and porcine submaxillary mucins and Chinese hamster ovary cells transfected with ST6GalNAc-I and/or the mucin polypeptide MUC1. (+info)
Physiological state of bull sperm affects fucose- and mannose-binding properties.
(24/1136)
In cattle, sperm are stored in a reservoir in the caudal isthmus of the oviduct until the time of ovulation approaches. Bull sperm are trapped in the reservoir by binding to fucosylated molecules on the oviductal epithelium. Capacitated sperm lose binding affinity for the epithelium; therefore this study was undertaken to determine whether this occurs because capacitated bull sperm lose binding affinity for fucose. BSA conjugated to alpha-L-fucopyranosylphenyl isothiocyanate and fluorescein isothiocyanate (fuc-BSA-FITC) was used in conjunction with flow cytometry to monitor the capacity of bull sperm to bind fucose. Dead sperm were identified using ethidium homodimer and were excluded from analysis. BSA-FITC conjugated with mannose (man-BSA-FITC) and BSA-FITC were used as controls. When examined by epifluorescence microscopy, motile bull sperm that exhibited labeling by any of the probes were fluorescent over the acrosomal region of the plasma membrane. By flow cytometry, labeling of live sperm was greatest for sperm that had been washed in TALP medium and probed with fuc-BSA-FITC (mean +/- SD:167 +/- 6.0 relative fluorescence units, collected in logarithmic mode). Labeling by fuc-BSA-FITC was lower in unwashed sperm (60 +/- 2.7) and in washed sperm with seminal plasma added back (56 +/- 8.0). Labeling was also reduced by centrifuging washed sperm through a Percoll step gradient (103 +/- 6.3) and by capacitating washed sperm in medium containing 10 microg/ml heparin (50 +/- 4.4). BSA-FITC labeling was barely detectable in all treatments. Man-BSA-FITC produced little labeling of washed sperm (22 +/- 0.6), as expected; however, intense labeling appeared over the acrosomal region of sperm incubated under capacitating conditions (128 +/- 21.6). It was concluded that removal of seminal plasma exposes fucose-binding sites, which are then lost or modified during capacitation, thereby allowing the release of sperm from the reservoir. At that time, mannose-binding sites are revealed or activated, which might serve to bind sperm to the zona pellucida. (+info)