Selective expression of different fucosylated epitopes on two distinct sets of Schistosoma mansoni cercarial O-glycans: identification of a novel core type and Lewis X structure.
The glycobiology of Schistosoma mansoni is dominated by developmentally regulated expression of various fucosylated structures, most notably the Lewis X epitope and a multifucosylated sequence, Fuc alpha1-->2Fuc alpha1-->, in its various forms. For the infective cercarial stage, Lewis X has been structurally identified on glycosphingolipids and N-glycans of total glycoprotein extracts, and a population of multifucosylated glycoproteins were found to carry a unique terminal sequence, +/-Fuc alpha1-->2Fuc alpha1-->[3GalNAc beta1-->4(Fuc alpha1-->2Fuc alpha1--> 2Fuc alpha1-->3) GlcNAc beta1-->3Gal alpha1-->](n), on their O-glycans. Using a mass spectrometry approach coupled with chromatographic separation, sequential exoglycosidase digestion, periodate oxidation, and other chemical derivatization, we demonstrate that Lewis X could also be carried on the cercarial O-glycans, but the two distinctive sets of fucosylated epitopes were conjugated to two different core structures. Lewis X, lacNAc, or single GlcNAc was found to attach directly to the -->3Gal beta1-->3GalNAc core and indirectly via another beta-Gal residue branching off from C6 of the reducing end GalNAc to give a biantennary-like structure. The -->3(+/-Gal beta1-->6)Gal beta1-->3(-->3Gal beta1-->6)GalNAc core thus characterized represents a novel core type for O-glycans. In contrast, the previously characterized multifucosylated terminal sequences were carried on conventional type 1 and 2 cores. The smallest structures of the reductively released O-glycans were defined as GalNAc beta1-->4GlcNAc beta1-->3Gal beta1-->3GalNAcitol with a total of two to four fucoses attached to the terminal lacdiNAc. alpha-Galactosylation of the nonreducing terminal beta-GalNAc instead of fucose capping leads to further elongation with another lacdiNAc unit that could also extend directly from C6 of the reducing end GalNAc and similarly elongated or terminated.
Huang
H H
HH
Institute of Biological Chemistry, Academia Sinica,128, Academia Road Sec 2, Nankang, Taipei 115, Taiwan, R.O.C.
Tsai
P L
PL
Khoo
K H
KH
D000818:Animals; D000947:Antigens, Helminth / Q000737:chemistry*; D002240:Carbohydrate Sequence; D000939:Epitopes / Q000737:chemistry; D005643:Fucose / Q000737:chemistry; D006023:Glycoproteins / Q000737:chemistry / Q000276:immunology; D015801:Helminth Proteins / Q000737:chemistry / Q000276:immunology; D006801:Humans; D016256:Lewis X Antigen / Q000737:chemistry*; D013058:Mass Spectrometry; D008969:Molecular Sequence Data; D010084:Oxidation-Reduction; D011134:Polysaccharides / Q000737:chemistry / Q000276:immunology; D012550:Schistosoma mansoni / Q000737:chemistry* / Q000276:immunology*; D016339:Spectrometry, Mass, Fast Atom Bombardment
D000947:Antigens, Helminth; D000939:Epitopes; D006023:Glycoproteins; D015801:Helminth Proteins; D016256:Lewis X Antigen; D011134:Polysaccharides; D005643:Fucose