Core structures of polysialylated glycans present in neural cell adhesion molecule from newborn mouse brain.
Polysialylation of the neural cell adhesion molecule (N-CAM) is known to destabilize cell-cell adhesion and to promote plasticity in cell-cell interactions. To gain more insights into the molecular mechanisms regulating the selective expression of polysialic acid on distinct glycan chains, the underlying core structures of polysialylated N-CAM glycans from newborn mouse brain were examined. Starting from low picomolar amounts of oligosaccharides, a multistep approach was used that was based on various mass spectrometric techniques with minimized sample consumption. Evidence could be provided that polysialylated murine N-CAM glycans comprise diantennary, triantennary and tetraantennary core structures carrying, in part, type-1 N-acetyllactosamine antennae, sulfate groups linked to terminal galactose or subterminal N-acetylglucosamine residues and, as a characteristic feature, a sulfated glucuronic acid unit which was bound exclusively to C3 of terminal galactose in Manalpha3-linked type-2 antennae. Hence, our results reveal that part of the murine N-CAM carbohydrates are modified within a single oligosaccharide by polysialic acid plus a HSO3-GlcA-moiety, which is likely to represent a HNK1-epitope. As HNK1-carbohydrates are also known to modulate cell-cell interactions, the simultaneous presence of both carbohydrate epitopes may reflect a new mechanism involved in the fine-tuning of N-CAM functions.
Geyer
H
H
Institute of Biochemistry, University of Giessen, Germany.
Bahr
U
U
Liedtke
S
S
Schachner
M
M
Geyer
R
R
D000818:Animals; D000831:Animals, Newborn; D001921:Brain / Q000166:cytology / Q000378:metabolism*; D002240:Carbohydrate Sequence; D015816:Cell Adhesion Molecules, Neuronal / Q000737:chemistry / Q000378:metabolism*; D002851:Chromatography, High Pressure Liquid; D051379:Mice; D008969:Molecular Sequence Data; D019158:N-Acetylneuraminic Acid / Q000737:chemistry*; D011134:Polysaccharides / Q000737:chemistry / Q000378:metabolism*; D021241:Spectrometry, Mass, Electrospray Ionization; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
D015816:Cell Adhesion Molecules, Neuronal; D011134:Polysaccharides; D019158:N-Acetylneuraminic Acid