Structures of the sugar chains of recombinant macrophage colony-stimulating factor produced in Chinese hamster ovary cells

Sialylated O-glycans and sulfated tyrosines in the NH2-terminal domain of CC chemokine receptor 5 contribute to high affinity binding of chemokines

The chemokine receptor CCR5 plays an important role in leukocyte chemotaxis and activation, and also acts as a coreceptor for human and simian immunodeficiency viruses (HIV-1, HIV-2, and SIV). We provide evidence that CCR5 is O-glycosylated on serine 6 in the NH2 terminus. The O-linked glycans, particularly sialic acid moieties, significantly contribute to binding of the chemokine ligands. By contrast, removal of O-linked oligosaccharide exerted little effect on HIV-1 infection. Sulfation of specific tyrosine residues in the CCR5 NH2 terminus was important for efficient beta-chemokine binding. Thus, as has been observed for the binding of selectins and their ligands, O-linked carbohydrates and tyrosine sulfates play major roles in promoting the interaction of chemokines with CCR5. The resulting flexible arrays of negative charges on the CCR5 surface may allow specific, high-affinity interactions with diverse chemokine ligands. Although this is the first example of O-linked oligosaccharides and tyrosine sulfates playing a role in chemokine binding, the high density of serines, threonines and tyrosines in the N-termini of many CC chemokine receptors suggests that these posttranslational modifications may commonly contribute to chemokine binding.

Study of the sugar chains of recombinant human amyloid precursor protein produced by Chinese hamster ovary cells

The N- and O-glycans of recombinant amyloid precursor protein (APP), purified from Chinese hamster ovary cells transfected with the human 695-amino acid form of APP, were separately released by hydrazinolysis under different conditions. The reducing ends of the released N- and O-glycans were reduced with NaB3H4 and derivatized with 2-aminobenzamide (2AB), respectively. After acidic N-glycans were obtained by anion-exchange column chromatography, these were converted to neutral oligosaccharides by sialidase digestion, demonstrating that their acidic nature was entirely due to sialylation. The sialidase-treated N-glycans were then fractionated by lectin column chromatography and their structures were determined by linkage-specific sequential exoglycosidase digestion. These results demonstrated that recombinant APP has bi- and triantennary complex type N-glycans with fucosylated and nonfucosylated trimannosyl cores. In a similar fashion, the 2AB-labeled O-glycans derived from APP were determined to be mono- and disialylated core type 1 structures. Taken together, these results indicate that recombinant APP has sialylated bi- and triantennary N-glycans with fucosylated and nonfucosylated cores and sialylated O-glycans with core type 1 structures.