Correlation between changes in cell adhesion and the ratio of N‐ to O‐linked glycopeptides during chick embryo development

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Abstract
After treatment with trypsin, chick embryo fibroblasts exhibited an age-related difference in their capacity to re-adhere to the substratum, since 8 day cells re-adhered more rapidly than 16 day cells. Treatment with tunicamycin altered embryo cell re-adhesion to the substratum in varying degrees, depending on the duration of drug treatment and of re-adhesion assay. The effect of tunicamycin was not toxic and was totally reversible with time after its removal. Embryo cell re-adhesion involved trypsin-sensitive cell surface glycoproteins. During embryo development, the glycosylation of cell surface glycoproteins altered markedly. The ratio of N-linked to O-linked glycan chains dropped from 80/20 in 8 day cells to 55/45 in 16 day cells, indicating that the relative labeling of O-linked glycan chains increased during embryo development. This result was confirmed by alkaline treatment of radiolabeled glycan chains, and by the fact that tunicamycin treatment reduced 14C-glucosamine incorporation by .gtoreq. 80% in 8 day cells but only 60% in 16 day cells. Marked changes were observed during embryo development in the structure of the N-linked glycan chains; concanavalin A-Sepharose chromatography showed that these changes concerned the glycopeptides containing complex type carbohydrate chains. The ratio of tri- plus tetra-antennary chains to bi-antennary chains increased about 2.5-fold between the 8th and 16th day of development. A correlation was noted between embryo cell re-adhesion to the substratum and N-glycosylation of cell surface glycoproteins. The N-linked glycoconjugates played a crucial part in cell re-adhesion. The possible role of O-linked structures in such re-adhesion is discussed.