Cell-surface carbohydrates, functions

Gene knockout experiments in mice clearly indicate that cell surface carbohydrates play many vital roles in development and health. Evidence suggests that cell surface carbohydrates function in many cellular activities by interacting with their microenvironment in vivo. Future studies should identify mechanisms underlying activation of cells by cell surface carbohydrates, which are vital for understanding the activities of malignant cancer cells. 

A major function of the immune system is thought to be destruction of cancer cells. In this case altered cell surface carbohydrates or proteins elicit an antibody response with destruction of the offending cells. 

Enhanced interest in the function of carbohydrate residues derives from the fact that all plant and animal cells are sugar coated. Because of their strategic position, cell-surface carbohydrates have been implicated in cell-cell communication and in the interaction of cells with their environment. 

FIGURE 16.1 Multivalent binding of a bacterium to the clustered carbohydrate ligand carrying matching terminal carbohydrate residue(s) found in the host cell surface. The multivalent interaction prevents the attachment of the bacterium to the host cell surface. The functional role of the linker is the optimal presentation of the glycan into the binding site of the receptor, but it may also be involved in additional hydrophobic contacts. 

MX was considered to be playing a subsidiary role to Mil. MX gene knockout mouse revealed an unexpected important function of MX in spermatogenesis. Therefore, the genetic approach elucidated the specific role of cell surface carbohydrates in specific cell types. 

In summary, gene knockout mouse technology has allowed us to determine the function of cell surface carbohydrates in mouse embryos in recent years. Some glycosyltransferases-deficient mutant mouse showed severe phenotypes, including embryonic lethality. However, we have not yet identified the mechanisms underlying these phenotypes. Identification of critical carbohydrate structure (s), specific proteins carrying specific carbohydrate structure(s), and the counter-receptors for those carbohydrates should be identified in future studies. 

Glycoconjugates are the most functionally and structurally diverse compounds in Nature and it is now well established that protein- and lipid-bound saccharides play essential roles in many molecular processes impacting eukaryotic biology and disease.Examples of such processes include fertilization, embiyogenesis, neuronal development, hormone activities, the proliferation of cells and their organization into specific tissues. Remarkable changes in the cell-surface carbohydrates occur with tumor progression, which... 

Supramolecular carbohydrate-lectin interactions on cell surfaces can have rather different characteristics. Figure 1 shows that the glycoproteins exposed on the cell surface can function as lectins, and they can also provide carbohydrate epitopes for lectin binding. Thus, carbohydrate-lectin interactions can occur between different cells and then they... 

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