Glycosylation of CD4 and Thy-1
Dwek RA, Ashford DA, Edge CJ, Parekh RB, Rademacher TW, Wing DR, Barclay AN, Davis SJ, Williams AF. (1993), Philos Trans R Soc Lond B Biol Sci. 342, 43-50
The site-specific glycosylation of soluble recombinant variants of human and rat CD4 (sCD4) expressed in Chinese hamster ovary (CHO) cells has been characterized. The presence of identical oligosaccharides at the conserved glycosylation site in domain 3 of rat and human sCD4 and the greater abundance of oligomannose and hybrid type glycans at the non-conserved glycosylation site of rat sCD4 clearly indicate that the protein structure influences oligosaccharide processing. Comparisons of rat sCD4 glycopeptides with mutant molecules with only single glycosylation sites and with a truncated form containing only the two NH2-terminal domains, indicate that independent processing occurs at each glycosylation site and that domain interactions can also affect oligosaccharide processing. These and other analyses of sCD2 expressed in CHO cells and Thy-1 purified from various tissues suggest that the diversity of oligosaccharide structures on a protein is regulated by the location of the glycosylation sites and the nature of the target protein, cell and tissue. The functional significance of this control remains to be determined.
Key figure: Schematic drawings of rat and human CD4, rat CD2 and Thy-1
The molecules are drawn with the circles representing immunoglobulin superfamily (IgSF) domains and the ‘lollipops’ N-linked oligosaccharides. The glycosylphosphatidylinositol membrane anchor of Thy-1 is depicted as a vertical arrow. The IgSF domains are designated as V set (V) or C2 set (C2) on the basis of sequence analysis (Williams et al. 1989). The positions of the mutations introduced in the CD4 and CD2 molecules to produce the recombinant soluble forms are indicated by horizontal arrows.