Cell surface glycoproteins: biochemical, immunological and molecular biological studies

This article briefly summarizes the author's contribution to the study of cell surface glycoproteins. At first, much effort was devoted to developing analytical methods, especially exoglycosidases and endoglycosidases. An endo-beta-N-acetylglucosaminidase found in Streptococcus pneumoniae was the first example of an endoglycosidase acting on glycoproteins. A combination of radioactive labeling, glycosidase digestion and lectin affinity chromatography enabled the characterization of carbohydrate moieties of cell surface glycoproteins derived from cultured cells. Application of the method to teratocarcinoma stem cells and preimplantation mouse embryos led to the discovery of marked changes in the carbohydrate moieties of cell surface glycoproteins during embryogenesis. Combining biochemical and immunohistochemical methods, an overall picture was obtained for carbohydrate changes in early embryogenesis of the mouse, and molecular biological approaches have been adopted to determine their biological significance. Furthermore, some core proteins carrying developmentally regulated carbohydrate markers were found and characterized by molecular cloning. One example of such a protein is embigin, which enhances integrin-mediated cell-substratum adhesion and established the existence of a new group in the immunoglobulin superfamily. Carbohydrate immunochemical markers useful in the analysis of mouse embryogenesis were also found to be effective in the classification of human carcinomas with respect to metastatic potential.