Lactosaminoglycan proteins are a group of glycoproteins present in plasma membranes. Their carbohydrates often serve as cell surface antigens, including Ii, ABH and SSEA-1, which change drastically during cellular differentiation, embryonal development and oncogenesis. Human embryonal carcinoma cell, PA1, resembles the cells of the preblastocyst or trophectoderm of the early blastocyst stage of mouse embryo in many ways. We have determined that large glycopeptides present in PA1 cells are branched lactosaminoglycans with novel disialosyl (NeuNAc alpha2 yields 9 NeuNAc) sequences. We plan to prepare monoclonal antibodies against the NeuNAc alpha2 yields 9 NeuNAc structure to study the distribution of this structure among embryonal cells and tumor cells. Such monoclonal antibodies with defined specificity would also be useful reagents to detect oncodifferentiation antigen and to diagnose tumors. We plan to elucidate the relationship between lactosaminoglycans and complex type oligosaccharides, focusing on their core structures, distribution of lactosaminyl side chains and the occurrence of disialyl structure. PA1 lactosaminoglycans are specifically carried by a glycoprotein (Gp95). Gp95 will be purified and antibodies specific to Gp95 will be prepared. We will examine the distribution of Gp95 among various cell lines by using the antibodies in order to evaluate this glycoprotein as a protein specific to human embryonal carcinoma cells as well as early embryonic cells. We have characterized glycolipids present in PA1 cells and have found that PA1 cells contain mono- and disialylated glycolipids with blood group type 1 sequence. We plan to characterize 0-glycosidic carbohydrates so that the overall structural features of cell surface glycoconjugates on PA1 cells can be established. These studies will provide us with structural information on carbohydrate antigens expressed in teratocarcinoma cells and early stage embryos. Our study will ultimately be helpful for understanding the role of cell surface glycoconjugates in cellular differentiation and oncogenesis.
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