The adhesive properties of recombinant soluble L-selectin are modulated by its glycosylation.

The leukocyte adhesion molecule L-selectin, which mediates the initial steps of leukocyte attachment to vascular endothelium, is intensely glycosylated. Different glycoforms of L-selectin are expressed on different leukocyte subsets and differences in L-selectin glycosylation appear to be correlated with the leukocyte's ability to attach to different endothelial targets. In the present study we addressed the question whether glycosylation of L-selectin influences L-selectin-ligand interactions. To obtain different glycoforms of L-selectin, recombinant proteins were expressed both in the baby hamster kidney (BHK) cell line and in the human myelogenous cell line K562, resulting in sL-sel[BHK] or sL-sel[K562], respectively. The glycosylation characteristics of the purified proteins were determined. The most striking differences in glycosylation were seen in the terminal sialylation. Each of the two proteins carried sialic acids in the alpha 2-3 position, while alpha 2-6-bound sialic acids were found exclusively on sL-sel[K562]. To investigate their adhesive properties, both recombinant sL-selectins were used in cell adhesion assays and interactions with the ligands present on various hematopoietic cell lines or activated human cardiac microvascular endothelial cells were examined. The binding capacity of sL-sel[K562] was about 1.6 fold higher compared to sL-sel[BHK] under static as well as under flow conditions. These findings indicate that the terminal sialylation pattern of L-selectin modulates its binding characteristics.

Carbohydrate structures of soluble human L-selectin recombinantly expressed in baby-hamster kidney cells.

A soluble form of L-selectin was recombinantly produced, which might be an effective therapeutic agent in inflammatory disorders, acting as an inhibitor for leucocyte endothelium adhesion. In the present study the oligosaccharide structures of soluble human L-selectin, recombinantly expressed in baby-hamster kidney cells, were determined. The N-linked glycans were enzymically released and fluorescently labelled with 2-aminobenzamide. Sialylation of the N-glycans was analysed by anion-exchange chromatography followed by rechromatography of the resulting fractions on amino-phase HPLC after release of the sialic acid residues. Desialylated oligosaccharides were separated using two-dimensional HPLC and characterized by digestion with exoglycosidases and MS. More than 30 oligosaccharide structures representing at least 95% of the overall glycosylation of this protein were determined. The results revealed that recombinant soluble human L-selectin carries bi-, tri- and tetra-antennary sugar chains, which are fucosylated on the innermost residue of N-acetylglucosamine. The number of sialic acid residues linked to these glycans ranges from 0 (neutral glycans) to 4 (tetrasialylated oligosaccharides). The sialic acid is found exclusively in the alpha 2-3 linkage to galactose. In addition to the main glycans, different minor structures containing terminal N-acetylgalactosamine, or the H (O) blood-group determinant were also identified. O-Glycosylation of mucin-type sugar chains was not detected in recombinant soluble human L-selectin.

H (0) blood group determinant is present on soluble human L-selectin expressed in BHK-cells.

In the present study we show that the H (0) blood group determinant Fuc alpha1-2Gal beta1-4GlcNAc beta1-R is present on N-linked glycans of soluble human L-selectin recombinantly expressed in baby hamster kidney (BHK) cells. The glycans were isolated using complementary HPLC techniques and characterized by a combination of exoglycosidase digestion and mass spectrometry. The linkage of the fucose residues was determined by incubation of the glycans with specific fucosidases. The H blood determinant Fuc alpha1-2Gal beta1-4GlcNAc beta1 was detected for bi-, 2,4 branched tri- and tetraantennary structures. To our knowledge, the proposed oligosaccharide structures represent a new glycosylation motif for recombinant glycoproteins expressed on BHK cells.

p53 hot-spot mutational analysis in advanced Western gallbladder carcinoma.

In gallbladder carcinoma, studies on the prime target of genetic alterations and gene therapy in human gallbladder malignancies, the p53 tumor suppressor gene, have been focusing on this gene's immunohistochemical detection. From November 1991 to October 1993, seven patients suffering from gallbladder carcinoma underwent surgical resection. Cancerous and normal liver tissues were obtained immediately after surgery, snap-frozen in liquid nitrogen, and stored at -80 degrees C for immunohistochemistry and DNA isolation. Exons 5, 6, 7, and 8 of the p53 gene were completely sequenced following polymerase chain reaction (PCR) amplification of a 1574-bp fragment. Missense mutations were detected in the cancerous tissues of two patients: one transition each on codons 134 (Phe-->Leu) and 146 (Trp-->Arg). Immunohistochemical p53 staining was positive in the latter patient only. This is the first report on sequence analysis and mutagenesis of the p53 gene in Caucasian patients with gallbladder cancer. Both mutations were transitions and seem to represent a rather rare event. The possible impact of p53 mutagenesis on gallbladder tumorigenesis requires evaluation in larger studies.