Human Golgi β-galactoside α-2,6-sialyltransferase generates a group of sialylated B lymphocyte differentiation antigens

✍ Scribed by Oliver T. Keppler; Gerhard Moldenhauer; Monika Oppenländer; Reinhard Schwartz-Albiez; Eric G. Berger; Steinar Funderud; Michael Pawlita

• Book ID: 102823878
• Publisher: John Wiley and Sons
• Year: 1992
• Tongue: English
• Weight: 618 KB
• Volume: 22
• Category: Article
• ISSN: 0014-2980
• DOI: 10.1002/eji.1830221104

✦ Synopsis

Human Golgi P-galactoside a-2,6-sialyltransferase generates a group of sialylated B lymphocyte differentiation antigens*

The role of the human P-galactoside a-2,6-sialyltransferase (hu a-2,6-ST) in the generation of B cell surface antigens was investigated by selecting subclones of COS cells (monkey kidney epithelial cells) constitutively expressing a transfected cDNA which encodes the hu a-2,6-ST (COS a-2,6-ST cells). Expression of hu a-2,6-ST in COS cells was sufficient to generate sialylated cell surface epitopes on different glycosylated antigens recognized by monoclonal antibodies to CDw75, CD76, and the unclustered monoclonal antibodies HB-4 and EBU-65. These epitopes were sensitive to sialidase treatment and are likely to contain terminal a-2,6-linked sialic acid residues. A novel antiserum raised against bacterially expessed hu a-2,6-ST fusion protein was used to localize the sialyltransferase in two cell lines with high expression of either endogenous (B cell line JOK-1) or recombinant (COS a-2,6-STcells) hu a-2,6-ST. In both cell lines, the enzyme was detected only intracellularly in the juxtanuclear region and not on the cell surface. In contrast, CDw75, formerly proposed to be identical with an a-2,6-ectosialyltransferase, was strongly expressed on the cell surface. The different expression patterns show that neither the CDw75 antigen nor any of the other sialylated antigens analyzed is identical with the hu a-2,6-ST. Furthermore, the presence of a surface-expressed a-2,6-ST appears unlikely in these cell lines. We propose that CDw75, CD76, HB-4, and EBU-65 represent a unique group of B cell differentiation antigens the production of which requires the enzymatic activity of a-2,6-ST.