Differential expression of an E-selectin ligand (SLe^x) by two Chinese hamster ovary cell lines transfected with the same α(1,3)-fucosyltransferase gene (ELFT)

The mammalian cDNA encoding α(1,3)-fucosyltransferase (α(1,3)Fuc-T) termed ELAM-1 ligand fucosyltransferase (ELFT) or Fuc-TIV was previously cloned by three groups who reported different results from transaction studies Goelz et al. (Goelz, S. E., Hession, C., Goff, D., Griffiths, B., Tizard, R., Newman, B., Chi-Rosso, G., and Lobb, R. (1990) Cell 63, 1349-1356) found that Chinese hamster ovary (CHO) cells expressing the ELFT cDNA had α(1,3)Fuc-T activity and were able to bind to E-selectin. In contrast, Lowe et al. (Lowe, J. B., Kukowska-Latallo, J. F., Nair, R. P., Larsen, R. D., Marks, R. M., Macher, B. A., Kelly, R. J., and Ernst, L. K. (1991) J. Biol. Chem. 266, 17467-17477) and Kumar et al. (Kumar, R., Potvin, B., Muller, W. A., and Stanley, P. (1991) J. Biol. Chem. 266, 21777-21783) found no binding to E-selectin of CHO transfectants expressing the same α(1,3)Fuc-T gene; nor did the latter transfectants synthesize a known E-selectin ligand, sialylated Le^x (SLe^x), although they had substantial α(1,3)Fuc-T activity. We now show that these discrepant results were due to a difference between the parental CHO cell lines. Following transfection of ELFT cDNA into Pro^-5 or dihydrofolate reductase (DHFR)^- CHO cells, only the DHFR^- transfectants expressed SLe^x and bound to E-selectin. Indirect evidence from monoclonal antibody and lectin binding studies indicates that the range of carbohydrate structures synthesized by the Pro^-5 and DHFR^- CHO cell lines differs. Since DHFR^-/ELFT transfectants expressed cell surface SLe^x but transferred fucose poorly to sialylated substrates in vitro, ELFT may be able to fucosylate a complex carbohydrate missing from Pro^-5 cells. Alternatively, either CHO line may have an activity (such as an α(2,3)-sialyltransferase), that modifies α(1,3)-fucosylated lactosamines.