Increased fucosylation of high‐molecular‐weight glycoproteins accompanies retinoic‐acid‐induced differentiation of f‐9 embryonal carcinoma cells

AbstractRetinoic acid (RA) treatment of F‐9 embryonal carcinoma cells resulted in cell flattening and increased production of laminin Bl chain, both indicating differentiation to endoderm‐like cells. In addition, RA caused a time‐ and dose‐ dependent decrease in growth rate in monolayer culture and a dose‐dependent decrease in the ability of the cells to form colonies in soft agarose. Differentiation was accompanied by an increase in the fucosylation of specific high‐molecular‐weight cellular and cell‐surface glycoproteins. The fucosylation of glycoproteins of Mr 175,000 (gp175), 250,000 (gp250), and 400,000 (gp400) increased as early as 24 hr after the addition of 5 ± 10−6 M RA to the culture medium. These changes preceded both growth inhibition and the induction of laminin BI expression, which were detected 48 to 72 hr after addition of RA. The increased fucosylation of these glycoproteins showed a distinct dose‐response relationship. Both gp 175 and gp250 showed the greatest increase in fucosylation at 10−5 M, which was also the dose at which RA induced laminin maximally, while the fucosylation of gp400 was greatest at 10−8 M RA and declined at higher concentrations. The overall synthesis of large fucosylated glycopeptides decreased in RA‐treated cells, in spite of the increases in the fucosylation of specific cellular glycoproteins. RA‐induced differentiation of F‐9 cells was also accompanied by a time‐ and dose‐dependent increase in fucosyltransferase activity. Although the functions of these glycoproteins are not currently known, the early increase in their fucosylation can be considered as a marker of differentiation in this system.