Modulation of neural carbohydrate epitope expression in Drosophila melanogaster cells

Neural pathways in invertebrates are often tracked using anti-horseradish peroxidase, a cross-reaction due to the presence of core alpha 1,3-fucosylated N-glycans. In order to investigate the molecular basis of this epitope in a cellular context, we compared two Drosophila melanogaster cell lines: the S2 and the neuronal-like BG2-c6 cell lines. As shown by mass spectrometric and chromatographic analyses, only the BG2-c6 cell line expresses alpha 1,3/alpha 1,6-difucosylated N-glycans, a result that correlates with anti-horseradish peroxidase binding. Of all four alpha 1,3-fucosyltransferase homologues previously identified, the core alpha 1,3-fucosyltransferase (FucTA; EC 2.4.1.214) is expressed in the neuronal cell line as well as throughout fly development and in heads and bodies of flies of both sexes. This pattern is distinctive in comparison with the expression of the other three alpha 1,3-fucosyltransferase homologues (FucTB, FucTC, and FucTD). Furthermore, only transfection of FucTA cDNA into S2 cells resulted in expression of the anti-horseradish peroxidase epitope, a result compatible with its substrate specificity in vitro. Finally, silencing of FucTA by RNAi in the neuronal cell line led to a significant reduction of anti-horseradish peroxidase binding. The present study, in conjunction with our previous in vitro data, thereby shows that FucTA is indispensable for expression of the neural carbohydrate epitope in Drosophila cells.