UDP-sugar transporter implicated in glycosylation and processing of Notch

Glycosylation modifies protein activities in various biological processes. Here, we report the functions of a novel UDP-sugar transporter (UST74C, an alternative name for Fringe connection (Frc)) localized to the Golgi appara tus in cellular signalling of Drosophila. Mutants in the frc gene exhibit p henotypes resembling wingless and Notch mutants. Both Fringe-dependent and Fringe-independent Notch pathways are affected, and both glycosylation and proteolytic maturation of Notch are defective in mutant larvae. The results suggest that changes in nucleotide-sugar levels can differently affect Win gless and two distinct aspects of Notch signalling.