Fucosylation of Cripto is required for its ability to facilitate nodal signaling

O-Linked fucose modification is rare and has been shown to occur almost exc lusively within epidermal growth factor (EGF)-like modules. We have found t hat the EGF-CFC family member human Cripto-1 (CR) is modified with fucose a nd through a combination of peptide mapping, mass spectrometry, and sequenc e analysis localized the site of attachment to Thr-88. The identification o f a fucose modification on human CR within its EGF-like domain and the pres ence of a consensus fucosylation site within all EGF-CFC family members sug gest that this is a biologically important modification in CR, which functi onally distinguishes it from the EGF ligands that bind the type 1 erbB grow th factor receptors. A single CR point mutation, Thr-88 --> Ala results in a form of the protein that is not fucosylated and has substantially weaker activity in cell-based CR/Nodal signaling assays, indicating that fucosylat ion is functionally important for CR to facilitate Nodal signaling.