Drosophila β1,4-N-acetylgalactosaminyltransferase-A synthesizes the LacdiNAc structures on several glycoproteins and glycosphingolipids

The GalNAcβ1,4GlcNAc (LacdiNAc or LDN) structure is a more common structural feature in invertebrate glycoconjugates when compared with the Galβ1,4GlcNAc structure. Recently, β1,4-N-acetylgalactosaminyltransferase (β4GalNAcT) was identified in some invertebrates including Drosophila. However, the LDN structure has not been reported in Drosophila, and the biological function of LDN remains to be determined. In this study, we examined acceptor substrate specificity of Drosophila β4GalNAcTA by using some N- and O-glycans on glycoproteins and neutral glycosphingolipids (GSLs). GalNAc was efficiently transferred toward N-glycans, O-glycans, and the arthro-series GSLs. Moreover, we showed that dβ4GalNAcTA contributed to the synthesis of the LDN structure in vivo. The dβ4GalNAcTA mRNA was highly expressed in the developmental and adult neuronal tissues. Thus, these results suggest that dβ4GalNAcTA acts on the terminal GlcNAc residue of some glycans for the synthesis of LDN, and the LDN structure may play a role in the physiological or neuronal development of Drosophila.