Neurite formation on laminin: effects of a galactosyltransferase on primary sensory neurons

Avian embryonic sensory neurons from ED8 chick possess a trypsin-labile cell surface galactosyltransferase (GalTase) activity that glycosylates laminin in the presence of uridine 5′galactose (UDPgal). In a 4 h biological assay concentration dependent partial inhibition of neurite growth on laminin was observed in the presence of (i) alpha-lactalbumin, a specific inhibitor of the enzyme, (ii) N-acetylglucosamine (GlcNac), the appropriate acceptor substrate, or its polymer chitotriose, and (iii) UDPgal, the catalytic substrate. Prior exposure of substrate-immobilized laminin to glycosidase partially inhibited neurite growth. Alpha-lactalbumin did not influence cell adhesion at saturating concentrations for inhibition of neurite formation. Neurite growth on fibronectin was not inhibited by prior exposure to glycosidase or by alpha-lactalbumin, and fibronectin was not an appropriate substrate for glycosylation by the sensory neurons. These observations extend the catalogue of domains of laminin that subserve neurite growth, and define in functional terms a class of neuronal receptors that interact with lactosaminoglycan-type oligosaccharides of laminin.