N-linked oligosaccharides are not required for neuron-neuron interactions mediated by neural cell adhesion molecule (original) (raw)

1988, Neuroscience Letters

Recent studies have described the role of various regions of the neural cell adhesion molecule (NCAM) in cell~zell interactions. Monoclonal antibodies (L2/HNK-1) directed against a sulfated, glucuronic acidcontaining, N-linked carbohydrate epitope have also been shown to inhibit NCAM-mediated neural cell adhesion. In the present study we show that dissociated retinal neurons in an in vitro model system can bind as well to normal NCAM as to NCAM lacking the L2/H:NK-l epitope or to glycopeptidase F-treated NCAM. These data suggest that N-linked oligosaccharide chains do not confer upon NCAM the adhesional properties associated with its role in neuron neuron interactions. Cell surface glycoproteins have been implicated in cell recognition processes during development, with the oligosaccharide chains possibly participating directly in the recognition events [8, 11, 13, 20, 30]. The roles of several neuronal glycoproteins in cell-cell interactions during neural development have been described [9, 16, 25, 27, 31], with the neural cell adhesion molecule (NCAM) being well characterized. NCAM is involved in neuron-neuron [35], neuron-muscle [15] and neuron glial [21] interactions. Although NCAM has been reported to mediate neural cell adhesion by a homophilic binding mechanism [32], the binding of heparan sulfate proteoglycan to NCAM also appears to be involved in NCAM function [3, 5-7]. Previous studies have demonstrated that NCAM contains unique N-linked oligosaccharide chains containing polysialic acid [12], whose degree of sialylation is developmentally regulated [18, 33]. However, these oligosaccharides do not appear to be involved directly in the formation of NCAM-NCAM linkages [18, 33]. A second