The L2/HNK-1 carbohydrate mediates adhesion of neural cells to laminin.

The L2/HNK-1 carbohydrate epitope shared by several neural adhesion molecules has been implicated in cell-to-cell and cell-to-laminin adhesion (Keilhauer et al., Nature, 316, 728-730, 1985; Künemund et al., J. Cell Biol., 106, 213-223, 1988). As demonstrated previously for chicken retinal ganglion cells (Cole et al., Neurosci. Lett., 93, 170-175, 1988), cerebral cortex astrocytes or cerebellar neurons could not be shown to adhere to the substrate-bound L2/HNK-1 carbohydrate. The cell-bound L2/HNK-1 carbohydrate, however, was a potent mediator of astrocytic and neuronal cell adhesion to laminin, which was strongly reduced in the presence of the L2/HNK-1 carbohydrate-carrying glycolipids or Fab fragments of a monoclonal antibody against it. Inhibition of adhesion could not be observed in the presence of the negatively charged gangliosides or sulphatide, but in the presence of heparin. To investigate whether the L2/HNK-1 carbohydrate and heparin use the same or different binding sites on laminin, adhesion of cells to laminin was determined in the presence of heparin and Fab fragments of a monoclonal L2 antibody, which gave an additive value of inhibition as compared to the inhibition caused by the single compounds. This result, as well as studies of the binding of the L2/HNK-1 glycolipids to laminin in the presence of heparin, indicates that the L2/HNK-1 carbohydrate and heparin are implicated in different aspects of neural cell adhesion to laminin.