Antibodies that recognize astrotactin block granule neuron binding to astroglia

To provide a rapid, specific assay for receptor systems involved in the binding of cerebellar granule neurons to astroglia, granule cells, purified from early postnatal mice, or from E15-E16 chicks, were radiolabeled with [35S]methionine and plasma membranes were prepared. The kinetics of binding of radiolabeled material to primary mouse or chick glia or to the mouse G26-24 astrocytoma cell line was measured in the presence or absence of antibodies against astrotactin, neural cell adhesion molecules, cadherins, or integrins. Addition of Fab fragments of astrotactin antibodies reduced the amount of granule cell membrane binding to astroglia by 70%. In contrast, Fab fragments of antibodies against the neural adhesion molecules N-CAM, L1, and N-cadherin and against integrin did not reduce the level of granule cell membrane binding to astroglia. Combinations of antibodies against N-CAM, L1, N-cadherin, and integrin also did not impair neuron binding to glia.