Functional identification of integrin laminin receptors that mediate process outgrowth by human SY5Y neuroblastoma cells.

Treatment of the human neuroblastoma cell line SY5Y with nerve growth factor (NGF) induces terminal neuronal differentiation of a subpopulation of cells which can be selected by treatment with a DNA synthesis inhibitor. We have examined the interactions of naive (untreated) and NGF-differentiated SY5Y cells with laminin, and identified integrin receptors that mediate laminin-induced process outgrowth. Differentiated cells displayed a greater capacity for process extension, which correlated with increased expression of integrin laminin receptors. Both naive and differentiated cells expressed integrins alpha 1/beta 1, alpha 2/beta 1, and alpha 3/beta 1 but the differentiated population expressed about 5-fold higher levels of alpha 1/beta 1 and about 2-fold more alpha 2/beta 1 and alpha 3/beta 1 on their surface. Function blocking monoclonal antibodies were used to identify integrin receptors mediating process outgrowth. The anti-alpha 1 monoclonal antibody SR84 was shown to block alpha 1 function and inhibit process outgrowth on laminin. Despite the presence of multiple integrins which have been shown to bind laminin in other cell types, alpha 1/beta 1 mediated the majority of process outgrowth in both naive and differentiated cells, with a minor role played by alpha 3/beta 1. These data indicate that alpha 1/beta 1 function is required for process outgrowth on laminin by SY5Y cells and suggest that increased expression may be a crucial aspect of neuronal differentiation.