SPECTRIN-ACTIN INTERACTION IS REQUIRED FOR NEURITE EXTENSION IN NE 2ADL NEUROBLASTOMA-CELLS/

Spectrin is an actin-binding membrane skeleton protein involved in the maintenance of cell shape and generation of distinct membrane protein domains. Actin binds to the N-terminal domain of beta-spectrin. To ex amine the function of spectrin-actin interaction in neurons, we sought to disrupt this interaction in differentiating NB 2a neuroblastoma ce lls by microinjecting an N-terminal domain-specific anti-beta-spectrin antibody. We found that microinjection of the affinity-purified N-ter minal domain-specific anti-beta-spectrin inhibited the extension of th e neurites in NB 2a/dl cells. The microinjected cells remained flat, a nd put out many filopodia-like processes; but these processes failed t o extend when the cells were induced to differentiate in the presence of dbc AMP or in serum-free medium. The N-terminal domain-specific ant i-beta-spectrin also inhibited the binding of spectrin to actin. By co ntrast, the microinjection of monospecific anti-beta-spectrin(G) did n ot inhibit neurite extension. These results suggest that beta-spectrin -actin interaction may be required for neurite extension, which is cri tical for development of polarity in nerve cells. (C) 1996 Wiley-Liss, Inc.