INHIBITION OF NEURITE OUTGROWTH FOLLOWING INTRACELLULAR DELIVERY OF ANTI-GAP-43 ANTIBODIES DEPENDS UPON CULTURE CONDITIONS AND METHOD OF NEURITE INDUCTION

NB2a/d1 neuroblastoma cells acquire a neuronal phenotype in response t o several differentiating agents, including dibutyryl cAMP (dbcAMP) an d the withdrawal of serum, As shown previously, antibodies to the grow th-associated protein, GAP-43, introduced intracellularly using a lipi d carrier, blocked the differentiation induced by dbcAMP, Antibodies t o GAP-43, at a low concentration, also blocked neurite outgrowth induc ed by serum withdrawal when cells were grown on a relatively unadhesiv e substrate, On more adhesive substrates such as poly-L-lysine and lam inin, however, anti-GAP-43 antibodies had less of an effect on neurite outgrowth, Previous studies have shown that the increased adhesivity of laminin allows a small but significant population of neurites to gr ow from serum-deprived cells, even in the presence of the microtubule- depolymerizing drug, colchicine. The outgrowth of this population of n eurites was blocked by antibodies to GAP-43, These results are in conf ormity with recent studies showing that the requirement for GAP-43 in neuritogenesis may be related to membrane adhesiveness, and may contri bute to an understanding of some of the apparent discrepancies in the literature concerning the involvement of GAP-43 in neuronal differenti ation. (C) 1995 Wiley-Liss, Inc.