Delivery of anti-GAP-43 antibodies into neuroblastoma cells reduces growth cone size.

We have previously demonstrated that antibodies to the growth-associated protein, GAP-43, introduced intracellularly using a lipid carrier inhibited neurite outgrowth in NB2a/d1 neuroblastoma cells, and that culturing of these cells on adhesive substrates such as laminin or poly-L-lysine overcame this restriction. These findings suggest that GAP-43 may facilitate neuritogenesis by increasing membrane adhesiveness. To address this issue, in the present study we examined the effect of intracellular delivery of this antibody on growth cone size. A statistically significant percentage of those neurites that did elaborate following intracellular delivery of GAP-43 exhibited either no observable growth cones or smaller growth cones versus cells receiving pre-immune IgG. These results support the hypothesis that the requirement for GAP-43 in neuritogenesis may be related to growth cone formation and membrane adhesiveness.