Inhibition of neurite outgrowth following intracellular delivery of anti-GAP-43 antibodies depends upon culture conditions and method of neurite induction.
NB2/dl neuroblastoma cells acquire a neuronal phenotype in response to several differentiating agents, including dibutyryl cAMP (dbcAMP) and the withdrawal of serum. As shown previously, antibodies to the growth-associated protein, GAP-43, introduced intracellularly using a lipid carrier, blocked the differentiation induced by dbcAMP. Antibodies to GAP-43, at a low concentration, also blocked neurite outgrowth induced by serum withdrawal when cells were grown on a relatively unadhesive substrate. On more adhesive substrates such as poly-L-lysine and laminin, 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 grow from serum-deprived cells, even in the presence of the microtubule-depolymerizing drug, colchicine. The outgrowth of this population of neurites was blocked by antibodies to GAP-43. These results are in conformity with recent studies showing that the requirement for GAP-43 in neuritogenesis may be related to membrane adhesiveness, and may contribute to an understanding of some of the apparent discrepancies in the literature concerning the involvement of GAP-43 in neuronal differentiation.
Shea
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Laboratory for Molecular Neuroscience, Mailman Research Center, McLean Hospital, Belmont, Massachusetts, USA.
Benowitz
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D000918:Antibody Specificity; D003994:Bucladesine / Q000494:pharmacology; D048429:Cell Size; D003078:Colchicine / Q000494:pharmacology; D003470:Culture Media; D016895:Culture Media, Serum-Free; D019922:GAP-43 Protein; D007797:Laminin / Q000494:pharmacology; D008562:Membrane Glycoproteins / Q000276:immunology*; D009419:Nerve Tissue Proteins / Q000276:immunology*; D016501:Neurites / Q000502:physiology*; D009447:Neuroblastoma; D016900:Neurofilament Proteins / Q000276:immunology*; D011107:Polylysine / Q000494:pharmacology; D014407:Tumor Cells, Cultured / Q000166:cytology
D003470:Culture Media; D016895:Culture Media, Serum-Free; D019922:GAP-43 Protein; D007797:Laminin; D008562:Membrane Glycoproteins; D009419:Nerve Tissue Proteins; D016900:Neurofilament Proteins; D011107:Polylysine; D003994:Bucladesine; D003078:Colchicine