Neuro-2a neuroblastoma cells form neurites in the presence of taxol and cytochalasin D.

We have examined the role of microtubules and microfilaments in neurite outgrowth by chemically modifying their interaction in Neuro-2a neuroblastoma cells. Cells exposed to taxol (1 microM), an agent that promotes microtubule polymerization and stabilization, did not form neurites over a 24 h period. Similarly, cells exposed to cytochalasin D (4 microM), an agent which promotes microfilament depolymerization, did not develop neurites. However, cells treated simultaneously with taxol (1 microM) and cytochalasin D (4 microM) produced long (50 microns) thin, unbranched neurites. Neurites formed during this simultaneous treatment grew in a circular pattern, lacked typical growth cones, were packed densely with microtubules and were deficient in microfilaments. Untreated cells maintained in control medium for 24 h formed short (15 microns), thick, highly branched neurites containing a dense meshwork of microtubules, microfilaments and neurofilaments. These results demonstrate that taxol does not block neurite outgrowth from Neuro-2a cells maintained under microfilament-limiting conditions. They suggest further that microtubules may provide the major cytoskeletal framework for neurite elongation.