Neuro-p24 plays an essential role in neurite extension: antisense oligonucleotide inhibition of neurite extension in cultured DRG neurons and neuroblastoma cells.

Neuro-p24 is a novel neuronal membrane protein that is specifically localized in neural processes, particularly in growing neurites. To explore the roles of Neuro-p24, we examined the immunocytochemical localization of this protein in cultured neurons during neural induction, and performed an antisense oligonucleotide transfection using two culture models, the mouse dorsal root ganglia (DRG) and the neuro2a neuroblastoma cell line. Intense Neuro-p24 immunoreactivity was observed in the soma and small vesicles in neurites at the early stage of culture, but it gradually disappeared as cultures proceeded. Intense immunoreactivity was often observed at the growing distal end of the neurites. Morphological changes in neurites after Neuro-p24 antisense oligonucleotide transfection were examined in DRG neurons by the continual observation of a group of identical neurons. Affected cells retracted neurites transiently, followed by the re-elongation and branching of newly formed neurites. The control oligonucleotide-treated neurons appeared unaffected. When neuro2a cells were similarly treated with antisense oligonucleotides, the results were similar to those obtained in the DRG neurons. The binding of Neuro-p24 to tubulin was confirmed by both in vivo and in vitro pull-down assays. The present results support our idea that Neuro-p24 plays an essential role in neurite extension through a vesicle transport system via microtubules.