Morphology of neurites from N18TG2 cell induced by protein kinase inhibitor H-7 and by cAMP

Abstract

Protein kinase inhibitor H-7 and dibutyryl (dB)-cAMP were found to induce neuritic processes in mouse neuroblastoma N18TG2 cells (36). In the present study, morphological differences between the neurites induced by H-7 and those by dB-cAMP were examined using electron microscopy (TEM and SEM) and tubulin immunohistochemistry. It was observed that: 1. 1) The neurites induced by H-7 were relatively thin and frequently had varicosities. On the other hand, the neurites induced by dB-cAMP were thick but they had few varicosities. 2. 2) Centrioles were frequently observed in the cells treated with dB-cAMP but were not encountered in the H-7-treated cells. 3. 3) TEM and tubulin immunohistochemistry revealed that the main shafts of the neurites induced either by H-7 or dB-cAMP were filled with microtubules, but that the varicosities induced by H-7 contained a smaller amount of microtubules. 4. 4) The stability to colchicine was greater in the neurites induced by H-7 than in those by dB-cAMP. From these features of the neurites, it was inferred that neurite outgrowth induced by dB-cAMP is deeply related to the formation of microtubules and that the neurites induced by H-7 were involved in other processes probably including an adhesive property of cell surfaces.