Proceedings of The Physiological Society

University of Cambridge (2008) Proc Physiol Soc 11, PC134

Poster Communications

1H-[1,2,4]oxadiazolo-[4,3-a]quinoxalin-1-one induces neurite retraction by depolymerization of microtubules

S. Kim1, H. Lee1, D. Kim1, S. Lee1, J. Seo1, D. Shin1

1. Department of Oral Biology, BK 21 Project for Yonsei Dental Sciences, Yonsei University College of Dentistry, Seoul, South Korea.

The effect of the potent soluble guanylyl cyclase (sGC) inhibitor, 1H-[1,2,4] oxadiazolo[4,3-a]quinoxalin-1-one (ODQ), on neurite outgrowth and retraction was investigated in PC12 cells. ODQ inhibited NGF-, Y-27632- and staurosporine-induced neurite outgrowth in a concentration-dependent manner and triggered neurite retraction. The nitric oxide (NO) scavenger, 2-(4-carboxyphenyl)-4,4,5,5-tetramethyl-imidazoline-1-oxyl-3-oxide (PTIO), had little effect on neurite outgrowth. In the presence of ODQ, treatment of PC12 cells with the cell permeable cGMP analogue, 8-bromo-cGMP, failed to re-trigger neurite outgrowth. Furthermore, the depletion of sGC by RNA interference failed to prevent Y-27632- and staurosporine-induced neurite outgrowth. These results indicate that the NO/sGC/cGMP signaling cascade is not critically involved in ODQ-induced neurite remodeling. We next investigated the effect of ODQ on microtubule network. Western blot analysis revealed that treatment of PC12 cells with ODQ increased the proportion of unpolymerized tubulin and decreased that of polymerized tubulin, suggesting that ODQ caused to disassemble the microtubule network. The effect of ODQ on microtubule network and neurite retraction was reversed by dithionite. In addition, ODQ was shown to depolymerize purified tubulin in vitro and the addition of reducing agents, such as dithionite and DTT, restored the polymerization activity of tubulin. These results suggest that ODQ induces neurite retraction probably by direct depolymerization of microtubules resulting from tubulin oxidation.

Where applicable, experiments conform with Society ethical requirements