Radicicol Potentiates Neurotrophin-Mediated Neurite Outgrowth and Survival of Cultured Sensory Neurons from Chick Embryo

Abstract: Radicicol, an antifungal antibiotic with markedly low toxicity, is a potent inhibitor of the Src family of protein tyrosine kinases and causes morphological reversion of v-src-transformed fibroblasts. Recently, this antibiotic was also found to inhibit Raf kinase. In the present study, we found that nanomolar concentrations of radicicol (10 ng/ml) enhanced the survival and neurite outgrowth of neurons from embryonic chick dorsal root ganglia (DRGs) and sympathetic ganglia. It potentiated the trophic effects of nerve growth factor, brain-derived neurotrophic factor, and neurotrophin-3 on the cultured DRG neurons. This concentration of radicicol did not alter the tyrosine phosphorylation of Trk receptors or the activity of mitogen-activated protein (MAP) kinases. Wortmannin, an inhibitor of phosphatidylinositol 3-kinase (P13-kinase), did not inhibit radicicol, excluding the involvement of P13-kinase in the radicicol-dependent trophic actions. These results suggest that radicicol mediates neuronal growth presumably via a mechanism not involving the activation of Trk receptors, MAP kinase, or P13-kinase.