Heat shock protein 90 is involved in regulation of hypoxia-driven proliferation of embryonic neural stem/progenitor cells

Hypoxia may regulate the proliferation of diverse stem cells. Our previous study showed that hypoxia promoted the proliferation of embryonic neural stem/progenitor cells (NPCs) and that hypoxia inducible factor-1(HIF-1) was critical in this process. HIF-1 could be stabilized under hypoxic conditions, and heat shock protein 90 (HSP90) is an essential protein that controls the activity and stabilization of HIF-1 alpha. In the present work, we investigate whether HSP90 is involved in proliferation of NPCs under hypoxia by regulating HIF-1 alpha stabilization. Geldanamycin (GA), an HSP90 inhibitor, decreased the expression of HIF-1 alpha in NPCs during hypoxia-driven proliferation and reduced the expression level of HIF-1 alpha protein under hypoxia in a time-dependent manner. The proliferation of NPCs induced by hypoxia was inhibited after GA treatment for 24 h. Another HSP90 inhibitor, radicicol, had the same effect on NPCs as GA. Furthermore, the expression of erythropoietin (EPO) and vascular endothelial growth factor (VEGF) in NPCs under hypoxia was suppressed by GA. The above data indicated that HSP90 might be involved in regulation of hypoxia-driven proliferation.