• Prion protein;
  • Stress inducible protein 1;
  • Neurospheres;
  • Self-renewal;
  • Proliferation


Prion protein (PrPC), when associated with the secreted form of the stress-inducible protein 1 (STI1), plays an important role in neural survival, neuritogenesis, and memory formation. However, the role of the PrPC-STI1 complex in the physiology of neural progenitor/stem cells is unknown. In this article, we observed that neurospheres cultured from fetal forebrain of wild-type (Prnp+/+) and PrPC-null (Prnp0/0) mice were maintained for several passages without the loss of self-renewal or multipotentiality, as assessed by their continued capacity to generate neurons, astrocytes, and oligodendrocytes. The homogeneous expression and colocalization of STI1 and PrPC suggest that they may associate and function as a complex in neurosphere-derived stem cells. The formation of neurospheres from Prnp0/0 mice was reduced significantly when compared with their wild-type counterparts. In addition, blockade of secreted STI1, and its cell surface ligand, PrPC, with specific antibodies, impaired Prnp+/+ neurosphere formation without further impairing the formation of Prnp0/0 neurospheres. Alternatively, neurosphere formation was enhanced by recombinant STI1 application in cells expressing PrPC but not in cells from Prnp0/0 mice. The STI1-PrPC interaction was able to stimulate cell proliferation in the neurosphere-forming assay, while no effect on cell survival or the expression of neural markers was observed. These data suggest that the STI1-PrPC complex may play a critical role in neural progenitor/stem cells self-renewal via the modulation of cell proliferation, leading to the control of the stemness capacity of these cells during nervous system development. STEM CELLS 2011;29:1126–1136