Cellular and Molecular Mechanisms Mediated by RecPrP Involved in the Neuronal Differentiation Process of Mesenchymal Stem Cells

Human Dental Pulp Stem Cells (hDPSCs) represent a type of adult mesenchymal stem cells that have the ability to differentiate in vitro in several lineages such as odontoblasts, osteoblasts, chondrocytes, adipocytes and neurons. In the current work, we used hDPSCs as the experimental model to study the role of recombinant prion protein 23⁻231 (recPrP) in the neuronal differentiation process, and in the signal pathway activation of ERK 1/2 and Akt. We demonstrated that recPrP was able to activate an intracellular signal pathway mediated by extracellular-signal-regulated kinase 1 and 2 (ERK 1/2) and protein kinase B (Akt). Moreover, in order to understand whether endogenous prion protein (PrP) was necessary to mediate the signaling induced by recPrP, we silenced PrP, demonstrating that the presence of endogenous PrP was essential for ERK 1/2 and Akt phosphorylation. Since endogenous PrP is a well-known lipid rafts component, we evaluated the role of these structures in the signal pathway induced by recPrP. Our results suggest that lipid rafts integrity play a key role in recPrP activity. In fact, lipid rafts inhibitors, such as fumonisin B1 and MβCD, significantly prevented ERK 1/2 and Akt phosphorylation induced by recPrP. In addition, we investigated the capacity of recPrP to induce hDPSCs neuronal differentiation process after long-term stimulation through the evaluation of typical neuronal markers expression such as B3-Tubulin, neurofilament-H (NFH) and growth associated protein 43 (GAP43). Accordingly, when we silenced endogenous PrP, we observed the inhibition of neuronal differentiation induced by recPrP. The combined data suggest that recPrP plays a key role in the neuronal differentiation process and in the activation of specific intracellular signal pathways in hDPSCs.