PrPc activation induces neurite outgrowth and differentiation in PC12 cells: role for caveolin-1 in the signal transduction pathway

Cellular prion protein (PrPc) is a ubiquitous glycoprotein, whose physiological role is poorly characterized. It has been suggested that PrPc participates in neuritogenesis, neuroprotection, copper metabolism, and signal transduction. In this study we detailed the intracellular events induced by PrPc antibody-mediated cross-linking in PC12 cells. We found a Fyn-dependent activation of the Ras-Raf pathway, which leads to a rapid and transient phosphorylation of extracellular regulated kinases. In addition, this activation cascade relies on the engagement of integrins, and involves focal adhesion kinase activation. We demonstrated the tyrosine phosphorylation of caveolin-1 as a consequence of PrPc stimulation, and showed that phosphocaveolin-1 scaffolds and coordinates protein complexes involved in PrPc-dependent signaling. Moreover, we found that caveolin-1 phosphorylation, is a mechanism for recruiting the C-terminal Src kinase and inactivating Fyn, so as to terminate cell signaling. Furthermore our data support a significant role for PrPc as a response mediator in neuritogenesis and cell differentiation.