Signal transduction in neurons: effects of cellular prion protein on fyn kinase and ERK1/2 kinase

BACKGROUND: It has been reported that cellular prion protein (PrP(c)) co-localizes with caveolin-1 and participates to signal transduction events by recruiting Fyn kinase. As PrP(c) is a secreted protein anchored to the outer surface membrane through a glycosylphosphatidylinositol (GPI) anchor ((sec)PrP) and caveolin-1 is located in the inner leaflet of plasma membrane, there is a problem of how the two proteins can physically interact each other and transduce signals. RESULTS: By using the GST-fusion proteins system we observed that PrP(c) strongly interacts with caveolin-1 scaffolding domain and with a caveolin-1 hydrophilic C-terminal region, but not with the caveolin-1 N-terminal region. In vitro binding experiments were also performed to define the site(s) of PrP(c) interacting with cav-1. The results are consistent with a participation of PrP(c) octapeptide repeats motif in the binding to caveolin-1 scaffolding domain. The caveolar localization of PrP(c) was ascertained by co-immunoprecipitation, by co-localization after flotation in density gradients and by confocal microscopy analysis of PrP(c) and caveolin-1 distributions in a neuronal cell line (GN11) expressing caveolin-1 at high levels. CONCLUSIONS: We observed that, after antibody-mediated cross-linking or copper treatment, PrP(c) was internalized probably into caveolae. We propose that following translocation from rafts to caveolae or caveolae-like domains, (sec)PrP could interact with caveolin-1 and induce signal transduction events.