Increased Src kinase level results in increased protein tyrosine phosphorylation in scrapie-infected neuronal cell lines

We have studied how prion infection may affect the Src kinase activity in three different neuronal cell lines, ScGT1 and ScN2a, where ScGT1 were generated in our laboratory. By immunoblotting, using clone 28 - a monoclonal antibody recognizing active Src, we have found a 32+/-6.3% and 75+/-7.7% elevation in Src activity in ScGT1 and ScN2a cells, respectively, compared to uninfected cells. Immunocomplex in vitro kinase assay confirmed the increased Src activity. The increased Src kinase activity in scrapie-infected cells was further shown to correlate to an increased level of Src protein. In addition, an important increase in the protein tyrosine phosphorylation signal was observed in ScGT1 and ScN2a cells, which was further shown to be Src-dependent, as treatment with PP2 - a Src family kinase specific inhibitor, reversed the protein tyrosine phosphorylation profile. Abnormal Src-kinase activation and subsequent protein tyrosine phosphorylation may be key elements in the neuropathology of the prion diseases.