Activation of the Jak-Stat pathway in cells that exhibit selective sensitivity to the antiviral effects of IFN-β compared with IFN-α

We determined whether selective activation of components of the Jak- Stat pathway by different type I interferons (IFN) occurs in human myocardial fibroblasts that exhibit much higher sensitivity to the antiviral effects of IFN-β than of IFN-α. Similar levels of activation of the Tyk2 kinase and the Stat3 transcription factor were induced in response to either IFN-β or IFN-α treatment. However, activation of the Jak1 tyrosine kinase was detectable only in IFN-β-treated but not IFN-α-treated cells. Consistent with this, tyrosine phosphorylation of Stat1 and Stat2 and formation of the IFN-stimulated gene factor 3 (ISGF3) complex occurred to a much higher degree in response to IFN-β stimulation. These findings demonstrate that differential activation of distinct components of the Jak-Stat pathway by different type I IFN can occur. Furthermore, they strongly suggest that such selective activation of accounts for the occurrence of differences in the antiviral properties of distinct type I IFN in certain cell types.