Biology Reference
In-Depth Information
Events in Uninfected Cells
Interferons also provide a warning system to uninfected cells in the
vicinity of infected ones and prepare the former to counter an
impending viral infection. These events in uninfected cells are based
on an interferon-signaling pathway (Fig. 3). The binding of IFN to
its cognate receptor results in activation of the JAK/STAT signaling
pathway, culminating in the activation of several IFN-
-inducible
genes. In an uninduced state, the cytoplasmic domains of type 1 IFN
receptors, IFNAR-1 and IFNAR-2, remain associated with Janus
tyrosine kinases Jak1 and Tyk2.
55,56
The binding to IFN-
α
/
β
to these
receptors causes the phosphorylation and activation of Jak1 and Tyk2;
these activated kinases in turn phosphorylate tyrosine residues in the
cytoplasmic domains of the receptor. These phosphotyrosines act as
binding sites for the STAT (signal transducers and activators of tran-
scription) proteins through their src homology 2 (SH2) domains.
α
/
β
Fig. 3.
The JAK-STAT interferon signaling pathway and the effects of
hepatitis viruses.
