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. 2019 Aug 23;8(9):963. doi: 10.3390/cells8090963

Figure 2.

Figure 2

Signaling pathways of type I and type III IFN receptors. Type I and type III IFN receptors are heterodimers and consist of different receptor chains (IFNAR1 and IFNAR2 for the type I IFN receptor and IFNLR1 and IL10R2 for the type III IFN receptor). Both receptors are associated with two kinases from the JAK family: JAK1 and TYK2 (tyrosine kinase 2). When ligating to their cognate ligand, JAK kinases auto-phosphorylate the IFN receptor, which results in the recruitment of signal transducer and activator of transcription (STAT) proteins, phosphorylation, dimerization, and nuclear translocation. In particular, STAT1, STAT2, and IFN-regulatory factor 9 (IRF9) form interferon-stimulated gene factor 3 (ISGF3) complexes and bind to IFN-stimulated response element (ISRE) sequences, thus activating classical antiviral genes. Additionally, STAT1 homodimers bind to gamma-activated sequences (GASs), thus inducing the activation of pro-inflammatory genes.