Multifaceted Activities of Type I Interferon Are Revealed by a Receptor Antagonist

Abstract

Type I interferons (IFNs), including various IFN-α isoforms and IFN-β, are a family of homologous, multifunctional cytokines. IFNs activate different cellular responses by binding to a common receptor that consists of two subunits, IFNAR1 and IFNAR2. In addition to stimulating antiviral responses, they also inhibit cell proliferation and modulate other immune responses. We characterized various IFNs, including a mutant IFN-α2 (IFN-1ant) that bound tightly to IFNAR2 but had markedly reduced binding to IFNAR1. Whereas IFN-1ant stimulated antiviral activity in a range of cell lines, it failed to elicit immunomodulatory and antiproliferative activities. The antiviral activities of the various IFNs tested depended on a set of IFN-sensitive genes (the “robust” genes) that were controlled by canonical IFN response elements and responded at low concentrations of IFNs. Conversely, these elements were not found in the promoters of genes required for the antiproliferative responses of IFNs (the “tunable” genes). The extent of expression of tunable genes was cell type–specific and correlated with the magnitude of the antiproliferative effects of the various IFNs. Although IFN-1ant induced the expression of robust genes similarly in five different cell lines, its antiviral activity was virus- and cell type–specific. Our findings suggest that IFN-1ant may be a therapeutic candidate for the treatment of specific viral infections without inducing the immunomodulatory and antiproliferative functions of wild-type IFN.

Type I Interferon Signaling Is Decoupled from Specific Receptor Orientation through Lenient Requirements of the Transmembrane Domain

“…In Fig. 1E, we show the level of gene induction (⌬⌬C T relative to non-treated) of a representative set of previously defined robust and tunable genes (15). Tunable genes were only slightly up-regulated in HUH7 cells, even at the highest IFN␣2 concentration (for example, CXCL10 levels were only 2-3-fold higher after induction with 1000 pM IFN␣2).…”

“…Data are presented using the NetWalker analysis tool. The upper eight genes are tunable genes, and the lower 12 genes are robust genes (15). The colors represent the value of a given gene (rows) in a specific mutant and concentration of interferon (columns).…”

“…These results demonstrate that the different IFNAR1 mutations activate the expression of IFI6 and MX1 to the same extent and that the efficacy of the receptors for activation is the same. IFI6 and MX1 are robust genes, which are highly sensitive to interferon induction (15). To evaluate a wider range of interferon-stimulated genes, including both robust and tunable genes (which are cell type-specific and require much higher IFN concentration for induction), we used the Fluidigm technology, where up to 96 different genes from 96 different biological samples can be evaluated simultaneously.…”

“…Structurally different members of type I IFNs bind to the same cell surface receptor but mediate differential responses that result from differences in binding affinities, concentration of IFN, and duration of activation (5-13). Differential signaling is realized through robust (antiviral) versus tunable (antiproliferative and immunomodulatory) gene induction leading to different phenotypic outcomes (14,15). Receptor dimerization drives the activation of cytosolic associated Janus family kinases (JAKs), which in turn initiate downstream signaling cascades that propagate the signal into the nucleus and regulate gene transcription mainly via signal transducer and activator of transcription (STAT) proteins (11, 13, 16 -18).…”

Cytokine Activation by Antibody Fragments Targeted to Cytokine-Receptor Signaling Complexes

“…AcCS Potentiate the Antiviral Activity of IFN Mutants without Activating Antiproliferative Activity-Genes required for AV activity have been shown to have robust promoters that respond to weak IFN signaling, whereas promoters in genes associated with AP activity require stronger IFN induction (7). Studies on HL116 cells suggest the IFN-IFNAR2 interaction mediates IFN potency, whereas IFNAR1 regulates IFN potency and gene expression levels.…”