How unique is interferon-β within the type I interferon family?

All type I interferons share structural homology and bind to a common heterodimeric receptor consisting of the IFNAR1 and IFNAR2 subunits, which are expressed on most cell types. Although binding to the same receptor pair, they evoke a broad range of activities within the cell affecting the expression of numerous genes and resulting in profound cellular changes. Differential activation results from multiple levels of cellular and molecular events including binding affinity, receptor density, cell type-specific variations, and post-translational modification of signaling molecules downstream. Within the type I interferon family the Asn-Gly-Arg (NGR) sequence motif is unique to interferon-β and, together with its deamidated variants Asp-Gly-Arg (DGR) and iso-Asp-Gly-Arg (iso-DGR), imparts additional binding specificities that go beyond that of the canonical IFNAR1/IFNAR2. These warrant further investigations and functional studies and may eventually shed new light on differential effects observed for this molecule in oncology and autoimmune diseases.