Interferon alpha/beta receptor 1 (Anifrolumab) is a ~63 kDa protein. Together with IFNAR2, forms the heterodimeric receptor for type I interferons (including interferons alpha, beta, epsilon, omega and kappa). Type I interferon binding activates the JAK-STAT signaling cascade, resulting in transcriptional activation or repression of interferon-regulated genes that encode the effectors of the interferon response. Mechanistically, type I interferon-binding brings the IFNAR1 and IFNAR2 subunits into close proximity with one another, driving their associated Janus kinases (JAKs) (TYK2 bound to IFNAR1 and JAK1 bound to IFNAR2) to cross-phosphorylate one another. The activated kinases phosphorylate specific tyrosine residues on the intracellular domains of IFNAR1 and IFNAR2, forming docking sites for the STAT transcription factors. STAT proteins are then phosphorylated by the JAKs, promoting their translocation into the nucleus to regulate expression of interferon-regulated genes. 1. Russell-Harde, D. et al. (1999) Biochemical and biophysical research communications 255, 539-44. PMID: 100497442. Kumar, KG. et al. (2003) The EMBO journal 22, 5480-90. PMID: 145321203. Kumar, KG. et al. (2004) The Journal of biological chemistry 279, 46614-20. PMID: 153377707. Hernandez, N. et al. (2019) The Journal of experimental medicine 216, 2057-2070. PMID: 312702478. Gothe, F. et al. (2022) Clinical infectious diseases : an official publication of the Infectious Diseases Society of America 74, 136-139. PMID: 332526449. Bastard, P. et al. (2022) The Journal of experimental medicine 219. PMID: 3544241810. Abramovich, C. et al. (1994) The EMBO journal 13, 5871-7. PMID: 7813427 | 
