Interferon-a Receptor, Type I, Subunit I (IFNAR1) associates with IFNAR2 to form the type I interferon receptor. This interferon receptor is a receceptor for interferons alpha and beta. Binding to type I IFNs triggers tyrosine phosphorylation of a number of proteins including JAKs, TYK2, STAT proteins and IFNR alpha- and beta-subunits themselves. IFN receptors are present in all tissues and even on the surface of most IFN-resistant cells. Down regulation of IFNAR1 is influenced by phosphorylation of Serine 535 and 539.