A hot spot on interferon alpha/beta receptor subunit 1 (IFNAR1) underpins its interaction with interferon-beta and dictates signaling.

Abstract

The interaction of IFN-beta with its receptor IFNAR1 (interferon alpha/beta receptor subunit 1) is vital for host-protective anti-viral and anti-proliferative responses, but signaling via this interaction can be detrimental if dysregulated. Whereas it is established that IFNAR1 is an essential component of the IFNAR signaling complex, the key residues underpinning the IFN-beta-IFNAR1 interaction are unknown. Guided by the crystal structure of the IFN-beta-IFNAR1 complex, we used truncation variants and site-directed mutagenesis to investigate domains and residues enabling complexation of IFN-beta to IFNAR1. We have identified an interface on IFNAR1-subdomain-3 that is differentially utilized by IFN-beta and IFN-alpha for signal transduction. We used surface Plasmon resonance and cell-based assays to investigate this important IFN-beta binding interface that is centered on IFNAR1 residues Tyr240 and Tyr274 binding the C and N termini of the Band Chelices of IFN-beta, respectively. Using IFNAR1 and IFN-beta variants, we show that this interface contributes significantly to the affinity of IFN-beta for IFNAR1, its ability to activate STAT1, the expression of interferon stimulated genes, and ultimately to the anti-viral and anti-proliferative properties of IFN-beta. These results identify a key interface created by IFNAR1 residues Tyr240 and Tyr274 interacting with IFN-beta residues Phe63, Leu64, Glu77, Thr78, Val81, and Arg82 that underlie IFN-beta-IFNAR1-mediated signaling and biological processes.Copyright © 2017 by The American Society for Biochemistry and Molecular Biology, Inc. Published in the U.S.A.