Poster Presentation The 47th Lorne Conference on Protein Structure and Function 2022

Does the Dimerization of IFNAR2 improve its affinity for JAK1 FERM-SH2? (#167)

Amarachi Amah 1 2 , Jason Brouwer 1 2 , Nadia Kershaw 1 2 , Jeff Babon 1 2
  1. Walter and Eliza Hall institute, Parkville, Victoria, Australia
  2. Medical biology, University of Melbourne , Parkville, Victoria, Australia

The interaction between Janus kinase 1 (JAK1) and the intracellular domain (ICD) of cytokine receptors is essential for cytokine signalling. JAK1 binds to specific sites termed box 1 and box 2 on the ICD of cytokine receptors through its FERM-SH2 domain.

Biochemical analysis revealed that JAK1 FERM-SH2 binds with high affinity (KD=70nM) to peptides containing both box 1 and box 2 from the class II cytokine receptor interferon lambda receptor 1 (IFNLR1). The specific motif “PxxLxF” in the ICD of IFNLR1 was shown to be essential for its interaction with JAK1 FERM-SH2.

Another class II cytokine receptor IFNAR2 is thought to associate with, and signal through, JAK1. Sequence alignment revealed that the PxxLxF motif is conserved in the ICD of interferon alpha receptor 2 (IFNAR2). Our preliminary results show that in contrast to IFNLR1, JAK1 FERM-SH2 binds weakly to IFNAR2 peptides containing the PxxLxF motif. Given the perceived importance of the conserved PxxLxF motif, it is unclear why JAK1 FERM-SH2 has only a weak affinity for IFNAR2.

Studies have shown that the dimerization of cytokine receptors is essential for the activation of JAK. However, there are no reports on how receptor dimerization directly affects binding affinities for JAK. This study aims to investigate whether the dimerization of IFNAR2 improves its association with JAK1 FERM-SH2. I generated IFNAR2 dimers using the FC-Fusion technology and investigated binding to JAK1 FERM-SH2 using surface plasmon resonance. I observed no significant difference between monomeric versus dimeric IFNAR2 in these assays.

In conclusion, the dimerization of IFNAR2 does not appear to improve affinity for JAK1 FERM-SH2. Further studies are needed to understand why JAK1 FERM-SH2 binds poorly to IFNAR2 box 1 and 2.