Domains of interaction between alpha interferon and its receptor components

Area of Science:

• Immunology
• Molecular Biology
• Virology

Background:

• Human interferons (IFNs) exhibit species-specific binding and activity.
• The interferon alpha/beta receptor (IFNAR) mediates IFN signaling.
• Understanding IFN-receptor interactions is crucial for therapeutic development.

Purpose of the Study:

• To investigate the role of bovine (Bo) or human (Hu) IFNAR in overcoming species-specific binding constraints of human IFNs on mouse cells.
• To identify key regions within IFNs responsible for receptor interaction and activity.
• To propose a model for IFN-IFNAR interaction.

Main Methods:

• Transfection of mouse cells with Bo or Hu IFNAR.
• Analysis of human IFN (alpha1, alpha2, alpha8) binding and activity on transfected cells.
• Site-directed mutagenesis of an IFN hybrid (alpha8[60]alpha1[92]alpha8) to alter receptor preference.
• Review of published IFN hybrid scanning and structural data.

Main Results:

• Bo IFNAR expression significantly increased binding of human IFNs alpha1, alpha2, and alpha8 on mouse cells.
• Increased activity was observed for IFN-alpha2 and IFN-alpha8, but not IFN-alpha1, upon Bo IFNAR expression.
• IFN-alpha1 acted as a competitive antagonist to IFN-alpha2 and IFN-alpha8 at low concentrations.
• Specific mutations (K84E, Y90D) in an IFN hybrid conferred parental IFN-alpha8-like binding preference for Hu IFNAR in mouse cells.
• Mutations at positions 84 and 90, located on IFN's C-helix, are critical for receptor interaction.

Conclusions:

• The IFNAR component plays a critical role in modulating species-specific IFN binding and activity.
• Specific residues on the IFN C-helix are crucial for determining receptor interaction and preference.
• A model of IFN-IFNAR interaction is proposed, distinguishing binding and activity phases and suggesting further receptor interactions.