The C-terminus of IFN gamma is sufficient for intracellular function

Area of Science:

• Immunology
• Molecular Biology
• Cell Signaling

Background:

• Murine interferon gamma (IFN-γ) and its C-terminal peptide bind to a specific region on the murine IFN-γ receptor's cytoplasmic domain.
• This receptor region shares high homology with its human counterpart.

Purpose of the Study:

• To investigate the binding of human IFN-γ and its C-terminal peptide to the human IFN-γ receptor.
• To determine if the interaction between IFN-γ peptides and receptors is species-specific.
• To explore the functional consequences of C-terminal IFN-γ peptide treatment on immune cells.

Main Methods:

• Peptide synthesis and binding assays using synthetic peptides representing receptor domains.
• Treatment of murine macrophage cell lines with murine and human IFN-γ C-terminal peptides.
• Assessment of MHC class II molecule expression via flow cytometry.
• Viral resistance assays using vesicular stomatitis virus (VSV).

Main Results:

• Human IFN-γ and its C-terminal peptide bind to the human IFN-γ receptor cytoplasmic domain.
• The binding interaction between IFN-γ peptides and receptor domains is species non-specific.
• Treatment with either murine or human IFN-γ C-terminal peptides upregulated MHC class II expression by 10-fold.
• Treated cells showed significantly increased resistance to VSV infection (10^6–10^9-fold reduction in yield).

Conclusions:

• The C-terminus of IFN-γ plays a direct role in initiating intracellular signaling pathways.
• The species non-specific binding suggests a conserved mechanism for IFN-γ receptor interaction.
• These findings may indicate a general signaling mechanism for extracellular signaling molecules.