UFMylation inhibits the proinflammatory capacity of interferon-γ-activated macrophages

Area of Science:

• Immunology
• Molecular Biology
• Cellular Biology

Background:

• Interferon-gamma (IFN-γ) is crucial for cellular immunity but requires balancing with inhibitory mechanisms to prevent tissue damage.
• Dysregulated IFN-γ responses can lead to immunopathology.
• Identifying negative regulators of IFN-γ signaling is essential for understanding immune homeostasis.

Purpose of the Study:

• To identify novel negative regulators of IFN-γ responses in macrophages using a genome-wide CRISPR knockout screen.
• To investigate the role of the ubiquitin-fold modifier (Ufm1) conjugation system (UFMylation) in modulating immune responses.
• To elucidate the molecular mechanisms by which UFMylation influences IFN-γ signaling and cellular immunity.

Main Methods:

• Genome-wide CRISPR knockout screen in a macrophage cell line.
• Analysis of transcriptional and cellular changes in response to IFN-γ and lipopolysaccharide.
• Investigation of endoplasmic reticulum stress pathways (Ern1, Xbp1) in UFMylation-deficient cells.
• Assessment of UFMylation's role in resistance to influenza infection in mice.

Main Results:

• The ubiquitin-fold modifier (Ufm1) conjugation system (UFMylation) was identified as a negative regulator of IFN-γ and lipopolysaccharide responses.
• UFMylation-deficient macrophages exhibited enhanced IFN-γ activation and increased transcriptional responses.
• IFN-γ response enhancement in UFMylation-deficient cells was dependent on endoplasmic reticulum stress pathways involving Ern1 and Xbp1.
• UFMylation in myeloid cells is essential for resistance to influenza infection in mice.

Conclusions:

• The UFMylation pathway plays a critical, previously unrecognized role in inhibiting inflammatory responses mediated by IFN-γ.
• UFMylation acts as a molecular brake on IFN-γ signaling, involving endoplasmic reticulum stress pathways.
• This study identifies a novel link between UFMylation and innate immunity, with implications for host defense against infections like influenza.