Tetrameric assembly disruption impairs CXCL4 chaperon ability for DNA and type I interferon immune amplification

Area of Science:

• Immunology
• Biochemistry
• Rheumatology

Background:

• Chemokine (C-X-C motif) ligand 4 (CXCL4) is a biomarker in systemic sclerosis (SSc) and implicated in other chronic inflammatory diseases.
• CXCL4 contributes to the interferon (IFN)-I signature in SSc by forming pro-inflammatory complexes with self-DNA, activating TLR9 and inducing IFN-α in plasmacytoid dendritic cells.

Purpose of the Study:

• To investigate the structural requirements of CXCL4 for effective DNA chaperoning and TLR9 activation.
• To explore the role of CXCL4 tetramerization in amplifying IFN-I secretion.
• To identify potential pharmacological targets for SSc and related autoimmune conditions.

Main Methods:

• Utilized mutated CXCL4 peptides with altered cationic charge and impaired tetramerization.
• Assessed the impact of these mutations on DNA binding and TLR9 activation.
• Investigated the effect of small molecules destabilizing CXCL4 tetramers on IFN-α production.

Main Results:

• CXCL4 requires intact tetramerization and liquid crystalline structure formation to effectively chaperone DNA and amplify TLR9 responses.
• Pre-assembly of CXCL4 into tetramers before DNA interaction is essential for robust IFN-I secretion.
• Small molecules that disrupt CXCL4 tetramerization inhibit plasmacytoid dendritic cell IFN-α response.

Conclusions:

• CXCL4 tetramerization is a critical functional step for its pro-inflammatory activity in autoimmune settings.
• Targeting CXCL4 tetramerization presents a promising therapeutic avenue for systemic sclerosis and other autoimmune diseases characterized by CXCL4-DNA complexes.