Effect of somatic mutation on DNA binding properties of anti-DNA autoantibodies

Area of Science:

• Immunology
• Molecular Biology
• Structural Biology

Background:

• Autoantibodies targeting DNA are key features of systemic lupus erythematosus (SLE).
• A subset of these autoantibody-DNA complexes accumulate in kidney tissue, causing damage and potentially leading to organ failure.
• Understanding the molecular basis of autoantibody-DNA interactions is crucial for elucidating SLE pathogenesis.

Purpose of the Study:

• To investigate the role of specific amino acid differences in mediating the DNA binding properties of clonally related autoantibodies.
• To explore the link between the thermodynamic and kinetic parameters of autoantibody-DNA recognition and disease pathogenesis in SLE.
• To provide a structural and mechanistic basis for understanding how autoantibody binding to DNA influences tissue damage.

Main Methods:

• Isolation and characterization of three clonally related anti-DNA autoantibodies (11F8, 9F11, 15B10) from an autoimmune mouse model.
• Determination of thermodynamic and kinetic parameters for the recognition of various DNA sequences by each antibody.
• Development of a molecular model of the 11F8 autoantibody bound to its high-affinity DNA sequence.

Main Results:

• The autoantibody 11F8 exhibits sequence-specific binding to single-stranded DNA (ssDNA) and is associated with tissue damage.
• Autoantibodies 9F11 and 15B10 display non-specific ssDNA binding and are considered benign.
• Five amino acid differences in the primary sequence were identified as critical for the distinct DNA binding properties of these antibodies.
• Structural analysis suggests specific residues and a somatic mutation in 11F8 contribute to its ssDNA recognition motif and specificity.

Conclusions:

• Specific amino acid variations within clonally related autoantibodies dictate their DNA binding characteristics, influencing their pathogenic potential in SLE.
• The distinct thermodynamic and kinetic profiles of these antibodies provide insights into molecular recognition strategies and their contribution to disease.
• The findings highlight the importance of autoantibody fine-tuning in SLE pathogenesis and offer a foundation for understanding disease mechanisms at a molecular level.