Dimer Dissociation and Aggregation Hot-spot Exposure Synergistically Accelerate Light Chain Variable Domain...

Area of Science:

• Biochemistry
• Molecular Biology
• Medical Science

Background:

• Light chain amyloidosis (AL) is a severe systemic disease.
• It results from antibody light chain (LC) fragment aggregation in organs.
• The cardiotoxic AL55 light chain's variable domain (VL) is prone to aggregation.

Purpose of the Study:

• Investigate early aggregation events of the AL55 VL domain.
• Understand factors regulating aggregation kinetics and pathways.
• Identify key regions involved in AL amyloid fibril formation.

Main Methods:

• Protein expression and purification of AL55 VL domain.
• Biophysical techniques (e.g., spectroscopy, size-exclusion chromatography) to monitor aggregation.
• pH and concentration-dependent studies to probe aggregation mechanisms.

Main Results:

• Dimer disruption and exposure of aggregation-prone regions (APRs) synergistically accelerate VL aggregation.
• At neutral pH, dimerization limits aggregation-competent monomers.
• Lowering pH or dilution disrupts dimers, exposing APRs and increasing aggregation rates.
• Chemical stabilization of APRs reduces aggregation despite high monomer availability.

Conclusions:

• AL55 VL domain aggregation is modulated by dimer dissociation and electrostatic interactions.
• A specific conformation involving N-terminal and dimeric interface regions drives aggregation.
• These findings elucidate mechanisms of AL amyloid formation and potential therapeutic targets.