Probing a salt-induced conformational switch in β₂-microglobulin under low pH conditions

Area of Science:

• Biochemistry
• Molecular Biology
• Structural Biology

Background:

• Protein and peptide self-assembly into amyloid fibrils is linked to diseases like Parkinson's and type II diabetes.
• Dialysis-related amyloidosis (DRA) involves the amyloidogenic protein beta2-microglobulin (β2m) misfolding and accumulating in tissues.
• Soluble β2m oligomers are implicated as more toxic than fibrils, causing cellular dysfunction and death.

Purpose of the Study:

• To identify and characterize the distinct conformers of β2m during amyloid aggregation.
• To elucidate the aggregation pathway of β2m under varying conditions.
• To provide insights into the early stages of dialysis-related amyloidosis.

Main Methods:

• Controlled aggregation of β2m under low pH, varying salt concentrations, and agitation.
• Kinetic analysis to determine aggregation pathways.
• Microscopic techniques and biochemical assays to verify conformer formation and stability.

Main Results:

• Identified and characterized three aggregation stages: oligomers, protofibrils, and fibrils.
• Demonstrated that β2m oligomers and protofibrils aggregate via a nucleation-independent pathway.
• Showed that β2m fibrils form through a classical nucleation-dependent process.

Conclusions:

• Distinct conformers of β2m aggregate through different pathways.
• Understanding these pathways is crucial for deciphering the initiation and progression of DRA.
• The findings contribute to the broader understanding of amyloid formation mechanisms in disease.