C-terminal unfolding of an amyloidogenic β₂-microglobulin fragment: ΔN6β₂-microglobulin

Abstract

Objectives: A β₂-microglobulin (β₂m) fragment that lacks the first six amino acids, i.e., ΔN6β₂-microglobulin (ΔN6β₂m), is an endogenous, proteolytically derived, amyloidogenic fragment of β₂m, the precursor protein in Aβ₂M amyloidosis (dialysis-related amyloidosis). As reports suggest the importance of C-terminal unfolding for the amyloidogenicity of β₂m, in this study we aimed to investigate conformational characteristics of ΔN6β₂m related to amyloidogenicity. We also measured the concentration of an amyloidogenic intermediate of β₂m with C-terminal unfolding (β₂m92-99) in serum samples from 10 patients undergoing hemodialysis (HD).

Methods: We utilized capillary electrophoretic analysis, surface plasmon resonance and enzyme-linked immunosorbent assay.

Results and conclusions: We confirmed the normal core structure of ΔN6β₂m with a commercial monoclonal anti-β₂m antibody. In addition, using the specific monoclonal antibody for the C-terminal peptide, i.e. mAb 92-99, we confirmed unfolding in the C-terminal region of ΔN6β₂m. On the basis of these findings, we established an ELISA to measure β₂m92-99 using ΔN6β₂m as a standard molecule in circulation. However, we did not detect β₂m92-99 in serum from 10 HD patients, despite the absence of uremic inhibitors in the serum.

• Amyloidogenicity
• capillary electrophoresis
• dialysis-related amyloidosis
• enzyme-linked immunosorbent assay
• hemodialysis
• monoclonal antibody 92-99
• surface plasmon resonance

Declaration of interest

The authors report no conflicts of interest. This work was supported by Health Labour Sciences Research KAKENHI Grant 11103528.