Abstract
Background
Systemic AL amyloidosis arises from the misfolding of patient-specific immunoglobulin light chains (LCs). Potential drivers of LC amyloid formation are mutational changes and post-translational modifications (PTMs). However, little information is available on the exact primary structure of the AL proteins and their precursor LCs.
Objective
We analyse the exact primary structure of AL proteins extracted from 10 λ AL amyloidosis patients and their corresponding precursor LCs.
Materials and Methods
By cDNA sequencing of the precursor LC genes in combination with mass spectrometry of the AL proteins, the exact primary structure and PTMs were determined. This information was used to analyse their biochemical properties.
Results
All AL proteins comprise the VL and a small part of the CL with a common C-terminal truncation region. While all AL proteins retain the conserved native disulphide bond of the VL, we found no evidence for presence of other common PTMs. The analysis of the biochemical properties revealed that the isoelectric point of the VL is significantly increased due to introduced mutations.
Conclusion
Our data imply that mutational changes influence the surface charge properties of the VL and that common proteolytic processes are involved in the generation of the cleavage sites of AL proteins.
Acknowledgements
We thank the Deutsche Forschungsgemeinschaft for funding (FOR2969; grant numbers: HA 7138/3 to C.H., HE 8472/1-1 to U.H., HU 2400/1-1 to S.H., SCHO 1364/2-1 to S. O. S.).
Disclosure statement
No potential conflict of interest was reported by the author(s).
Data availability statement
The data that support the findings of this study are available from the corresponding author, C. H., upon reasonable request. In addition, the MS data are accessible in the MassIVE database under the dataset identifier MassIVE MSV000089772.