Dissecting the molecular unfolding and fibril formation pathway of patient-derived light chain variants in AL amyloidosis

• Applicant: Professor Dr. Johannes Buchner
• Subject Area: Biochemistry ; Biophysics
• Term: since 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 528242583

Antibodies are a pillar of our immune system. However, mutated antibody light chains (LCs) are also the causative agents of a deadly systemic disease called light chain amyloidosis (AL) in which LCs or fragments thereof form amyloid fibrils in patients which accumulate in different organs and destroy their functions. What sets this disease apart from other amyloidoses is that each patient has different mutations in the LC, which makes every case unique. In the current funding period, we have established that patient LCs contain both silent and active, disease-promoting mutations, which render the LC variable domain (VL) unstable, susceptible to proteolysis, and conformationally more dynamic. Further, we identified stabilizing or destabilizing domain interactions in the LC that influence fibril formation. Mechanistic analyses allowed us to define a pathway of molecular changes taking place during the early stages of the AL pathway. Building up on our results, we want to achieve a general picture of the traits of amyloidogenic LCs and their fragments, both biophysically and in the cellular context. The detailed aims are: (i) a comprehensive understanding of the influence of mutations on the mechanism of amyloid formation, (ii) determination of the effects of AL mutations on the biosynthesis of LCs in mammalian cells, and (iii) analysis of the influences of plasma factors on LC fibril formation. Our analysis of a large number of patient variants, including LCs from the same subtype, will identify biophysical and biochemical determinants that govern LC fibril formation including the roles that the individual LC domains play and how they influence each other. Together with our analysis of the modulating effects of extrinsic factors on amyloid formation and the biosynthesis of pathogenic LCs in mammalian cells, we aim to determine the molecular principles governing AL amyloidosis. This will lay the foundation for future research on diagnostic tools and novel therapeutic options.

• DFG Programme: Research Grants