Collagen I weakly interacts with the β-sheets of β₂-microglobulin and enhances conformational exchange to induce amyloid formation

Abstract

Amyloidogenesis is significant in both protein function and pathology. Amyloid formation of folded, globular proteins is commonly initiated by partial unfolding. However, how this unfolding event is triggered for proteins that are otherwise stable in their native environments is not well understood. The accumulation of the immunoglobulin protein β 2 -microglobulin (β 2 m) into amyloid plaques in the joints of long-term hemodialysis patients is the hallmark of Dialysis Related Amyloidosis (DRA). While β 2 m does not form amyloid unassisted near neutral pH in vitro, the localization of β 2 m deposits to joint spaces suggests a role for the local extracellular matrix (ECM) proteins, specifically collagens, in promoting amyloid formation. Indeed, collagen and other ECM components have been observed to facilitate β 2 m amyloid formation, but the large size and anisotropy of the complex, combined with the low affinity of these interactions, has limited atomic-level elucidation of the amyloid-promoting mechanism by these molecules. Using solution NMR approaches that uniquely probe weak interactions and large complexes, we are able to derive binding interfaces for collagen I on β 2 m and detect collagen I-induced µsms timescale dynamics in the β 2 m backbone. By combining solution NMR relaxation methods and 15 N-dark state exchange saturation transfer experiments, we propose a model in which weak, multimodal collagen I-β 2 m interactions promote exchange with a minor population of an amyloid-competent species to induce fibrillogenesis. The results portray the intimate role of the environment in switching an innocuous protein into an amyloid-competent state, rationalizing the localization of amyloid deposits in DRA. ACKNOWLEDGMENTWe acknowledge Arthur Palmer for helpful discussions. We also acknowledge with thanks the many discussions with our group members. We thank Ana Monica Nunes for contributions in the beginning of this project and Nuria Benseny-Cases, who provided critical insights in the early stages of the work. ABBREVIATIONS β 2 m, β 2 -microglobulin; DRA, Dialysis Related Amyloidosis; ECM, extracellular matrix; MHC-I, major histocompatibility complex-I; GAGglycosaminoglycan; NMR, nuclear magnetic resonance; ELISA, enzyme-linked immunosorbent assay; ThT, thioflavin T; AFM, atomic force microscopy; HSQC, heteronuclear single quantum correlation; DEST, dark-state exchange saturation transfer; OSCAR, osteoclast associated receptor; LAIR-1, leukocyte associated immunoglobulin-like receptor-1; GPVI, glycoprotein VI; CPMG, Carr-Purcell-Meiboom-Gill.

NMR unveils an N-terminal interaction interface on acetylated-α-synuclein monomers for recruitment to fibrils

“…More recently, studies have used DEST to determine site specific interactions of IDPs with membranes (32), lipopolysaccharides (33), unilamellar vesicles (34), and in self-assembly (35,36). Our laboratory has recently used 15 N-DEST to determine the interaction interfaces on immunoglobulin protein β 2 -microglobulin (β 2 m) for collagen I, which facilitates β 2 m amyloid formation (37).…”