Systematic Search for a Predictor for the Clinical Observables of Alzheimer's Disease

A Self-Consistent Molecular Mechanism of β2-Microglobulin Aggregation

Despite the consensus on the origin of dialysis-related amyloidosis (DRA) being β2-microglobulin (β2m) aggregation, the debate on the underlying mechanism persists because of the continuous emergence of β2m variant- and pH-dependent contradictory results. By characterizing the native monomeric (initiation) and aggregated fibrillar (termination) states of β2m via a combination of two enhanced sampling approaches, we here propose a mechanism that explains the heterogeneous behavior of wild-type (WT) and pathogenic (V27M and D76N) β2m variants in physiological and disease-pertinent acidic pH environments. It appears that the higher retainment of monomeric native folds at neutral pH (native-like) distinguishes pathogenic β2m mutants from the WT (moderate loss). However, at acidic pH, all three variants behave similarly in producing a substantial amount of partially unfolded states (conformational switch, propensity), though with different extents (WT < V27M < D76N). Whereas at the fibrillar end, all β2m variants display a pH-dependent protofilament separation pathway and a higher protofilament binding affinity (stability) at acidic pH, where the relative order of binding affinity (WT < V27M < D76N) remains consistent with pH modulation. Combining these observations, we conclude that β2m variants possibly shift from native-like aggregation to conformational switch-initiated fibrillation as the pH is altered from neutral to acidic. The combined propensity-stability approach based on the initiation and termination points of β2m aggregation not only assists us in deciphering the mechanism but also emphasizes the protagonistic roles of both terminal points in the overall aggregation process.

Scan-Find-Scan-Model: Discrete Site-Targeted Suppressor Design Strategy for Amyloid-β

Alzheimer's disease is undoubtedly the most well-studied neurodegenerative disease. Consequently, the amyloid-β (Aβ) protein ranks at the top in terms of getting attention from the scientific community for structural property-based characterization. Even after decades of extensive research, there is existing volatility in terms of understanding and hence the effective tackling procedures against the disease that arises due to the lack of knowledge of both specific target- and site-specific drugs. Here, we develop a multidimensional approach based on the characterization of the common static-dynamic-thermodynamic trait of the monomeric protein, which efficiently identifies a small target sequence that contains an inherent tendency to misfold and consequently aggregate. The robustness of the identification of the target sequence comes with an abundance of a priori knowledge about the length and sequence of the target and hence guides toward effective designing of the target-specific drug with a very low probability of bottleneck and failure. Based on the target sequence information, we further identified a specific mutant that showed the maximum potential to act as a destabilizer of the monomeric protein as well as enormous success as an aggregation suppressor. We eventually tested the drug efficacy by estimating the extent of modulation of binding affinity existing within the fibrillar form of the Aβ protein due to a single-point mutation and hence provided a proof of concept of the entire protocol.