Structural and Thermodynamic Characteristics of Amyloidogenic Intermediates of ß-2-Microglobulin.

ß-2-microglobulin (ß2m) self-aggregates to form amyloid fibril in renal patients taking long-term dialysis treatment. Despite the extensive structural and mutation studies carried out so far, the molecular details on the factors that dictate amyloidogenic potential of ß2m remain elusive. Here we report molecular dynamics simulations followed by the solvation thermodynamic analyses on the wild-type ß2m and D76N, D59P, and W60C mutants at the native (N) and so-called aggregation-prone intermediate (IT) states, which are distinguished by the native cis- and non-native trans-Pro32 backbone conformations. Three major structural and thermodynamic characteristics of the IT-state relative to the N-state in ß2m protein are detected that contribute to the increased amyloidogenic potential: (i) the disruption of the edge D-strand, (ii) the increased solvent-exposed hydrophobic interface, and (iii) the increased solvation free energy (less affinity toward solvent water). Mutation effects on these three factors are shown to exhibit a good correlation with the experimentally observed distinct amyloidogenic propensity of the D76N (+), D59P (+), and W60C (-) mutants (+/- for enhanced/decreased). Our analyses thus identify the structural and thermodynamic characteristics of the amyloidogenic intermediates, which will serve to uncover molecular mechanisms and driving forces in ß2m amyloid fibril formation.

Chemical Fluorescent Probe for Detection of Aß Oligomers.

Aggregation of amyloid ß-peptide (Aß) is implicated in the pathology of Alzheimer's disease (AD), with the soluble, Aß oligomeric species thought to be the critical pathological species. Identification and characterization of intermediate species formed during the aggregation process is crucial to the understanding of the mechanisms by which oligomeric species mediate neuronal toxicity and following disease progression. Probing these species proved to be extremely challenging, as evident by the lack of reliable sensors, due to their heterogeneous and transient nature. We describe here an oligomer-specific fluorescent chemical probe, BoDipy-Oligomer (BD-Oligo), developed through the use of the diversity-oriented fluorescent library approach (DOFLA) and high-content, imaging-based screening. This probe enables dynamic oligomer monitoring during fibrillogenesis in vitro and shows in vivo Aß oligomers staining possibility in the AD mice model.