Genipin and pyrogallol: Two natural small molecules targeting the modulation of disordered proteins in Alzheimer's disease.

Alzheimer's disease (AD) is characterized by the aggregation of disordered proteins, such as amyloid beta (Aß) and tau, leading to neurotoxicity and disease progression. Despite numerous efforts, effective inhibitors of Aß and tau aggregates have not been developed. Thus, we aimed to screen natural small molecules from crude extracts that target various pathologies and are prescribed for patients with neurological diseases. In this study, we screened 162 natural small molecules prescribed for neurological diseases and identified genipin and pyrogallol as hit compounds capable of simultaneously regulating the aggregation of Aß and tau K18. Moreover, we confirmed the dual modulatory effects of these compounds on the reduction of amyloid-mediated neurotoxicity in vitro and the disassembly of preformed Aß42 and tau K18 fibrils. Furthermore, we observed the alleviatory effects of genipin and pyrogallol against AD-related pathologies in triple transgenic AD mice. Molecular dynamics and docking simulations revealed the molecular interaction dynamics of genipin and pyrogallol with Aß42 and tau K18, providing insights into their suppression of aggregation. Our findings suggest the therapeutic potential of genipin and pyrogallol as dual modulators for the treatment of AD by inhibiting aggregation or promoting dissociation of Aß and tau.

Decoding the Roles of Amyloid-ß (1-42)'s Key Oligomerization Domains toward Designing Epitope-Specific Aggregation Inhibitors.

Fibrillar amyloid aggregates are the pathological hallmarks of multiple neurodegenerative diseases. The amyloid-ß (1-42) protein, in particular, is a major component of senile plaques in the brains of patients with Alzheimer's disease and a primary target for disease treatment. Determining the essential domains of amyloid-ß (1-42) that facilitate its oligomerization is critical for the development of aggregation inhibitors as potential therapeutic agents. In this study, we identified three key hydrophobic sites (17LVF19, 32IGL34, and 41IA42) on amyloid-ß (1-42) and investigated their involvement in the self-assembly process of the protein. Based on these findings, we designed candidate inhibitor peptides of amyloid-ß (1-42) aggregation. Using the designed peptides, we characterized the roles of the three hydrophobic regions during amyloid-ß (1-42) fibrillar aggregation and monitored the consequent effects on its aggregation property and structural conversion. Furthermore, we used an amyloid-ß (1-42) double point mutant (I41N/A42N) to examine the interactions between the two C-terminal end residues with the two hydrophobic regions and their roles in amyloid self-assembly. Our results indicate that interchain interactions in the central hydrophobic region (17LVF19) of amyloid-ß (1-42) are important for fibrillar aggregation, and its interaction with other domains is associated with the accessibility of the central hydrophobic region for initiating the oligomerization process. Our study provides mechanistic insights into the self-assembly of amyloid-ß (1-42) and highlights key structural domains that facilitate this process. Our results can be further applied toward improving the rational design of candidate amyloid-ß (1-42) aggregation inhibitors.

Ion Mobility Mass Spectrometry Analysis of Oxygen Affinity-Associated Structural Changes in Hemoglobin.

Hemoglobin (Hb) is a major oxygen-transporting protein with allosteric properties reflected in the structural changes that accompany binding of O2. Glycated hemoglobin (GHb), which is a minor component of human red cell hemolysate, is generated by a nonenzymatic reaction between glucose and hemoglobin. Due to the long lifetime of human erythrocytes (∼120 days), GHb is widely used as a reliable biomarker for monitoring long-term glucose control in diabetic patients. Although the structure of GHb differs from that of Hb, structural changes relating to the oxygen affinity of these proteins remain incompletely understood. In this study, the oxygen-binding kinetics of Hb and GHb are evaluated, and their structural dynamics are investigated using solution small-angle X-ray scattering (SAXS), electrospray ionization mass spectrometry equipped with ion mobility spectrometry (ESI-IM-MS), and molecular dynamic (MD) simulations to understand the impact of structural alteration on their oxygen-binding properties. Our results show that the oxygen-binding kinetics of GHb are diminished relative to those of Hb. ESI-IM-MS reveals structural differences between Hb and GHb, which indicate the preference of GHb for a more compact structure in the gas phase relative to Hb. MD simulations also reveal an enhancement of intramolecular interactions upon glycation of Hb. Therefore, the more rigid structure of GHb makes the conformational changes that facilitate oxygen capture more difficult creating a delay in the oxygen-binding process. Our multiple biophysical approaches provide a better understanding of the allosteric properties of hemoglobin that are reflected in the structural alterations accompanying oxygen binding.