α-Helix Mimetics as Modulators of Aβ Self-Assembly

Area of Science:

• Neuroscience
• Biochemistry
• Drug Discovery

Background:

• Alzheimer's disease (AD) is characterized by amyloid plaques, primarily composed of Aβ42.
• Soluble Aβ oligomers are identified as the key neurotoxic species driving AD pathology.
• Aβ42 adopts α-helical conformations in certain environments, presenting a potential therapeutic target.

Purpose of the Study:

• To design and identify α-helical mimetics targeting the central α-helix of Aβ (Aβ13-26).
• To evaluate the efficacy of identified compounds in inhibiting Aβ fibrillation and oligomerization.
• To investigate the specificity and mechanism of action of potent inhibitors.

Main Methods:

• Design and synthesis of oligopyridylamide-based α-helical mimetics.
• Inhibition assays for amyloid-assembly kinetics.
• Structural analysis using Transmission Electron Microscopy (TEM) and Atomic Force Microscopy (AFM).
• Biochemical assays including Dot blot and ELISA for Aβ oligomer detection.
• Specificity testing against Islet Amyloid Polypeptide (IAPP).
• Spectroscopic studies (NMR, CD) and binding affinity measurements (calorimetry, fluorescence titration).

Main Results:

• A tripyridylamide, ADH-41, was identified as a potent antagonist of Aβ fibrillation.
• ADH-41 suppressed Aβ aggregation at substoichiometric doses, as confirmed by TEM and AFM.
• Dot blot and ELISA assays showed ADH-41 inhibited the formation of neurotoxic Aβ oligomers.
• ADH-41 demonstrated sequence and structure-specific inhibition, with no effect on IAPP aggregation.
• Spectroscopic studies confirmed ADH-41 induces α-helicity in Aβ, with binding affinities in the low micromolar range.
• ADH-41 inhibited seed-catalyzed Aβ aggregation by promoting fiber-incompetent structures.

Conclusions:

• ADH-41 is a highly effective inhibitor of Aβ fibrillation and neurotoxic oligomer formation.
• The compound acts in a sequence and structure-specific manner, targeting Aβ's α-helical subdomain.
• ADH-41 shows potential as a therapeutic agent by directing Aβ into off-pathway structures.
• Further cell-based assays are ongoing to assess the in vivo efficacy of ADH-41.