Many peptides and proteins with large sequences and structural differences self-assemble into disease-causing amyloids that share very similar biochemical and biophysical characteristics, which may contribute to their cross-interaction. Here, we demonstrate how the self-assembled, cyclic d,l-α-peptide CP-2, which has similar structural and functional properties to those of amyloids, acts as a generic inhibitor of the Parkinson's disease associated α-synuclein (α-syn) aggregation to toxic oligomers by an "off-pathway" mechanism. We show that CP-2 interacts with the N-terminal and the non-amyloid-β component region of α-syn, which are responsible for α-syn's membrane intercalation and self-assembly, thus changing the overall conformation of α-syn. CP-2 also remodels α-syn fibrils to nontoxic amorphous species and permeates cells through endosomes/lysosomes to reduce the accumulation and toxicity of intracellular α-syn in neuronal cells overexpressing α-syn. Our studies suggest that targeting the common structural conformation of amyloids may be a promising approach for developing new therapeutics for amyloidogenic diseases.

Inhibiting the toxic aggregation of amyloid-β and the tau protein, the key pathological agents involved in Alzheimer's, is a leading approach in modulating disease progression. Using an aggregative tau-derived model peptide, Ac-PHF6-NH , the substitution of its amino acids with proline, a known efficient β-breaker, is shown to reduce self-assembly. This effect is attributed to the steric hindrance created by the proline substitution, which results in disruption of the β-sheet formation process. Moreover, several of the proline-substituted peptides inhibit the aggregation of Ac-PHF6-NH amyloidogenic peptide. Two of these modified inhibitors also disassemble pre-formed Ac-PHF6-NH fibrils and one inhibits induced cytotoxicity of the fibrils. Taken together, these lead β-breaker peptides may be developed into novel Alzheimer's disease therapeutics.

Cataract, the leading cause of vision impairment worldwide, arises from abnormal aggregation of crystallin lens proteins. Presently, surgical removal is the only therapeutic approach. Recent findings have triggered renewed interest in development of non-surgical treatment alternatives. However, emerging treatments are yet to achieve full and consistent lens clearance. Here, the first ex vivo assay to screen for drug candidates that reduce human lenticular protein aggregation was developed. This assay allowed the identification of two leading compounds as facilitating the restoration of nearly-complete transparency of phacoemulsified cataractous preparation ex vivo. Mechanistic studies demonstrated that both compounds reduce cataract microparticle size and modify their amyloid-like features. In vivo studies confirmed that the lead compound, rosmarinic acid, delays cataract formation and reduces the severity of lens opacification in model rats. Thus, the ex vivo assay may provide an initial platform for broad screening of potential novel therapeutic agents towards pharmacological treatment of cataract.

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