Inhibiting α-Synuclein Oligomerization by Stable Cell-Penetrating β-Synuclein Fragments Recovers Phenotype of Parkinson's Disease Model Flies

The intracellular oligomerization of α-synuclein is associated with Parkinson's disease and appears to be an important target for disease-modifying treatment. Yet, to date, there is no specific inhibitor for this aggregation process. Using unbiased systematic peptide array analysis, we indentified molecular interaction domains within the β-synuclein polypeptide that specifically binds α-synuclein. Adding such peptide fragments to α-synuclein significantly reduced both amyloid fibrils and soluble oligomer formation in vitro. A retro-inverso analogue of the best peptide inhibitor was designed to develop the identified molecular recognition module into a drug candidate. While this peptide shows indistinguishable activity as compared to the native peptide, it is stable in mouse serum and penetrates α-synuclein over-expressing cells. The interaction interface between the D-amino acid peptide and α-synuclein was mapped by Nuclear Magnetic Resonance spectroscopy. Finally, administering the retro-inverso peptide to a Drosophila model expressing mutant A53T α-synuclein in the nervous system, resulted in a significant recovery of the behavioral abnormalities of the treated flies and in a significant reduction in α-synuclein accumulation in the brains of the flies. The engineered retro-inverso peptide can serve as a lead for developing a novel class of therapeutic agents to treat Parkinson's disease

A Novel, Sensitive Assay for Behavioral Defects in Parkinson's Disease Model Drosophila

Parkinson's disease is a common neurodegenerative disorder with the pathology of α-synuclein aggregation in Lewy bodies. Currently, there is no available therapy that arrests the progression of the disease. Therefore, the need of animal models to follow α-synuclein aggregation is crucial. Drosophila melanogaster has been researched extensively as a good genetic model for the disease, with a cognitive phenotype of defective climbing ability. The assay for climbing ability has been demonstrated as an effective tool for screening new therapeutic agents for Parkinson's disease. However, due to the assay's many limitations, there is a clear need to develop a better behavioral test. Courtship, a stereotyped, ritualized behavior of Drosophila, involves complex motor and sensory functions in both sexes, which are controlled by large number of neurons; hence, behavior observed during courtship should be sensitive to disease processes in the nervous system. We used a series of traits commonly observed in courtship and an additional behavioral trait—nonsexual encounters—and analyzed them using a data mining tool. We found defective behavior of the Parkinson's model male flies that were tested with virgin females, visible at a much younger age than the climbing defects. We conclude that this is an improved behavioral assay for Parkinson's model flies

Structural basis for inhibiting β-amyloid oligomerization by a non-coded β-breaker-substituted endomorphin analogue

The distribution of endomorphins (EM) 1 and 2 in the human brain inversely correlates with cerebral neurodegeneration in Alzheimer's disease (AD), implying a protective role. These endogenous opioid peptides incorporate aromatic residues and a β-breaker motif, as seen in several optimized inhibitors of Aβ aggregation. The activity of native endomorphins was studied, as well as the rationally designed analogue Aib-1, which includes a remarkably efficient β-breaker, α-aminoisobutyric acid (Aib). In vitro and GFP fusion protein assays showed that Aib-1 interacted with Aβ and markedly inhibited the formation of toxic oligomer and fibril growth. Moreover, Aib-1 prevented the toxicity of Aβ toward neuronal PC12 cells and markedly rectified reduced longevity of an AD fly model. Atomistic simulations and NMR-derived solution structures revealed that Aib-1 significantly reduced the propensity of Aβ to aggregate due to multimode interactions including aromatic, hydrophobic, and polar contacts. We suggest that hindering the self-assembly process by interfering with the aromatic core of amyloidogenic peptides may pave the way toward developing therapeutic agents to treat amyloid-associated diseases