title: Selection and characterization of D-enantiomeric peptides for the investigation of options for therapy and diagnosis of Alzheimer’s disease
Creators: name: Malhis, Marwa
Publisher: name: University of Bayreuth
Year: 2021
Subjects: subject: Morbus Alzheimer
subject: Tau aggregation inhibitors
subject: therapy
subject: D-peptides
subject: phage display
subject: 570

description: Morbus Alzheimer (AD) is a neurodegenerative disease, characterized by steady loss of cognitive functions, behavioral changes and neuropsychological symptoms. Today, AD can be treated only symptomatically. There is no drug available, which stops or reverses the pathological changes in AD. Alzheimer's disease is characterized by two pathological hallmarks, amyloid plaques and neurofibrillary tangles (NFTs). NFTs are composed of aggregated tau protein. The accumulation of tau into NFTs reduces normal tau function and causes neuronal dysfunction. The formation of tau aggregates is triggered by two hexapeptide sequences within tau: VQIINK (PHF6*), which is located at the beginning of the second repeat (R2) and VQIVYK (PHF6), which is located at the beginning of the third repeat (R3). PHF6* segment has recently been described as a more potent driver of tau aggregation than PHF6. Peptides that inhibit the pathological aggregation of tau are potentially useful candidates for future therapies in AD. The use of the molecular biology screening technique, phage display, allows fast and simple selection of peptides that bind to a desired target protein. The aim of this study was to develop specific D-enantiomeric peptides that inhibit the pathological aggregation of tau. D-enantiomeric peptides were chosen as they are protease stable and considerably less immunogenic than L-peptides. Another objective of this project was to investigate which of the both sequences within tau, PHF6 or PHF6*, is the more effective target for the development of tau aggregation inhibiting peptides. Employing phage display and mirror image phage display, we selected specific peptides to inhibit tau fibril formation. Two selections were performed; the first selection was conducted using monomers of L-enantiomeric full-length tau as a target for phage display. In addition, we performed a second selection using fibrils of the D-enantiomeric hexapeptide VQIINK (PHF6*) as a target for mirror image phage display. PHF6* segment was targeted in our second selection since PHF6* was recently reported as a more powerful driver for tau aggregation as PHF6. The most interesting obtained peptide, designated MMD3, was found both in the selection against tau monomer and in the selection against D-PHF6* fibrils. MMD3 and its retro-inverso form, designated MMD3rev, clearly inhibited PHF6* aggregation as well as full-length tau aggregation in Thioflavin T (THT) assays. In addition, we performed preliminary experiments to investigate which of the both sequences, PHF6 or PHF6*, is the more effective target for inhibitors of tau fibril formation. We compared the tau aggregation inhibiting effects of MMD3 and MMD3rev with other peptides, which were previously described in the literature and target either PHF6 or PHF6*, respectively. From our early preliminary data, it seems likely that PHF6 and PHF6* aggregation inhibitors are comparably effective in inhibiting the aggregation of full-length tau. However, further characterization using different biochemical and biophysical methods is still required. Our selected peptides MMD3 and MMD3rev present promising candidates for therapeutic and diagnostic applications in AD research. Currently, MMD3 and MMD3rev are further characterized in the German Center for Neurodegenerative Diseases (DZNE).