A novel D-amino acid peptide with therapeutic potential (ISAD1) inhibits aggregation of neurotoxic disease-relevant mutant Tau and prevents Tau toxicity in vitro

Abstract

Background Alzheimer’s disease (AD), the most common form of dementia, is a progressive neurodegenerative disorder that mainly affects older adults. One of the pathological hallmarks of AD is abnormally aggregated Tau protein that forms fibrillar deposits in the brain. In AD, Tau pathology correlates strongly with clinical symptoms, cognitive dysfunction, and neuronal death. Methods We aimed to develop novel therapeutic D-amino acid peptides as Tau fibrillization inhibitors. It has been previously demonstrated that D-amino acid peptides are protease stable and less immunogenic than L-peptides, and these characteristics may render them suitable for in vivo applications. Using a phage display procedure against wild type full-length Tau (TauFL), we selected a novel Tau binding L-peptide and synthesized its D-amino acid version ISAD1 and its retro inversed form, ISAD1rev, respectively. Results While ISAD1rev inhibited Tau aggregation only moderately, ISAD1 bound to Tau in the aggregation-prone PHF6 region and inhibited fibrillization of TauFL, disease-associated mutant full-length Tau (TauFLΔK, TauFL-A152T, TauFL-P301L), and pro-aggregant repeat domain Tau mutant (TauRDΔK). ISAD1 and ISAD1rev induced the formation of large high molecular weight TauFL and TauRDΔK oligomers that lack proper Thioflavin-positive β-sheet conformation even at lower concentrations. In silico modeling of ISAD1 Tau interaction at the PHF6 site revealed a binding mode similar to those known for other PHF6 binding peptides. Cell culture experiments demonstrated that ISAD1 and its inverse form are taken up by N2a-TauRDΔK cells efficiently and prevent cytotoxicity of externally added Tau fibrils as well as of internally expressed TauRDΔK. Conclusions ISAD1 and related peptides may be suitable for therapy development of AD by promoting off-pathway assembly of Tau, thus preventing its toxicity.

Tau Aggregation Inhibiting Peptides as Potential Therapeutics for Alzheimer Disease

“…ISAD1 and ISAD1rev were tested in cell culture, where it was evident that the peptides were taken up by neuronal Tau expressing cells and accumulated in the cytosol. The peptides were non-toxic to cells and prevented Tau fibril-mediated cell toxicity of externally added and internally expressed Tau (Aillaud et al 2022).…”

“…Peptide drugs might also have disadvantages such as biological instability and membrane and blood-brain barrier impermeability (Henninot et al 2018), but at least some peptides were demonstrated to cross cell membranes or/and the blood-brain barrier (Pappenheimer et al 1997;Funke et al 2010;Dammers et al 2016;Zhang et al 2020;Malhis et al 2021;Aillaud et al 2022). The problem of in vivo instability due to proteases can be overcome by chemical modification or the usage of D-amino acid peptides (Liu et al 2010;Leithold et al 2016;Lee et al 2019).…”

Rational and Translational Implications of D-Amino Acids for Treatment-Resistant Schizophrenia: From Neurobiology to the Clinics

“…Several D-peptides have recently emerged as potential therapeutic candidates for Alzheimer’s disease and other neurological conditions [ 397 , 398 ]. D-peptides, synthetized in D-enantiomer form by mirror image phage display methodology, are designed to extend the half-life of the peptides and increase resistance to enzyme degradation, prolonging in vivo activity [ 399 ].…”

“…In particular, D-enantiomeric forms of L-peptides interact with the target proteins of the natural L-amino acid configuration. This technique was employed to develop Tau aggregation inhibitors [ 398 , 400 ] as well as promising D-Aβ-peptides to reduce plaque formation and inflammatory reactions [ 401 , 402 , 403 ] in Alzheimer’s disease.…”

Amylin and Secretases in the Pathology and Treatment of Alzheimer’s Disease

“…One such peptide is KLVFF which has been shown to have inhibitory properties on Aβ aggregation, and has been strategically manipulated in order to disrupt pathogenic peptide aggregation [ 22 ]. More recently, Aillaud et al found the novel D-amino acid peptide, ISAD1, successfully inhibited the fibrillization of tau protein [ 23 ]. In addition, studies have also demonstrated a high level of expression of ion channels in microglia implicated in AD that are potentially targetable by synthetic peptide therapy [ 24 ].…”