Search

Alzheimer’s disease and other tauopathies are the world’s leading causes of dementia and memory loss. These diseases are thought to be caused by the misfolding and aggregation of the intracellular tau protein, ultimately leading to neurodegeneration. The tau protein is involved in a multitude of different neurodegenerative diseases. During the onset of tauopathies, tau undergoes structural changes and posttranslational modifications and aggregates into amyloid fibrils that are able to spread with a prion-like behavior. Up to now, there is no therapeutic agent which effectively controls or reverses the disease. Most of the therapeutics that were developed and underwent clinical trials targeted misfolded or aggregated forms of tau. In the current manuscript, we present the selection and characterization of two all D-enantiomeric peptides that bind monomeric tau protein with a low nanomolar KD, stabilize tau in its monomeric intrinsically disordered conformation, and stop the conversion of monomers into aggregates. We show that the effect of the two all D-enantiomeric peptides is strong enough to stop ongoing tau aggregation in vitro and is able to significantly reduce tau fibril assembly in cell culture. Both compounds may serve as new lead components for the development of therapeutic agents against Alzheimer’s disease and other tauopathies.

Positron emission tomography (PET) imaging with radiotracers that bind to fibrillary amyloid β (Aβ) deposits is an important tool for the diagnosis of Alzheimer's disease (AD) and for the recruitment of patients into clinical trials. However, it has been suggested that rather than the fibrillary Aβ deposits, it is smaller, soluble Aβ aggregates that exert a neurotoxic effect and trigger AD pathogenesis. The aim of the current study is to develop a PET probe that is capable of detecting small aggregates and soluble Aβ oligomers for improved diagnosis and therapy monitoring. An 18F-labeled radioligand was prepared based on the Aβ-binding d-enantiomeric peptide RD2, which is currently being evaluated in clinical trials as a therapeutic agent to dissolve Aβ oligomers. 18F-labeling was carried out using palladium-catalyzed S-arylation of RD2 with 2-[18F]fluoro-5-iodopyridine ([18F]FIPy). Specific binding of [18F]RD2-cFPy to brain material from transgenic AD (APP/PS1) mice and AD patients was demonstrated with in vitro autoradiography. In vivo uptake and biodistribution of [18F]RD2-cFPy were evaluated using PET analyses in wild-type and transgenic APP/PS1 mice. Although brain penetration and brain wash-out kinetics of the radioligand were low, this study provides proof of principle for a PET probe based on a d-enantiomeric peptide binding to soluble Aβ species.

During the replication process of SARS-CoV-2 the main protease of the virus (3-chymotrypsin-like protease (3CLpro)) plays a pivotal role and is essential for the life cycle of the pathogen. Numerous studies have been conducted so far, which have confirmed 3CLpro as an attractive drug target to combat COVID-19. We describe a novel and efficient next generation sequencing (NGS) supported phage display selection strategy for the identification of a set of SARS-CoV-2 3CLpro targeting peptide ligands that inhibit the 3CL protease, in a competitive or non-competetive mode, in the low µM range. From the most efficient L-peptides obtained from the phage display, we designed all-D-peptides based on the retro-inverso (ri) principle. They had IC50 values also in the low µM range, and in combination even in the sub-micromolar range. The inhibition modes of these D-ri peptides were the same as their respective L-peptide versions. Our results demonstrate that retro-inverso obtained all-D-peptides interact with high-affinity and inhibit the SARS-CoV-2 3CL protease, thus reinforcing their potential as therapeutic agents. The here described D-ri peptides address limitations associated with current L-peptide inhibitors and are promising lead compounds. Further optimization regarding pharmacokinetic properties will allow the development of even more potent D-peptides to be used for the prevention and treatment of COVID-19.

Since its outbreak in 2019, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has spread with high transmission efficiency across the world, putting health care as well as economic systems under pressure. During the course of the pandemic, the originally identified SARS-CoV-2 variant has been multiple times replaced by various mutant versions, which showed enhanced fitness due to increased infection and transmission rates. In order to find an explanation for why SARS-CoV-2 and its emerging mutated versions showed enhanced transmission efficiency compared with SARS-CoV (2002), an enhanced binding affinity of the spike protein to human angiotensin converting enzyme 2 (hACE2) has been proposed by crystal structure analysis and was identified in cell culture models. Kinetic analysis of the interaction of various spike protein constructs with hACE2 was considered to be best described by a Langmuir-based 1:1 stoichiometric interaction. However, we demonstrate in this report that the SARS-CoV-2 spike protein interaction with hACE2 is best described by a two-step interaction, which is defined by an initial binding event followed by a slower secondary rate transition that enhances the stability of the complex by a factor of ~190 (primary versus secondary state) with an overall equilibrium dissociation constant (KD) of 0.20 nM. In addition, we show that the secondary rate transition is not only present in SARS-CoV-2 wild type (“wt”; Wuhan strain) but also found in the B.1.1.7 variant, where its transition rate is 5-fold increased.IMPORTANCE The current SARS-CoV-2 pandemic is characterized by the high infectivity of SARS-CoV-2 and its derived variants of concern (VOCs). It has been widely assumed that the reason for its increased cell entry compared with SARS-CoV (2002) is due to alterations in the viral spike protein, where single amino acid residue substitutions can increase affinity for hACE2. So far, the interaction of a single unit of the CoV-2 spike protein has been described using the 1:1 Langmuir interaction kinetic. However, we demonstrate here that there is a secondary state binding step that may be essential for novel VOCs in order to further increase their infectivity. These findings are important for quantitatively understanding the infection process of SARS-CoV-2 and characterization of emerging SARS-CoV-2 variants of spike proteins. Thus, they provide a tool for predicting the potential infectivity of the respective viral variants based on secondary rate transition and secondary complex stability.

Alzheimeŕs disease (AD) is the most prominent neurodegenerative disorder with high medical need. Protein-protein-interactions (PPI) interactions have a critical role in AD where β-amyloid structures (Aβ) build toxic oligomers. Design of disease modifying multi target directed ligand (MTDL) has been performed, which disable PPI on the one hand and on the other hand, act as procognitive antagonists at the histamine H

Since its outbreak in 2019 SARS-CoV-2 has spread with high transmission efficiency across the world, putting health care as well as economic systems under pressure [1, 2]. During the course of the pandemic, the originally identified SARS-CoV-2 variant has been widely replaced by various mutant versions, which showed enhanced fitness due to increased infection and transmission rates [3, 4]. In order to find an explanation, why SARS-CoV-2 and its emerging mutated versions showed enhanced transfection efficiency as compared to SARS-CoV 2002, an improved binding affinity of the spike protein to human ACE has been proposed by crystal structure analysis and was identified in cell culture models [5-7]. Kinetic analysis of the interaction of various spike protein constructs with the human ACE2 was considered to be best described by a Langmuir based 1:1 stoichiometric interaction. However, we demonstrate in this report that the SARS-CoV-2 spike protein interaction with ACE2 is best described by a two-step interaction, which is defined by an initial binding event followed by a slower secondary rate transition that enhances the stability of the complex by a factor of ∼190 with an overall KD of 0.20 nM. In addition, we show that the secondary rate transition is not only present in SARS-CoV-2 wt but is also found in B.1.1.7 where its transition rate is five-fold increased.

International journal of molecular sciences 22(13), 7066 (2021). doi:10.3390/ijms22137066 special issue: "Molecular pathology, diagnostics, and therapeutics / Kurt A. Jellinger, section editor-in-chief; Stephen Bustin, section editor-in-chief; Xiaofeng Jia, section editor-in-chief", Published by Molecular Diversity Preservation International, Basel

Amyloid-β (Aβ) plays a central role in the development and progression of Alzheimer's disease (AD) with Aβ oligomers representing the most toxic species. The all-d-enantiomeric peptide RD2, which recently successfully completed clinical phase I, specifically eliminates Aβ oligomers in vitro as well as in vivo and improves cognitive deficits in various transgenic AD mouse models even after oral administration. To further enhance the oral absorption of RD2, folic acid has been conjugated to the d-peptide promoting an endocytosis-mediated uptake via a folate receptor located in the intestine. Two different conjugation strategies were selected to obtain prodrugs with folic acid being cleaved after intestinal absorption releasing unmodified RD2 in order to enable RD2's unaltered systemic efficacy. Both conjugates remained stable in simulated gastrointestinal fluids. But only one of them was suitable as prodrug as it was cleaved to RD2 in vitro in human blood plasma and liver microsomes and in vivo in mice after intravenous injection leading to a systemic release of RD2. Furthermore, the conjugate's permeability in vitro and after oral administration in mice was strongly enhanced compared to unconjugated RD2 demonstrating the prodrug's functionality. However, the conjugate seemed to have impaired the mice's wellbeing shortly after oral administration possibly resulting from strain-specific hypersensitivity to folic acid. Nevertheless, we assume that the prodrug is actually non-toxic, especially in lower concentrations as verified by a cell viability test. Furthermore, lower dosages can be applied with unaltered efficacy due to its enhanced oral absorption.

Alzheimeŕs disease (AD) is the most prominent neurodegenerative disorder with high medical need. Protein-protein-interactions (PPI) interactions have a critical role in AD where β-amyloid structures (Aβ) build toxic oligomers. Design of disease modifying multi target directed ligand (MTDL) has been performed, which disable PPI on the one hand and on the other hand, act as procognitive antagonists at the histamine H3 receptor (H3R). The synthetized compounds are structurally based on peptidomimetic amino acid-like structures mainly as keto, diketo-, or acyl variations of a piperazine moiety connected to an H3R pharmacophore. Most of them showed low nanomolar affinities at H3R and some with promising affinity to Aβ-monomers. The structure–activity relationships (SAR) described offer new possibilities for MTDL with an optimized profile combining symptomatic and potential causal therapeutic approaches in AD.

The aggregation of amyloid-β (Aβ) into oligomers and fibrillary structures is critical for the pathogenesis of Alzheimer’s disease (AD). Recently, research effort has been focused on developing novel agents that can preferentially suppress Aβ oligomer mediated toxicities, for example, by directly targeting these toxic assemblies. The compound RD2 has been developed and optimized for Aβ42 monomer binding and stabilization of the monomer in its native intrinsically disordered conformation. It has been demonstrated to improve and even reverse the cognitive and behavioral deficits in AD mouse models, while the detailed mechanism of action is not fully clarified. Here we focused on exploring the interaction between RD2 and Aβ42 monomers and its consequences for the fibrillation of Aβ42. RD2 binds to Aβ42 monomers with nanomolar affinities, according to microscale thermophoresis and surface plasmon resonance measurements. Complexes between RD2 and Aβ42 monomers are formed at 1:1 and other stoichiometries, as revealed by analytical ultracentrifugation. At substoichiometric levels, RD2 slows down the secondary structure conversion of Aβ42 and significantly delays the fibril formation. Our research provides experimental evidence in supporting that RD2 eliminates toxic Aβ assemblies by stabilizing Aβ monomers in their native intrinsically disordered conformation. The study further supports the promising application of RD2 in counteracting Aβ aggregation related pathologies.