Polyoxometalates as Effective Nano-inhibitors of Amyloid Aggregation of Pro-inflammatory S100A9 Protein Involved in Neurodegenerative Diseases

Abstract

Pro-inflammatory and amyloidogenic S100A9 protein is central to the amyloid-neuroinflammatory cascade in neurodegenerative diseases. Polyoxometalates (POMs) constitute a diverse group of nanomaterials, which showed potency in amyloid inhibition. Here, we have demonstrated that two selected nanosized niobium POMs, Nb 10 and TiNb 9 , can act as potent inhibitors of S100A9 amyloid assembly. Kinetics analysis based on ThT fluorescence experiments showed that addition of either Nb 10 or TiNb 9 reduces the S100A9 amyloid formation rate and amyloid quantity. Atomic force microscopy imaging demonstrated the complete absence of long S100A9 amyloid fibrils at increasing concentrations of either POM and the presence of only round-shaped and slightly elongated aggregates. Molecular dynamics simulation revealed that both Nb 10 and TiNb 9 bind to native S100A9 homo-dimer by forming ionic interactions with the positively charged Lys residue-rich patches on the protein surface. The acrylamide quenching of intrinsic fluorescence showed that POM binding does not perturb the Trp 88 environment. The far and near UV circular dichroism revealed no large-scale perturbation of S100A9 secondary and tertiary structures upon POM binding. These indicate that POM binding involves only local conformational changes in the binding sites. By using intrinsic and 8-anilino-1-naphthalene sulfonate fluorescence titration experiments, we found that POMs bind to S100A9 with a K d of ca. 2.5 μM. We suggest that the region, including Lys 50 to Lys 54 and characterized by high amyloid propensity, could be the key sequences involved in S1009 amyloid self-assembly. The inhibition and complete hindering of S100A9 amyloid pathways may be used in the therapeutic applications targeting the amyloid-neuroinflammatory cascade in neurodegenerative diseases.

Computational Modelling of the Interactions Between Polyoxometalates and Biological Systems

“…( Narasimhan et al, 2011 ; Prudent et al, 2010 ; Prudent et al, 2008 ; Hu et al, 2007 ; Tiago et al, 2007 ; Pezza et al, 2002 ; Judd et al, 2001 ; Sarafianos et al, 1996 ). Owing to the intrinsic limitations of docking methods, atomistic molecular dynamics (MD) simulations have been more recently performed to reveal the driving forces that are responsible for the specific interactions ( Figure 1A )[ ( Solé-Daura et al, 2016 ; Paul et al, 2018 ; Solé-Daura et al, 2020a ; Sciortino et al, 2021 ; Chaudhary et al, 2021 )] Pioneer MD simulations analysed the interaction between model protein hen egg-white lysoszyme (HEWL) and three different POMs, the Ce-substituted Keggin-type anion [PW 11 O 39 Ce(OH 2 ) 4 ] 3− the corresponding 1:2 dimer [Ce(PW 11 O 39 ) 2 ] 10− and the Zr-substituted Lindqvist-type anion [W 5 O 18 Zr(OH 2 ) (OH)] 3− , which differ in the overall charge, the size, the shape and the type of substituted metal. ( Solé-Daura et al, 2016 ).…”

Co-Aggregation of S100A9 with DOPA and Cyclen-Based Compounds Manifested in Amyloid Fibril Thickening without Altering Rates of Self-Assembly

“…It is important to note that DOPA and cyclen-based ligands did not interact with the region on the S100A9 surface, including Lys 50 to Lys 54, which has been shown previously to be critical for S100A9 amyloid self-assembly and by blocking this specific amino acid sequence by polyoxoniobates, we were able effectively hinder S100A9 amyloid growth [53]. However, as the S100A9 amyloid surface is important for its quaternary complex formation and amyloid co-aggregation with Aβ peptide [18] and potentially with other proteins and disease-related and functional amyloids, the amyloid morphology-modifying effect of DOPA and cyclen-based compounds co-aggregated together with S100A9 into fibrils should be taken into account in future studies of protein hetero-aggregation.…”

“…The amyloid formation of S100A9 in the absence and presence of DOPA and cyclenbased compounds was monitored by ThT fluorescence and is presented in Figure 2. The amyloid formation correlates with the increase of the ThT fluorescence, and the initial parts of the fibrillation kinetic curves were fitted by using an isodesmic polymerization model [50,51] to derive the kinetic rates; this model has previously been used in kinetic analysis of S100A9 amyloid self-assembly [52,53]. The rates of fibrillation in the presence of the compounds do not deviate significantly from the rate of self-assembly of S100A9 alone (Table 1).…”

“…An isodesmic polymerization model was used to fit the kinetic dependencies of S100A9 amyloid formation monitored by ThT fluorescence as described previously [53], since these curves displayed hyperbolic dependences characteristic of this model [45,46].…”

Nanotechnology-Based Drug Delivery Strategies to Repair the Mitochondrial Function in Neuroinflammatory and Neurodegenerative Diseases

“…POMs are effective in the degradation and prevention of toxic effects of Aβ displaying both protease-like activity for Aβ disaggregation and SOD-like activity to scavenge ROS produced by Aβ reactivity [344]. POM nanostructures associated with Niobium act as potent inhibitors of S100A9 assembly [345], which is a protein present in neuron cells and involved in the aggregation of Aβ and α-syn [366,367] and related to cognitive deficits in an AD animal model [368]. A bimetallic nanosystem composed of a nanozyme core of platinum-copper (PtCu) and coated with polyvinyl pyrrolidone significantly inhibits α-syn aggregation and spread in the brain of mice after intrastriatal injection of α-syn fibrils.…”