C1 Inhibits Liquid–Liquid Phase Separation and Oligomerization of Tau and Protects Neuroblastoma Cells against Toxic Tau Oligomers

Abstract

The pathological aggregation of tau is one of the major contributing factors for several neurodegenerative tauopathies, including Alzheimer's disease. Here, we report that C1, a synthetic derivative of curcumin, strongly inhibited both the aggregation and filament formation of purified tau and protected neuroblastoma cells from the deleterious effects of the tau oligomers. Using confocal microscopy, C1 was found to reduce both the size and number of the tau droplets and increased the critical concentration of tau required for the droplet formation in vitro indicating that C1 suppressed the liquid−liquid phase separation of tau. C1 inhibited the aggregation of tau with a halfmaximal inhibitory concentration of 1.5 ± 0.1 μM. An analysis of the aggregation kinetics data indicated that C1 strongly reduced the initial rate of the aggregation of tau. A dot blot analysis using tau-oligomerspecific antibody indicated that C1 inhibited the oligomerization of tau. Furthermore, dynamic light scattering experiments suggested that C1 strongly reduced the mean diameter of the tau oligomers. Atomic force microscopy experiments showed that C1 treatment reduced both the size and number of tau oligomers, suppressed the transition of tau oligomers into filaments, and also disintegrated preformed tau filaments. Also, the binding interaction of C1 with tau was monitored using absorbance and fluorescence spectroscopy. C1 bound to Y310W-tau with a dissociation constant of 2.0 ± 0.5 μM. The findings suggested that C1 is a potent inhibitor of tau aggregation and provided insights into the inhibitory mechanism of C1 on the oligomerization and fibril formation of tau.

Manganese promotes α-synuclein amyloid aggregation through the induction of protein phase transition

“…As other factors that modulate α-Syn aggregations have the possibilities to regulate LLPS as well, the phase transition of α-Syn could be a general key target for PD treatment. In support of this, recent studies have reported that protein LLPS can be modulated by small molecules, either inducing or preventing the formation of liquid droplets ( 77 , 78 ).…”

Contrasting Effects of Ferric and Ferrous Ions on Oligomerization and Droplet Formation of Tau: Implications in Tauopathies and Neurodegeneration

“…Thioflavin S binds to amyloids, and the fluorescence intensity of Thioflavin S increases upon binding to amyloids. − Therefore, the increase in the fluorescence intensity of Thioflavin S is widely used to determine tau aggregation. Tau is a highly soluble unstructured protein and it forms oligomers and filaments in vitro when incubated in the presence of either heparin, RNA, or arachidonic acid. − In this work, we monitored the effects of several trivalent metal ions (Fe 3+ , Cr 3+ , Al 3+ , La 3+ , and V 3+ ) on the aggregation of tau in the absence and presence of heparin using Thioflavin S fluorescence (Figure A–G). Thioflavin S displayed weak fluorescence when incubated with tau without heparin (Figure A,F).…”

“…Tau (8 μM) in 25 mM PIPES buffer pH 7.4 was incubated without or with 10 μM Fe 2+ /Fe 3+ for 10 min and further, incubated with 8 μM heparin for 6 h at 37 °C in shaking conditions. Then, 1 mL from each sample was analyzed in the DLS instrument (Zetasizer, Malvern) as described earlier . The samples were also analyzed for atomic force microscopy as reported previously. , Briefly, the samples were adsorbed onto a freshly cleaved mica disc and tau aggregates was observed using the Asylum MFP-3D Bio-AFM.…”

“…Then, 1 mL from each sample was analyzed in the DLS instrument (Zetasizer, Malvern) as described earlier . The samples were also analyzed for atomic force microscopy as reported previously. , Briefly, the samples were adsorbed onto a freshly cleaved mica disc and tau aggregates was observed using the Asylum MFP-3D Bio-AFM. The image analysis was performed using WSxM software version 9.4 …”

Alzheimer’s Disease and Diabetes Mellitus in Comparison: The Therapeutic Efficacy of the Vanadium Compound

“…It was shown that BCOV could reduce the serum LDL level significantly in obese rats [ 140 ]. Curcumin is both an antioxidant and an antidiabetic agent [ 141 ]; it had been reported that curcumin inhibited the oligomerize of tau [ 142 ]. This vanadium compound is deserved to be investigated in further studies in order to determine the therapeutic effects of vanadium compounds on AD.…”