Controlling Amyloid Beta Peptide Aggregation and Toxicity by Protease-Stable Ligands

Abstract

Polymerization of soluble amyloid beta (Aβ) peptide into protease-stable insoluble fibrillary aggregates is a critical step in the pathogenesis of Alzheimer's disease (AD). The N-terminal (NT) hydrophobic central domain fragment 16KLVFF20 plays an important role in the formation and stabilization of β-sheets by self-recognition of the parent Aβ peptide, followed by aggregation of Aβ in the AD brain. Here, we analyze the effect of the NT region inducing β-sheet formation in the Aβ peptide by a single amino acid mutation in the native Aβ peptide fragment. We designed 14 hydrophobic peptides (NT-01 to NT-14) by a single mutation at 18Val by using hydrophobic residues leucine and proline in the natural Aβ peptide fragment (KLVFFAE) and analyzed its effect on the formation of Aβ aggregates. Among all these peptides, NT-02, NT-03, and NT-13 significantly affected the Aβ aggregate formation. When the NT peptides were coincubated with the Aβ peptide, a significant reduction in β-sheet formation and increment in random coil content of Aβ was seen, confirmed by circular dichroism spectroscopy and Fourier transform infrared spectroscopy, followed by the reduction of fibril formation measured by the thioflavin-T (ThT) binding assay. The aggregation inhibition was monitored by Congo red and ThT staining and electron microscopic examination. Moreover, the NT peptides protect the PC-12 differentiated neurons from Aβ-induced toxicity and apoptosis in vitro. Thus, manipulation of the Aβ secondary structure with protease-stable ligands that promote the random coil conformation may provide a tool to control the Aβ aggregates observed in AD patients.

Power of Dopamine: Multifunctional Compound Assisted Conversion of the Most Risk Factor into Therapeutics of Alzheimer’s Disease

“…To demonstrate the neuroprotective effect against cellular H 2 O 2 , live and dead PC12 derived neurons in various groups were stained with Calcein-AM/propidium iodide (PI) and observed by a fluorescence microscope imaging. , To generate H 2 O 2 , the cells were treated with Aβ 42 -Cu 2+ -ascorbate. SB-4 (20 μM) was also treated to reduce the cellular H 2 O 2 .…”

Hydrophobic C-Terminal Peptide Analog Aβ31–41 Protects the Neurons from Aβ-Induced Toxicity

“…The formation of Aβ 42 peptide fibrillary aggregates and the effect of ACT peptides were studied by dynamic light scattering (DLS), and it showed the change in the Aβ 42 dynamic radius from ∼4000–5000 to ∼100–2500 nm (Figure B,E). Then, the incubated ThT samples were used in the dot blot assay , to check the formation of fibrils and oligomers by using antibodies A11 (oligomers), 6E10 (all forms of Aβ 42 ), and OC (fibrils), the results clearly showed the inhibition of oligomers and fibril formation (Figure G–I), and the bar diagram shows the intensity of the blots (Figure J–L). From the above ThT assay, DLS, and dot blot assays, we found that ACT-7 inhibited the oligomer and fibril formations.…”

Ratiometric Fluorescent Probe Promotes Trans-differentiation of Human Mesenchymal Stem Cells to Neurons

“…The purple formazan product formed by the reduction of MTT was observed, and then 1:1 DMSO/methanol (V/V) solution was added to dissolve it. Absorbance was recorded at 550 nm in a microplate reader (Thermo Scientific, Varioskan Lux). , …”

“…Absorbance was recorded at 550 nm in a microplate reader (Thermo Scientific, Varioskan Lux). 42,43 Cellular Uptake. Cells were cultured in 35-mm glass-bottom dishes for 24 h. The treatment was given with the molecules and incubated for 6 h. Post-incubation, the cells were fixed using 4% formaldehyde for 1 h at 37 °C.…”