Novel Peptide-Calix[4]arene Conjugate Inhibits Aβ Aggregation and Rescues Neurons from Aβ’s Oligomers Cytotoxicity In Vitro

Abstract

Alzheimer’s disease (AD) is a progressive neurodegenerative condition affecting people in the elderly. Targeting aggregation of β-amyloid peptides (Aβ) is considered a promising approach for the therapeutic treatment of the disease. Peptide based inhibitors of β-amyloid fibrillation are emerging as safe drug candidates as well as interesting compounds for early diagnosis of AD. Peptide conjugation via covalent bond with functional moieties enables the resultant hybrid system to acquire desired functions. Here we report the synthesis, the structural characterization, and the Aβ42 interaction of a p-amino-calix­[4]­arene derivative bearing a GPGKLVFF peptide pendant at the lower rim. We demonstrate that the p-amino-calix­[4]­arene–GPGKLVFF conjugate alters the Aβ42 aggregation pathways by preventing Aβ42’s conformational transition from random coil to β-sheet with concomitant changes of the aggregation kinetic profile as evidenced by circular dichroism (CD), thioflavin T (ThT), and dynamic light scattering (DLS) measurements, respectively. High resolution mass spectrometry (HR-MS) confirmed a direct interaction of the p-amino-calix­[4]­arene–GPGKLVFF conjugate with Aβ42 monomer which provided insight into a possible working mechanism, whereas the alteration of the Aβ42’s fibrillary architecture, by the calix-peptide conjugate, was further validated by atomic force microscopy (AFM) imaging. Finally, the herein proposed compound was shown to be effective against Aβ42 oligomers’ toxicity in differentiated neuroblastoma cells, SH-SY5Y.

Inhibition Of Tau Protein Aggregation By a Chaperone-like β-Boswellic Acid Conjugated To Gold Nanoparticles

“…Kinetic parameters have been estimated by fitting a sigmoid curve (equation), which is commonly used to explain the kinetics of amyloid aggregation regardless of protein type. 49 Where F is the fluorescence intensity at time t and F 0 and F final indicate the initial and final fluorescence intensity in order. Furthermore, t 1/2 is the needed time for the formation of half of the protein aggregation amounts, and k app is the evident aggregation constant so that the lag time can be calculated.…”

Modulating the aggregation of amyloid proteins by macrocycles

“…The conjugation of macrocycles with other molecules increases their capability to inhibit the aggregation of amyloid proteins. [10,76,93] Heteromultivalent recognition methods with two types of macrocycles have also demonstrated great potential for inhibiting fibrillation. [79] Novel derivatives of the macrocycles are expected to be developed for different amyloid proteins.…”

“…Pappalardo et al constructed a conjugate of peptide and calix [4]arene, and this conjugate exerts better inhibitory effects on the aggregation and cytotoxicity of Aβ 1-42 than the peptide or calix [4]arene alone (1:5, Aβ:conjugate). [76] The sequence of the peptide is gly-pro-gly, lys-leu-val-phe-phe (GPGKLVFF). The KLVFF (Aβ 16-20 ) motif is widely used to bind to Aβ and inhibit its aggregation.…”

Tolcapone Derivative (Tol-D) Inhibits Aβ42 Fibrillogenesis and Ameliorates Aβ42-Induced Cytotoxicity and Cognitive Impairment

“…ThT fluorescence analysis was used to study the inhibitory effects of certain compounds on Aβ42 fibrillogenesis. − The lyophilized Aβ42 was dissolved in 20 mM NaOH to make 275 μM mother liquor, and the final concentration of Aβ42 and ThT was diluted with 100 mM PBS buffer (pH 7.4, 10 mM sodium chloride) to 25 μM. The Aβ42 solution with different concentrations of Tol-D was added into a 96-well plate at 200 μL per well and incubated with constant shaking at 250 rpm, 37 °C.…”

“…AFM is often used to observe the morphology of Aβ aggregates. ,, The same samples obtained from ThT experiments were added dropwise to the mica slices and incubated for 10 min. After incubation, the mica slices were washed with ultrapure water and allowed to dry overnight.…”