Inhibition of the formation of lysozyme fibrillar assemblies by the isoquinoline alkaloid coralyne

Abstract

Protein aggregation into oligomeric and fibrillar species is the hallmark of many degenerative diseases like Alzheimer's and prion diseases, as well as type II diabetes. Compounds that can modulate protein aggregation or disintegrate the preformed fibrils can serve as potential drug candidates for the remedial treatment of aggregation diseases. In the present study we have examined the anti-amyloidogenic potency of the synthetic isoquinoline alkaloid coralyne by employing various spectroscopic and imaging approaches. The kinetics of amyloid fibrillation of hen egg-white lysozyme (HEWL) and the anti-amyloidogenic influence of coralyne on the fibrillogenesis process were studied using thioflavin T assay. The kinetics of HEWL fibrillation were significantly modulated in the presence of coralyne. We have demonstrated that coralyne significantly inhibits the fibrillation of HEWL. A complementary Congo red assay was also performed to reaffirm the fibril inhibition propensity of coralyne. The changes in the surface hydrophobicity of the protein upon fibrillation were monitored by Nile red assay. The steady-state fluorescence studies, anisotropy measurements and circular dichroism measurements collectively confirm the attenuation of amyloid fibrillation in the presence of isoquinoline alkaloid coralyne. Atomic force microscopic imaging suggested that the fibrillation was reduced in the presence of coralyne and the fibrils formed were less matured. The complete binding thermodynamics was also elucidated using microcalorimetry and docking studies provided insights into the type of forces governing the binding interaction. Since lysozyme is an important model system for studying protein aggregation, the synthetic isoquinoline alkaloid coralyne can serve as a promising model compound for the treatment of amyloidosis.