Effect of trifluoroethanol on α‐crystallin: folding, aggregation, amyloid, and cytotoxicity analysis

Abstract

α-Crystallin, a member of small heat shock proteins, is the major structural protein within the eye lens and is believed to play an exceptional role in the stability of lens proteins and its transparency. In the current manuscript, we have investigated the effect of an organic solvent, trifluoroethanol (TFE), on the structure and function of α-crystallin isolated from camel eye lens. Incubation of this protein with TFE changed the secondary and tertiary structures, which resulted in the aggregation of α-crystallin as evidenced by intrinsic fluorescence, Rayleigh's scattering, Thioflavin T assay, and circular dichroism spectroscopic studies. The treatment with different concentrations of TFE led to increased exposure of hydrophobic domains of α-crystallin, which was observed by 8-anilino 1-napthalene sulfonic acid extrinsic fluorescence assay. These results clearly indicate that TFE induced significant changes in the secondary and tertiary structures of α-crystallin, leading to aggregation and amyloid formation. Furthermore, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide assay established the cytotoxicity of the aggregated α-crystallin towards HepG2 cell lines through reactive oxygen species production. In conclusion, α-crystallin protein was found to be susceptible to conformational changes by TFE, suggesting that α-crystallin, although basically acting like a heat shock protein and functionally displaying chaperone-like activity, might capitulate to change in lens environment induced by diseased conditions or age-related changes, resulting in cataract formation.