UV-B induced fibrillization of crystallin protein mixtures

PLoS One. 2017 May 25;12(5):e0177991. doi: 10.1371/journal.pone.0177991. eCollection 2017.

Abstract

Environmental factors, mainly oxidative stress and exposure to sunlight, induce the oxidation, cross-linking, cleavage, and deamination of crystallin proteins, resulting in their aggregation and, ultimately, cataract formation. Various denaturants have been used to initiate the aggregation of crystallin proteins in vitro. All of these regimens, however, are obviously far from replicating conditions that exist in vivo that lead to cataract formation. In fact, it is our supposition that only UV-B radiation may mimic the observed in vivo cause of crystallin alteration leading to cataract formation. This means of inducing cataract formation may provide the most appropriate in vitro platform for in-depth study of the fundamental cataractous fibril properties and allow for testing of possible treatment strategies. Herein, we showed that cataractous fibrils can be formed using UV-B radiation from α:β:γ crystallin protein mixtures. Characterization of the properties of formed aggregates confirmed the development of amyloid-like fibrils, which are in cross-β-pattern and possibly in anti-parallel β-sheet arrangement. Furthermore, we were also able to confirm that the presence of the molecular chaperone, α-crystallin, was able to inhibit fibril formation, as observed for 'naturally' occurring fibrils. Finally, the time-dependent fibrillation profile was found to be similar to the gradual formation of age-related nuclear cataracts. This data provided evidence for the initiation of fibril formation from physiologically relevant crystallin mixtures using UV-B radiation, and that the formed fibrils had several traits similar to that expected from cataracts developing in vivo.

MeSH terms

  • Amyloid / metabolism*
  • Cataract / metabolism*
  • Humans
  • Molecular Chaperones / metabolism
  • Ultraviolet Rays / adverse effects*
  • alpha-Crystallins / metabolism*
  • gamma-Crystallins / metabolism*

Substances

  • Amyloid
  • Molecular Chaperones
  • alpha-Crystallins
  • gamma-Crystallins

Supplementary concepts

  • Cataract, Age-Related Nuclear

Grants and funding

This work was funded by Alberta Innovates – Technology Futures (Grant # 20090279/PSI14420-2011) and Canada Research Chair (Award Reference # 229249 as Tier 1 in Integrative Technology). The funder had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.