Journal of Biological Chemistry

Γ-Crystallins play a major role in age-related lens transparency. Their destabilization by mutations and physical chemical insults are associated with cataract formation. Therefore, drugs that increase their stability should have anticataract properties. To this end, we screened 2560 Federal Drug Agency–approved drugs and natural compounds for their ability to suppress or worsen H2O2 and/or heat-mediated aggregation of bovine γ-crystallins. The top two drugs, closantel (C), an antihelminthic drug, and gambogic acid (G), a xanthonoid, attenuated thermal-induced protein unfolding and aggregation as shown by turbidimetry fluorescence spectroscopy dynamic light scattering and electron microscopy of human or mouse recombinant crystallins. Furthermore, binding studies using fluorescence inhibition and hydrophobic pocket–binding molecule bis-8-anilino-1-naphthalene sulfonic acid revealed static binding of C and G to hydrophobic sites with medium-to-low affinity. Molecular docking to HγD and other γ-crystallins revealed two binding sites, one in the “NC pocket” (residues 50–150) of HγD and one spanning the “NC tail” (residues 56–61 to 168–174 in the C-terminal domain). Multiple binding sites overlap with those of the protective mini αA-crystallin chaperone MAC peptide. Mechanistic studies using bis-8-anilino-1-naphthalene sulfonic acid as a proxy drug showed that it bound to MAC sites, improved Tm of both H2O2 oxidized and native human gamma D, and suppressed turbidity of oxidized HγD, most likely by trapping exposed hydrophobic sites. The extent to which these drugs act as α-crystallin mimetics and reduce cataract progression remains to be demonstrated. This study provides initial insights into binding properties of C and G to γ-crystallins.

fluorescence spectroscopy

oxidation

glycation

unfolding

diabetes

aging

drug repurposing

bis-8-anilino-1-naphthalene sulfonic acid

dynamic light scattering

diethylenetriaminepentaacetic acid

phenylalanine to serine mutation at ninth position of WT mouse gamma S crystallin

heteronuclear single quantum coherence

PBS with 0.1% Tween-20

mini-αA-crystallin chaperone

arginine to cysteine mutation at 14th position of WT human gamma D crystallin

arginine to histidine replacement at 58th position of WT human gamma D crystallin

tetradecyl sulfate sodium

tryptophan to arginine mutation at 43rd position of WT human gamma D crystallin

© 2022 The Authors. Published by Elsevier Inc on behalf of American Society for Biochemistry and Molecular Biology.