S209W mutation enhance π-π interactions in the fourth Greek-key of βA3/A1-crystallin linking with aggregation formation and stress susceptibility.

Congenital cataracts are genetically heterogeneous disorders that result in childhood visual impairment. The S209W mutation in the CRYΒA1/ΒA3 gene, located in the fourth Greek-key motif, has been associated with nuclear cataracts, but its pathogenic mechanism remains unclear. In this study, we investigated the effects of the S209W mutation on βA3/A1-crystallin stability and function. The S209W variant was generated via site-directed mutagenesis and analyzed under both physiological and stress conditions. The mutation caused increased protein aggregation, reduced solubility, and decreased structural stability. Molecular dynamics simulations revealed that the S209W mutation introduced π-π interactions between tryptophan at position 209 and adjacent aromatic residues, disrupting protein structural integrity. Cellular models showed that the S209W mutant had heightened sensitivity to UV and oxidative stress, resulting in increased apoptosis. Co-expression of αB-crystallin alleviated these effects by reducing protein aggregation and cytotoxicity. These findings provide insights into the molecular mechanisms of cataract formation due to the S209W mutation and suggest potential protective roles for αB-crystallin.