Toward Molecular-Scale Models of Congenital and Age-Related Cataract: a Concerted Computational and Experimental Approach

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 DESCRIPTION (provided by applicant): Cataract, an opacification of the eye lens caused by a loss of solubility of the crystallin proteins, is a leading cause of blindness worldwide. The overarching goal of the proposed research is to use computational modeling and a broad suite of biophysical experiments to gain new insight into cataract formation on the molecular level that could ultimately guide the development of new therapies for cataract prevention and treatment. The primary hypothesis driving the proposed research is that altered protein-protein interactions, resulting from point mutations (in the case of congenital cataract) or post- translational modifications (in the case of age-related cataract), lead to aggregation of the crystallins which, in turn, leads to loss of transparency in the lens. We propose a concerted experimental and computational investigation of protein structure, organization, and aggregation in solutions of human γD- and γS-crystallins. We will employ a multiscale computational modeling approach, consisting of Monte Carlo and atomistic molecular dynamics simulations, validated and refined using experimental data (NMR, light scattering, and small angle scattering), to gain molecular-scale insight into the interprotein interactions that stabilize concentrated solutions of wild-type γD- and γS- crystallins, or lead to the formation of insolubl aggregates in solutions of variants associated with congenital cataracts. The same approach will be applied in the first systematic computational and biophysical investigation of deamidated variants of γS- crystallin that mimic the changes observed in age-related cataract. Once the concerted application of MC simulations, biophysical experiments, small angle scattering measurements, and solution and solid-state NMR experiments has been developed for single-component γ-crystallin solutions, the approach will be applied to the determination of a molecular-level description of the interactions between αB-crystallins and wild-type γ-crystallin and their cataract-related variants. Thus, we will gain crucial insight into the chaperone function of the αB-crystallins, as well as the ability of the αB-crystallins to maintain the delicate balace of interactions that maintains the transparency of solutions of wild-type γ-crystallins.