Clarifying Alpha Crystallin Chaperone Function by using an Insulin B-Chain Aggregation Model

The crystallin family of proteins exist in high concentrations in the lens of the eye by are also found throughout the body. In the lens, alpha-crystallin isoforms A and B exist in a ratio of 2 to 3. Their role in the eye is to provide a structural matrix and prevent protein misfolding. The inducible aggregation of the insulin-B chain serves as a model to the protein aggregation that occurs in the human lens over time. This protein aggregation contributes to lens opacity, which is the beginning of cataract formation. In this study, we explore the kinetic and thermodynamics of such system in order to understanding the mechanism of alpha-crystallin chaperone function in insulin aggregation. Insulin aggregation can be measured through light scattering. Our preliminary result suggest a mechanism for aggregation in which a B-chain insulin dimer formation precedes aggregation and that alpha crystallin and insulin monomer form a 2 to 1 complex that inhibits this aggregation. Thermodynamic and kinetic constants will be presented for the purified alpha chrystallins as well as mixtures and bulk protein.