Date of Award
Bachelor of Science (B.S.) in Biochemistry and University Honors
Cataracts are a result of age-related protein aggregate formation in the eye lens, and the leading cause of blindness worldwide. α-crystallin, a small heat shock protein, acts a molecular chaperone that serves as the primary defense mechanism against protein aggregate formation in the lens. Recent evidence suggest amyloid formation in the lens may contribute to cataract formation, and that β-amyloid is present in lens epithelia of age-related cataracts. Previous studies have shown that αB-crystallin in other parts of the body, such as the brain, is protective against neurodegenerative diseases such as Alzheimer’s disease that are associated with plaque deposits containing β-amyloid. In vitro, αB-crystallin inhibits fibril elongation of β-amyloid. However, the capacity of native lens crystallin protection against β-amyloid formation is still unclear. The aim of this thesis was to determine if the native lens specific αL-crystallin, a 3:1 ratio of the isoforms αA- and αB-crystallin, would prevent the fibril elongation of β-amyloid comparatively to αB-crystallin.
Thioflavin T (ThT) based chaperone assays, biochemical analysis by SDS-PAGE, and structural characterization by electron microscopy were used to determine if αL-crystallin can prevent fibril elongation of the amyloidogenic peptide Aβ 1-42. Detection of β-amyloid formation by ThT assay showed that αL-crystallin prevented fibril nucleation/elongation, but was less effectively than αB-crystallin. Assessment of co-aggregation of the chaperone/β-amyloid complex by SDS-PAGE were inconclusive. However, negative stain electron micrographs showed that αL-crystallin interacted effectively with β-amyloid fibrils under varying stoichiometric ratios. From these data, it was found that αL-crystallin was an effective chaperone for β-amyloid in vitro. Further experimentation could help understand the mechanism behind αL-crystallin function against preventing the formation of amyloid species in the eye lens.
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Lopes, Leilani A., "The Role of Native Lens α-crystallin in Amyloid Suppression Using β-amyloid as a Model Amyloid Client" (2021). University Honors Theses. Paper 1033.
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