The Cardiomyopathy and Lens Cataract Mutation in αB-crystallin Alters Its Protein Structure, Chaperone Activity, and Interaction with Intermediate Filaments in Vitro

• Published in: The Journal of biological chemistry 1999-11, Vol.274 (47), p.33235-33243
• Main Authors: Perng, Ming Der, Muchowski, Paul J., van den IJssel, Paul, Wu, Gabrielle J.S., Hutcheson, Aileen M., Clark, John I., Quinlan, Roy A.
• Format: Article
• Language: English
• Subjects: aB-crystallin
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.274.47.33235

Desmin-related myopathy and cataract are both caused by the R120G mutation in αB-crystallin. Desmin-related myopathy is one of several diseases characterized by the coaggregation of intermediate filaments with αB-crystallin, and it identifies intermediate filaments as important physiological substrates for αB-crystallin. Using recombinant human αB-crystallin, the effects of the disease-causing mutation R120G upon the structure and the chaperone activities of αB-crystallin are reported. The secondary, tertiary, and quaternary structural features of αB-crystallin are all altered by the mutation as deduced by near- and far-UV circular dichroism spectroscopy, size exclusion chromatography, and chymotryptic digestion assays. The R120G αB-crystallin is also less stable than wild type αB-crystallin to heat-induced denaturation. These structural changes coincide with a significant reduction in thein vitro chaperone activity of the mutant αB-crystallin protein, as assessed by temperature-induced protein aggregation assays. The mutation also significantly altered the interaction of αB-crystallin with intermediate filaments. It abolished the ability of αB-crystallin to prevent those filament-filament interactions required to induce gel formation while increasing αB-crystallin binding to assembled intermediate filaments. These activities are closely correlated to the observed disease pathologies characterized by filament aggregation accompanied by αB-crystallin binding. These studies provide important insight into the mechanism of αB-crystallin-induced aggregation of intermediate filaments that causes disease.