The cardiomyopathy and lens cataract mutation in alphaB-crystallin alters its protein structure, chaperone activity, and interaction with intermediate filaments in vitro.
Desmin-related myopathy and cataract are both caused by the R120G mutation in alphaB-crystallin. Desmin-related myopathy is one of several diseases characterized by the coaggregation of intermediate filaments with alphaB-crystallin, and it identifies intermediate filaments as important physiological substrates for alphaB-crystallin. Using recombinant human alphaB-crystallin, the effects of the disease-causing mutation R120G upon the structure and the chaperone activities of alphaB-crystallin are reported. The secondary, tertiary, and quaternary structural features of alphaB-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 alphaB-crystallin is also less stable than wild type alphaB-crystallin to heat-induced denaturation. These structural changes coincide with a significant reduction in the in vitro chaperone activity of the mutant alphaB-crystallin protein, as assessed by temperature-induced protein aggregation assays. The mutation also significantly altered the interaction of alphaB-crystallin with intermediate filaments. It abolished the ability of alphaB-crystallin to prevent those filament-filament interactions required to induce gel formation while increasing alphaB-crystallin binding to assembled intermediate filaments. These activities are closely correlated to the observed disease pathologies characterized by filament aggregation accompanied by alphaB-crystallin binding. These studies provide important insight into the mechanism of alphaB-crystallin-induced aggregation of intermediate filaments that causes disease.
Perng
M D
MD
Department of Biochemistry, Medical Science Institute, The University, Dundee DD1 5EH, United Kingdom.
Muchowski
P J
PJ
van Den IJssel
P
P
Wu
G J
GJ
Hutcheson
A M
AM
Clark
J I
JI
Quinlan
R A
RA
D009202:Cardiomyopathies / Q000235:genetics*; D002386:Cataract / Q000235:genetics*; D002918:Chymotrypsin / Q000378:metabolism; D002942:Circular Dichroism; D003459:Crystallins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D008854:Microscopy, Electron; D016296:Mutagenesis; D011487:Protein Conformation; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D013056:Spectrophotometry, Ultraviolet
D003459:Crystallins; D011994:Recombinant Proteins; D002918:Chymotrypsin