α-crystallin chaperone-like activity and membrane binding in age-related cataracts

被引:83
作者
Cobb, BA
Petrash, JM
机构
[1] Washington Univ, Sch Med, Dept Ophthalmol & Visual Sci, St Louis, MO 63110 USA
[2] Washington Univ, Sch Med, Dept Genet, St Louis, MO 63110 USA
关键词
D O I
10.1021/bi0112457
中图分类号
Q5 [生物化学]; Q7 [分子生物学];
学科分类号
071010 ; 081704 ;
摘要
alpha-Crystallin, the major protein component of the vertebrate lens, is thought to play a critical role in the maintenance of transparency through its ability to inhibit stress-induced protein aggregation. However, during aging and cataract formation the amount of membrane-bound alpha-crystallin increases significantly while high molecular weight complexes (HMWCs) comprised of alpha-crystallin and other lens crystallins accumulate. These and other recent data suggest a possible link between cataract formation, the formation of high molecular weight alpha-crystallin aggregates, and the progressive increase in membrane association of alpha-crystallin. To better understand these processes, we characterized the chaperone-like activity (CLA) and subunit exchange of membrane bound alpha-crystallin. In addition, we measured the membrane binding properties of in vitro constituted HMWCs to understand the mechanism by which increased alpha-crystallin is bound to the membrane of old and cataractous lens cells in vivo. Membrane-associated alpha-crystallin complexes have measurably reduced CLA compared to complexes in solution; however, membrane binding does not alter the time required for alpha-crystallin complexes to reach subunit exchange equilibrium. In addition, HMWCs prepared in vitro have a profoundly increased membrane binding capacity as compared to native alpha-crystallin. These results are consistent with a model in which increased membrane binding of alpha-crystallin is an integral step in the pathogenesis of many forms of cataracts.
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页码:483 / 490
页数:8
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