DAHLMAN, J.M.*; MARGOT, K.; HORWITZ, J.; POSNER, M.; Ashland University; Ashland University; Univ. of California, Los Angeles; Ashland University: Chaperone function of the heat shock protein alpha crystallin in the zebrafish lens
Alpha crystallin is a small heat shock protein that is expressed in the ocular lens of all vertebrates. It contributes to the refractive properties of the lens and prevents aggregation of denatured proteins caused by stress and aging. Essentially all research on the protective chaperone function of alpha crystallin is performed in mammalian systems. We are assaying the chaperone function of zebrafish alpha crystallin to develop a broader understanding of the role of this protein in vertebrate lens physiology. We have cloned the genes for both zebrafish alpha crystallin subunits and produced recombinant protein by overexpression in bacteria. The chaperone function of each subunit was assayed by measuring its ability to prevent the aggregation of denatured target proteins. At the approximate physiological temperature for the zebrafish (30° C) the alpha A subunit showed greater chaperone activity than the alpha B subunit. This differs from the mammalian condition in which the alpha B subunit shows greater chaperone activity at physiological temperature (37° C). The chaperone activity of zebrafish alpha A crystallin increased with temperature, similar to its mammalian orthologue. These data suggest that the structural changes in alpha A crystallin that occur with changing temperature may be conserved between bony fishes and mammals. But the relative protection provided by the two subunits at physiological temperature has changed. Natural variations in alpha crystallin function can help to elucidate the role of this protein in the vertebrate lens.
