BIOLOGICAL ROLE OF PHOSPHORYLATION OF ALPHA-CRYSTALLIN

Alpha crystallin, alpha, is a major protein of the lens contributing to the transparency of the organ by its known structural and putative chaperone like characteristics. It is known that alpha is phosphorylated to a significant extent on both of its subunits alphaA and alphaB. Since phosphorylation required a considerable amount of energy, it is apparent that these are important reactions. My work has shown that with oxidative stress, phosphorylation of alpha is significantly increased. However, it is clear that phosphorylation does not effect the known chaperone activity of alpha or significantly change its physical structure. Therefore, the objective of this grant is to define the biological roles of phosphorylation of alphaA and alphaB, especially its possible contribution to the prevention of the development of maturity onset cataract. The effect of a variety of stresses, which are believed to contribute to the development of cataract, on the phosphorylation of alphaA and alphaB in rat lenses in normal and transfected lens epithelial cells will be studied to determine the function of phosphorylation of alphaA and alphaB. The distribution of alphaA or alphaB within the cell will be examined before and after such stresses to determine changes in cellular localization and binding sites of the alpha macromolecule. The sites of the oxidative stress-induced phosphorylation will also be determined. The binding of phosphorylated and nonphosphorylated alphaA and alphaB to a variety of biomolecules and cell structures will be studied to determine whether alpha is involved in reactions with cell matrix modeling plasma membrane, nuclear membrane structure, and proteolytic pathways. This work is a logical extension of my previous studies. The project should significantly increase our understanding of alpha-crystallin function.