The overall goal of this project has been to provide a biochemical mechanism for formation of selenite cataract in young rats. The steps in the working hypothesis for selenite cataract are: oxidation by selenite, influx of calcium, activation of calcium activated protease (m-calpain), loss of the N-terminal extensions on beta-crystallin polypeptides, insolubilization of crystallins, and opacity. This fundamental proteolytic- insolubilization mechanism occurs in most other models of rodent cataracts (galactose, xylose, H2O2, diamide, A23187, BSO), regardless of the initial insult allowing influx of calcium, and even in normal maturation of rodent lenses. This suggested important follow up studies on interactions between proteolyzed beta-crystallins (aims 1 and 2) as well as a new, major direction for this grant concerning epithelium (aim 3):
Aim 1 : Measure improper molecular interactions between proteolyzed crystallin polypeptides in selenite cataract.
Aim 2. Discover the conditions and mechanisms causing in vitro light scattering after proteolysis of lens crystallins from non-rat species, including man.
Aim 3. Determine the role of metabolic changes in lens epithelium in the formation of selenite cataract. Techniques to be used include differential display, recombinant expression, yeast two hybrid system, RT-PCR, 2D electrophoresis with Edman sequencing, and in vitro light scattering. The results will extend our on-going studies concerning how crystallins become insoluble as well as show how the lens epithelium responds to a cataractogenic insult. The hope is that this will help development of anti-cataract drugs based on inhibiting proteolysis and protecting the epithelium.
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