PROTEIN MODIFICATION IN AGE-RELATED RETINAL DEGENERATION

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Our goal is to elucidate the moleccular mechanisms involved in degeneration of the retina, as occurs in age-related macular degeneration. Recent evidence suggests that the pathogenesis includes increased protein and lipid oxidation and inadequate recycling of cell constituents. The proteasome is the proteolytic enzyme responsible for recycling the majority of cell proteins, including oxidized and misfolded proteins. Oxidized proteins could accumulate due to diminished proteasome function. We will test the gypothesis that defects in proteasome function and the accumulation of oxidized proteins result in retinal degeneration. Proteasome function and the extent of oxidative damage to proteins will be investigated in rod outer segments (ROS) and the retinal pigment epithelium (RPE) of the retinas from Fisher 344 rats (10, 23, 26 months). The retina is particularly susceptible to oxidative damage because of the combination of (a) light, (b) an oxygen-rich environment, and (c) membranes containing a high concentration of polyunsaturated fatty acids that are easily oxidized. The following aims will be pursued: (1) Define age-related changes in proteasome expression and function. This aim will test the hypothesis that aging is accompanied by decreased proteasome activity. (2) Quantify the extent of protein oxidation. We predict more extensive oxidative modifications in aged compared with younger rats. Biochemical and immunohistochemical techniques will be used to investigate proteasome function, protein oxidation, and the extent of retinal degeneration in the retinas from three different age rats. Although there is considerable evidence linking increased oxidative stress and diminished protein turnover in other tissues, the pilot project is needed to provide the first clear evidence that these effects correlate with age-related retinal degeneration. The accumulation of oxidized or misfolded proteins has been demonstrated in a host of age-related degenerative diseases, such as Alzheimer's and Parkinson's diseases. Thus proteasome dysfunction may be the common, underlying mechanism for a number of age- related degeneration diseases. This study will extend our knowledge of the basic mechanism of proteasome function, a first step in developing therapeutic interventions.