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JR Dunlevy, RM Darrow, DT Organisciak; Retinal Light Damage Alters the Level of the Novel Protein SH3BP4 . Invest. Ophthalmol. Vis. Sci. 2002;43(13):3610.
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Purpose: SH3BP4 is a 107 kD protein that has a putative death domain located at its C-terminus and may play an important role in apoptosis. The purpose of this study is to determine if SH3BP4 is a component of the neural retina and if SH3BP4 protein levels are affected by intense light damage induced apoptosis. Methods: Rats were reared in either dim cyclic light (20-30 Lux) or in darkness. Light damage was induced by exposing rats to intense green light (1200 Lux) for various periods of time. Rats were sacrificed, neural retinas dissected, proteins separated by electrophoresis and Western blotted using a SH3BP4 specific antibody. Data was quantitated by measuring band intensity in pixels / µg total protein. Results: Preliminary studies using young dystrophic RCS rats and P23H transgenic rats show that SH3BP4 is present in the retina prior to photoreceptor cell degeneration. However, SH3BP4 concentrations are reduced by 50% in 58 day old RCS rats and ≷ 7 month old P23H rats indicating that SH3BP4 may be a component of both the inner and outer retinal layers. In light damage studies, dark reared rats showed a 2.5 fold increase in SH3BP4 expression after exposure to 8 hrs of intense light. Similarly, cyclic-light reared rats showed a 2-3 fold increase in SH3BP4 expression in response to 2-12 hrs of intense light. After 24 hrs of recovery in the dark SH3BP4 levels increased as photoreceptor cell loss occurred. 24 hrs of light damage caused a decrease in SH3BP4 compared to controls that may also be attributable to progressive cell death. These results correlate well with in vitro studies using RPE cells where an increase in SH3BP4 expression is observed 2-8 hrs after incubation with a pro-oxidant followed by rapid degradation of SH3BP4. Conclusion: These results show that SH3BP4 is a component of the neural retina and is mostly likely present in both the inner and outer layers. SH3BP4 also appears to have a potential role in apoptosis where protein levels increase in response to light damage.
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