Retinal pigment epithelium lipofuscin proteomics
Kwok-Peng Ng1, Bogdan Gugiu, Kutralanathan Renganathan
1Cole Eye Institute and Lerner Research Institute, Cleveland Clinic Foundation, Case Western Reserve University, Cleveland, Ohio 44195, USA.
Molecular & Cellular Proteomics : MCP
|April 26, 2008
Summary
Lipofuscin in retinal pigment epithelium (RPE) aged with age may contribute to macular degeneration. Purified lipofuscin retains toxicity, suggesting pathogenesis is independent of associated proteins, and involves reactive species from lipids and retinoids.
Area of Science:
- Ophthalmology
- Cell Biology
- Biochemistry
Background:
- Lipofuscin accumulates in the retinal pigment epithelium (RPE) with age, potentially contributing to age-related macular degeneration.
- The precise composition and pathogenic mechanisms of RPE lipofuscin are not fully understood due to preparation heterogeneity.
Purpose of the Study:
- To investigate the protein content and pathogenic role of RPE lipofuscin.
- To determine if lipofuscin's toxicity is protein-dependent or related to its core components.
Main Methods:
- Purification of RPE lipofuscin granules using proteinase K or SDS.
- Quantitative comparison of crude and purified lipofuscin using LC-MS/MS proteomics, immunoassays, amino acid analysis, HPLC, and phototoxicity assays.
- Microscopic analysis (light, confocal, transmission electron) of purified granules.
Main Results:
- Purified lipofuscin granules contained minimal protein (approximately 2% w/w) but retained full phototoxicity.
- No significant differences in granule size, shape, or bisretinoid content were observed between crude and purified preparations.
- Purified granules showed oxidative modifications, indicating generation of reactive species from lipids and retinoids.
Conclusions:
- RPE lipofuscin pathogenesis is largely independent of associated proteins.
- Reactive species generated from lipids and retinoids within lipofuscin granules are likely key contributors to RPE dysfunction and age-related macular degeneration.
