Proteomic Analysis of Retinal Protein Expression With the Progression of AMD

Abstract

Abstract: : Purpose: Age–related macular degeneration (AMD) is characterized by drusen formation, retinal pigment epithelium (RPE) changes, geographic atrophy, and other clinical features. However, the etiology of the disease remains unclear. Since degeneration of photoreceptors precedes loss of the RPE layer, identification of changes in the neurosensory retina may provide insight into the early mechanisms of the disease. This study identified proteins that exhibited altered expression at specified stages of AMD. Methods: Human eyes from aged (60–90 yr) donors were obtained from the MN Lions Eye Bank. The eyes were graded using the Minnesota Grading System (MGS) (Olsen and Feng, IOVS, 45; 2004). Neurosensory retinal proteins from both the macular and peripheral regions were resolved using 2D polyacrylamide gel electrophoresis. Gels were silver stained and protein expression was analyzed using densitometry. For protein spots showing significant changes in expression, MALDI–TOF mass spectrometry (MS) was utilized to obtain protein identification. Protein identities were confirmed by tandem MS. Results: After analysis of ∼600 protein spots, we detected a subset of proteins demonstrating ∼2–fold protein expression changes (both increases and decreases) in both the macular and peripheral retina. Several of these protein spots show statistically significant expression changes between early onset and late stage disease. Proteins exhibiting 2–fold expression changes include proteins involved in metabolic, chaperone and signaling pathways. Conclusions: Resolution of neurosensory retinal proteins allows comparison for expression level changes from early to late stages of AMD defined by the MGS. These comparisons led to identification of region–specific subsets of proteins indicating 2–fold changes with increasing levels of AMD. The regional variation indicates that the protein profile changes differently in the macular region as compared with the peripheral region in AMD. Identification of specific proteins with altered expression may identify pathways involved in the pathogenesis of AMD.

Keywords: proteomics • age-related macular degeneration • retina