Membrane Perturbation by A2E, an RPE Lipofuscin Constitutent

Abstract

Abstract: : Purpose: A2E is a major constituent of RPE lipofuscin, the accumulation of which is likely to be relevant to AMD etiology. We previously showed that A2E can disrupt cell membranes, a property consistent with its amphiphilic structure. Here we further examine this behavior. Methods: The accumulation of A2E by ARPE-19 cells was compared to that of A1E, a nonphysiological single side-armed analog of A2E.The intracellular localization of A1E was studied in relation to an acidophilic dye that targets to lysosomes and the effect of A2E/A1E on the permeability of unilamellar vesicles was examined by fluorescence spectroscopy. Membrane blebbing was assayed in ARPE-19 cells that had been transduced to express GFP by lentivirus vector cDNA transfer. Anthocyanins were isolated from bilberry, a nutritional supplement. Results: A1E was accumulated by ARPE-19 cells at a faster rate than A2E, it induced cell death at lower concentrations and unlike A2E, it did not co-localize with a lysosomal marker. A1E also increased the permeability of phospholipid vesicles. When anthocyanins were incorporated prior to incubation with A2E, the accumulation of the latter across the phospholipid bilayer was reduced. A2E induced the formation of GFP-labeled membrane blebs.Conclusions: The wedge-shaped structure of A2E influences the mode in which it interacts with membranes and, in this model system, is targeted to lysosomes.

Keywords: retinal pigment epithelium • cell membrane/membrane specializations • cell death/apoptosis