Escrevente, C; Falcao, AS; Hall, MJ; Lopes-da-Silva, M; Antas, P; Mesquita, MM; Ferreira, IS; ... Seabra, MC; + view all Escrevente, C; Falcao, AS; Hall, MJ; Lopes-da-Silva, M; Antas, P; Mesquita, MM; Ferreira, IS; Cardoso, MH; Oliveira, D; Fradinho, AC; Ciossek, T; Nicklin, P; Futter, CE; Tenreiro, S; Seabra, MC; - view fewer (2021) Formation of Lipofuscin-Like Autofluorescent Granules in the Retinal Pigment Epithelium Requires Lysosome Dysfunction. Investigative Ophthalmology & Visual Science , 62 (9) , Article 39. 10.1167/iovs.62.9.39.

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Abstract

PURPOSE: We aim to characterize the pathways required for autofluorescent granule (AFG) formation by RPE cells using cultured monolayers. METHODS: We fed RPE monolayers in culture with a single pulse of photoreceptor outer segments (POS). After 24 hours the cells started accumulating AFGs that were comparable to lipofuscin in vivo. Using this model, we used a variety of light and electron microscopical techniques, flow cytometry and Western blot to analyze the formation of AFGs. We also generated a mutant RPE line lacking cathepsin D by gene editing. RESULTS: AFGs seem to derive from incompletely digested POS-containing phagosomes and after 3 days are surrounded by a single membrane positive for lysosome markers. We show by various methods that lysosome-phagosome fusion is required for AFG formation, and that impairment of lysosomal pH or catalytic activity, particularly cathepsin D activity, enhances AF accumulation. CONCLUSIONS: We conclude that lysosomal dysfunction results in incomplete POS degradation and enhanced AFG accumulation.

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