Photoreceptor outer segment (POS) phagocytosis (POS phagocytosis)

Photoreceptor outer segment (POS) phagocytosis is a vital homeostatic process performed by the retinal pigment epithelium (RPE) to maintain visual function and retinal health [1]. Every day, the distal tips of photoreceptor outer segments are shed and must be engulfed and degraded by the adjacent RPE cells to prevent the accumulation of photo-oxidized lipids and proteins [2]. This process is mediated by a complex molecular machinery involving the αvβ5 integrin for binding and the MERTK receptor tyrosine kinase for engulfment, triggered by ligands such as Gas6 and Protein S [1, 3]. Defects in this pathway, particularly mutations in the MERTK gene, lead to the accumulation of undigested POS debris in the subretinal space, resulting in the death of photoreceptors and causing diseases like Retinitis Pigmentosa [3]. Therapeutic strategies targeting this process include gene replacement therapies for specific pathway components and small molecules designed to enhance RPE phagocytic efficiency in the context of aging and macular degeneration [4, 6].

Other names

RPE phagocytosisRetinal phagocytosisOuter segment clearancePOS clearance

Restoration of MERTK-mediated engulfment and enhancement of RPE clearance of outer segment debris [4, 6]