Role of RPE Phagocytosis in the Retina Metabolic Ecosystem

Photoreceptors are the most glycolytically active cells in the body. Vital to glucose homeostasis is the metabolic relationship between the photoreceptors and the retinal pigment epithelium (RPE). The photoreceptors and RPE are in metabolic symbiosis, wherein the RPE takes up glucose from circulation and passes it on to the photoreceptors to fuel glycolysis. In turn, the photoreceptors produce energy substrates that are taken up by the RPE to support their metabolism. One of the main roles of the RPE is to phagocytose "used" photoreceptor outer segments (POS), a process that occurs to mitigate damage accrued by light. This mini-review explores the role that POS phagocytosis has in supporting the metabolic ecosystem linking photoreceptors and the RPE.