Progranulin Insufficiency Affects Lysosomal Homeostasis in Retinal Pigment Epithelium

Abstract

Background: Homozygous loss-of-function progranulin gene (GRN) mutation carriers develop adult-onset neuronal ceroid lipofuscinosis (NCL), a lysosomal storage disease. Clinically, NCL patients display retinal degeneration and visual dysfunction. However, there is little information about the effects of progranulin dysfunction on lysosomal function of the retinal pigment epithelium (RPE). Materials and Methods: We performed RNA interference knock down of progranulin in primary human RPE (hRPE) cells and observed RPE function and lysosomal activity. Results: Progranulin localized to the lysosome in RPE cells. Loss of progranulin did not affect the biogenesis of lysosomes in RPE cells, while it was necessary for the activation of lysosomal proteases. Furthermore, progranulin deficiency decreased cell viability and disrupted the cell-cell junctions. Conclusion: Our results demonstrate that progranulin insufficiency disturbs lysosomal activity and physiological functions in RPE cells.