ART4 and frontotemporal dementia: The glycoprotein PGRN, which has been implicated in neurodegenerative diseases such as frontotemporal dementia, lysosomal storage disorders, and neuronal ceroid lipofuscinosis, traffics to lysosomes, where it is processed to GRNs and performs critical functions, including regulating lysosomal pH and degrading proteins and lipids (19, 20).