The lysosome and proteostatic stress at the intersection of pediatric neurological disorders and adult neurodegenerative diseases.

In the last two decades, many gene mutations have been identified that when homozygous, lead to childhood neurological disorders, but when heterozygous, result in adult-onset neurodegenerative disease. A shared feature linking these genes? They encode proteins residing in or impacting the function of the lysosome, a key organelle in macromolecular degradation and recycling whose loss leads to the inability to manage proteostatic stress. Here, we propose that lysosomes connect a subset of genetic neurological and neurodegenerative disorders as they occur in two distinct life epochs-development and aging-that endure high levels of proteostatic and other physiological stresses. In this Perspective, we highlight the differing mechanisms of three genes that exemplify this link: glucocerebrosidase A (GBA: Gaucher's disease and Parkinson's disease), progranulin (GRN: neuronal ceroid lipofuscinosis and frontotemporal dementia), and tuberous sclerosis complex 1 (TSC1: tuberous sclerosis complex and frontotemporal dementia). We discuss why neurons seem particularly vulnerable to lysosomal dysfunction and ways in which lysosomes potentially contribute to selective neuronal vulnerability. Finally, as disrupted lysosomal catabolism of macromolecules connects these diseases of the nervous system, we propose that they be jointly conceptualized as "Lysosomal Clearance Disorders."