Fig. 4.

Lysosomal regulation of NSC quiescence. To maintain proteostasis, active NSCs have higher proteasomal activity and lower lysosomal activity, while quiescent NSCs have lower proteasomal activity and higher lysosomal activity. Quiescent NSCs contain more lysosomes, but lysosomal abundance decreases over the course of the aging process. On the other hand, the level of protein aggregates and ROS increases with age, in turn affecting the depth of quiescence. In active NSCs, TFEB activation induces quiescence, whereas in quiescent NSCs, it rejuvenates the cells and decreases the abundance of aggregates. Thus, lysosomes serve as a switch for maintaining NSC quiescence.