CTSS and Alzheimer disease: The link between AD and the lysosomal system is strengthened by observations that polymorphisms in several cathepsin genes increase the risk for AD (Bhojak et al., 2001, Papassotiropoulos et al., 1999) and deletions of lysosomal protease inhibitors cystatin B/C largely ameliorate symptoms in AD mouse models (Mi et al., 2007, Yang et al., 2011, Yang et al., 2014).