The cell biology of disease Lysosomal storage disorders : The cellular impact of lysosomal dysfunction

Correspondence to Frances M. Platt: [email protected]; Barry Boland: [email protected]; or Aarnoud C. van der Spoel: [email protected] Abbreviations used in this paper: CNS, central nervous system; LSD, lysosomal storage disease; NPC, Niemann-Pick type C. Lysosomal storage disorders: A brief overview Inborn errors of metabolism are a common cause of inherited disease (Burton, 1998), of which lysosomal storage diseases (LSDs) are a significant subgroup (Platt and Walkley, 2004; Fuller et al., 2006; Ballabio and Gieselmann, 2009). The combined incidence of LSDs is estimated to be approximately 1:5,000 live births (Fuller et al., 2006), but the true figure is likely greater when undiagnosed or misdiagnosed cases are accounted for. Common to all LSDs is the initial accumulation of specific macromolecules or monomeric compounds inside organelles of the endosomal–autophagic–lysosomal system. Initial biochemical characterization of stored macromolecules in these disorders led to the implication of defective lysosomal enzymes as a common cause of pathogenesis (Hers, 1963; Winchester, 2004). Although most LSDs result from acidic hydrolase deficiencies (Winchester, 2004), a considerable number of these conditions result from defects in lysosomal membrane proteins or non-enzymatic soluble lysosomal proteins (Saftig and Klumperman, 2009). Therefore, LSDs offer a window into the normal functions of both enzymatic and non-enzymatic lysosomal proteins.