The cell biology of lysosomal storage disorders

Lysosomal storage disorders, of which more than 40 are known, are caused by the defective activity of lysosomal proteins, which results in the intra-lysosomal accumulation of undegraded metabolites. Despite years of study of the genetic and molecular bases of lysosomal storage disorders, little is known about the events that lead from this intra-lysosomal accumulation to pathology. Here, we summarize the biochemistry of lysosomal storage disorders. We then discuss downstream cellular pathways that are potentially affected in these disorders and that might help us to delineate their pathological mechanisms

When cells stash their trash

Lysosomal disorders of the brai

In vivo inactivation of glycosidases by conduritol B epoxide and cyclophellitol as revealed by activity-based protein profiling

Glucocerebrosidase (GBA) is a lysosomal β-glucosidase degrading glucosylceramide. Its deficiency causes Gaucher disease (GD), a common lysosomal storage disorder. Carrying a genetic abnormality in GBA constitutes at present the largest genetic risk factor for Parkinson's disease (PD). Conduritol B epoxide (CBE), a mechanism-based irreversible inhibitor of GBA, is used to generate cell and animal models for investigations on GD and PD. However, CBE may have additional glycosidase targets besides GBA. Here, we present the first in vivo target engagement study for CBE, employing a suite of activity-based probes to visualize catalytic pocket occupancy of candidate off-target glycosidases. Only at significantly higher CBE concentrations, non-lysosomal glucosylceramidase (GBA2) and lysosomal α-glucosidase were identified as major off-targets in cells and zebrafish larvae. A tight, but acceptable window for selective inhibition of GBA in the brain of mice was observed. On the other hand, cyclophellitol, a closer glucose mimic, was found to inactivate with equal affinity GBA and GBA2 and therefore is not suitable to generate genuine GD-like models. This article is protected by copyright. All rights reserved.Medical BiochemistryBio-organic Synthesi

Ablation of the pro-inflammatory master regulator miR-155 does not mitigate neuroinflammation or neurodegeneration in a vertebrate model of Gaucher's disease

Bi-allelic mutations in the glucocerebrosidase gene (GBA1) cause Gaucher's disease, the most common human lysosomal storage disease. We previously reported a marked increase in miR-155 transcript levels and early microglial activation in a zebrafish model of Gaucher's disease (gba1 −/− ). miR-155 is a master regulator of inflammation and has been implicated in a wide range of different neurodegenerative disorders. The observed miR-155 upregulation preceded the subsequent development of widespread pathology with marked neuroinflammation, closely resembling human Gaucher's disease pathology. We now report similar increases of miR-155 expression in mammalian models of GD, confirming that miR-155 upregulation is a shared feature in glucocerebrosidase (GCase) deficiency across different species. Using CRISPR/Cas9 mutagenesis we then generated a miR-155 mutant zebrafish line (miR-155 −/− ) with completely abolished miR-155 expression. Unexpectedly, loss of miR-155 did not mitigate either the reduced lifespan or the robust inflammatory phenotypes of gba1 −/− mutant zebrafish. Our data demonstrate that neither neuroinflammation nor disease progression in GCase deficiency are dependent on miR-155 and suggest that miR-155 inhibition would not be a promising therapeutic target in Gaucher's disease