Question: 

Gaucher disease (GD) is a lysosomal storage disorder caused by deficiency of human b-glucocerebrosidase (GCB), an enzyme that catalyzes the hydrolysis of glucosylceramide in lysosomes. The clinical course of the disease is well described and treatment options exist but the mechanisms underlying cellular pathology are not entirely understood. As C. elegans turned out to be a useful system for several lysosomal storage disorders, we investigated whether it might serve as a model for GD as well.

Methods: 

Orthologues of GCB were searched in Wormbase database by BLASTP. cDNAs were provided by Y. Kohara or obtained by RT-PCR. Protein expression in C. elegans was examined with Northern blotting. For functional analyses orthologues were expressed in HEK293-cells and catalytic activity was measured with MU-substrate.

Results: 

There are four putative orthologues of GCB in C. elegans: C33C12.3 (gcb-1), C33C12.8 (gcb-2), F11E6.1 (gcb-3) and Y4C6B.6 (gcb-4). Potential disulfide bond-forming cysteine residues and N-glycosylation sites are conserved as well as critical residues in the active site with exemption of E274 in gcb-1. Northern blotting indicated high expression levels for gcb-3 and gcb-4, low expression levels for gcb-1 and -2. Expressed in HEK293, GCB-3 and -4 showed high glucosylceramidase activity at acidic pH. Despite the substitution in the catalytic site, GCB-1 was slightly active, too. No activity was measured for GCB-2.

Conclusion: 

Results suggest that C. elegans might serve as a model for GD as three orthologues show glucosylceramidase activity at acidic pH. Further studies have to be made on the subcellular localization. The question has to be cleared if a functional redundancy of the orthologues may avoid storage in an extent that subcellular structural changes are detectable.