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Glucosylceramide modulates endolysosomal pH in Gaucher disease
1Cell Signalling Lab. Leicester School of Pharmacy, De Montfort University, The Gateway, Leicester, LE1 9BH, UK. dsillence@dmu.ac.uk
Molecular Genetics and Metabolism
|May 1, 2013
Summary
Glucosylceramide (GlcCer) accumulation in Gaucher disease disrupts lysosomal pH. Modulating GlcCer levels impacts endolysosomal pH and lipid storage, offering insights into Gaucher disease mechanisms.
Area of Science:
- Cell Biology
- Biochemistry
- Lysosomal Storage Diseases
Background:
- Gaucher disease results from impaired glucocerebrosidase activity, leading to GlcCer accumulation.
- In Gaucher disease, endocytosed glycolipids are mistargeted to lysosomes, unlike in normal cells where they are directed to the Golgi.
- Understanding GlcCer's role in endocytic sorting is crucial for Gaucher disease pathogenesis.
Purpose of the Study:
- To investigate the role of GlcCer in endocytic sorting and its impact on lysosomal pH.
- To determine if GlcCer accumulation or depletion affects endolysosomal pH in macrophages and patient cells.
- To explore the relationship between GlcCer levels, lipid accumulation, and lysosomal function.
Main Methods:
- RAW macrophages were treated with Conduritol B-epoxide to inhibit GlcCer breakdown.
- Lipid analysis was performed to quantify GlcCer, triacylglycerol, and cholesterol levels.
- Ratio imaging using acridine orange and lysosensor yellow/blue was employed to measure endolysosomal pH.
Main Results:
- Inhibition of GlcCer breakdown led to accumulation of triacylglycerol and cholesterol, correlating with increased lysosomal pH.
- Increased endolysosomal pH was observed in treated macrophages and Gaucher patient lymphoblasts, but not in other lysosomal storage disease lymphoblasts.
- Inhibitors of GlcCer synthesis also increased cholesterol, triacylglycerol, and endolysosomal pH, with glucosylsphingosine specifically reversing these effects.
Conclusions:
- GlcCer accumulation or depletion significantly modulates endolysosomal pH in lymphocytes.
- The findings suggest a multistep model where pH alterations drive altered trafficking via cholesterol accumulation.
- GlcCer plays a critical role in maintaining normal lysosomal function, and its disruption is implicated in Gaucher disease pathology.
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