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Macrophage Cholesterol Depletion and Its Effect on the Phagocytosis of Cryptococcus neoformans
Published on: December 19, 2014
Cholesterol accumulation sequesters Rab9 and disrupts late endosome function in NPC1-deficient cells
Ian G Ganley1, Suzanne R Pfeffer
1Department of Biochemistry, Stanford University School of Medicine, 279 Campus Drive, Stanford, CA 94305-5307, USA.
The Journal of Biological Chemistry
|April 29, 2006
Summary
Niemann-Pick type C disease causes cholesterol buildup, impairing Rab9 protein function and disrupting essential receptor transport in late endosomes. This study reveals cholesterol directly sequesters Rab9, hindering mannose 6-phosphate receptor trafficking.
Area of Science:
- Cell Biology
- Molecular Biology
- Genetics
Background:
- Niemann-Pick type C (NPC) disease is an autosomal recessive disorder characterized by cholesterol and glycosphingolipid accumulation in late endosomes and lysosomes.
- Understanding the molecular mechanisms of NPC disease is crucial for developing targeted therapies.
Purpose of the Study:
- To investigate the impact of cholesterol accumulation on Rab9-dependent export of mannose 6-phosphate receptors (MPRs) from late endosomes in NPC disease.
- To elucidate the role of cholesterol in regulating Rab9 protein stability and membrane association.
Main Methods:
- Utilized primary fibroblasts from NPC patients and RNA interference to model NPC disease.
- Quantified endogenous Rab9 levels and half-life.
- Assessed Rab9 extractability from endosome membranes using guanine nucleotide dissociation inhibitor.
- Investigated the effect of cholesterol on prenylated Rab9 stability in liposomes.
- Analyzed MPR missorting and the effect of Rab9 overexpression.
Main Results:
- Rab9 levels and half-life were significantly elevated in NPC cells, indicating impaired protein turnover.
- Rab9 showed increased stabilization on endosome membranes in NPC cells, with reduced extractability.
- Cholesterol directly stabilized Rab9, decreasing its extractability from liposomes.
- Overexpression of Rab9 reversed the missorting of cation-dependent mannose 6-phosphate receptors to lysosomes for degradation.
Conclusions:
- Cholesterol directly contributes to Rab9 sequestration on NPC cell membranes, leading to its inactivation.
- This Rab9 sequestration disrupts the proper trafficking of mannose 6-phosphate receptors, contributing to NPC disease pathology.
- Targeting cholesterol accumulation or Rab9 stabilization may offer therapeutic strategies for NPC disease.
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