Analysis of cholesterol export from endo-lysosomes by Niemann Pick C2 protein using combined fluorescence and X-ray microscopy

  title={Analysis of cholesterol export from endo-lysosomes by Niemann Pick C2 protein using combined fluorescence and X-ray microscopy},
  author={Alice Dupont and Frederik W. Lund and Maria Louise V. Jensen and Maria Szomek and Gitte Krogh Nielsen and Christian W Heegaard and Peter Guttmann and Stephan Werner and James G. McNally and Gerd Schneider and Sergey Kapishnikov and Daniel W{\"u}stner},
The Niemann-Pick C2 protein (NPC2) is a sterol transfer protein in late endosomes and lysosomes (LE/LYSs). How its capacity to transport cholesterol between membranes is linked to endo-lysosomal membrane trafficking is not known. Using quantitative fluorescence imaging combined with soft X-ray tomography (SXT); we show that NPC2 mediated sterol efflux is accompanied by large changes in distribution, size and ultrastructure of endocytic organelles. We observed clearance of intra-luminal lipid… 



Mechanism of Cholesterol Transfer from the Niemann-Pick Type C2 Protein to Model Membranes Supports a Role in Lysosomal Cholesterol Transport*♦

The results suggest that NPC2 rapidly transports cholesterol to phospholipid vesicles via a collisional mechanism which involves a direct interaction with the acceptor membrane, and support a role for the NPC2 protein in the egress of LDL derived cholesterol out of the endosomal/lysosomal compartment.

Cholesterol Accumulation Sequesters Rab9 and Disrupts Late Endosome Function in NPC1-deficient Cells*

It is concluded that cholesterol contributes directly to the sequestration of Rab9 on Niemann-Pick type C cell membranes, which in turn, disrupts mannose 6-phosphate receptor trafficking.

The Niemann-Pick C1 Protein Resides in a Vesicular Compartment Linked to Retrograde Transport of Multiple Lysosomal Cargo*

It is concluded that a distinctive organelle containing NPC1 mediates retrograde lysosomal transport of endocytosed cargo that is not restricted to sterol.

Elevated endosomal cholesterol levels in Niemann-Pick cells inhibit rab4 and perturb membrane recycling.

The data suggest that abnormal membrane recycling in NPFs results from specific inhibition of rab4 function by excess cholesterol in EEs, which is similar to that seen in normal HSFs.

Multiple Surface Regions on the Niemann-Pick C2 Protein Facilitate Intracellular Cholesterol Transport*

It is hypothesized that, in part, NPC2 rapidly traffics cholesterol between closely appositioned membranes within the multilamellar interior of late endosomal/lysosomal proteins, ultimately effecting cholesterol egress from this compartment.

Niemann-Pick C1 Functions Independently of Niemann-Pick C2 in the Initial Stage of Retrograde Transport of Membrane-impermeable Lysosomal Cargo*

It is shown here that cells with mutated NPC1 have significantly reduced rates of late endosome/lysosome fusion relative to wild type cells, whereas cells with mutations in NPC2 have rates that are similar to those observed in wildtype cells, suggesting that NPC1 and NPC2 can function independently in the egress of certain membrane-impermeable lysosomal cargo.

Late Endosomal Cholesterol Accumulation Leads to Impaired Intra-Endosomal Trafficking

It is suggested that back fusion of intralumenal vesicles with the limiting membrane of late endosomes is dramatically perturbed upon cholesterol accumulation, which leads to an increase in the size of the compartment.

Development of an assay for the intermembrane transfer of cholesterol by Niemann-Pick C2 protein

A cell-free assay for measuring intermembrane lipid transport and identifying for the first time the ability of other lysosomal proteins, most notably the GM2-activator protein, to mediate inter Membrane cholesterol transfer are identified.