Monitoring the itinerary of lysosomal cholesterol in Niemann-Pick Type C1-deficient cells after cyclodextrin treatment

Abstract

Niemann-Pick disease type C (NPC) disease is a lipid-storage disorder that is caused by mutations in the genes encoding NPC proteins and results in lysosomal cholesterol accumulation. 2-Hydroxypropyl-β-cyclodextrin (CD) has been shown to reduce lysosomal cholesterol levels and enhance sterol homeostatic responses, but CD’s mechanism of action remains unknown. Recent work provides evidence that CD stimulates lysosomal exocytosis, raising the possibility that lysosomal cholesterol is released in exosomes. However, therapeutic concentrations of CD do not alter total cellular cholesterol, and cholesterol homeostatic responses at the ER are most consistent with increased ER membrane cholesterol. To address these disparate findings, here we used stable isotope labeling to track the movement of lipoprotein cholesterol cargo in response to CD in NPC1-deficient U2OS cells. Although released cholesterol was detectable, it was not associated with extracellular vesicles. Rather, we demonstrate that lysosomal cholesterol trafficks to the plasma membrane (PM), where it exchanges with lipoprotein-bound cholesterol in a CD-dependent manner. We found that in the absence of suitable extracellular cholesterol acceptors, cholesterol exchange is abrogated, cholesterol accumulates in the PM, and reesterification at the ER is increased. These results support a model in which CD promotes intracellular redistribution of lysosomal cholesterol, but not cholesterol exocytosis or efflux, during the restoration of cholesterol homeostatic responses.

Single Cell Transcriptome Analysis of Niemann–Pick Disease, Type C1 Cerebella

“…Of the 36 genes showing increased expression, 18 (50%) encode secreted proteins. Promoting lysosomal exocytosis has been proposed as a mechanism for clearance of stored cholesterol [ 53 , 54 , 55 , 56 ]. Thus, it is possible that this represents minor pathway that cells utilize to redistribute cholesterol resulting in increased expression of secreted proteins to compensate for their loss.…”

NPC1-mTORC1 Signaling Couples Cholesterol Sensing to Organelle Homeostasis and Is a Targetable Pathway in Niemann-Pick Type C

“…NPC is triggered by inactivating mutations in NPC1, a polytopic transmembrane cholesterol transporter located on the lysosomal limiting membrane (Gong et al, 2016;Kwon et al, 2009;Li et al, 2016;Winkler et al, 2019). In conjunction with NPC2, a cholesterol-binding protein of the lysosomal lumen, NPC1 exports cholesterol released from low-density lipoprotein (LDL) to acceptor compartments, such as the endoplasmic reticulum (ER), the Golgi, and the plasma membrane (Feltes et al, 2020;Infante and Radhakrishnan, 2017;Infante et al, 2008;Pfeffer, 2019).…”

NPC1-mTORC1 signaling Couples Cholesterol Sensing to Organelle Homeostasis and is a Targetable Pathway in Niemann-Pick type C

“…NPC is triggered by inactivating mutations in NPC1, a polytopic transmembrane cholesterol transporter located on the lysosomal limiting membrane (Gong et al, 2016;Kwon et al, 2009;Li et al, 2016;Winkler et al, 2019). In conjunction with NPC2, a cholesterol-binding protein of the lysosomal lumen, NPC1 exports cholesterol released from Low-Density Lipoprotein (LDL) to acceptor compartments such as the endoplasmic reticulum (ER), the Golgi and the plasma membrane (Feltes et al, 2020;Infante and Radhakrishnan, 2017;Infante et al, 2008;Pfeffer, 2019).…”