Lysosomal cholesterol accumulation is commonly found in most peroxisomal disorders and reversed by 2-hydroxypropyl-β-cyclodextrin

Peroxisomal disorders(PDs)are a heterogenous group of diseases caused by defects in peroxisome biogenesis or functions.Xlinked adrenoleukodystrophy is the most prevalent form of PDs and results from mutations in the ABCD1 gene,which encodes a transporter mediating the uptake of very long-chain fatty acids(VLCFAs).The curative approaches for PDs are very limited.Here,we investigated whether cholesterol accumulation in the lysosomes is a biochemical feature shared by a broad spectrum of PDs.We individually knocked down fifteen PD-associated genes in cultured cells and found ten induced cholesterol accumulation in the lysosome.2-Hydroxypropyl-β-cyclodextrin(HPCD)effectively alleviated the cholesterol accumulation phenotype in PD-mimicking cells through reducing intracellular cholesterol content as well as promoting cholesterol redistribution to other cellular membranes.In ABCD1 knockdown cells,HPCD treatment lowered reactive oxygen species and VLCFA to normal levels.In Abcd1 knockout mice,HPCD injections reduced cholesterol and VLCFA sequestration in the brain and adrenal cortex.The plasma levels of adrenocortical hormones were increased and the behavioral abnormalities were greatly ameliorated upon HPCD administration.Together,our results suggest that defective cholesterol transport underlies most,if not all,PDs,and that HPCD can serve as a novel and effective strategy for the treatment of PDs.

Cholesterol transport through the peroxisome-ER membrane contacts tethered by PI（4,5）P2 and extended synaptotagmins

Most mammalian cells take up cholesterol from low-density lipoproteins(LDLs) via receptor-mediated endocytosis.After reaching lysosomes,LDL-derived cholesterol continues to transport to downstream organelles including the ER for specific structural and functional needs.Peroxisomes are recently found to receive cholesterol from lysosomes through lysosomeperoxisome membrane contacts.However,whether and how cholesterol is conveyed from peroxisomes to the ER remain unknown.Here,by combining high-resolution microscopic analyses and in vitro reconstitution of highly purified organelles or artificial liposomes,we demonstrate that peroxisomes form membrane contacts with the ER through the interaction between peroxisomal PI(4,5)P2 and ER-resident extended synaptotagmin-1,2 and 3(E-Syts).Depletion of peroxisomal PI(4,5)P2 or ESyts markedly decreases peroxisome-ER membrane contacts and induces cholesterol accumulation in lysosomes.Furthermore,we show that cholesterol is delivered from 3H-labeled peroxisomes or PI(4,5)P2-containing liposomes to the ER in vitro,and that the presence of peroxisomes augments cholesterol transfer from lysosomes to the ER.Together,our study reveals a new cholesterol transport pathway along the lysosome-peroxisome-ER membrane contacts in the cell.

The non-canonical NF-κB pathway promotes NPC2 expression and regulates intracellular cholesterol trafficking

Niemann-Pick type C2(NPC2) is a lysosome luminal protein that functions in concert with NPC1 to mediate egress of lowdensity lipoprotein-derived cholesterol from lysosome. The nuclear factor kappa B subunit 2(NF-κB2) protein is a component of NF-κB transcription factor complex critically implicated in immune and inflammatory responses. Here, we report that NF-κB2 regulates intracellular cholesterol transport by controlling NPC2 expression. RNAi-mediated disruption of NF-κB2, as well as other signaling members of the non-canonical NF-κB pathway, caused intracellular cholesterol accumulation. Blockage of the non-canonical NF-κB pathway suppressed NPC2 expression, whereas Lymphotoxin β receptor(LTβR) activation or Baff receptor(BaffR) stimulation up-regulated the mRNA abundance and protein level of NPC2. Further, NF-κB2 activated NPC2 transcription through direct binding to its promoter region. We also observed cholesterol accumulation in NF-κB2-deficient zebrafish embryo and NF-κB2 mutant mice. Collectively, these data identify a regulatory role for the non-canonical NF-κB pathway in intracellular cholesterol trafficking and suggest a link between cholesterol transport and immune system.