Journal
BIOCHEMICAL JOURNAL
Volume 410, Issue -, Pages 81-92Publisher
PORTLAND PRESS LTD
DOI: 10.1042/BJ20070976
Keywords
Alzheimer's disease (AD); ceramide; electrospray ionization MS (ESI-MS); metachromatic leukodystrophy; shotgun lipidomics; sulfatide
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Funding
- NIA NIH HHS [R01 AG31675, R01 AG23168] Funding Source: Medline
- NIDDK NIH HHS [P30 DK056341-08, P30 DK056341-07, P30 DK056341] Funding Source: Medline
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Alterations in stilfatide metabolism, trafficking and homoeostasis are present at the earliest clinically recognizable stages of Alzheimer's disease and are associated with metachromatic leukodystrophy. However, the role of sulfatide in these disease states remains unknown. In the present study, we investigated the sequelae of NB (neuroblastoma) cells upon sulfatide supplementation and the biochemical mechanisms contributing to the sulfatide-induced changes. By using shotgun lipidomics, we showed dramatic accumulations of sulfatide, ceramide and sphingosine in NB cells in a time- and dose-dependent manner. Further studies utilizing subcellular fractionation and shotgun lipidomics analyses demonstrated that most of the increased ceramide content was generated in the endosomal compartment, whereas sulfatides predominantly accumulated in lysosomes. In addition, we determined that the sulfatide-mediated increase in endosomal ceramide content mainly resulted from beta-galactosidase activity, which directly hydrolyses sulfatide to ceramide without a prior desulfation step. Substantial cell apoptosis occurred in parallel with the accumulation of sulfatides and ceramides, as revealed by mitochondrial membrane depolarization, by phosphatidylserine translocation and by the TUNEL (terminal deoxynucleotidyl transferase-mediated dUTP nick-end labelling) assay. These findings were also demonstrated with primary neuron cultures. Collectively, our results demonstrate that abnormal sulfatide metabolism can induce cell apoptosis due to endosome-mediated ceramide generation and the accumulation of cytotoxic levels of sulfatides in lysosomes.
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