Endosomes and lysosomes play distinct roles in sulfatide-induced neuroblastoma apoptosis: potential mechanisms contributing to abnormal sulfatide metabolism in related neuronal diseases

Abstract

Alterations in sulfatide 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.

Role of Sulfatide in Influenza A Virus Replication

“…An ASA-independent pathway of sulfatide has been suggested in a neuroblastoma cell line, which directly generates ceramide from sulfatide without prior desulfation in lysosomes. 16) Deficiency of ASA activity or mutations in the gene coding for SapB lead to the accumulation of sulfatide in lysosomes, resulting in a demyelinating disease called metachromatic leukodystrophy (MLD). 23) Sulfatide has been reported to be involved in many biological activities including the nervous system, cancer, insulin secretion in the islet of Langerhans, hemostasis/thrombosis, immune system, and microbial infection.…”

“…Abundant expression of sulfatide is detected in many human cancer tissues, such as human serous papillary ovarian carcinoma tissues, 10) human ovarian malignant and benign cancer tissues, 11) primary human colorectal cancer tissues, 12) human renal carcinoma tissues, 13) human gastric cancer tissues, 14) and primary human lung adenocarcinoma tissues. 15) Cellular sulfatide is mainly localized in the Golgi apparatus, 16) cellular membrane, and lysosomes in the cytosol.…”

Methods in Comprehensive Mass Spectrometry-Based Measurement of Sphingolipids

“…Direct infusion based shotgun lipidomics enables determination of the levels of many low-abundance sphingolipid metabolites e.g. ceramide-phosphates, sphinganine and sphingosinephosphates in a variety of biological samples [25,26]. In a recent study the determination of sphingosine levels in the lysosome was achieved using this method [25].…”

“…ceramide-phosphates, sphinganine and sphingosinephosphates in a variety of biological samples [25,26]. In a recent study the determination of sphingosine levels in the lysosome was achieved using this method [25]. Although shotgun lipidomics has some limitations, these methods are very useful and efficient to quantify the molecular species of one entire lipid class from any unknown sample.…”

Role of sulfatide in virus infection and replication

“…1). Recently, an alternative sulfatase-independent pathway of sulfatide degradation has been suggested by indications in a neuroblastoma cell line for direct generation of ceramide from endocytosed sulfatide without prior desulfation (9). Sulfatide exhibits various structures, including diŠerent lengths of the acyl chain and ceramide moiety, which can also be hydroxylated as well as other sphingolipids.…”