Cholesterol-dependent increases in glucosylceramide synthase activity in Niemann-Pick disease type C model cells: Abnormal trafficking of endogenously formed ceramide metabolites by inhibition of the enzyme.

Sphingolipids such as sphingomyelin and glycosphingolipids (GSLs) derived from glucosylceramide (GlcCer), in addition to cholesterol, accumulate in cells/neurons in Niemann-Pick disease type C (NPC). The activities of acid sphingomyelinase and lysosomal glucocerebrosidase (GCase), which degrade sphingomyelin and GlcCer, respectively, are down-regulated in NPC cells, however, changes in GlcCer synthase activity have not yet been elucidated. We herein demonstrated for the first time that GlcCer synthase activity for the fluorescent ceramide, 4-nitrobenzo-2-oxa-1,3-diazole-labeled C6-ceramide (NBD-ceramide) increased in intact NPC1((-/-)) cells and cell lysates without affecting the protein levels.

Effects of Hsp90 inhibitors, geldanamycin and its analog, on ceramide metabolism and cytotoxicity in PC12 cells.

The inhibitors of heat shock protein-90 (Hsp90), geldanamycin (GA) and 17-(allylamino)-17-desmethoxygeldanamycin, show various cellular effects including destabilization of Hsp90 clients and expression of other chaperones, etc. and modulate cytotoxicity depending on cell types and stimuli. In this study, we investigated the effects of Hsp90 inhibitors on survival of PC12 cells with and without cytotoxic stimuli including orthovanadate, Na(3)VO(4).

Arachidonic acid metabolism via cytosolic phospholipase A2 α induces cytotoxicity in niemann-pick disease type C cells.

Niemann-Pick disease type C (NPC) is a neurodegenerative lipid storage disorder caused by mutations in NPC1 or NPC2 genes. Loss of function of either protein results in the endosomal accumulation of cholesterol and other lipids. Here, we report that NPC1-deficient Chinese hamster ovary cells exhibit increased release of arachidonic acid (AA) and synthesis of prostaglandin E(2) compared with wild-type cells.

Activation of cytosolic phospholipase A2alpha by epidermal growth factor (EGF) and phorbol ester in HeLa cells: different effects of inhibitors for EGF receptor, protein kinase C, Src, and C-Raf.

In several types of cancer cells, prostaglandins produced via the over-expression of epidermal growth factor receptor (EGFR) and cyclooxygenases regulate cell growth. We investigated the signaling mechanisms for the release of arachidonic acid (AA, a precursor for prostaglandins) in human cervical carcinoma HeLa cells. Treatment with EGF and 4beta-phorbol 12-myristate 13-acetate (PMA) with A23187 released AA accompanied by the phosphorylation of extracellular signal-regulated kinases (ERK1/2).