Effect of HFE Variants on Sphingolipid Expression by SH-SY5Y Human Neuroblastoma Cells

Abstract

C282Y and H63D are two common variants of the hemochromatosis protein HFE. SH-SY5Y human neuroblastoma cells stably transfected to express either wild type HFE (WT-HFE), or the C282Y or H63D allele were analyzed for effect of expression of the mutant proteins on transcription of 14 enzymes involved in sphingolipid metabolism. Cells expressing the C282Y variant showed significant increases (>2-fold) in transcription of five genes and decreases in two compared to that seen for cells expressing WT-HFE, while cells expressing the H63D variant showed an elevation in transcription of one gene and a decrease in two. These changes were seen as alterations in ganglioside composition, cell surface binding by the binding subunit of cholera toxin, expression of sphingosine-kinase-1 and synthesis of sphingosine-1-phosphate. These changes may explain why C282Y-HFE is a risk factor for colon and breast cancer and possibly protective against Alzheimer's disease while H63D-HFE is a risk factor for neurodegenerative diseases.

HFE gene variants, iron, and lipids: a novel connection in Alzheimer’s disease

“…Intriguingly, there is evidence that an increase in GM1, or a change in its accessibility to GM1-binding proteins can occur upon reduction of cellular cholesterol (Lingwood et al, 2011). A link for a relationship between iron, cholesterol, and GM1, was provided by our finding that H63D-HFE human neuroblastoma cells contained more iron (Lee et al, 2007), expressed more cholera toxin binding GM1 (Ali-Rahmani et al, 2011) and had less cholesterol than cells expressing WT-HFE (Ali-Rahmani et al, 2014a). Taken together, our findings and the studies of the role of APP metabolism in AD and its relationship to either iron or cholesterol, provide the basis for the proposed mechanism ( Figure 3 ) by which effects induced by expression of H63D-HFE may lead to the symptoms associated with AD.…”

“…Changes in the composition of rafts by depletion of cholesterol or sphingolipids can affect the structure (assembly and disassembly) and function of lipid rafts and ultimately, cellular phenotype (Keller et al, 2004; Veatch and Keller, 2005). Evidence is also accumulating to support the concept that there is a dynamic equilibrium between cholesterol and sphingolipids within the rafts and that when levels of one of these components is altered it affects the concentration of the other (Ali-Rahmani et al, 2011). …”

“…Experimental results indicate that H63D-HFE creates a permissive milieu for pathogenic processes (Lee et al, 2007; Mitchell et al, 2009a,b; Hall et al, 2010, 2011; Mairuae et al, 2010; Ali-Rahmani et al, 2011; Liu et al, 2011). These observations raise the question of how the effects of iron accumulation and resulting oxidative stress, elevation of extracellular glutamate, increased secretion of MCP-1 and 24S-HC in one cell type impacts other cells in the brain and vice versa .…”

“…This striking difference is important because the subcellular localization could affect protein-protein interactions and cell signaling. Of potential importance with regard to cell signaling is our observation that while WT-HFE and H63D-HFE were localized in fractions containing lipid rafts, C282Y-HFE was not (Ali-Rahmani et al, 2011). Because lipid rafts provide a platform for a number of cell signaling pathways, an intriguing possibility is that expression of C282Y-HFE alters at least some cell signaling thereby disrupting normal homeostasis.…”

Etoposide-loaded immunoliposomes as active targeting agents for GD2-positive malignancies

“…GD2-negative HeLa cervical carcinoma cells and SY5Y neuroblastoma cell lines each expressed little 3F8 reactivity suggesting low GD2 expression as previously described. 38 These data suggest that GD2 expression varies widely across tumor types and between different neuroblastoma cell lines.…”