Molecular consequences of altered neuronal cholesterol biosynthesis.

Korade Z, Kenworthy AK, Mirnics K
J Neurosci Res. 2009 87 (4): 866-75

PMID: 18951487 · PMCID: PMC4360921 · DOI:10.1002/jnr.21917

The first dedicated step in de novo cholesterol biosynthesis begins with formation of squalene and ends with the reduction of 7-dehydrocholesterol by 7-dehydrocholesterol reductase (Dhcr7) into cholesterol, which is an essential structural and signaling molecule. Mutations in the Dhcr7 gene lead to Smith-Lemli-Opitz syndrome (SLOS), which is characterized by developmental deformities, incomplete myelination, and mental retardation. To understand better the molecular consequences of Dhcr7 deficiency in neuronal tissue, we analyzed the effect of cholesterol deficiency on the transcriptome in Neuro2a cells. Transient down-regulation of Dhcr7 by siRNA led to altered expression of multiple molecules that play critical roles in intracellular signaling or vesicular transport or are inserted into membrane rafts (e.g. Egr1, Snx, and Adam19). A similar down-regulation was also observed in stable Dhrc7-shRNA-transfected cell lines, and the findings were verified by qPCR. Furthermore, we investigated the Dhcr7-deficient and control cells for the expression of several critical genes involved in lipid biosynthesis. Among these, fatty acid synthase, sterol-regulatory element binding protein 2, SREBF chaperone, site-1 protease, and squalene synthase showed a significant down-regulation, suggesting that, in a neuronal cell line, Dhcr7 is a potent regulator of lipid biosynthesis. Importantly, the gene expression changes were present in both lipid-containing and cholesterol-deficient media, suggesting that intrinsic cholesterol biosynthesis is necessary for normal neuronal function and cannot be supplemented from extrinsic sources.

MeSH Terms (22)

Animals Blotting, Northern Cell Line Cholesterol Down-Regulation Farnesyl-Diphosphate Farnesyltransferase Fatty Acids Fatty Acid Synthases Gene Expression Gene Expression Profiling Intracellular Signaling Peptides and Proteins Mice Neurons Oxidoreductases Acting on CH-CH Group Donors Polymerase Chain Reaction Proprotein Convertases RNA, Small Interfering Serine Endopeptidases Sterol Regulatory Element Binding Protein 2 Sterols Transfection Vesicular Transport Proteins

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