title: Signaling regulates activity of DHCR24, the final enzyme in cholesterol synthesis.
abstract: The role of signaling in regulating cholesterol homeostasis is gradually becoming more widely recognized. Here, we explored how kinases and phosphorylation sites regulate the activity of the enzyme involved in the final step of cholesterol synthesis, 3β-hydroxysterol Δ24-reductase (DHCR24). Many factors are known to regulate DHCR24 transcriptionally, but little is known about its posttranslational regulation. We developed a system to specifically test human ectopic DHCR24 activity in a model cell-line (Chinese hamster ovary-7) using siRNA targeted only to hamster DHCR24, thus ensuring that all activity could be attributed to the human enzyme. We determined the effect of known phosphorylation sites and found that mutating certain residues (T110, Y299, and Y507) inhibited DHCR24 activity. In addition, inhibitors of protein kinase C ablated DHCR24 activity, although not through a known phosphorylation site. Our data indicate a novel mechanism whereby DHCR24 activity is regulated by signaling.
authors.affiliation: School of Biotechnology and Biomolecular Sciences The University of New South Wales, Sydney, NSW 2052, Australia.
authors.forename: Winnie
authors.initials: W
authors.lastname: Luu
authors.forename: Eser J
authors.initials: EJ
authors.lastname: Zerenturk
authors.forename: Ika
authors.initials: I
authors.lastname: Kristiana
authors.forename: Martin P
authors.initials: MP
authors.lastname: Bucknall
authors.forename: Laura J
authors.initials: LJ
authors.lastname: Sharpe
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Brown
mesh_terms: D000818:Animals; D001665:Binding Sites / Q000235:genetics; D015153:Blotting, Western; D016466:CHO Cells; D002784:Cholesterol / Q000378:metabolism*; D006224:Cricetinae; D003412:Cricetulus; D017868:Cyclic AMP-Dependent Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D003897:Desmosterol / Q000378:metabolism; D015870:Gene Expression; D006801:Humans; D007211:Indoles / Q000494:pharmacology; D007546:Isoquinolines / Q000494:pharmacology; D009154:Mutation; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism*; D044925:Oxidoreductases Acting on CH-CH Group Donors / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation / Q000187:drug effects; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D051057:Proto-Oncogene Proteins c-akt / Q000037:antagonists & inhibitors / Q000378:metabolism; D034622:RNA Interference; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction; D013449:Sulfonamides / Q000494:pharmacology; D014443:Tyrosine / Q000235:genetics / Q000378:metabolism
chemical_list: D007211:Indoles; D007546:Isoquinolines; D009419:Nerve Tissue Proteins; D047428:Protein Kinase Inhibitors; D013449:Sulfonamides; D003897:Desmosterol; D014443:Tyrosine; D002784:Cholesterol; D044925:Oxidoreductases Acting on CH-CH Group Donors; C499055:DHCR24 protein, human; D051057:Proto-Oncogene Proteins c-akt; D017868:Cyclic AMP-Dependent Protein Kinases; D011493:Protein Kinase C; C063509:N-(2-(4-bromocinnamylamino)ethyl)-5-isoquinolinesulfonamide; C064758:Ro 31-8220
keywords: 3β-hydroxysterol Δ24-reductase; bisindolylmaleimide I; desmosterol; gas chromatography-mass spectrometry; phosphorylation; protein kinase C; regulation