title: Mifepristone treatment results in differential regulation of glycerolipid biosynthesis in baby hamster kidney cells expressing a mifepristone-inducible ABCA1.
abstract: ATP binding cassette A1 (ABCA1) transports cholesterol, phospholipids and lipophilic molecules to and across cellular membranes. We examined if ABCA1 expression altered cellular de novo glycerolipid biosynthesis in growing Baby hamster kidney (BHK) cells. Mock BHK cells or cells expressing a mifepristone-inducible ABCA1 (ABCA1) were incubated plus or minus mifepristone and then with [(3)H]serine or [(3)H]inositol or [(3)H]ethanolamine or [methyl-(3)H]choline or [(3)H]glycerol or [(14)C]oleate and radioactivity incorporated into glycerolipids determined. Mifepristone did not affect [1,3-(3)H]glycerol or [(14)C]oleate or [(3)H]ethanolamine or [methyl-(3)H]choline uptake in BHK cells. In contrast, [(3)H]glycerol and [(14)C]oleate incorporated into phosphatidylserine (PtdSer) were elevated 2.4-fold (p < 0.05) and 54% (p < 0.05), respectively, upon ABCA1 induction confirming increased PtdSer biosynthesis from these precursors. However, mifepristone inhibited [(3)H]serine uptake and incorporation into PtdSer indicating that PtdSer synthesis from serine in BHK cells is dependent on serine uptake. Mifepristone stimulated [(3)H]inositol uptake in mock and ABCA1 cells but not its incorporation into phosphatidylinositol indicating that its synthesis from inositol is independent of inositol uptake in BHK cells. [(3)H]glycerol and [(14)C]oleate incorporated into triacylglycerol were reduced and into diacylglycerol elevated only in mifepristone-induced ABCA1 expressing cells due to a decrease in diacylglycerol acyltransferase-1 (DGAT-1) activity. The presence of trichostatin A, a class I and II histone deacetylase inhibitor, reversed the ABCA1-mediated reduction in DGAT-1 activity but did not affect DGAT-1 mRNA expression. Thus, mifepristone has diverse effects on de novo glycerolipid synthesis. We suggest that caution should be exercised when using mifepristone-inducible systems for studies of glycerolipid metabolism in cells expressing glucocorticoid responsive receptors.
authors.affiliation: Department of Pharmacology and Therapeutics, Manitoba Institute of Child Health, Faculty of Medicine, University of Manitoba, 715 McDermot Avenue, Winnipeg, MB, R3E 0T6, Canada.
authors.forename: Kristin D
authors.initials: KD
authors.lastname: Hauff
authors.forename: Ryan W
authors.initials: RW
authors.lastname: Mitchell
authors.forename: Fred Y
authors.initials: FY
authors.lastname: Xu
authors.forename: Thomas
authors.initials: T
authors.lastname: Dembinski
authors.forename: David
authors.initials: D
authors.lastname: Mymin
authors.forename: Xiaohui
authors.initials: X
authors.lastname: Zha
authors.forename: Patrick C
authors.initials: PC
authors.lastname: Choy
authors.forename: Grant M
authors.initials: GM
authors.lastname: Hatch
mesh_terms: D064286:ATP Binding Cassette Transporter 1; D018528:ATP-Binding Cassette Transporters / Q000235:genetics* / Q000378:metabolism; D000818:Animals; D002460:Cell Line; D006224:Cricetinae; D051048:Diacylglycerol O-Acyltransferase / Q000235:genetics / Q000378:metabolism; D057075:Enzyme Assays; D015870:Gene Expression / Q000187:drug effects*; D005989:Glycerides / Q000096:biosynthesis*; D005990:Glycerol / Q000378:metabolism; D020404:Glycerophospholipids / Q000378:metabolism; D056572:Histone Deacetylase Inhibitors / Q000494:pharmacology; D006877:Hydroxamic Acids / Q000494:pharmacology; D007294:Inositol / Q000378:metabolism; D015735:Mifepristone / Q000494:pharmacology*; D019301:Oleic Acid / Q000378:metabolism; D010718:Phosphatidylserines / Q000096:biosynthesis; D012694:Serine / Q000378:metabolism
chemical_list: D064286:ATP Binding Cassette Transporter 1; D018528:ATP-Binding Cassette Transporters; D005989:Glycerides; D020404:Glycerophospholipids; D056572:Histone Deacetylase Inhibitors; D006877:Hydroxamic Acids; D010718:Phosphatidylserines; D019301:Oleic Acid; D015735:Mifepristone; C012589:trichostatin A; D012694:Serine; D007294:Inositol; D051048:Diacylglycerol O-Acyltransferase; D005990:Glycerol