title: Cardiolipin synthesis is required to support human cholesterol biosynthesis from palmitate upon serum removal in Hela cells.
abstract: We examined whether cardiolipin (CL) synthesis was required to support cholesterol (CH) production from palmitate in Hela cells. Knockdown of human cardiolipin synthase-1 (hCLS1) in Hela cells has been shown to reduce CL synthesis. Therefore Hela cells stably expressing shRNA for hCLS1 and mock control cells were incubated for 16 h with [14C(U)]palmitate bound to albumin (1:1 molar ratio) in the absence or presence of serum. Knockdown of hCLS1 in Hela cells resulted in a reduction in [14C(U)]palmitate incorporation into CL and CH. This reduction in [14C(U)]palmitate incorporation into CH was most pronounced during incubation under serum-free conditions. The reduction in [14C(U)]palmitate incorporation into CH was not due to alterations in total uptake of [14C(U)]palmitate into cells or altered palmitate metabolism, since [14C(U)]palmitate incorporation into phosphatidylcholine, the major [14C(U)]palmitate-containing lipid, and its immediate precursor, 1,2-diacyl-sn-glycerol, were unaffected by hCLS1 knockdown. In addition, knockdown of hCLS1 did not affect CH pool size, indicating that CH catabolism was unaltered. Hydroxymethylglutaryl coenzyme A reductase enzyme activity and its mRNA expression were reduced by knockdown of hCLS1 and this was most pronounced in Hela cells cultured under serum-free conditions. These data indicate that CL synthesis is required to support human de novo CH biosynthesis under conditions of increased demand for CH.
authors.affiliation: Department of Pharmacology and Therapeutics, Faculty of Medicine, University of Manitoba, Winnipeg, Canada.
authors.forename: Kristin D
authors.initials: KD
authors.lastname: Hauff
authors.forename: Seok-Yong
authors.initials: SY
authors.lastname: Choi
authors.forename: Michael A
authors.initials: MA
authors.lastname: Frohman
authors.forename: Grant M
authors.initials: GM
authors.lastname: Hatch
mesh_terms: D002308:Cardiolipins / Q000096:biosynthesis*; D002784:Cholesterol / Q000096:biosynthesis*; D002786:Cholesterol Side-Chain Cleavage Enzyme / Q000378:metabolism; D016895:Culture Media, Serum-Free; D006367:HeLa Cells; D006801:Humans; D006903:Hydroxymethylglutaryl CoA Reductases / Q000378:metabolism; D050356:Lipid Metabolism / Q000235:genetics; D008565:Membrane Proteins / Q000096:biosynthesis; D010084:Oxidation-Reduction; D010168:Palmitates / Q000378:metabolism*; D010713:Phosphatidylcholines / Q000378:metabolism; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017855:Transferases (Other Substituted Phosphate Groups) / Q000096:biosynthesis
chemical_list: D002308:Cardiolipins; D016895:Culture Media, Serum-Free; D008565:Membrane Proteins; D010168:Palmitates; D010713:Phosphatidylcholines; D012333:RNA, Messenger; D002784:Cholesterol; D006903:Hydroxymethylglutaryl CoA Reductases; D002786:Cholesterol Side-Chain Cleavage Enzyme; D017855:Transferases (Other Substituted Phosphate Groups); C100091:cardiolipin synthetase