Mechanism of the elevation in cardiolipin during HeLa cell entry into the S-phase of the human cell cycle.
CL (cardiolipin) is a key phospholipid involved in ATP generation. Since progression through the cell cycle requires ATP we examined regulation of CL synthesis during S-phase in human cells and investigated whether CL or CL synthesis was required to support nucleotide synthesis in S-phase. HeLa cells were made quiescent by serum depletion for 24 h. Serum addition resulted in substantial stimulation of [methyl-(3)H]thymidine incorporation into cells compared with serum-starved cells by 8 h, confirming entry into the S-phase. CL mass was unaltered at 8 h, but increased 2-fold by 16 h post-serum addition compared with serum-starved cells. The reason for the increase in CL mass upon entry into S-phase was an increase in activity and expression of CL de novo biosynthetic and remodelling enzymes and this paralleled the increase in mitochondrial mass. CL de novo biosynthesis from D-[U-(14)C]glucose was elevated, and from [1,3-(3)H]glycerol reduced, upon serum addition to quiescent cells compared with controls and this was a result of differences in the selection of precursor pools at the level of uptake. Triascin C treatment inhibited CL synthesis from [1-(14)C]oleate but did not affect [methyl-(3)H]thymidine incorporation into HeLa cells upon serum addition to serum-starved cells. Barth Syndrome lymphoblasts, which exhibit reduced CL, showed similar [methyl-(3)H]thymidine incorporation into cells upon serum addition to serum-starved cells compared with cells from normal aged-matched controls. The results indicate that CL de novo biosynthesis is up-regulated via elevated activity and expression of CL biosynthetic genes and this accounted for the doubling of CL seen during S-phase; however, normal de novo CL biosynthesis or CL itself is not essential to support nucleotide synthesis during entry into S-phase of the human cell cycle.
Hauff
Kristin
K
Department of Pharmacology and Therapeutics, Center for Research and Treatment of Atherosclerosis, Center on Aging, Faculty of Medicine, University of Manitoba, Winnipeg, Manitoba, Canada.
Linda
Dorota
D
Hatch
Grant M
GM
D002308:Cardiolipins / Q000378:metabolism*; D002950:Citrate (si)-Synthase / Q000378:metabolism; D005786:Gene Expression Regulation; D005947:Glucose / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D012333:RNA, Messenger / Q000235:genetics; D016196:S Phase
D002308:Cardiolipins; D012333:RNA, Messenger; D002950:Citrate (si)-Synthase; D005947:Glucose