Geranylgeraniol overcomes the block of cell proliferation by lovastatin in C6 glioma cells.
It is well documented that 3-hydroxy-3-methylglutaryl-CoA reductase inhibitors prevent cultured mammalian cells from progressing through the cell cycle, suggesting a critical role for a mevalonate-derived product. Recently, it has been shown that free geranylgeraniol (GG-OH) and farnesol (F-OH) can be utilized by C6 glioma cells for protein isoprenylation. The ability of GG-OH and F-OH to restore protein geranylgeranylation or farnesylation selectively has enabled us to examine the possibility that mevalonate is essential for cell proliferation because it is a precursor of farnesyl pyrophosphate or geranylgeranyl pyrophosphate, the isoprenyl donors involved in the posttranslational modification of key regulatory proteins. In this study we report that GG-OH, as well as mevalonate, overcomes the arrest of cell proliferation of C6 glioma cells treated with lovastatin, as assessed by increased cell numbers and a stimulation in [3H]thymidine incorporation. The increase in cell number and [3H]thymidine incorporation were significantly lower when F-OH was added. Under these conditions [3H]mevalonate and [3H]GG-OH are actively incorporated into a set of isoprenylated proteins in the size range of small, GTP-binding proteins (19-27 kDa) and a polypeptide with the molecular size (46 kDa) of the smaller isoform of 2 ',3'-cyclic nucleotide 3'-phosphodiesterase. Analysis of the proteins metabolically labeled by [3H]mevalonate and [3H]GG-OH reveals the presence of labeled proteins containing geranylgeranylated cysteinyl residues. Consistent with geranylgeranylated proteins playing a critical role in the entry of C6 cells into the cell cycle, a (phosphonoacetamido)oxy derivative of GG-OH, a drug previously shown to interfere with protein geranylgeranylation, prevented the increase in cell number when mevalonate or GG-OH was added to lovastatin-treated cells. These results strongly suggest that geranylgeranylated proteins are essential for progression of C6 cells into the S phase of the cell cycle and provide the first evidence that the "salvage" pathway for the utilization of the free isoprenols is physiologically significant in the CNS.
Crick
D C
DC
Department of Biochemistry, University of Kentucky College of Medicine, Lexington 40536, USA.
Andres
D A
DA
Danesi
R
R
Macchia
M
M
Waechter
C J
CJ
D000818:Animals; D002455:Cell Division / Q000187:drug effects / Q000502:physiology; D004224:Diterpenes / Q000378:metabolism* / Q000494:pharmacology; D004591:Electrophoresis, Polyacrylamide Gel; D005204:Farnesol / Q000378:metabolism / Q000494:pharmacology; D005910:Glioma / Q000378:metabolism / Q000473:pathology*; D019161:Hydroxymethylglutaryl-CoA Reductase Inhibitors / Q000494:pharmacology*; D008148:Lovastatin / Q000494:pharmacology*; D008798:Mevalonic Acid / Q000378:metabolism / Q000494:pharmacology; D008970:Molecular Weight; D009419:Nerve Tissue Proteins / Q000737:chemistry / Q000378:metabolism; D011106:Polyisoprenyl Phosphates / Q000378:metabolism; D017368:Protein Prenylation / Q000502:physiology; D051381:Rats; D013936:Thymidine / Q000378:metabolism; D014407:Tumor Cells, Cultured
D004224:Diterpenes; D019161:Hydroxymethylglutaryl-CoA Reductase Inhibitors; D009419:Nerve Tissue Proteins; D011106:Polyisoprenyl Phosphates; D005204:Farnesol; D008148:Lovastatin; C017338:geranylgeraniol; C002963:geranylgeranyl pyrophosphate; D008798:Mevalonic Acid; D013936:Thymidine