Geranylgeraniol overcomes the block of cell proliferation by lovastatin in C6 glioma cells

J Neurochem. 1998 Jun;70(6):2397-405. doi: 10.1046/j.1471-4159.1998.70062397.x.

Abstract

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.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Cell Division / drug effects
  • Cell Division / physiology
  • Diterpenes / metabolism*
  • Diterpenes / pharmacology
  • Electrophoresis, Polyacrylamide Gel
  • Farnesol / metabolism
  • Farnesol / pharmacology
  • Glioma / metabolism
  • Glioma / pathology*
  • Hydroxymethylglutaryl-CoA Reductase Inhibitors / pharmacology*
  • Lovastatin / pharmacology*
  • Mevalonic Acid / metabolism
  • Mevalonic Acid / pharmacology
  • Molecular Weight
  • Nerve Tissue Proteins / chemistry
  • Nerve Tissue Proteins / metabolism
  • Polyisoprenyl Phosphates / metabolism
  • Protein Prenylation / physiology
  • Rats
  • Thymidine / metabolism
  • Tumor Cells, Cultured

Substances

  • Diterpenes
  • Hydroxymethylglutaryl-CoA Reductase Inhibitors
  • Nerve Tissue Proteins
  • Polyisoprenyl Phosphates
  • Farnesol
  • Lovastatin
  • geranylgeraniol
  • geranylgeranyl pyrophosphate
  • Mevalonic Acid
  • Thymidine