Mevalonic acid is limiting for N-linked glycosylation and translocation of the insulin-like growth factor-1 receptor to the cell surface. Evidence for a new link between 3-hydroxy-3-methylglutaryl-coenzyme a reductase and cell growth.
Depletion of mevalonic acid (MVA), obtained by inhibition of 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase using lovastatin, depressed the biosynthesis of dolichyl-phosphate and the rate of N-linked glycosylation and caused growth arrest in the melanoma cell line SK-MEL-2. The growth arrest was partially prevented by addition of high concentrations of insulin-like growth factor-1 (IGF-1) to the cells, indicating that MVA depletion may inhibit cell growth through decreasing the number of IGF-1 receptors (IGF-1R) at the cell surface. Such a decrease in receptor number might be a result of a lowered translocation of de novo synthesized receptors to the cell membrane which in turn might be a result of a decreased N-linked glycosylation of the receptor proteins. We could also demonstrate that IGF-1R became underglycosylated and that the amount of de novo synthesized IGF-1R proteins at the cell membrane was drastically decreased upon MVA depletion. Analysis of receptor proteins cross-linked with IGF-1, as well as binding assays and immunocytostaining confirmed that the number of functional membrane-bound IGF-1R was substantially reduced. The N-linked glycosylation and the expression of de novo synthesized IGF-1R proteins at the cell surface as well as the number of IGF-1 binding sites were completely restored upon replenishment of MVA. These effects of MVA were efficiently abrogated by the glycosylation inhibitor tunicamycin. The translocation of IGF-1R to the cell membrane was shown to take place just prior to initiation of DNA synthesis in arrested cells stimulated with MVA. Additionally, there was a clear correlation between IGF-1 binding and initiation of DNA synthesis with regard to the MVA dose requirement. It was confirmed that inhibition of HMG-CoA reductase activity and N-linked glycosylation also depressed the expression of functional IGF-1R in other cell types (i.e. hepatoblastoma cells and colon cancer cells). Our data suggest that this mechanism is involved in MVA-regulated cell growth.
Carlberg
M
M
Department of Tumor Pathology, Karolinska Institutet, S-17177 Stockholm, Sweden.
Dricu
A
A
Blegen
H
H
Wang
M
M
Hjertman
M
M
Zickert
P
P
Höög
A
A
Larsson
O
O
D001483:Base Sequence; D002455:Cell Division / Q000187:drug effects; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D003110:Colonic Neoplasms; D017931:DNA Primers; D004273:DNA, Neoplasm / Q000096:biosynthesis; D004288:Dolichol Phosphates / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D015870:Gene Expression / Q000187:drug effects; D006031:Glycosylation; D006133:Growth Substances / Q000494:pharmacology*; D018197:Hepatoblastoma; D006801:Humans; D006903:Hydroxymethylglutaryl CoA Reductases / Q000378:metabolism*; D019161:Hydroxymethylglutaryl-CoA Reductase Inhibitors; D007328:Insulin / Q000494:pharmacology; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology; D007700:Kinetics; D008113:Liver Neoplasms; D008148:Lovastatin / Q000494:pharmacology*; D008545:Melanoma; D008798:Mevalonic Acid / Q000378:metabolism*; D008954:Models, Biological; D008969:Molecular Sequence Data; D016376:Oligonucleotides, Antisense / Q000138:chemical synthesis / Q000494:pharmacology; D011499:Protein Processing, Post-Translational / Q000187:drug effects; D012333:RNA, Messenger / Q000096:biosynthesis; D017526:Receptor, IGF Type 1 / Q000096:biosynthesis / Q000378:metabolism*; D014158:Transcription, Genetic / Q000187:drug effects; D014407:Tumor Cells, Cultured
D017931:DNA Primers; D004273:DNA, Neoplasm; D004288:Dolichol Phosphates; D004791:Enzyme Inhibitors; D006133:Growth Substances; D019161:Hydroxymethylglutaryl-CoA Reductase Inhibitors; D007328:Insulin; D016376:Oligonucleotides, Antisense; D012333:RNA, Messenger; D007334:Insulin-Like Growth Factor I; D008148:Lovastatin; D006903:Hydroxymethylglutaryl CoA Reductases; D017526:Receptor, IGF Type 1; D008798:Mevalonic Acid