Consequences of mevalonate depletion. Differential transcriptional, translational, and post-translational up-regulation of Ras, Rap1a, RhoA, AND RhoB.
Ras-related proteins are small GTPases that are post-translationally modified with mevalonate-derived isoprenoids. Although the effects of inhibition of isoprenylation on protein function have been examined, the consequences of depletion of isoprenoid pools on regulation of expression of isoprenylated proteins have yet to be investigated. In these studies we have shown that depletion of mevalonate results in increased total levels of Ras, Rap1a, RhoA, and RhoB in K562 cells. Cycloheximide and [(35)S]methionine pulse/pulse-chase experiments reveal that mevalonate depletion increases the de novo synthesis of Ras and RhoA and decreases the degradation of existing Ras and RhoA protein. Pretreatment with actinomycin D completely prevents the induced up-regulation of RhoB and only partially prevents the up-regulation of Ras, Rap1a, and RhoA. Although depletion of mevalonate does not alter steady state levels of Ras mRNA, there is an increase in RhoB mRNA. Our results are the first to demonstrate that mevalonate depletion induces up-regulation of Ras and Ras-related proteins by discrete mechanisms that include modulation of transcriptional, translational, and post-translational processes.
Holstein
Sarah A
SA
Department of Pharmacology, University of Iowa, Iowa City, Iowa 52242, USA.
Wohlford-Lenane
Christine L
CL
Hohl
Raymond J
RJ
D000970:Antineoplastic Agents / Q000494:pharmacology; D015153:Blotting, Western; D002460:Cell Line; D003513:Cycloheximide / Q000494:pharmacology; D003609:Dactinomycin / Q000494:pharmacology; D006801:Humans; D020014:K562 Cells; D008148:Lovastatin / Q000494:pharmacology; D008798:Mevalonic Acid / Q000378:metabolism* / Q000494:pharmacology*; D014176:Protein Biosynthesis; D011499:Protein Processing, Post-Translational; D017434:Protein Structure, Tertiary; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D012313:RNA / Q000378:metabolism; D013997:Time Factors; D014158:Transcription, Genetic; D015854:Up-Regulation; D020827:rap1 GTP-Binding Proteins / Q000378:metabolism*; D018631:ras Proteins / Q000378:metabolism*; D020742:rhoA GTP-Binding Protein / Q000378:metabolism*; D020743:rhoB GTP-Binding Protein / Q000378:metabolism*
D000970:Antineoplastic Agents; D011500:Protein Synthesis Inhibitors; D003609:Dactinomycin; D012313:RNA; D003513:Cycloheximide; D008148:Lovastatin; D020827:rap1 GTP-Binding Proteins; D018631:ras Proteins; D020742:rhoA GTP-Binding Protein; D020743:rhoB GTP-Binding Protein; D008798:Mevalonic Acid