Isoprenylation of RhoB is necessary for its degradation. A novel determinant in the complex regulation of RhoB expression by the mevalonate pathway.
Statins improve vascular functions by mechanisms independent from their cholesterol-lowering effect. Rho GTPases are emerging as key targets for the vascular effects of statins. RhoB is a short-lived, early-response inducible protein involved in receptor endocytosis, apoptosis, and gene expression. Here we show that statins regulate RhoB expression by acting at multiple levels. Simvastatin increased RhoB protein levels by 8- to 10-fold. This effect was related to a depletion of isoprenoid intermediates, as deduced from the observation that several metabolites of the cholesterol biosynthetic pathway, namely, mevalonate and geranylgeranyl-pyrophosphate, attenuated simvastatin-induced RhoB up-regulation. Moreover, prenyltransferase inhibitors mimicked simvastatin effect. Cholesterol supplementation did not prevent simvastatin-elicited up-regulation but increased RhoB levels per se. Simvastatin moderately augmented RhoB transcript levels, but markedly impaired the degradation of RhoB protein, which accumulated in the cytosol in its non-isoprenylated form. Inhibition of RhoB isoprenylation was apparently required for simvastatin-induced up-regulation, because levels of an isoprenylation-deficient RhoB mutant were not affected by simvastatin. Moreover, this mutant was found to be markedly more stable than the wild-type protein. These results show that RhoB isoprenylation is necessary for rapid turnover of this protein and identify a novel link between the cholesterol biosynthetic pathway and the regulation of G-protein expression.
Stamatakis
Konstantinos
K
Departamento de Estructura y Función de Proteinas, Centro de Investigaciones Biológicas, Consejo Superior de Investigaciones Cientificas (C.S.I.C.), Velázquez, 144, 28006 Madrid, Spain.
Cernuda-Morollón
Eva
E
Hernández-Perera
Octavio
O
Pérez-Sala
Dolores
D
D016475:3T3 Cells; D000818:Animals; D000924:Anticholesteremic Agents / Q000494:pharmacology; D015152:Blotting, Northern; D015153:Blotting, Western; D002417:Cattle; D002478:Cells, Cultured; D002784:Cholesterol / Q000378:metabolism / Q000494:pharmacology; D018076:DNA, Complementary / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004591:Electrophoresis, Polyacrylamide Gel; D004730:Endothelium, Vascular / Q000166:cytology; D005786:Gene Expression Regulation; D006367:HeLa Cells; D006801:Humans; D015151:Immunoblotting; D017403:In Situ Hybridization; D008798:Mevalonic Acid / Q000378:metabolism*; D051379:Mice; D008954:Models, Biological; D009154:Mutation; D037342:Pertussis Toxin / Q000494:pharmacology; D010957:Plasmids / Q000378:metabolism; D011485:Protein Binding; D017368:Protein Prenylation; D012333:RNA, Messenger / Q000378:metabolism; D019821:Simvastatin / Q000494:pharmacology; D013347:Subcellular Fractions; D013997:Time Factors; D014162:Transfection; D015854:Up-Regulation; D020743:rhoB GTP-Binding Protein / Q000737:chemistry / Q000378:metabolism*
D000924:Anticholesteremic Agents; D018076:DNA, Complementary; D012333:RNA, Messenger; D002784:Cholesterol; D019821:Simvastatin; D037342:Pertussis Toxin; D020743:rhoB GTP-Binding Protein; D008798:Mevalonic Acid