title: Simvastatin inhibits T-cell activation by selectively impairing the function of Ras superfamily GTPases.
abstract: Statins are widely used hypocholesterolemic drugs that inhibit 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase, a rate-limiting enzyme of the mevalonate pathway whose biosynthetic end product is cholesterol. In addition to lowering circulating cholesterol, statins perturb the composition of cell membranes, resulting in disruption of lipid rafts, which function as signaling platforms in immunoreceptor signaling. Furthermore, by inhibiting protein prenylation, a process also dependent on mevalonate, statins block membrane targeting and hence activity of small GTPases, which control multiple pathways triggered by these receptors. T-cell activation is crucially dependent on Ras, Rho and Rab GTPases. Furthermore TCR signaling is orchestrated at lipid rafts, identifying T-cells as potential cellular targets of statins. Here we report that simvastatin suppresses T-cell activation and proliferation as the result of its capacity to inhibit HMG-CoA reductase. T-cell treatment with simvastatin does not affect intracellular cholesterol levels or raft integrity nor, accordingly, the initial tyrosine phosphorylation-dependent cascade. Conversely, inhibition of protein prenylation by simvastatin results in a dramatic impairment in the pathways regulated by small GTPases, including the Ras/MAP kinase pathway, the Rac/stress kinase pathway, and the Rab-dependent pathway of receptor endocytosis. The results identify Ras superfamily GTPases as strategic molecular targets in T-cell immunosuppression by statins.
authors.affiliation: Department of Evolutionary Biology, University of Siena, Italy.
authors.forename: Raffaella
authors.initials: R
authors.lastname: Ghittoni
authors.forename: Laura
authors.initials: L
authors.lastname: Patrussi
authors.forename: Katja
authors.initials: K
authors.lastname: Pirozzi
authors.forename: Michela
authors.initials: M
authors.lastname: Pellegrini
authors.forename: Pietro E
authors.initials: PE
authors.lastname: Lazzerini
authors.forename: P Leopoldo
authors.initials: PL
authors.lastname: Capecchi
authors.forename: Franco Laghi
authors.initials: FL
authors.lastname: Pasini
authors.forename: Cosima T
authors.initials: CT
authors.lastname: Baldari
mesh_terms: D004705:Endocytosis; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D006801:Humans; D019161:Hydroxymethylglutaryl-CoA Reductase Inhibitors / Q000494:pharmacology; D007165:Immunosuppression Therapy; D019169:Jurkat Cells; D008213:Lymphocyte Activation / Q000187:drug effects*; D008563:Membrane Lipids / Q000378:metabolism; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D020559:Monomeric GTP-Binding Proteins / Q000037:antagonists & inhibitors* / Q000378:metabolism; D011948:Receptors, Antigen, T-Cell / Q000502:physiology; D015398:Signal Transduction; D019821:Simvastatin / Q000494:pharmacology*; D013601:T-Lymphocytes / Q000187:drug effects / Q000276:immunology*; D020691:rab GTP-Binding Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism; D020741:rho GTP-Binding Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism
chemical_list: D004791:Enzyme Inhibitors; D019161:Hydroxymethylglutaryl-CoA Reductase Inhibitors; D008563:Membrane Lipids; D011948:Receptors, Antigen, T-Cell; D019821:Simvastatin; D020928:Mitogen-Activated Protein Kinases; D020559:Monomeric GTP-Binding Proteins; D020691:rab GTP-Binding Proteins; D020741:rho GTP-Binding Proteins