title: Simvastatin inhibits the MHC class II pathway of antigen presentation by impairing Ras superfamily GTPases.
abstract: Statins are widely used hypocholesterolemic drugs that inhibit 3-hydroxy-3-methyl-glutaryl-coenzyme A reductase, a rate-limiting enzyme of the mevalonate pathway whose biosynthetic endproduct is cholesterol. As a result of this activity, statins may perturb the composition of cell membranes, resulting in lipid raft disruption. Furthermore, by inhibiting protein prenylation, a process also dependent on mevalonate, statins block membrane targeting and activity of small GTPases. Antigen uptake, processing and presentation involve the interplay of Rab and Rho family GTPases. Furthermore, lipid rafts have been implicated both in antigen internalization by the BCR and in MHC class II clustering at the immunological synapse. Here we have addressed the effects of simvastatin on antigen processing and presentation by human B cells and dendritic cells. The results show that simvastatin potently suppresses tetanus toxoid processing and presentation to CD4+ T cells by HLA-DR by inhibiting protein antigen uptake through both receptor-mediated endocytosis and macropinocytosis. This effect can be largely accounted for by defective prenylation of Rho and Rab GTPases in the absence of any measurable perturbation of lipid rafts. In addition, simvastatin was found to preferentially affect the invariant chain-dependent MHC class II pathway, thereby identifying this route of antigen processing and presentation as a selective target of statins.
authors.affiliation: Department of Evolutionary Biology, University of Siena, Siena, Italy.
authors.forename: Raffaella
authors.initials: R
authors.lastname: Ghittoni
authors.forename: Giorgio
authors.initials: G
authors.lastname: Napolitani
authors.forename: Daniela
authors.initials: D
authors.lastname: Benati
authors.forename: Cristina
authors.initials: C
authors.lastname: Ulivieri
authors.forename: Cristina
authors.initials: C
authors.lastname: Uliveri
authors.forename: Laura
authors.initials: L
authors.lastname: Patrussi
authors.forename: Franco
authors.initials: F
authors.lastname: Laghi Pasini
authors.forename: Antonio
authors.initials: A
authors.lastname: Lanzavecchia
authors.forename: Cosima T
authors.initials: CT
authors.lastname: Baldari
mesh_terms: D000924:Anticholesteremic Agents / Q000494:pharmacology*; D017951:Antigen Presentation / Q000187:drug effects*; D001402:B-Lymphocytes / Q000187:drug effects / Q000201:enzymology / Q000276:immunology; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology; D002478:Cells, Cultured; D003713:Dendritic Cells / Q000187:drug effects / Q000201:enzymology / Q000276:immunology; D005802:Genes, MHC Class II; D000949:Histocompatibility Antigens Class II / Q000187:drug effects*; D006801:Humans; D017368:Protein Prenylation / Q000187:drug effects*; D019821:Simvastatin / Q000494:pharmacology*; D013745:Tetanus Toxoid / Q000276:immunology; D018631:ras Proteins / Q000187:drug effects* / Q000378:metabolism
chemical_list: D000924:Anticholesteremic Agents; D000949:Histocompatibility Antigens Class II; D013745:Tetanus Toxoid; D019821:Simvastatin; D018631:ras Proteins