title: MicroRNA-15b/16 Enhances the Induction of Regulatory T Cells by Regulating the Expression of Rictor and mTOR.
abstract: CD4(+) regulatory T cells (Tregs) are essential for controlling immune responses and preventing autoimmunity. Their development requires regulation of gene expression by microRNAs (miRNAs). To understand miRNA function in Treg development, we searched for important miRNAs and their relevant target genes. Of the more abundantly expressed miRNAs in Tregs, only miR-15b/16, miR-24, and miR-29a impacted the production of in vitro-induced Tregs (iTregs) in overexpression and blocking experiments. miRNA mimics for these significantly enhanced the induction of iTregs in Dicer(-/-) CD4(+) T cells. Furthermore, the overexpression of miR-15b/16 in conventional CD4(+) T cells adoptively transferred into Rag2(-/-) mice increased the in vivo development of peripheral Tregs and diminished the severity of autoimmune colitis. In searching for targets of miR-15b/16, we observed that the mammalian target of rapamycin (mTOR) signaling pathway was enhanced in Dicer(-/-) CD4(+) T cells, and its pharmacological inhibition restored induction of iTregs. Suppression of mTOR signaling is essential for induction of iTregs from naive CD4(+) T cells, and the mTORC2 component, Rictor, contained a functional target site for miR-15b/16. Rictor was more abundantly expressed in Dicer(-/-) T cells as was mTOR, and their expression was downregulated by the overexpression of miR-15b/16. This led to a reduction in mTOR signaling, as measured by phosphorylation of the downstream target, ribosomal protein S6. Finally, knockdown of Rictor by small interfering RNAs enhanced Treg induction in Dicer(-/-) CD4(+) T cells. Therefore, an important mechanism of miRNA regulation of Treg development is through regulation of the mTOR signaling pathway.
authors.affiliation: Department of Comparative Biomedical Sciences, The Royal Veterinary College, London NW1 0TU, United Kingdom; Institute of Physiology I, Eberhard Karls University of Tübingen, D-72076 Tübingen, Germany; and.
authors.forename: Yogesh
authors.identifier: http://orcid.org/0000-0001-6919-6273
authors.initials: Y
authors.lastname: Singh
authors.affiliation: Department of Clinical Sciences and Services, The Royal Veterinary College, London NW1 0TU, United Kingdom.
authors.forename: Oliver A
authors.initials: OA
authors.lastname: Garden
authors.affiliation: Institute of Physiology I, Eberhard Karls University of Tübingen, D-72076 Tübingen, Germany; and.
authors.forename: Florian
authors.initials: F
authors.lastname: Lang
authors.affiliation: Department of Comparative Biomedical Sciences, The Royal Veterinary College, London NW1 0TU, United Kingdom; bcobb@rvc.ac.uk.
authors.forename: Bradley S
authors.identifier: http://orcid.org/0000-0001-6783-0509
authors.initials: BS
authors.lastname: Cobb
mesh_terms: D019264:Adoptive Transfer; D000818:Animals; D001327:Autoimmune Diseases / Q000276:immunology*; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D049109:Cell Proliferation; D002478:Cells, Cultured; D003092:Colitis / Q000276:immunology*; D004268:DNA-Binding Proteins / Q000235:genetics; D005786:Gene Expression Regulation; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D035683:MicroRNAs / Q000235:genetics / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000235:genetics; D000076226:Rapamycin-Insensitive Companion of mTOR Protein; D043244:Ribonuclease III / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction; D016176:T-Lymphocyte Subsets / Q000276:immunology*; D050378:T-Lymphocytes, Regulatory / Q000276:immunology*; D058570:TOR Serine-Threonine Kinases / Q000378:metabolism*
chemical_list: D002352:Carrier Proteins; D004268:DNA-Binding Proteins; C547014:MIRN29 microRNA, mouse; D035683:MicroRNAs; C570833:Mirn15 microRNA, mouse; C522604:Mirn16 microRNA, mouse; C529080:Mirn24 microRNA, mouse; D034741:RNA, Small Interfering; C499308:Rag2 protein, mouse; D000076226:Rapamycin-Insensitive Companion of mTOR Protein; C525637:rictor protein, mouse; C546843:mTOR protein, mouse; D058570:TOR Serine-Threonine Kinases; D043244:Ribonuclease III