title: A versatile role of mammalian target of rapamycin in human dendritic cell function and differentiation.
abstract: The mammalian target of rapamycin (mTOR) regulates cell growth and survival and exists as rapamycin-sensitive mTOR complex (mTORC) 1 and as rapamycin-insensitive mTORC2. Although mTOR is a well-known regulator of diverse immune cells, its detailed role in human dendritic cell (DC) function and differentiation is only incompletely understood. In this study, we demonstrate divergent roles of mTOR during activation and differentiation of myeloid DCs (mDCs) and monocyte-derived DCs (moDCs). Inhibition of mTORC1 in mDCs activated with TLR-dependent or -independent stimuli increased proinflammatory cytokines and NF-κB, whereas IL-10 and STAT3 were blocked. Rapamycin regulated the costimulatory/surface molecules CD86, programmed death ligand-1, and CD25 on mDCs and significantly increased the T cell allostimulatory potential of mDCs. In contrast, rapamycin suppressed immunostimulatory molecules and the allostimulatory potential of LPS-stimulated moDCs by an inability to augment NF-κB signaling. In differentiating moDCs, the PI3K/Akt-dependent mTOR pathway was constitutively activated by GM-CSF to induce DC differentiation in an mTORC1-dependent manner. Inhibition of mTORC1 or mTORC1/2 during moDC differentiation decreased moDC survival and markedly hampered its immunostimulatory phenotype. Analyzing the fate of DCs in vivo, we found that kidney transplant patients treated with rapamycin displayed an increased immunostimulatory potential of mDCs compared with patients treated with calcineurin inhibitors. Furthermore, rapamycin did not interfere with mDC differentiation in these patients. Collectively, mTOR exerts divergent immunoregulatory functions during DC activation and differentiation depending on the DC type that lead to opposing T cell responses, which might be of clinical importance in transplantation, cancer, and also for novel vaccination strategies.
authors.affiliation: Clinical Division of Nephrology and Dialysis, Department of Internal Medicine III, Medical University of Vienna, Vienna, Austria.
authors.forename: Michael
authors.initials: M
authors.lastname: Haidinger
authors.forename: Marko
authors.initials: M
authors.lastname: Poglitsch
authors.forename: Rene
authors.initials: R
authors.lastname: Geyeregger
authors.forename: Sudhir
authors.initials: S
authors.lastname: Kasturi
authors.forename: Maximilian
authors.initials: M
authors.lastname: Zeyda
authors.forename: Gerhard J
authors.initials: GJ
authors.lastname: Zlabinger
authors.forename: Bali
authors.initials: B
authors.lastname: Pulendran
authors.forename: Walter H
authors.initials: WH
authors.lastname: Hörl
authors.forename: Marcus D
authors.initials: MD
authors.lastname: Säemann
authors.forename: Thomas
authors.initials: T
authors.lastname: Weichhart
mesh_terms: D002454:Cell Differentiation / Q000276:immunology*; D002469:Cell Separation; D016207:Cytokines / Q000096:biosynthesis / Q000276:immunology; D003713:Dendritic Cells / Q000166:cytology / Q000276:immunology* / Q000378:metabolism; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D005434:Flow Cytometry; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000276:immunology* / Q000378:metabolism; D016030:Kidney Transplantation / Q000276:immunology; D008297:Male; D008856:Microscopy, Fluorescence; D008875:Middle Aged; D016328:NF-kappa B / Q000276:immunology / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000276:immunology* / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000276:immunology*; D058570:TOR Serine-Threonine Kinases
chemical_list: D016207:Cytokines; D047908:Intracellular Signaling Peptides and Proteins; D016328:NF-kappa B; C546842:MTOR protein, human; D017346:Protein Serine-Threonine Kinases; D058570:TOR Serine-Threonine Kinases