title: Lipid raft-associated GTPase signaling controls morphology and CD8+ T cell stimulatory capacity of human dendritic cells.
abstract: Their eponymous morphology and unique ability to activate naive T cells are hallmark features of dendritic cells (DCs). Specific properties of the actin cytoskeleton may define both characteristics. In search for regulators that coordinate DC phenotype and function, we observed strongly increased expression of the actin-remodeling GTPases Cdc42 and Rac1 during DC development from human stem cells. Cdc42 and Rac1 are constitutively active in immature DCs, and their activity is further up-regulated by maturational stimuli such as LPS or CD40L. Activation of Rac1 is associated with its rapid recruitment into lipid rafts. Cdc42 is not recruited into rafts, but readily activated by raft-associated moieties. The functional interplay of rafts, GTPases, and cortical actin is further shown by GTPase activation and actin remodeling after pharmacological disruption of lipid rafts and by the loss of the actin-based DC morphology by transfection of dominant-negative Cdc42 and Rac1. Both Cdc42 and Rac1 also control the transport of essential immunostimulatory molecules to the DC surface. Transfection with dominant-negative GTPases led to reduced surface expression of MHC class I and CD86. Consecutively, DCs display a reduced stimulatory capacity for CD8(+) T cells, whereas MHC class II-dependent stimulation of CD4(+) T cells remains unperturbed. We conclude that Cdc42 and Rac1 signaling controls DC morphology and conditions DCs for efficient CD8(+) T cell stimulation.
authors.affiliation: Center of Molecular Medicine of the Austrian Academy of Sciences, and Division of Immunology, Allergy and Infectious Diseases, Department of Dermatology, Medical University of Vienna, Austria.
authors.forename: Silvia
authors.initials: S
authors.lastname: Jaksits
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Bauer
authors.forename: Ernst
authors.initials: E
authors.lastname: Kriehuber
authors.forename: Maximilian
authors.initials: M
authors.lastname: Zeyda
authors.forename: Thomas M
authors.initials: TM
authors.lastname: Stulnig
authors.forename: Georg
authors.initials: G
authors.lastname: Stingl
authors.forename: Edda
authors.initials: E
authors.lastname: Fiebiger
authors.forename: Dieter
authors.initials: D
authors.lastname: Maurer
mesh_terms: D000199:Actins / Q000378:metabolism; D015703:Antigens, CD / Q000378:metabolism; D051940:B7-2 Antigen; D001692:Biological Transport / Q000502:physiology; D023201:CD40 Ligand / Q000494:pharmacology; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology*; D003505:Cyclodextrins / Q000494:pharmacology; D003599:Cytoskeleton / Q000378:metabolism / Q000648:ultrastructure; D003713:Dendritic Cells / Q000201:enzymology* / Q000276:immunology / Q000648:ultrastructure; D004789:Enzyme Activation; D004790:Enzyme Induction; D005799:Genes, Dominant; D015395:Histocompatibility Antigens Class I / Q000378:metabolism; D006801:Humans; D018664:Interleukin-12 / Q000378:metabolism; D008070:Lipopolysaccharides / Q000494:pharmacology; D008213:Lymphocyte Activation / Q000502:physiology*; D007959:Lymphocyte Culture Test, Mixed; D008264:Macrophages / Q000648:ultrastructure; D008562:Membrane Glycoproteins / Q000378:metabolism; D021962:Membrane Microdomains / Q000187:drug effects / Q000201:enzymology*; D009479:Neuropeptides / Q000172:deficiency / Q000235:genetics / Q000502:physiology*; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D015398:Signal Transduction; D014162:Transfection; D047392:beta-Cyclodextrins; D020764:cdc42 GTP-Binding Protein / Q000172:deficiency / Q000235:genetics / Q000502:physiology*; D054462:p21-Activated Kinases; D020744:rac GTP-Binding Proteins; D020830:rac1 GTP-Binding Protein / Q000172:deficiency / Q000235:genetics / Q000502:physiology*
chemical_list: D000199:Actins; D015703:Antigens, CD; D051940:B7-2 Antigen; C497964:CD86 protein, human; D003505:Cyclodextrins; D015395:Histocompatibility Antigens Class I; D008070:Lipopolysaccharides; D008562:Membrane Glycoproteins; D009479:Neuropeptides; C107953:RAC1 protein, human; D047392:beta-Cyclodextrins; C108732:methyl-beta-cyclodextrin; D023201:CD40 Ligand; D018664:Interleukin-12; C515903:PAK1 protein, human; D017346:Protein Serine-Threonine Kinases; D054462:p21-Activated Kinases; D020764:cdc42 GTP-Binding Protein; D020744:rac GTP-Binding Proteins; D020830:rac1 GTP-Binding Protein