title: Dephosphorylation of Carma1 by PP2A negatively regulates T-cell activation.
abstract: The Carma1-Bcl10-Malt1 (CBM) complex bridges T-cell receptor (TCR) signalling to the canonical IκB kinase (IKK)/NF-κB pathway. NF-κB activation is triggered by PKCθ-dependent phosphorylation of Carma1 after TCR/CD28 co-stimulation. PKCθ-phosphorylated Carma1 was suggested to function as a molecular scaffold that recruits preassembled Bcl10-Malt1 complexes to the membrane. We have identified the serine-threonine protein phosphatase PP2A regulatory subunit Aα (PPP2R1A) as a novel interaction partner of Carma1. PPP2R1A is associated with Carma1 in resting as well as activated T cells in the context of the active CBM complex. By siRNA-mediated knockdown and in vitro dephosphorylation, we demonstrate that PP2A removes PKCθ-dependent phosphorylation of Ser645 in Carma1, and show that maintenance of this phosphorylation is correlated with increased T-cell activation. As a result of PP2A inactivation, we find that enhanced Carma1 S645 phosphorylation augments CBM complex formation, NF-κB activation and IL-2 or IFN-γ production after stimulation of Jurkat T cells or murine Th1 cells. Thus, our data define PP2A-mediated dephosphorylation of Carma1 as a critical step to limit T-cell activation and effector cytokine production.
authors.affiliation: Department of Cellular Signal Integration, Helmholtz Zentrum München-German Research Center for Environmental Health, Institute of Toxicology, Neuherberg, Germany.
authors.forename: Andrea C
authors.initials: AC
authors.lastname: Eitelhuber
authors.forename: Sebastian
authors.initials: S
authors.lastname: Warth
authors.forename: Gisela
authors.initials: G
authors.lastname: Schimmack
authors.forename: Michael
authors.initials: M
authors.lastname: Düwel
authors.forename: Kamyar
authors.initials: K
authors.lastname: Hadian
authors.forename: Katrin
authors.initials: K
authors.lastname: Demski
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Beisker
authors.forename: Hisaaki
authors.initials: H
authors.lastname: Shinohara
authors.forename: Tomohiro
authors.initials: T
authors.lastname: Kurosaki
authors.forename: Vigo
authors.initials: V
authors.lastname: Heissmeyer
authors.forename: Daniel
authors.initials: D
authors.lastname: Krappmann
mesh_terms: D000818:Animals; D053468:CARD Signaling Adaptor Proteins / Q000235:genetics / Q000378:metabolism*; D015496:CD4-Positive T-Lymphocytes / Q000502:physiology*; D017931:DNA Primers / Q000235:genetics; D024202:Electrophoretic Mobility Shift Assay; D004797:Enzyme-Linked Immunosorbent Assay; D005434:Flow Cytometry; D055785:Gene Knockdown Techniques; D006162:Guanylate Cyclase / Q000235:genetics / Q000378:metabolism*; D057809:HEK293 Cells; D006801:Humans; D047468:Immunoprecipitation; D019169:Jurkat Cells; D008156:Luciferases; D008213:Lymphocyte Activation / Q000502:physiology*; D051379:Mice; D008822:Mice, Transgenic; D046912:Multiprotein Complexes / Q000378:metabolism*; D016328:NF-kappa B / Q000378:metabolism*; D010766:Phosphorylation; D054648:Protein Phosphatase 2 / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014161:Transduction, Genetic
chemical_list: D053468:CARD Signaling Adaptor Proteins; D017931:DNA Primers; D046912:Multiprotein Complexes; D016328:NF-kappa B; C517191:PPP2R1A protein, human; D008156:Luciferases; D054648:Protein Phosphatase 2; C426242:CARD11 protein, human; D006162:Guanylate Cyclase