Dephosphorylation of Carma1 by PP2A negatively regulates T-cell activation

EMBO J. 2011 Feb 2;30(3):594-605. doi: 10.1038/emboj.2010.331. Epub 2010 Dec 14.

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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • CARD Signaling Adaptor Proteins / genetics
  • CARD Signaling Adaptor Proteins / metabolism*
  • CD4-Positive T-Lymphocytes / physiology*
  • DNA Primers / genetics
  • Electrophoretic Mobility Shift Assay
  • Enzyme-Linked Immunosorbent Assay
  • Flow Cytometry
  • Gene Knockdown Techniques
  • Guanylate Cyclase / genetics
  • Guanylate Cyclase / metabolism*
  • HEK293 Cells
  • Humans
  • Immunoprecipitation
  • Jurkat Cells
  • Luciferases
  • Lymphocyte Activation / physiology*
  • Mice
  • Mice, Transgenic
  • Multiprotein Complexes / metabolism*
  • NF-kappa B / metabolism*
  • Phosphorylation
  • Protein Phosphatase 2 / metabolism*
  • Reverse Transcriptase Polymerase Chain Reaction
  • Transduction, Genetic

Substances

  • CARD Signaling Adaptor Proteins
  • DNA Primers
  • Multiprotein Complexes
  • NF-kappa B
  • PPP2R1A protein, human
  • Luciferases
  • Protein Phosphatase 2
  • CARD11 protein, human
  • Guanylate Cyclase