Visit our Expo - Redox and Inflammation signaling 2012

Session XIV : Transcriptional and translational control Poster XIV, 55
Identification and characterization of signaling pathways to NF-kB in lymphocytes
Andrea Oeckinghaus1, Elmar Wegener1, Alexander Beck2, Claus Scheidereit1, Daniel
Krappmann1,3
1 Max-Delbrück-Center for Molecular Medicine, Robert-Rössle-Str. 10, 13125 Berlin,
Germany
2 University Hospital Tübingen, Internal Medicine IV, Otfried-Müller-Str. 10, 72076
Tübingen
3 GSF - Research Center for Environment and Health, Institute of Toxicology,
Ingolstädter
Landstr.1, 85764 Neuherberg, Germany
Activation, differentiation and clonal expansion of T-lymphocytes are initiated upon the
concerted action of the T-cell receptor (TCR) and the CD28 co-stimulatory receptor.
TCR/CD28 engagement initiates canonical NF-kB signaling, which involves IKK (IkB
kinase) dependent phosphorylation and degradation of inhibitors of NF-kB (IkBs) enabling
nuclear translocation of NF-kB. Genetic ablation in mice has identified PKCq, Carma1, Malt1
and Bcl10 as essential mediators of antigen receptor induced IKK activation. Formation of a
Carma1/Bcl10/Malt1 (CBM) complex represents a crucial step. But the composition of the
regulatory CBM complex, that forms after T cell stimulation in vivo, and the mechanism of
signal transduction from the TCR to the IKK complex are not understood to date.
Using gel filtration analysis, GST pull down experiments, tandem affinity purifications and
antibody immunoprecipitations of signaling mediators, we have analyzed the composition and
the dynamics of the cellular CBM complex. We find that Bcl10-Malt1 associates with IKK#
in unstimulated T cells and is rapidly recruited to Carma1 in response to TCR signaling.
Sustained TCR/CD28 signaling leads to a disengagement of the CBM complex and
abrogation of downstream signaling. Further, we find that antigen induced phosphorylation of
Bcl10 requires the putative downstream kinase IKKb. Mapping and functional studies of
phospho-acceptor sites on Bcl10 reveal, that IKKb triggered Bcl10 phosphorylation serves to
balance TCR induced lymphocyte activation. Our studies indicate that the formation of large
signaling clusters upon T cell activation initiates a network of protein interactions and
modifications and thereby facilitates a non-linear order of signaling to IKK/NF-kB.
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