Phosphorylation of CARMA1 by HPK1 is critical for NF-κB activation in T cells

Dirk Brenner, Markus Brechmann, Simone Röhling, Myriam Tapernoux, Thomas Mock, Dominic Winter, Wolf D. Lehmann, Friedemann Kiefer, Margot Thome, Peter H. Krammer, Rüdiger Arnold*

*Corresponding author for this work

Research output: Contribution to journalArticleResearchpeer-review

50 Citations (Scopus)


Activation of the NF-κB pathway in T cells is required for induction of an adaptive immune response. Hematopoietic progenitor kinase (HPK1) is an important proximal mediator of T-cell receptor (TCR)-induced NF-κB activation. Knock-down of HPK1 abrogates TCR-induced IKKβ and NF-κB activation, whereas active HPK1 leads to increased IKKβ activity in T cells. Yet, the precise molecular mechanism of this process remains elusive. Here, we show that HPK1-mediated NF-κB activation is dependent on the adaptor protein CARMA1. HPK1 interacts with CARMA1 in a TCR stimulation- dependent manner and phosphorylates the linker region of CARMA1. Interestingly, the putative HPK1 phosphorylation sites in CARMA1 are different from known PKCθ consensus sites. Mutations of residues S549, S551, and S552 in CARMA1 abrogated phosphorylation of a CARMA1-linker construct by HPK1 in vitro. In addition, CARMA1 S551A or S5549A/S551A point mutants failed to restore HPK1-mediated and TCR-mediated NF-κB activation and IL-2 expression in CARMA1-deficient T cells. Thus, we identify HPK1 as a kinase specific for CARMA1 and suggest HPK1-mediated phosphorylation of CARMA1 as an additional regulatory mechanism tuning the NF-κB response upon TCR stimulation.

Original languageEnglish
Pages (from-to)14508-14513
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number34
Publication statusPublished - 25 Aug 2009
Externally publishedYes


  • CBM complex
  • IKK
  • PKC
  • TCR


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