RESUMO
The activation of NF-κB downstream of T cell receptor (TCR) engagement is a key signaling step required for normal lymphocyte function during the adaptive immune response. During TCR signaling, the adaptor protein Bcl10 is inducibly recruited to the CARD11 scaffold protein as part of a multicomponent complex that induces IκB kinase (IKK) activity and NF-κB activation. Here, we show that a consequence of this recruitment is the TCR-induced conjugation of Bcl10 with linear-linked polyubiquitin chains to generate the signaling intermediate Lin(Ub)n-Bcl10, which is required for the association of Bcl10 with the NEMO subunit of the IKK complex. The TCR-induced generation of Lin(Ub)n-Bcl10 requires Bcl10 lysines 17, 31, and 63, CARD11, MALT1, and the HOIP subunit of the linear ubiquitin chain assembly complex (LUBAC) but not the HOIP accessory protein SHARPIN. CARD11 promotes signal-induced Lin(Ub)n-Bcl10 generation by co-recruiting Bcl10 with HOIP, thereby bringing substrate to enzyme. The CARD11-HOIP interaction is rendered TCR-inducible by the four autoinhibitory repressive elements in the CARD11 inhibitory domain and involves the CARD11 coiled-coil domain and two independent regions of HOIP. Interestingly, oncogenic CARD11 variants associated with diffuse large B cell lymphoma spontaneously induce Lin(Ub)n-Bcl10 production to extents that correlate with their abilities to activate NF-κB and with their enhanced abilities to bind HOIP and Bcl10. Our results define molecular determinants that control the production of Lin(Ub)n-Bcl10, an important signaling intermediate in TCR and oncogenic CARD11 signaling.
Assuntos
Proteínas Adaptadoras de Transdução de Sinal/metabolismo , Proteínas Adaptadoras de Sinalização CARD/metabolismo , Guanilato Ciclase/metabolismo , Receptores de Antígenos de Linfócitos T/metabolismo , Transdução de Sinais/fisiologia , Ubiquitinação/fisiologia , Proteínas Adaptadoras de Transdução de Sinal/genética , Proteína 10 de Linfoma CCL de Células B , Proteínas Adaptadoras de Sinalização CARD/genética , Caspases/genética , Caspases/metabolismo , Guanilato Ciclase/genética , Células HEK293 , Humanos , Células Jurkat , Proteína de Translocação 1 do Linfoma de Tecido Linfoide Associado à Mucosa , NF-kappa B/genética , NF-kappa B/metabolismo , Proteínas de Neoplasias/genética , Proteínas de Neoplasias/metabolismo , Domínios Proteicos , Receptores de Antígenos de Linfócitos T/genética , Ubiquitina-Proteína Ligases/genética , Ubiquitina-Proteína Ligases/metabolismoRESUMO
CARD11 functions as a key signaling scaffold that controls antigen-induced lymphocyte activation during the adaptive immune response. Somatic mutations in CARD11 are frequently found in Non-Hodgkin lymphoma, and at least three classes of germline CARD11 mutations have been described as the basis for primary immunodeficiency. In this review, we summarize our current understanding of how CARD11 signals, how its activity is regulated, and how mutations bypass normal regulation to cause disease.