The adaptive immune response is initiated when microbial or tumor-specific molecules are recognized by antigen receptors present at lymphocyte cell surface. Engagement of these immunoreceptors induces signaling cascades that ultimately activate the transcription factors NF-κB (Nuclear Factor-κB) and NFAT (nuclear factor of activated T-cells) responsible for the establishment of gene expression programs controlling the stimulation, proliferation and survival of activated lymphocytes. Cloning the products of three distinct translocation events found in lymphoma of mucosa-associated lymphoid tissue (MALT lymphoma) led to the identification and characterization of a novel NF-κB-activating complex following antigenic stimulation composed by the CARMA1, BCL10, and MALT1 proteins and called the CBM complex. Since the identification of this complex, other regulatory components were discovered which greatly improve our understanding of this signaling pathways.Interestingly, CBM complex activity is not only altered in MALT lymphomas but also in a subtype of activated B cell-like (ABC) of diffuse large B-cell (DLBCL) lymphoma. In this review, we described the key players involved in antigen-induced NF-κB activation and covered the recent advances in the molecular mechanisms that are responsible for the regulation of the components of the CBM complex. Understanding these mechanisms is critical for the elucidation of the role of this NF-κB signaling network in both normal and pathologic conditions and we described how dysregulation of this network leads to the uncontrolled activation of NF-κB and development of two particular subtypes of human B cell lymphomas: the MALT and the DLBCL lymphomas.
DAP12) [1]. Engagement of these receptors initiate a signal-activation cascade that includes phosphorylation of two specific tyrosine residues located in the ITAM by the Src family kinases [1]. Tyrosine kinase Syk or ZAP-70 (zeta-chain-associated protein 70 kD) are then recruited to the phosphorylated ITAM through their tandem Src homology 2 (SH2) regions, initiating downstream signaling cascades that lead to the stimulation of mitogen-activated protein kinase (MAPK) activities and ultimately to the activation of the transcription factors NF-κB and NF-AT (nuclear factor of activated T-cells).An outstanding issue of lymphocyte activation was the identification of a complex of proteins comprising CARMA1, BCL10 and MALT1 (also called the CBM complex) as critical regulators of the immunoreceptor signaling pathways. In this review, we will focus on the recent advances concerning the role of the CBM function in antigen-induced NF-κB signaling and detail how this pathway may selectively become dysregulated in lymphoma.
The key players of antigen-mediated NF-κB activationAntigen receptor activation initiates a phosphorylation cascade that promotes assembly of the CBM signalosome complex composed of CARMA1, BCL10, and MALT1 that ultimately activates the NEMO/ IKK complex to promote NF-κB transcription (Figure 1). In this