Cutting Edge: The “Death” Adaptor CRADD/RAIDD Targets BCL10 and Suppresses Agonist-Induced Cytokine Expression in T Lymphocytes

Abstract

The expression of proinflammatory cytokines and chemokines in response to T cell receptor (TCR) agonists is regulated by the CARMA1 signalosome through the coordinated assembly of complexes containing the BCL10 adaptor protein. We describe a novel mechanism to negatively regulate the CARMA1 signalosome by the “death” adaptor protein, CRADD/RAIDD. We show that CRADD interacts with BCL10 through its caspase recruitment domain (CARD) and suppresses interactions between BCL10 and CARMA1. TCR agonist-induced interaction between CRADD and BCL10 coincides with reduction of its complex formation with CARMA1 in wild-type, as compared to Cradd-deficient, primary cells. Finally, Cradd-deficient spleen cells, CD4+ T cells, and mice respond to T cell agonists with strikingly higher production of proinflammatory mediators, including γ-interferon, IL-2, TNF-α, and IL-17. These results define a novel role for CRADD as a negative regulator of the CARMA1 signalosome and suppressor of T helper (Th)1- and Th17-mediated inflammatory responses.

The Adaptor CRADD/RAIDD Controls Activation of Endothelial Cells by Proinflammatory Stimuli

“…ϩ/ϩ and knock-out cradd Ϫ/Ϫ mice were generated and maintained as previously described (6). All work with animals was carried out in strict accordance with the recommendations in the Guide for the Care and Use of Laboratory Animals of the National Institutes of Health, and approved by the Vanderbilt University Institutional Animal Care and Use Committee.…”

“…Complexes were immunoprecipitated from cell lysates with antibody to IRAK-1 (Santa Cruz) and protein A/G-agarose beads (Thermo) then analyzed by quantitative immunoblotting using antibodies to IRAK-1 and BCL10. All immunoblots were analyzed with the LI-COR Odyssey Infrared Imaging System as previously described (6,30).…”

“…Recently, we added the "death" adaptor caspase and receptor interacting protein adaptor with death domain/receptor interacting protein-associated ICH-1/CED-3 homologous protein with a death domain (CRADD/RAIDD), hereafter designated as CRADD, to this list. CRADD negatively regulates NFB-dependent cytokine and chemokine expression in T cells by targeting the NH 2 -terminal caspase recruitment domain (CARD) of B-cell CLL/Lymphoma 10 (BCL10) (6). In immune cells, the CARD of BCL10 functions as an oligomerization region and interacts with the CARD of the CARD membraneassociated guanylate kinase (CARMA) 1 (6,7), which is required for activation of the NFB pathway (8 -12).…”

“…CRADD negatively regulates NFB-dependent cytokine and chemokine expression in T cells by targeting the NH 2 -terminal caspase recruitment domain (CARD) of B-cell CLL/Lymphoma 10 (BCL10) (6). In immune cells, the CARD of BCL10 functions as an oligomerization region and interacts with the CARD of the CARD membraneassociated guanylate kinase (CARMA) 1 (6,7), which is required for activation of the NFB pathway (8 -12). In nonimmune cells, such as endothelial cells, a CARMA3 signalo-some containing BCL10 and mucosa-associated lymphoid tissue lymphoma translocation protein 1 (MALT1), operates to regulate the NFB signaling pathway (13,14).…”

“…Here we analyzed the potential role of CRADD in endothelial cell homeostasis by employing three approaches: (i) reduction of CRADD expression in murine endothelial cells with shRNA, (ii) analysis of microvascular endothelial cells isolated from CRADD-deficient mice (6), and (iii) intracellular delivery of a novel recombinant cell-penetrating CRADD protein homolog (CP-CRADD) to CRADD-deficient and sufficient endothelial cells. We documented a protective role for CRADD in maintaining the permeability barrier of primary lung microvascular endothelial cells (LMEC) by demonstrating increased agonistinduced permeability of cradd Ϫ/Ϫ LMEC monolayers compared with cradd ϩ/ϩ LMEC monolayers.…”