{"gene":"CRADD","run_date":"2026-04-28T17:28:53","timeline":{"discoveries":[{"year":1997,"finding":"RAIDD/CRADD was identified as a bipartite adaptor molecule with a C-terminal death domain (DD) that binds to the DD of RIP (a serine/threonine kinase), and an N-terminal CARD homologous to the prodomain of ICE/CED-3 family members (caspase-2/ICH-1 and CED-3) that mediates homophilic binding to these caspases, directly linking RIP signaling to caspase activation.","method":"Yeast two-hybrid, co-immunoprecipitation, domain mapping, mutagenesis of N-terminal CARD equivalent to ced-3 inactivating mutations","journal":"Nature","confidence":"High","confidence_rationale":"Tier 1-2 — original discovery with reciprocal binding assays, mutagenesis, and multiple orthogonal methods; highly cited foundational paper","pmids":["8985253"],"is_preprint":false},{"year":1997,"finding":"CRADD was independently shown to have an NH2-terminal caspase homology domain (CARD) that interacts with caspase-2 and a COOH-terminal death domain that interacts with RIP, constituting a dual-domain adaptor that induces apoptosis.","method":"Co-immunoprecipitation, domain deletion constructs, apoptosis assays","journal":"Cancer research","confidence":"High","confidence_rationale":"Tier 2 — independent replication of RAIDD/CRADD binding partners with reciprocal co-IP, consistent with Nature paper","pmids":["9044836"],"is_preprint":false},{"year":1998,"finding":"The NMR solution structure of the RAIDD CARD was solved, revealing six tightly packed helices in a topology homologous to the Fas death domain, with a basic and acidic patch on opposite sides that mediate CARD/CARD interaction with ICH-1/caspase-2; mutagenesis of these patches disrupted CARD/CARD binding.","method":"NMR structure determination, homology modeling, mutagenesis of surface residues","journal":"Cell","confidence":"High","confidence_rationale":"Tier 1 — atomic-resolution NMR structure with mutagenesis validation, highly cited","pmids":["9695946"],"is_preprint":false},{"year":2000,"finding":"Endogenous RAIDD is predominantly cytoplasmic with some nuclear localization; upon co-expression with caspase-2, a fraction of RAIDD is recruited to the nucleus. The RAIDD CARD mediates oligomerization into filamentous structures similar to death effector filaments (DEFs), and CARD-dependent colocalization of RAIDD and caspase-2 occurs at discrete subcellular structures. Intramolecular folding of RAIDD may regulate CARD oligomerization.","method":"Subcellular fractionation, immunofluorescence, co-transfection with deletion mutants, live-cell imaging of CARD-only constructs","journal":"Cell death and differentiation","confidence":"Medium","confidence_rationale":"Tier 2-3 — direct localization with functional domain mapping; single lab but multiple orthogonal approaches","pmids":["10713730"],"is_preprint":false},{"year":2005,"finding":"PIDD-induced apoptosis and growth suppression in embryonic fibroblasts depends on the adaptor protein RAIDD (genetic epistasis); PIDD-induced cell death is associated with early caspase-2 activation and later caspase-3 and -7 activation. Caspase-2 knockout cells are only partially resistant, while RAIDD knockout cells are fully resistant to PIDD-induced death.","method":"RAIDD-/- and caspase-2-/- mouse embryonic fibroblasts, genetic epistasis, caspase activity assays","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 — clean knockout genetic epistasis with defined phenotypic readout, multiple genotypes compared","pmids":["16183742"],"is_preprint":false},{"year":2006,"finding":"Crystal structure of RAIDD DD was solved at 2.0 Å resolution, revealing structural features important for DD folding, dynamics, and PIDDosome assembly via DD:DD interaction with PIDD.","method":"X-ray crystallography at 2.0 Å resolution","journal":"Journal of molecular biology","confidence":"High","confidence_rationale":"Tier 1 — high-resolution crystal structure with direct functional implication for PIDDosome assembly","pmids":["16434054"],"is_preprint":false},{"year":2004,"finding":"RAIDD interacts with caspase-2 via CARD in neuronal (PC12) cells; overexpression of RAIDD induces caspase-2 CARD- and caspase-9-dependent apoptosis in PC12 cells and sympathetic neurons, correlating with formation of discrete perinuclear aggregates. Both death and aggregate formation require full-length RAIDD.","method":"RAIDD overexpression, CARD deletion mutants, caspase-2 and caspase-9 inhibition assays, immunofluorescence","journal":"Cell death and differentiation","confidence":"Medium","confidence_rationale":"Tier 2-3 — functional overexpression with domain dissection and specific caspase inhibition in neuronal cells","pmids":["14765136"],"is_preprint":false},{"year":2006,"finding":"Endogenous RAIDD is required for trophic deprivation-induced apoptosis of PC12 cells and sympathetic neurons; siRNA-mediated knockdown of RAIDD inhibited trophic-deprivation-induced (caspase-2-mediated) death but not DNA-damage-induced death, placing RAIDD specifically in the trophic factor withdrawal pathway upstream of caspase-2.","method":"siRNA knockdown, dominant-negative CARD-only caspase-2 expression, apoptosis assays with distinct stimuli","journal":"Cell death and differentiation","confidence":"Medium","confidence_rationale":"Tier 2 — specific knockdown with pathway specificity control (DNA damage not affected), single lab","pmids":["15947787"],"is_preprint":false},{"year":2007,"finding":"The PIDD DD and RAIDD DD form an oligomeric complex of ~150 kDa in solution (as measured by gel filtration and MALS), establishing the stoichiometry and physical basis for the PIDDosome core; crystals were obtained for structural studies.","method":"Recombinant protein purification, gel filtration, multi-angle light scattering (MALS), crystallization","journal":"Acta crystallographica. Section F, Structural biology and crystallization communications","confidence":"Medium","confidence_rationale":"Tier 1-2 — reconstituted complex with biophysical characterization of stoichiometry","pmids":["17329820"],"is_preprint":false},{"year":2010,"finding":"PIDDosome assembly is time-dependent and salt concentration-dependent; point mutations RAIDD R147E and PIDD Y814A act as dominant negatives for PIDDosome formation but cannot disassemble pre-formed PIDDosome, revealing key residues at the RAIDD DD:PIDD DD interface.","method":"Recombinant protein reconstitution, mutagenesis, dominant-negative biochemical assays","journal":"Biochimica et biophysica acta","confidence":"Medium","confidence_rationale":"Tier 1-2 — in vitro reconstitution with mutagenesis identifying critical interface residues; single lab","pmids":["20406701"],"is_preprint":false},{"year":2012,"finding":"RAIDD is required for caspase-2 activity and caspase-2-dependent neuronal death induced by NGF deprivation and amyloid-β, but PIDD is dispensable; treatment induces formation of a caspase-2/RAIDD complex independent of PIDD in neurons, defining a PIDD-independent neuronal activation complex for caspase-2.","method":"RAIDD-/- and PIDD-/- mouse neurons, co-immunoprecipitation, caspase-2 activity assays, NGF deprivation and Aβ treatments","journal":"The Biochemical journal","confidence":"High","confidence_rationale":"Tier 2 — genetic knockout epistasis with reciprocal co-IP and activity assays, replicated with two stimuli","pmids":["22515271"],"is_preprint":false},{"year":2012,"finding":"CRADD interacts with BCL10 through its CARD domain, suppressing BCL10-CARMA1 complex formation and thereby negatively regulating TCR agonist-induced NF-κB-dependent cytokine production (IFN-γ, IL-2, TNF-α, IL-17). CRADD-deficient T cells and mice show heightened proinflammatory cytokine responses to TCR agonists.","method":"Co-immunoprecipitation (CRADD-BCL10 interaction), Cradd-/- primary T cells and mice, cytokine measurement, domain mapping","journal":"Journal of immunology (Baltimore, Md. : 1950)","confidence":"High","confidence_rationale":"Tier 2 — reciprocal co-IP, knockout primary cells and in vivo model with defined signaling phenotype","pmids":["22323537"],"is_preprint":false},{"year":2013,"finding":"PIDD DD must bind to RAIDD first to open the closed conformation of full-length RAIDD, allowing subsequent recruitment of caspase-2 via CARD:CARD interaction; caspase-2 CARD alone is insoluble but is solubilized by RAIDD CARD or by full-length RAIDD in the presence of PIDD DD, defining the ordered assembly of the PIDDosome.","method":"Recombinant protein purification of all DD superfamily members, solubility assays, biochemical reconstitution","journal":"BMB reports","confidence":"Medium","confidence_rationale":"Tier 1 — in vitro reconstitution revealing ordered assembly mechanism; single lab","pmids":["24064063"],"is_preprint":false},{"year":2014,"finding":"CRADD interacts with BCL10 to negatively regulate the CARMA3 signalosome in endothelial cells; CRADD-deficient endothelial cells display increased IL-6 and MCP-1 expression and increased permeability with more F-actin polymerization and disrupted adherens junctions in response to LPS and thrombin. Delivery of recombinant cell-penetrating CRADD restores barrier function.","method":"cradd-/- primary murine endothelial cells, cytokine assays, permeability assays, F-actin staining, recombinant CP-CRADD protein delivery","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 — knockout primary cells with multiple functional readouts and rescue experiment; single lab","pmids":["24958727"],"is_preprint":false},{"year":2015,"finding":"Genetic epistasis in the Eμ-Myc mouse lymphoma model shows that Raidd deficiency does not phenocopy Caspase-2 or Pidd1 deficiency in tumor suppression or promotion, indicating that the tumor-modulatory effects of Caspase-2 and Pidd1 can be uncoupled from their interaction with Raidd, implying alternative signaling modules.","method":"Eμ-Myc/Raidd-/- mice, tumor onset analysis, DNA-damage-driven cancer models, genetic epistasis","journal":"Cell death and differentiation","confidence":"Medium","confidence_rationale":"Tier 2 — clean knockout epistasis in in vivo cancer model; single lab but rigorous genetic approach","pmids":["25857265"],"is_preprint":false},{"year":2016,"finding":"CRADD/RAIDD mutations in the death domain (G128R, F164C, R170C, R170H) identified in patients with thin lissencephaly do not disrupt co-immunoprecipitation interactions with caspase-2 or PIDD, but abolish CRADD's ability to activate caspase-2, resulting in reduced neuronal apoptosis in vitro; homozygous Cradd knockout mice display megalencephaly and seizures, establishing CRADD/caspase-2 signaling as required for normal cortical development.","method":"Co-immunoprecipitation of TLIS variants with caspase-2 and PIDD, caspase-2 activation assays in neurons, Cradd-/- mice","journal":"American journal of human genetics","confidence":"High","confidence_rationale":"Tier 2 — multiple patient mutations functionally characterized, knockout mouse model, in vitro caspase activation assays, orthogonal methods","pmids":["27773430"],"is_preprint":false},{"year":2016,"finding":"RAIDD interacts with IRF7 and the kinase IKKε via co-immunoprecipitation; both the CARD and DD of RAIDD are required for IKKε- and IRF7-mediated type I interferon production (IFN-4α), placing RAIDD as a scaffold coordinating IKKε-IRF7 interaction downstream of TLR3 activation.","method":"Co-immunoprecipitation, shRNA knockdown, IFN-4α-driven dual luciferase assay, CARD and DD deletion constructs","journal":"Cellular physiology and biochemistry","confidence":"Medium","confidence_rationale":"Tier 2-3 — co-IP plus functional luciferase assay and domain deletion in RAIDD-deficient cells; single lab","pmids":["27606466"],"is_preprint":false},{"year":2016,"finding":"TAT-fused peptides derived from helix 3 (H3) of RAIDD and PIDD block PIDDosome formation in vitro and inhibit rotenone-induced caspase-2-dependent apoptosis in neuronal cells, confirming H3 as a critical interface for RAIDD:PIDD DD interaction.","method":"In vitro PIDDosome reconstitution assay, TAT-peptide inhibition, caspase-2 activity assay, neuronal cell death assay","journal":"Scientific reports","confidence":"Medium","confidence_rationale":"Tier 1-2 — in vitro reconstitution with peptide inhibitors targeting defined structural interface validated in cells","pmids":["27502430"],"is_preprint":false},{"year":2018,"finding":"TLIS-associated RAIDD DD mutations (G128R, F164C, R170C, R170H) were shown by mutagenesis and biochemical assays to disrupt DD:DD interaction with PIDD, providing the molecular mechanism by which these mutations reduce caspase-2-mediated neuronal apoptosis.","method":"Mutagenesis, biochemical binding assays (pulldown/co-IP of DD mutants with PIDD DD)","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 1-2 — systematic mutagenesis with biochemical validation; single lab","pmids":["30281648"],"is_preprint":false},{"year":2014,"finding":"HDAC1 binds directly to the CRADD promoter and represses its expression in gastric cancer; HDAC1 siRNA upregulates CRADD, and CRADD induction by the HDAC inhibitor TSA activates caspase-2-dependent apoptosis, establishing HDAC1 as a negative transcriptional regulator of the CRADD-caspase-2 axis.","method":"ChIP (HDAC1 binding to CRADD promoter), siRNA knockdown, TSA treatment, caspase-2 activation assay","journal":"American journal of translational research","confidence":"Medium","confidence_rationale":"Tier 2 — ChIP establishes direct promoter binding; functional link to caspase-2 pathway confirmed; single lab","pmids":["25360218"],"is_preprint":false}],"current_model":"CRADD/RAIDD is a bipartite adaptor protein with an N-terminal CARD that recruits and activates caspase-2 via homophilic CARD:CARD interaction and a C-terminal death domain that engages RIP/RIPK1 and PIDD to assemble the PIDDosome (PIDD DD:RAIDD DD:caspase-2 CARD), where ordered assembly (PIDD binding first opens RAIDD to then recruit caspase-2) drives proximity-induced caspase-2 activation in stress- and p53-induced apoptosis; CRADD also acts as a negative regulator of NF-κB signaling in immune and endothelial cells by engaging BCL10 through its CARD to suppress CARMA1/CARMA3 signalosomes, and as a scaffold for IKKε-IRF7 interaction in type I interferon production, while CRADD loss-of-function mutations in the death domain impair caspase-2 activation causing reduced neuronal apoptosis and cortical malformation (thin lissencephaly) in humans and megalencephaly in mice."},"narrative":{"teleology":[{"year":1997,"claim":"The fundamental question of how RIP kinase signaling connects to caspase activation was answered by the discovery that CRADD/RAIDD is a bipartite adaptor whose DD binds RIP and whose CARD binds caspase-2, establishing the first molecular bridge between death-domain signaling and the caspase cascade.","evidence":"Yeast two-hybrid, co-immunoprecipitation, domain mapping, and mutagenesis in two independent studies","pmids":["8985253","9044836"],"confidence":"High","gaps":["Whether CRADD mediates RIP-dependent caspase activation in vivo was not tested","Upstream signals triggering the RIP–CRADD–caspase-2 axis were unknown"]},{"year":1998,"claim":"How the CARD of RAIDD physically recognizes caspase-2 was resolved by solving the NMR structure, revealing a six-helix bundle with complementary charged patches that mediate CARD:CARD interaction.","evidence":"NMR solution structure with mutagenesis of acidic and basic surface patches disrupting caspase-2 binding","pmids":["9695946"],"confidence":"High","gaps":["Structure of the full-length RAIDD including the DD was not determined","No structure of the CARD:CARD complex itself"]},{"year":2000,"claim":"The question of where RAIDD acts in the cell was addressed by showing it is predominantly cytoplasmic, can form CARD-dependent filamentous oligomers, and is partially recruited to the nucleus by caspase-2, suggesting intramolecular autoinhibition regulates its oligomerization.","evidence":"Subcellular fractionation, immunofluorescence, and live-cell imaging of CARD-only versus full-length constructs","pmids":["10713730"],"confidence":"Medium","gaps":["Whether nuclear recruitment is physiologically relevant was unclear","Autoinhibition was inferred but not structurally resolved"]},{"year":2005,"claim":"Genetic epistasis in RAIDD-knockout and caspase-2-knockout MEFs established that RAIDD is absolutely required for PIDD-induced apoptosis, placing it as the essential adaptor between PIDD and caspase-2 in the PIDDosome.","evidence":"RAIDD−/− and caspase-2−/− mouse embryonic fibroblasts with PIDD overexpression and caspase activity assays","pmids":["16183742"],"confidence":"High","gaps":["Whether endogenous PIDD-dependent stimuli require RAIDD in vivo remained untested","The stoichiometry and assembly order of the PIDDosome were unknown"]},{"year":2006,"claim":"The crystal structure of the RAIDD DD at 2.0 Å and functional studies in neurons together defined the structural basis for PIDDosome DD:DD interaction and showed that RAIDD activates caspase-2-dependent apoptosis specifically in trophic factor withdrawal but not DNA-damage pathways.","evidence":"X-ray crystallography of RAIDD DD; siRNA knockdown in PC12 cells and sympathetic neurons with pathway-specific stimuli","pmids":["16434054","15947787","14765136"],"confidence":"High","gaps":["Structure of the RAIDD DD:PIDD DD complex was not yet solved","The identity of upstream signals channeling through RAIDD in trophic deprivation was unknown"]},{"year":2010,"claim":"Biochemical reconstitution revealed that PIDDosome assembly is ordered and governed by critical interface residues (RAIDD R147, PIDD Y814), with dominant-negative mutants blocking new assembly but unable to disassemble preformed complexes.","evidence":"Recombinant protein reconstitution, mutagenesis, and dominant-negative biochemical assays","pmids":["20406701","17329820"],"confidence":"Medium","gaps":["The precise stoichiometry of the PIDDosome was not fully resolved","Whether the same assembly rules apply in living cells was untested"]},{"year":2012,"claim":"Two distinct non-apoptotic roles for CRADD were uncovered: in neurons, RAIDD activates caspase-2 independently of PIDD during NGF deprivation and Aβ-induced death; in T cells, CRADD suppresses NF-κB by engaging BCL10 through its CARD to disrupt CARMA1-BCL10 signalosome formation.","evidence":"RAIDD−/− and PIDD−/− neurons with co-IP and caspase-2 activity assays; CRADD−/− primary T cells with cytokine measurement and BCL10 co-IP","pmids":["22515271","22323537"],"confidence":"High","gaps":["How CRADD is recruited to the BCL10–CARMA1 complex is unknown","Whether PIDD-independent caspase-2 activation uses an alternative DD partner was not identified"]},{"year":2013,"claim":"The ordered assembly mechanism of the PIDDosome was defined: PIDD DD binding opens the autoinhibited full-length RAIDD, which then solubilizes and recruits the otherwise insoluble caspase-2 CARD, establishing sequential conformational gating.","evidence":"Recombinant reconstitution of all three DD superfamily domains with solubility and binding assays","pmids":["24064063"],"confidence":"Medium","gaps":["No structural snapshot of the conformational change in full-length RAIDD upon PIDD binding","Kinetics of the conformational switch in cells remain uncharacterized"]},{"year":2014,"claim":"CRADD's negative regulation of NF-κB was extended to endothelial cells (CARMA3 signalosome), and HDAC1 was identified as a direct transcriptional repressor of CRADD, linking epigenetic regulation to the CRADD–caspase-2 apoptotic axis in gastric cancer.","evidence":"CRADD−/− endothelial cells with permeability/cytokine assays and recombinant CRADD rescue; ChIP showing HDAC1 at the CRADD promoter with siRNA and HDAC inhibitor validation","pmids":["24958727","25360218"],"confidence":"Medium","gaps":["Whether HDAC1-mediated CRADD repression is relevant beyond gastric cancer is unknown","The transcription factor through which HDAC1 represses CRADD was not identified"]},{"year":2016,"claim":"CRADD DD mutations (G128R, F164C, R170C, R170H) were identified as causal for thin lissencephaly by abolishing caspase-2 activation without disrupting protein–protein interactions in co-IP, and peptide inhibitors targeting the DD helix-3 interface validated this surface as critical for PIDDosome function; CRADD was also shown to scaffold IKKε–IRF7 for type I interferon production.","evidence":"Patient mutation functional characterization with co-IP and caspase-2 assays; Cradd−/− mice showing megalencephaly; TAT-peptide inhibition of PIDDosome in vitro and in neuronal cells; co-IP of RAIDD with IRF7 and IKKε with luciferase reporter","pmids":["27773430","27502430","27606466"],"confidence":"High","gaps":["How DD mutations abolish caspase-2 activation while preserving binary interactions is mechanistically unclear","The role of CRADD in IFN signaling was shown only in overexpression/reporter systems"]},{"year":2018,"claim":"The molecular mechanism of lissencephaly-causing mutations was clarified: TLIS DD mutations specifically disrupt the DD:DD interaction with PIDD, resolving the apparent paradox of preserved co-IP but lost caspase-2 activation.","evidence":"Systematic mutagenesis and pulldown/co-IP of DD mutants with PIDD DD","pmids":["30281648"],"confidence":"Medium","gaps":["No high-resolution structure of mutant DD:PIDD DD complexes","Whether residual PIDDosome assembly occurs in vivo with these mutations is untested"]},{"year":null,"claim":"Key unresolved questions include the identity of the upstream signal or DD partner that activates RAIDD–caspase-2 independently of PIDD in neurons, the structural basis of RAIDD autoinhibition and its conformational opening, and the physiological relevance of CRADD's NF-κB and IFN regulatory functions in vivo.","evidence":"","pmids":[],"confidence":"Low","gaps":["No PIDD-independent DD partner for RAIDD has been identified in neurons","No structure of full-length autoinhibited RAIDD exists","In vivo validation of CRADD's role in IFN signaling is lacking"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0060090","term_label":"molecular adaptor activity","supporting_discovery_ids":[0,1,4,12,15]},{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[11,13]}],"localization":[{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[3]},{"term_id":"GO:0005634","term_label":"nucleus","supporting_discovery_ids":[3]}],"pathway":[{"term_id":"R-HSA-5357801","term_label":"Programmed Cell Death","supporting_discovery_ids":[0,1,4,6,7,10,15]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[11,13,16]},{"term_id":"R-HSA-168256","term_label":"Immune System","supporting_discovery_ids":[11,16]},{"term_id":"R-HSA-1266738","term_label":"Developmental Biology","supporting_discovery_ids":[15]}],"complexes":["PIDDosome (PIDD DD:RAIDD DD:caspase-2 CARD)","RAIDD-caspase-2 complex (PIDD-independent)"],"partners":["CASP2","PIDD1","RIPK1","BCL10","IRF7","IKBKE"],"other_free_text":[]},"mechanistic_narrative":"CRADD (RAIDD) is a bipartite death-fold adaptor protein that bridges upstream death-domain signaling to caspase-2 activation and additionally functions as a negative regulator of NF-κB signaling. Its C-terminal death domain (DD) engages PIDD via DD:DD interaction to nucleate the PIDDosome, wherein PIDD binding opens RAIDD's autoinhibited conformation and permits its N-terminal CARD to recruit and activate caspase-2 through homophilic CARD:CARD interaction; this ordered assembly drives proximity-induced caspase-2 activation in stress-induced apoptosis, including trophic factor withdrawal in neurons [PMID:8985253, PMID:16183742, PMID:24064063, PMID:22515271]. CRADD also suppresses NF-κB-dependent inflammatory signaling by engaging BCL10 through its CARD to disrupt CARMA1/CARMA3 signalosomes in T cells and endothelial cells, and serves as a scaffold coordinating IKKε–IRF7 interaction for type I interferon production [PMID:22323537, PMID:24958727, PMID:27606466]. Homozygous loss-of-function mutations in the CRADD death domain cause thin lissencephaly in humans by abolishing caspase-2 activation and reducing developmental neuronal apoptosis, while Cradd-knockout mice display megalencephaly and seizures [PMID:27773430, PMID:30281648]."},"prefetch_data":{"uniprot":{"accession":"P78560","full_name":"Death domain-containing protein CRADD","aliases":["Caspase and RIP adapter with death domain","RIP-associated protein with a death domain"],"length_aa":199,"mass_kda":22.7,"function":"Adapter protein that associates with PIDD1 and the caspase CASP2 to form the PIDDosome, a complex that activates CASP2 and triggers apoptosis (PubMed:15073321, PubMed:16652156, PubMed:17159900, PubMed:17289572, PubMed:9044836). Also recruits CASP2 to the TNFR-1 signaling complex through its interaction with RIPK1 and TRADD and may play a role in the tumor necrosis factor-mediated signaling pathway (PubMed:8985253)","subcellular_location":"Cytoplasm; Nucleus","url":"https://www.uniprot.org/uniprotkb/P78560/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/CRADD","classification":"Not Classified","n_dependent_lines":1,"n_total_lines":1208,"dependency_fraction":0.0008278145695364238},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/CRADD","total_profiled":1310},"omim":[{"mim_id":"620653","title":"INTELLECTUAL DEVELOPMENTAL DISORDER, AUTOSOMAL RECESSIVE 80, WITH VARIANT LISSENCEPHALY; MRT80","url":"https://www.omim.org/entry/620653"},{"mim_id":"619827","title":"INTELLECTUAL DEVELOPMENTAL DISORDER, AUTOSOMAL RECESSIVE 75, WITH NEUROPSYCHIATRIC FEATURES AND VARIANT LISSENCEPHALY; MRT75","url":"https://www.omim.org/entry/619827"},{"mim_id":"614499","title":"INTELLECTUAL DEVELOPMENTAL DISORDER, AUTOSOMAL RECESSIVE 34, WITH VARIANT LISSENCEPHALY; MRT34","url":"https://www.omim.org/entry/614499"},{"mim_id":"611649","title":"MINDY LYSINE-48 DEUBIQUITINASE 3; MINDY3","url":"https://www.omim.org/entry/611649"},{"mim_id":"606831","title":"NLR FAMILY, CASPASE RECRUITMENT DOMAIN-CONTAINING 4; NLRC4","url":"https://www.omim.org/entry/606831"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Cytosol","reliability":"Approved"},{"location":"Nucleoplasm","reliability":"Additional"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/CRADD"},"hgnc":{"alias_symbol":["RAIDD"],"prev_symbol":[]},"alphafold":{"accession":"P78560","domains":[{"cath_id":"1.10.533.10","chopping":"2-94","consensus_level":"high","plddt":78.0754,"start":2,"end":94},{"cath_id":"1.10.533.10","chopping":"107-196","consensus_level":"high","plddt":86.5137,"start":107,"end":196}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/P78560","model_url":"https://alphafold.ebi.ac.uk/files/AF-P78560-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-P78560-F1-predicted_aligned_error_v6.png","plddt_mean":79.44},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=CRADD","jax_strain_url":"https://www.jax.org/strain/search?query=CRADD"},"sequence":{"accession":"P78560","fasta_url":"https://rest.uniprot.org/uniprotkb/P78560.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/P78560/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/P78560"}},"corpus_meta":[{"pmid":"8985253","id":"PMC_8985253","title":"RAIDD is a new 'death' adaptor molecule.","date":"1997","source":"Nature","url":"https://pubmed.ncbi.nlm.nih.gov/8985253","citation_count":455,"is_preprint":false},{"pmid":"9695946","id":"PMC_9695946","title":"Solution structure of the RAIDD CARD and model for CARD/CARD interaction in caspase-2 and caspase-9 recruitment.","date":"1998","source":"Cell","url":"https://pubmed.ncbi.nlm.nih.gov/9695946","citation_count":271,"is_preprint":false},{"pmid":"9044836","id":"PMC_9044836","title":"CRADD, a novel human apoptotic adaptor molecule for caspase-2, and FasL/tumor necrosis factor receptor-interacting protein RIP.","date":"1997","source":"Cancer research","url":"https://pubmed.ncbi.nlm.nih.gov/9044836","citation_count":225,"is_preprint":false},{"pmid":"16183742","id":"PMC_16183742","title":"Apoptosis caused by p53-induced protein with death domain (PIDD) depends on the death adapter protein RAIDD.","date":"2005","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/16183742","citation_count":89,"is_preprint":false},{"pmid":"10903735","id":"PMC_10903735","title":"Fas ligand-induced c-Jun kinase activation in lymphoid cells requires extensive receptor aggregation but is independent of DAXX, and Fas-mediated cell death does not involve DAXX, RIP, or RAIDD.","date":"2000","source":"Journal of immunology (Baltimore, Md. : 1950)","url":"https://pubmed.ncbi.nlm.nih.gov/10903735","citation_count":56,"is_preprint":false},{"pmid":"10713730","id":"PMC_10713730","title":"Subcellular localization and CARD-dependent oligomerization of the death adaptor RAIDD.","date":"2000","source":"Cell death and differentiation","url":"https://pubmed.ncbi.nlm.nih.gov/10713730","citation_count":52,"is_preprint":false},{"pmid":"27773430","id":"PMC_27773430","title":"Mutations in CRADD Result in Reduced Caspase-2-Mediated Neuronal Apoptosis and Cause Megalencephaly with a Rare Lissencephaly Variant.","date":"2016","source":"American journal of human genetics","url":"https://pubmed.ncbi.nlm.nih.gov/27773430","citation_count":50,"is_preprint":false},{"pmid":"21242994","id":"PMC_21242994","title":"LBH589, a deacetylase inhibitor, induces apoptosis in adult T-cell leukemia/lymphoma cells via activation of a novel RAIDD-caspase-2 pathway.","date":"2011","source":"Leukemia","url":"https://pubmed.ncbi.nlm.nih.gov/21242994","citation_count":43,"is_preprint":false},{"pmid":"22515271","id":"PMC_22515271","title":"Neuronal caspase 2 activity and function requires RAIDD, but not PIDD.","date":"2012","source":"The Biochemical journal","url":"https://pubmed.ncbi.nlm.nih.gov/22515271","citation_count":35,"is_preprint":false},{"pmid":"16434054","id":"PMC_16434054","title":"Crystal structure of RAIDD death domain implicates potential mechanism of PIDDosome assembly.","date":"2006","source":"Journal of molecular 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Part A","url":"https://pubmed.ncbi.nlm.nih.gov/28686357","citation_count":20,"is_preprint":false},{"pmid":"14765136","id":"PMC_14765136","title":"RAIDD aggregation facilitates apoptotic death of PC12 cells and sympathetic neurons.","date":"2004","source":"Cell death and differentiation","url":"https://pubmed.ncbi.nlm.nih.gov/14765136","citation_count":18,"is_preprint":false},{"pmid":"11771742","id":"PMC_11771742","title":"Expression of apoptosis related proteins: RAIDD, ZIP kinase, Bim/BOD, p21, Bax, Bcl-2 and NF-kappaB in brains of patients with Down syndrome.","date":"2001","source":"Journal of neural transmission. 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EJHG","url":"https://pubmed.ncbi.nlm.nih.gov/30914828","citation_count":13,"is_preprint":false},{"pmid":"15947787","id":"PMC_15947787","title":"RAIDD is required for apoptosis of PC12 cells and sympathetic neurons induced by trophic factor withdrawal.","date":"2006","source":"Cell death and differentiation","url":"https://pubmed.ncbi.nlm.nih.gov/15947787","citation_count":12,"is_preprint":false},{"pmid":"22323537","id":"PMC_22323537","title":"Cutting edge: the \"death\" adaptor CRADD/RAIDD targets BCL10 and suppresses agonist-induced cytokine expression in T lymphocytes.","date":"2012","source":"Journal of immunology (Baltimore, Md. : 1950)","url":"https://pubmed.ncbi.nlm.nih.gov/22323537","citation_count":12,"is_preprint":false},{"pmid":"25360218","id":"PMC_25360218","title":"Regulation of CRADD-caspase 2 cascade by histone deacetylase 1 in gastric cancer.","date":"2014","source":"American journal of translational 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of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 1997,\n      \"finding\": \"RAIDD/CRADD was identified as a bipartite adaptor molecule with a C-terminal death domain (DD) that binds to the DD of RIP (a serine/threonine kinase), and an N-terminal CARD homologous to the prodomain of ICE/CED-3 family members (caspase-2/ICH-1 and CED-3) that mediates homophilic binding to these caspases, directly linking RIP signaling to caspase activation.\",\n      \"method\": \"Yeast two-hybrid, co-immunoprecipitation, domain mapping, mutagenesis of N-terminal CARD equivalent to ced-3 inactivating mutations\",\n      \"journal\": \"Nature\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — original discovery with reciprocal binding assays, mutagenesis, and multiple orthogonal methods; highly cited foundational paper\",\n      \"pmids\": [\"8985253\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1997,\n      \"finding\": \"CRADD was independently shown to have an NH2-terminal caspase homology domain (CARD) that interacts with caspase-2 and a COOH-terminal death domain that interacts with RIP, constituting a dual-domain adaptor that induces apoptosis.\",\n      \"method\": \"Co-immunoprecipitation, domain deletion constructs, apoptosis assays\",\n      \"journal\": \"Cancer research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — independent replication of RAIDD/CRADD binding partners with reciprocal co-IP, consistent with Nature paper\",\n      \"pmids\": [\"9044836\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"The NMR solution structure of the RAIDD CARD was solved, revealing six tightly packed helices in a topology homologous to the Fas death domain, with a basic and acidic patch on opposite sides that mediate CARD/CARD interaction with ICH-1/caspase-2; mutagenesis of these patches disrupted CARD/CARD binding.\",\n      \"method\": \"NMR structure determination, homology modeling, mutagenesis of surface residues\",\n      \"journal\": \"Cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — atomic-resolution NMR structure with mutagenesis validation, highly cited\",\n      \"pmids\": [\"9695946\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"Endogenous RAIDD is predominantly cytoplasmic with some nuclear localization; upon co-expression with caspase-2, a fraction of RAIDD is recruited to the nucleus. The RAIDD CARD mediates oligomerization into filamentous structures similar to death effector filaments (DEFs), and CARD-dependent colocalization of RAIDD and caspase-2 occurs at discrete subcellular structures. Intramolecular folding of RAIDD may regulate CARD oligomerization.\",\n      \"method\": \"Subcellular fractionation, immunofluorescence, co-transfection with deletion mutants, live-cell imaging of CARD-only constructs\",\n      \"journal\": \"Cell death and differentiation\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 — direct localization with functional domain mapping; single lab but multiple orthogonal approaches\",\n      \"pmids\": [\"10713730\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"PIDD-induced apoptosis and growth suppression in embryonic fibroblasts depends on the adaptor protein RAIDD (genetic epistasis); PIDD-induced cell death is associated with early caspase-2 activation and later caspase-3 and -7 activation. Caspase-2 knockout cells are only partially resistant, while RAIDD knockout cells are fully resistant to PIDD-induced death.\",\n      \"method\": \"RAIDD-/- and caspase-2-/- mouse embryonic fibroblasts, genetic epistasis, caspase activity assays\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — clean knockout genetic epistasis with defined phenotypic readout, multiple genotypes compared\",\n      \"pmids\": [\"16183742\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"Crystal structure of RAIDD DD was solved at 2.0 Å resolution, revealing structural features important for DD folding, dynamics, and PIDDosome assembly via DD:DD interaction with PIDD.\",\n      \"method\": \"X-ray crystallography at 2.0 Å resolution\",\n      \"journal\": \"Journal of molecular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — high-resolution crystal structure with direct functional implication for PIDDosome assembly\",\n      \"pmids\": [\"16434054\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"RAIDD interacts with caspase-2 via CARD in neuronal (PC12) cells; overexpression of RAIDD induces caspase-2 CARD- and caspase-9-dependent apoptosis in PC12 cells and sympathetic neurons, correlating with formation of discrete perinuclear aggregates. Both death and aggregate formation require full-length RAIDD.\",\n      \"method\": \"RAIDD overexpression, CARD deletion mutants, caspase-2 and caspase-9 inhibition assays, immunofluorescence\",\n      \"journal\": \"Cell death and differentiation\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 — functional overexpression with domain dissection and specific caspase inhibition in neuronal cells\",\n      \"pmids\": [\"14765136\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"Endogenous RAIDD is required for trophic deprivation-induced apoptosis of PC12 cells and sympathetic neurons; siRNA-mediated knockdown of RAIDD inhibited trophic-deprivation-induced (caspase-2-mediated) death but not DNA-damage-induced death, placing RAIDD specifically in the trophic factor withdrawal pathway upstream of caspase-2.\",\n      \"method\": \"siRNA knockdown, dominant-negative CARD-only caspase-2 expression, apoptosis assays with distinct stimuli\",\n      \"journal\": \"Cell death and differentiation\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — specific knockdown with pathway specificity control (DNA damage not affected), single lab\",\n      \"pmids\": [\"15947787\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"The PIDD DD and RAIDD DD form an oligomeric complex of ~150 kDa in solution (as measured by gel filtration and MALS), establishing the stoichiometry and physical basis for the PIDDosome core; crystals were obtained for structural studies.\",\n      \"method\": \"Recombinant protein purification, gel filtration, multi-angle light scattering (MALS), crystallization\",\n      \"journal\": \"Acta crystallographica. Section F, Structural biology and crystallization communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1-2 — reconstituted complex with biophysical characterization of stoichiometry\",\n      \"pmids\": [\"17329820\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"PIDDosome assembly is time-dependent and salt concentration-dependent; point mutations RAIDD R147E and PIDD Y814A act as dominant negatives for PIDDosome formation but cannot disassemble pre-formed PIDDosome, revealing key residues at the RAIDD DD:PIDD DD interface.\",\n      \"method\": \"Recombinant protein reconstitution, mutagenesis, dominant-negative biochemical assays\",\n      \"journal\": \"Biochimica et biophysica acta\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1-2 — in vitro reconstitution with mutagenesis identifying critical interface residues; single lab\",\n      \"pmids\": [\"20406701\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"RAIDD is required for caspase-2 activity and caspase-2-dependent neuronal death induced by NGF deprivation and amyloid-β, but PIDD is dispensable; treatment induces formation of a caspase-2/RAIDD complex independent of PIDD in neurons, defining a PIDD-independent neuronal activation complex for caspase-2.\",\n      \"method\": \"RAIDD-/- and PIDD-/- mouse neurons, co-immunoprecipitation, caspase-2 activity assays, NGF deprivation and Aβ treatments\",\n      \"journal\": \"The Biochemical journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — genetic knockout epistasis with reciprocal co-IP and activity assays, replicated with two stimuli\",\n      \"pmids\": [\"22515271\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"CRADD interacts with BCL10 through its CARD domain, suppressing BCL10-CARMA1 complex formation and thereby negatively regulating TCR agonist-induced NF-κB-dependent cytokine production (IFN-γ, IL-2, TNF-α, IL-17). CRADD-deficient T cells and mice show heightened proinflammatory cytokine responses to TCR agonists.\",\n      \"method\": \"Co-immunoprecipitation (CRADD-BCL10 interaction), Cradd-/- primary T cells and mice, cytokine measurement, domain mapping\",\n      \"journal\": \"Journal of immunology (Baltimore, Md. : 1950)\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — reciprocal co-IP, knockout primary cells and in vivo model with defined signaling phenotype\",\n      \"pmids\": [\"22323537\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"PIDD DD must bind to RAIDD first to open the closed conformation of full-length RAIDD, allowing subsequent recruitment of caspase-2 via CARD:CARD interaction; caspase-2 CARD alone is insoluble but is solubilized by RAIDD CARD or by full-length RAIDD in the presence of PIDD DD, defining the ordered assembly of the PIDDosome.\",\n      \"method\": \"Recombinant protein purification of all DD superfamily members, solubility assays, biochemical reconstitution\",\n      \"journal\": \"BMB reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 — in vitro reconstitution revealing ordered assembly mechanism; single lab\",\n      \"pmids\": [\"24064063\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"CRADD interacts with BCL10 to negatively regulate the CARMA3 signalosome in endothelial cells; CRADD-deficient endothelial cells display increased IL-6 and MCP-1 expression and increased permeability with more F-actin polymerization and disrupted adherens junctions in response to LPS and thrombin. Delivery of recombinant cell-penetrating CRADD restores barrier function.\",\n      \"method\": \"cradd-/- primary murine endothelial cells, cytokine assays, permeability assays, F-actin staining, recombinant CP-CRADD protein delivery\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — knockout primary cells with multiple functional readouts and rescue experiment; single lab\",\n      \"pmids\": [\"24958727\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"Genetic epistasis in the Eμ-Myc mouse lymphoma model shows that Raidd deficiency does not phenocopy Caspase-2 or Pidd1 deficiency in tumor suppression or promotion, indicating that the tumor-modulatory effects of Caspase-2 and Pidd1 can be uncoupled from their interaction with Raidd, implying alternative signaling modules.\",\n      \"method\": \"Eμ-Myc/Raidd-/- mice, tumor onset analysis, DNA-damage-driven cancer models, genetic epistasis\",\n      \"journal\": \"Cell death and differentiation\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — clean knockout epistasis in in vivo cancer model; single lab but rigorous genetic approach\",\n      \"pmids\": [\"25857265\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"CRADD/RAIDD mutations in the death domain (G128R, F164C, R170C, R170H) identified in patients with thin lissencephaly do not disrupt co-immunoprecipitation interactions with caspase-2 or PIDD, but abolish CRADD's ability to activate caspase-2, resulting in reduced neuronal apoptosis in vitro; homozygous Cradd knockout mice display megalencephaly and seizures, establishing CRADD/caspase-2 signaling as required for normal cortical development.\",\n      \"method\": \"Co-immunoprecipitation of TLIS variants with caspase-2 and PIDD, caspase-2 activation assays in neurons, Cradd-/- mice\",\n      \"journal\": \"American journal of human genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple patient mutations functionally characterized, knockout mouse model, in vitro caspase activation assays, orthogonal methods\",\n      \"pmids\": [\"27773430\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"RAIDD interacts with IRF7 and the kinase IKKε via co-immunoprecipitation; both the CARD and DD of RAIDD are required for IKKε- and IRF7-mediated type I interferon production (IFN-4α), placing RAIDD as a scaffold coordinating IKKε-IRF7 interaction downstream of TLR3 activation.\",\n      \"method\": \"Co-immunoprecipitation, shRNA knockdown, IFN-4α-driven dual luciferase assay, CARD and DD deletion constructs\",\n      \"journal\": \"Cellular physiology and biochemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 — co-IP plus functional luciferase assay and domain deletion in RAIDD-deficient cells; single lab\",\n      \"pmids\": [\"27606466\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"TAT-fused peptides derived from helix 3 (H3) of RAIDD and PIDD block PIDDosome formation in vitro and inhibit rotenone-induced caspase-2-dependent apoptosis in neuronal cells, confirming H3 as a critical interface for RAIDD:PIDD DD interaction.\",\n      \"method\": \"In vitro PIDDosome reconstitution assay, TAT-peptide inhibition, caspase-2 activity assay, neuronal cell death assay\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1-2 — in vitro reconstitution with peptide inhibitors targeting defined structural interface validated in cells\",\n      \"pmids\": [\"27502430\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"TLIS-associated RAIDD DD mutations (G128R, F164C, R170C, R170H) were shown by mutagenesis and biochemical assays to disrupt DD:DD interaction with PIDD, providing the molecular mechanism by which these mutations reduce caspase-2-mediated neuronal apoptosis.\",\n      \"method\": \"Mutagenesis, biochemical binding assays (pulldown/co-IP of DD mutants with PIDD DD)\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1-2 — systematic mutagenesis with biochemical validation; single lab\",\n      \"pmids\": [\"30281648\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"HDAC1 binds directly to the CRADD promoter and represses its expression in gastric cancer; HDAC1 siRNA upregulates CRADD, and CRADD induction by the HDAC inhibitor TSA activates caspase-2-dependent apoptosis, establishing HDAC1 as a negative transcriptional regulator of the CRADD-caspase-2 axis.\",\n      \"method\": \"ChIP (HDAC1 binding to CRADD promoter), siRNA knockdown, TSA treatment, caspase-2 activation assay\",\n      \"journal\": \"American journal of translational research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — ChIP establishes direct promoter binding; functional link to caspase-2 pathway confirmed; single lab\",\n      \"pmids\": [\"25360218\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"CRADD/RAIDD is a bipartite adaptor protein with an N-terminal CARD that recruits and activates caspase-2 via homophilic CARD:CARD interaction and a C-terminal death domain that engages RIP/RIPK1 and PIDD to assemble the PIDDosome (PIDD DD:RAIDD DD:caspase-2 CARD), where ordered assembly (PIDD binding first opens RAIDD to then recruit caspase-2) drives proximity-induced caspase-2 activation in stress- and p53-induced apoptosis; CRADD also acts as a negative regulator of NF-κB signaling in immune and endothelial cells by engaging BCL10 through its CARD to suppress CARMA1/CARMA3 signalosomes, and as a scaffold for IKKε-IRF7 interaction in type I interferon production, while CRADD loss-of-function mutations in the death domain impair caspase-2 activation causing reduced neuronal apoptosis and cortical malformation (thin lissencephaly) in humans and megalencephaly in mice.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"CRADD (RAIDD) is a bipartite death-fold adaptor protein that bridges upstream death-domain signaling to caspase-2 activation and additionally functions as a negative regulator of NF-κB signaling. Its C-terminal death domain (DD) engages PIDD via DD:DD interaction to nucleate the PIDDosome, wherein PIDD binding opens RAIDD's autoinhibited conformation and permits its N-terminal CARD to recruit and activate caspase-2 through homophilic CARD:CARD interaction; this ordered assembly drives proximity-induced caspase-2 activation in stress-induced apoptosis, including trophic factor withdrawal in neurons [PMID:8985253, PMID:16183742, PMID:24064063, PMID:22515271]. CRADD also suppresses NF-κB-dependent inflammatory signaling by engaging BCL10 through its CARD to disrupt CARMA1/CARMA3 signalosomes in T cells and endothelial cells, and serves as a scaffold coordinating IKKε–IRF7 interaction for type I interferon production [PMID:22323537, PMID:24958727, PMID:27606466]. Homozygous loss-of-function mutations in the CRADD death domain cause thin lissencephaly in humans by abolishing caspase-2 activation and reducing developmental neuronal apoptosis, while Cradd-knockout mice display megalencephaly and seizures [PMID:27773430, PMID:30281648].\",\n  \"teleology\": [\n    {\n      \"year\": 1997,\n      \"claim\": \"The fundamental question of how RIP kinase signaling connects to caspase activation was answered by the discovery that CRADD/RAIDD is a bipartite adaptor whose DD binds RIP and whose CARD binds caspase-2, establishing the first molecular bridge between death-domain signaling and the caspase cascade.\",\n      \"evidence\": \"Yeast two-hybrid, co-immunoprecipitation, domain mapping, and mutagenesis in two independent studies\",\n      \"pmids\": [\"8985253\", \"9044836\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether CRADD mediates RIP-dependent caspase activation in vivo was not tested\", \"Upstream signals triggering the RIP–CRADD–caspase-2 axis were unknown\"]\n    },\n    {\n      \"year\": 1998,\n      \"claim\": \"How the CARD of RAIDD physically recognizes caspase-2 was resolved by solving the NMR structure, revealing a six-helix bundle with complementary charged patches that mediate CARD:CARD interaction.\",\n      \"evidence\": \"NMR solution structure with mutagenesis of acidic and basic surface patches disrupting caspase-2 binding\",\n      \"pmids\": [\"9695946\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structure of the full-length RAIDD including the DD was not determined\", \"No structure of the CARD:CARD complex itself\"]\n    },\n    {\n      \"year\": 2000,\n      \"claim\": \"The question of where RAIDD acts in the cell was addressed by showing it is predominantly cytoplasmic, can form CARD-dependent filamentous oligomers, and is partially recruited to the nucleus by caspase-2, suggesting intramolecular autoinhibition regulates its oligomerization.\",\n      \"evidence\": \"Subcellular fractionation, immunofluorescence, and live-cell imaging of CARD-only versus full-length constructs\",\n      \"pmids\": [\"10713730\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether nuclear recruitment is physiologically relevant was unclear\", \"Autoinhibition was inferred but not structurally resolved\"]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"Genetic epistasis in RAIDD-knockout and caspase-2-knockout MEFs established that RAIDD is absolutely required for PIDD-induced apoptosis, placing it as the essential adaptor between PIDD and caspase-2 in the PIDDosome.\",\n      \"evidence\": \"RAIDD−/− and caspase-2−/− mouse embryonic fibroblasts with PIDD overexpression and caspase activity assays\",\n      \"pmids\": [\"16183742\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether endogenous PIDD-dependent stimuli require RAIDD in vivo remained untested\", \"The stoichiometry and assembly order of the PIDDosome were unknown\"]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"The crystal structure of the RAIDD DD at 2.0 Å and functional studies in neurons together defined the structural basis for PIDDosome DD:DD interaction and showed that RAIDD activates caspase-2-dependent apoptosis specifically in trophic factor withdrawal but not DNA-damage pathways.\",\n      \"evidence\": \"X-ray crystallography of RAIDD DD; siRNA knockdown in PC12 cells and sympathetic neurons with pathway-specific stimuli\",\n      \"pmids\": [\"16434054\", \"15947787\", \"14765136\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structure of the RAIDD DD:PIDD DD complex was not yet solved\", \"The identity of upstream signals channeling through RAIDD in trophic deprivation was unknown\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Biochemical reconstitution revealed that PIDDosome assembly is ordered and governed by critical interface residues (RAIDD R147, PIDD Y814), with dominant-negative mutants blocking new assembly but unable to disassemble preformed complexes.\",\n      \"evidence\": \"Recombinant protein reconstitution, mutagenesis, and dominant-negative biochemical assays\",\n      \"pmids\": [\"20406701\", \"17329820\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"The precise stoichiometry of the PIDDosome was not fully resolved\", \"Whether the same assembly rules apply in living cells was untested\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Two distinct non-apoptotic roles for CRADD were uncovered: in neurons, RAIDD activates caspase-2 independently of PIDD during NGF deprivation and Aβ-induced death; in T cells, CRADD suppresses NF-κB by engaging BCL10 through its CARD to disrupt CARMA1-BCL10 signalosome formation.\",\n      \"evidence\": \"RAIDD−/− and PIDD−/− neurons with co-IP and caspase-2 activity assays; CRADD−/− primary T cells with cytokine measurement and BCL10 co-IP\",\n      \"pmids\": [\"22515271\", \"22323537\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How CRADD is recruited to the BCL10–CARMA1 complex is unknown\", \"Whether PIDD-independent caspase-2 activation uses an alternative DD partner was not identified\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"The ordered assembly mechanism of the PIDDosome was defined: PIDD DD binding opens the autoinhibited full-length RAIDD, which then solubilizes and recruits the otherwise insoluble caspase-2 CARD, establishing sequential conformational gating.\",\n      \"evidence\": \"Recombinant reconstitution of all three DD superfamily domains with solubility and binding assays\",\n      \"pmids\": [\"24064063\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No structural snapshot of the conformational change in full-length RAIDD upon PIDD binding\", \"Kinetics of the conformational switch in cells remain uncharacterized\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"CRADD's negative regulation of NF-κB was extended to endothelial cells (CARMA3 signalosome), and HDAC1 was identified as a direct transcriptional repressor of CRADD, linking epigenetic regulation to the CRADD–caspase-2 apoptotic axis in gastric cancer.\",\n      \"evidence\": \"CRADD−/− endothelial cells with permeability/cytokine assays and recombinant CRADD rescue; ChIP showing HDAC1 at the CRADD promoter with siRNA and HDAC inhibitor validation\",\n      \"pmids\": [\"24958727\", \"25360218\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether HDAC1-mediated CRADD repression is relevant beyond gastric cancer is unknown\", \"The transcription factor through which HDAC1 represses CRADD was not identified\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"CRADD DD mutations (G128R, F164C, R170C, R170H) were identified as causal for thin lissencephaly by abolishing caspase-2 activation without disrupting protein–protein interactions in co-IP, and peptide inhibitors targeting the DD helix-3 interface validated this surface as critical for PIDDosome function; CRADD was also shown to scaffold IKKε–IRF7 for type I interferon production.\",\n      \"evidence\": \"Patient mutation functional characterization with co-IP and caspase-2 assays; Cradd−/− mice showing megalencephaly; TAT-peptide inhibition of PIDDosome in vitro and in neuronal cells; co-IP of RAIDD with IRF7 and IKKε with luciferase reporter\",\n      \"pmids\": [\"27773430\", \"27502430\", \"27606466\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How DD mutations abolish caspase-2 activation while preserving binary interactions is mechanistically unclear\", \"The role of CRADD in IFN signaling was shown only in overexpression/reporter systems\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"The molecular mechanism of lissencephaly-causing mutations was clarified: TLIS DD mutations specifically disrupt the DD:DD interaction with PIDD, resolving the apparent paradox of preserved co-IP but lost caspase-2 activation.\",\n      \"evidence\": \"Systematic mutagenesis and pulldown/co-IP of DD mutants with PIDD DD\",\n      \"pmids\": [\"30281648\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No high-resolution structure of mutant DD:PIDD DD complexes\", \"Whether residual PIDDosome assembly occurs in vivo with these mutations is untested\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"Key unresolved questions include the identity of the upstream signal or DD partner that activates RAIDD–caspase-2 independently of PIDD in neurons, the structural basis of RAIDD autoinhibition and its conformational opening, and the physiological relevance of CRADD's NF-κB and IFN regulatory functions in vivo.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No PIDD-independent DD partner for RAIDD has been identified in neurons\", \"No structure of full-length autoinhibited RAIDD exists\", \"In vivo validation of CRADD's role in IFN signaling is lacking\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [0, 1, 4, 12, 15]},\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [11, 13]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [3]},\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [3]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-5357801\", \"supporting_discovery_ids\": [0, 1, 4, 6, 7, 10, 15]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [11, 13, 16]},\n      {\"term_id\": \"R-HSA-168256\", \"supporting_discovery_ids\": [11, 16]},\n      {\"term_id\": \"R-HSA-1266738\", \"supporting_discovery_ids\": [15]}\n    ],\n    \"complexes\": [\n      \"PIDDosome (PIDD DD:RAIDD DD:caspase-2 CARD)\",\n      \"RAIDD-caspase-2 complex (PIDD-independent)\"\n    ],\n    \"partners\": [\n      \"CASP2\",\n      \"PIDD1\",\n      \"RIPK1\",\n      \"BCL10\",\n      \"IRF7\",\n      \"IKBKE\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}