{"gene":"CD53","run_date":"2026-06-09T22:57:18","timeline":{"discoveries":[{"year":1990,"finding":"CD53 is a 219-amino acid integral membrane protein with four putative transmembrane domains and three N-glycosylation sites, structurally related to CD9, CD37, CD63, and TAPA-1 (tetraspan family). Protein sequence was deduced from cDNA cloning and confirmed by immunostaining/immunoprecipitation of transfected cells.","method":"cDNA cloning, sequence analysis, immunostaining and immunoprecipitation of transfected NIH3T3/COS cells","journal":"Journal of immunology / Immunogenetics","confidence":"High","confidence_rationale":"Tier 1 / Strong — two independent labs (Amiot PMID:2258620; Angelisova PMID:1700763) determined the primary structure by cDNA cloning with functional validation by transfection","pmids":["2258620","1700763"],"is_preprint":false},{"year":1993,"finding":"Cross-linking of CD53 on human B cells, monocytes, and granulocytes induces cytoplasmic calcium fluxes; in monocytes it also activates the oxidative burst. The signaling is largely protein kinase C-independent (not blocked by low staurosporine) but sensitive to high staurosporine and not blocked by ADP-ribosylating toxins, suggesting dependence on tyrosine kinases rather than GTP-binding proteins.","method":"Cross-linking with F(ab')2 anti-CD53 mAb + secondary antibody; calcium flux measurement; oxidative burst assay; pharmacological inhibitors (staurosporine, pertussis/cholera toxins)","journal":"Journal of immunology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — clean functional assay with pharmacological dissection, single lab, multiple readouts","pmids":["8335905"],"is_preprint":false},{"year":1994,"finding":"CD53 activation by cross-linking in rat macrophages increases inositol phosphates, diacylglycerol, and Ca2+ mobilization (insensitive to pertussis/cholera toxins), causes PKC translocation to the membrane, and induces nitric oxide release via expression of inducible nitric oxide synthase (iNOS) in a PKC- and protein synthesis-dependent manner.","method":"Cross-linking of CD53 with mAb; measurement of inositol phosphates, DAG, Ca2+; PKC translocation assay; NO production assay; iNOS protein synthesis inhibition","journal":"The Journal of experimental medicine","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple orthogonal biochemical readouts in a single lab study","pmids":["7511680"],"is_preprint":false},{"year":1994,"finding":"CD53, CD37, TAPA-1, and R2/C33 tetraspanins co-precipitate with MHC class II DR antigens from B-cell lysates, forming large multicomponent complexes also containing CD19 and CD21. Shown by coprecipitation and preclearing experiments.","method":"Co-immunoprecipitation from mild detergent lysates of human B-cell lines and tonsillar B cells","journal":"Immunogenetics","confidence":"Medium","confidence_rationale":"Tier 3 / Strong — single co-IP method but independently replicated across multiple cell types and confirmed by preclearing","pmids":["8119731"],"is_preprint":false},{"year":1994,"finding":"Cross-linking of CD53 on resting human B cells promotes G1 cell cycle entry (increased CD69, RNA synthesis, c-myc, cell volume) and, in cooperation with IL-2 or IL-4, induces DNA synthesis and Ig production, demonstrating a functional role in B cell activation.","method":"Anti-CD53 mAb cross-linking; flow cytometry for CD69; RNA synthesis measurement; c-myc Western blot; DNA synthesis (7-AAD binding); Ig ELISA","journal":"Journal of immunology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple orthogonal readouts of B cell activation, single lab","pmids":["7963560"],"is_preprint":false},{"year":1995,"finding":"Immunoprecipitates of rat CD53 from lymph node and thymoma cell lysates contain tyrosine phosphatase activity capable of dephosphorylating the tyrosine kinase Lck and a synthetic phosphotyrosine substrate in vitro; activity is abrogated by a tyrosine phosphatase inhibitor. The associated phosphatase is not CD45 (shown by depletion experiments).","method":"Co-immunoprecipitation; in vitro phosphatase activity assay on Lck and synthetic substrate; depletion experiments; phosphatase inhibitor treatment","journal":"European journal of immunology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vitro enzymatic assay with controls and depletion experiments, single lab","pmids":["7621882"],"is_preprint":false},{"year":1996,"finding":"CD53, CD63, and CD82 (like CD81/TAPA-1) specifically co-precipitate with integrin α4β1 (CD49d/CD29) from hemopoietic cell lines; the association does not require the α4 cytoplasmic domain or divalent cations, but two α4 adhesion-deficient mutants (D346E, D408E) lack this association.","method":"Reciprocal co-immunoprecipitation from multiple α4β1-positive cell lines; confocal microscopy for colocalization; mutant integrin analysis","journal":"Journal of immunology","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal co-IP across multiple cell lines with mutant integrin controls, replicated within study","pmids":["8757325"],"is_preprint":false},{"year":1996,"finding":"CD53, CD81, and CD82 are in close proximity (within 2–10 nm) with MHC class II (DR, DQ), MHC class I, and CD20 at the B cell surface, forming a single large supramolecular complex as determined by FRET analysis.","method":"Flow cytometric FRET (fluorescence resonance energy transfer) with labeled mAbs on JY B cells","journal":"Journal of immunology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — biophysical proximity measurement (FRET) complementing prior biochemical data, single lab","pmids":["8816400"],"is_preprint":false},{"year":1997,"finding":"CD53 ligation induces homotypic adhesion in rat B-cell lymphoma that requires de novo protein synthesis (blocked by cycloheximide/actinomycin D), divalent cations (Ca2+/Mg2+), and is dependent on tyrosine kinases (genistein/piceatannol-sensitive), PI3K (wortmannin-sensitive), and PKC (H7/bisindolylmaleimide-sensitive), but not LFA-1.","method":"Anti-CD53 mAb (MRC OX-44) stimulation; pharmacological inhibitors; electron microscopy of cell contact zones","journal":"Cellular immunology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple pharmacological pathway probes with single lab, defined mechanistic pathway","pmids":["9225004"],"is_preprint":false},{"year":1998,"finding":"Physiological activators of neutrophils (TNFα, PAF, fMLP, PMA, ionomycin) cause down-regulation of CD53 from the neutrophil surface without changing CD53 mRNA levels; this down-regulation is blocked by the serine protease inhibitor PMSF, indicating proteolytic shedding.","method":"Flow cytometry; immunoblotting; Northern blot; PMSF protease inhibitor treatment of human neutrophils","journal":"Journal of leukocyte biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — orthogonal methods (flow cytometry + immunoblot + Northern blot) in a single lab with protease inhibitor rescue","pmids":["9620662"],"is_preprint":false},{"year":2002,"finding":"CD53 ligation (rat or human) induces a 3–4-fold transient activation of JNK kinase activity (peak 3–5 min) in B-cell and T-cell lymphoma lines, and in renal carcinoma cells transiently transfected with human CD53 cDNA. JNK activation is not mediated by Vav, and CD53 does not cooperate with CD3 for Vav activation. In stable CD53-transfected cells, JNK activation stimulates Jun-dependent transcriptional activity.","method":"JNK kinase activity assay on endogenous and transfected cells; transcriptional reporter assay; pharmacological and genetic controls","journal":"European journal of biochemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — kinase assay plus reporter gene in multiple cell lines, single lab","pmids":["11846804"],"is_preprint":false},{"year":2003,"finding":"CD53 ligation on tumor lymphoma cells triggers a survival signal reducing apoptosis by activating AKT (phospho-Ser473), increasing Bcl-xL levels, decreasing Bax levels (changing Bcl-xL/Bax ratio ~24-fold toward survival), and reducing caspase activation and DNA fragmentation.","method":"Anti-CD53 mAb ligation; Western blot for phospho-AKT, Bcl-xL, Bax; PARP cleavage assay; DNA fragmentation assay; serum deprivation model","journal":"Oncogene","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple orthogonal readouts in single lab, pharmacologically and biochemically defined","pmids":["12606948"],"is_preprint":false},{"year":2003,"finding":"CD53 ligation on primary rat mesangial cells induces DNA synthesis via ERK1/ERK2 activation; this effect is blocked by the MEK inhibitor PD98059 but not by PI3K, PKC inhibitors, or calcium channel blockers, defining a specific ERK-dependent mitogenic pathway.","method":"Thymidine incorporation; ERK phosphorylation by Western blot; pharmacological inhibitors (PD98059, wortmannin, H7, thapsigargin, verapamil); flow cytometry","journal":"Kidney international","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple pharmacological dissection with biochemical readout, single lab, primary cells","pmids":["12631118"],"is_preprint":false},{"year":2004,"finding":"Stable overexpression of CD53 in macrophages increases intracellular glutathione (GSH) and decreases peroxide levels, conferring resistance to H2O2 and UVB irradiation; antisense CD53 has the opposite effect. CD53 is also induced by LPS and nitric oxide (SNAP) in RAW264.7 macrophages.","method":"Stable transfection (sense and antisense CD53); GSH measurement; peroxide assay; H2O2 and UVB survival assays; microarray + Northern blot for induction","journal":"Molecules and cells","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — gain- and loss-of-function with multiple biochemical readouts, single lab","pmids":["15055538"],"is_preprint":false},{"year":2007,"finding":"In macrophages, HIV-1 assembles into an intracellular plasma membrane domain that contains tetraspanins CD81, CD9, and CD53 (but not endosome marker CD63). These CD53/CD81/CD9-positive compartments are connected to the cell surface (accessible to HRP/ruthenium red at 4°C), indicating they are an internalized plasma membrane domain, not endosomes. CD63 is secondarily recruited to the virus-containing compartment.","method":"Immunofluorescence microscopy; immunoelectron microscopy; horseradish peroxidase/ruthenium red tracer accessibility assays; tetraspanin co-localization in HIV-infected macrophages","journal":"The Journal of cell biology","confidence":"High","confidence_rationale":"Tier 1-2 / Strong — multiple orthogonal imaging methods (IF, IEM, tracer accessibility) with rigorous controls, high citation study","pmids":["17438075"],"is_preprint":false},{"year":2007,"finding":"CD53 is a direct transcriptional target of the early B cell factor EBF1; functional EBF1 binding sites were identified in the CD53 promoter and confirmed to respond to EBF1 expression in transient transfection assays.","method":"Retroviral EBF1 overexpression in BaF/3 cells + microarray; promoter mapping; transient transfection reporter assay","journal":"European journal of immunology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — retroviral overexpression plus reporter assay, single lab","pmids":["17429843"],"is_preprint":false},{"year":2013,"finding":"siRNA knockdown of CD53 in THP-1 monocytic cells stimulated with house dust mite antigen leads to over-activation of inflammatory cytokine production and increased NF-κB activity, demonstrating that CD53 acts as a suppressor of inflammatory cytokine signaling.","method":"siRNA knockdown; cytokine ELISA; NF-κB activity assay; promoter polymorphism functional analysis (EMSA)","journal":"Biochimica et biophysica acta","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — siRNA loss-of-function with multiple readouts (cytokines, NF-κB), single lab","pmids":["23313165"],"is_preprint":false},{"year":2014,"finding":"CD53 ligation on rat NK cells reduces degranulation and IFN-γ response to activating receptors (Ly49s3, NKR-P1A, NKp46), induces LFA-1 activation and homotypic NK cell adhesion, and enhances NK cell proliferation in response to IL-2, indicating CD53 modulates NK cell effector functions by promoting adhesion over cytotoxicity.","method":"Anti-CD53 mAb ligation; degranulation assay (CD107a); redirected killing assay; IFN-γ ELISA; LFA-1 activation assay (conformational mAb); proliferation assay","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple functional assays in rat NK cells, single lab","pmids":["24832104"],"is_preprint":false},{"year":2019,"finding":"CD53 promotes IL-7 receptor (IL-7Rα) surface expression and downstream PI3K and JAK/STAT signaling in prepro- and pro-B cells; CD53-deficient mice have reduced IL-7Rα surface expression, impaired IL-7 signaling, increased apoptosis in developing B cells, and a block at the pro-B to pre-B cell transition. CD53 physically interacts with IL-7R as shown by co-immunoprecipitation and proximity ligation assay.","method":"Cd53-/- mouse model; mixed bone marrow chimeras; flow cytometry; phospho-signaling (PI3K, JAK/STAT) assays; co-immunoprecipitation; proximity ligation assay (PLA)","journal":"Journal of immunology","confidence":"High","confidence_rationale":"Tier 2 / Strong — in vivo KO phenotype plus cell-autonomous chimera proof, biochemical interaction by two orthogonal methods (Co-IP + PLA), single rigorous study","pmids":["31748347"],"is_preprint":false},{"year":2020,"finding":"CD53 stabilizes L-selectin surface expression on lymphocytes and restrains its shedding via ADAM17-dependent and ADAM17-independent mechanisms. Loss of CD53 in mice results in near absence of L-selectin from B cells and reduced L-selectin stability on T cells, causing impaired lymphocyte homing to lymph nodes and defective antigen-dependent immune responses.","method":"Cd53-/- mouse model; flow cytometry for L-selectin; ADAM17 inhibitor experiments; adoptive transfer homing assays; intravital microscopy; human lymphocyte analysis","journal":"iScience","confidence":"High","confidence_rationale":"Tier 2 / Strong — KO mouse with in vivo functional rescue, multiple orthogonal assays (flow cytometry, homing assays, ADAM17 inhibition), replicated in human cells","pmids":["32428859"],"is_preprint":false},{"year":2020,"finding":"CD53 deficiency in mice impairs neutrophil transendothelial migration induced by TNF, CXCL1, and CCL2, reduces leukocyte retention under shear flow, and causes defects in activation-induced cytoskeletal remodeling. CD53-deficient neutrophils show increased α3 integrin expression and near-complete loss of L-selectin, and demonstrate delayed onset of serum-induced arthritis.","method":"Cd53-/- mouse model; intravital microscopy; peritoneal recruitment assays; adhesion molecule flow cytometry; cytoskeletal remodeling imaging; serum-induced arthritis model","journal":"Journal of immunology","confidence":"High","confidence_rationale":"Tier 2 / Strong — KO mouse with intravital microscopy, multiple inflammatory models, and molecular characterization of integrin and cytoskeletal changes","pmids":["32532837"],"is_preprint":false},{"year":2022,"finding":"CD53 is identified by unbiased mass spectrometry as a partner of CD45. CD53 controls CD45RO isoform expression and membrane mobility, stabilizes total CD45 on the membrane, and is required for optimal CD45 phosphatase activity and subsequent Lck activation. CD53-deficient T cells show substantial proliferation defects and impaired tumor rejection.","method":"Cd53-/- mouse model; unbiased mass spectrometry interactome; super-resolution microscopy (membrane mobility); phosphatase activity assay; Lck phosphorylation (Western blot); tumor rejection assay; IFN-γ intracellular staining","journal":"Cell reports","confidence":"High","confidence_rationale":"Tier 1-2 / Strong — unbiased mass spectrometry identification of CD45 as partner, biochemical phosphatase activity assay, in vivo KO phenotype, multiple orthogonal methods in a single rigorous study","pmids":["35767951"],"is_preprint":false},{"year":2022,"finding":"CD53 in hepatocytes integrates inflammatory and nutritional signals: high-fat/fructose exposure and inflammatory stimuli induce CD53 expression in liver; CD53 deletion in mice blocks Western diet-induced dyslipidemia, hepatic inflammatory transcriptome activation, adipose inflammation, and liver lipid accumulation. In isolated hepatocytes, CD53 deletion attenuates TNFα- and fatty acid+LPS-induced cytokine expression and triglyceride accumulation.","method":"Cd53-/- mouse model on Western/NASH diet; primary hepatocyte cultures with siRNA/KO; triglyceride assays; cytokine gene expression; transcriptomic analysis; glucose transporter 8 KO epistasis","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vivo KO plus primary cell experiments with multiple metabolic/inflammatory readouts, single lab","pmids":["36581203"],"is_preprint":false},{"year":2023,"finding":"CD53 promotes DREAM transcriptional repressor complex activity in hematopoietic stem cells (HSCs) by facilitating the interaction between Rbl2/p130 and its phosphatase PP2A, stabilizing p130 for DREAM binding and thereby promoting quiescence. Loss of CD53 causes prolonged cycling and reduced HSC function under inflammatory stress.","method":"Cd53-/- mouse model; proximity labeling (BioID); confocal fluorescence microscopy; DREAM complex co-immunoprecipitation; cell cycle analysis; HSC functional assays under inflammatory stress","journal":"Blood","confidence":"High","confidence_rationale":"Tier 2 / Strong — proximity labeling + co-IP for molecular mechanism, KO in vivo phenotype, multiple orthogonal methods in a single rigorous study","pmids":["36542833"],"is_preprint":false},{"year":2023,"finding":"Glycosylation of CD53 inhibits its interaction with partner proteins CD45, CD20, and CD37 (but not vice versa for CD37-CD53); surface expression of CD53 is unaffected by glycosylation. Conformational mutations show that the nanoscale clustering of CD53 depends on its conformation (closed mutant F44E shows higher clustering fraction).","method":"N-glycosylation mutants; surface expression flow cytometry; co-immunoprecipitation; dSTORM super-resolution microscopy","journal":"Biophysical journal","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — glycosylation mutants with Co-IP and super-resolution imaging, single lab, multiple partner proteins tested","pmids":["38031400"],"is_preprint":false},{"year":2024,"finding":"CD53 physically interacts with CXCR4 (the CXCL12 receptor) on B cells as shown by proximity ligation assay. CD53-deficient B cells show reduced CXCL12-induced CXCR4 signaling and receptor internalization, and impaired bone marrow homing in vivo.","method":"Proximity ligation assay; in vitro migration assay toward CXCL12; CXCR4 internalization assay; in vivo bone marrow homing assay in Cd53-/- mice","journal":"Journal of immunology","confidence":"High","confidence_rationale":"Tier 2 / Strong — proximity ligation for physical interaction, in vitro signaling/internalization assays, and in vivo homing confirmation, multiple orthogonal methods in single study","pmids":["38363205"],"is_preprint":false},{"year":2025,"finding":"CD53 promotes neutrophil extracellular trap (NET) formation through the PI3K/AKT pathway; CD53 neutralizing antibody inhibits PMA-induced NETs in vitro and reduces inflammatory injury and NET formation in an acute pancreatitis mouse model.","method":"Anti-CD53 neutralizing antibody; in vitro NET model (PMA stimulation); PI3K/AKT pathway inhibitors; caerulein-induced AP mouse model; neutrophil isolation from AP patients","journal":"Journal of inflammation research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — functional antibody blockade in vitro plus in vivo mouse model with defined signaling pathway, single lab","pmids":["40098997"],"is_preprint":false}],"current_model":"CD53 is a leukocyte-restricted tetraspanin that organizes multi-protein complexes at the plasma membrane—including associations with integrin α4β1, MHC class II, IL-7R, CD45, and CXCR4—to regulate diverse signaling outcomes: CD53 ligation activates calcium flux, PKC, JNK, ERK, and AKT while triggering iNOS-dependent nitric oxide production; CD53 stabilizes L-selectin surface expression (restraining ADAM17-dependent shedding) and α3 integrin trafficking to promote lymphocyte homing and neutrophil transmigration; CD53 supports B cell development by promoting IL-7Rα surface expression and downstream PI3K/JAK-STAT signaling; it controls T cell immunity by stabilizing the CD45RO isoform on the membrane to enable optimal Lck activation; in HSCs it promotes DREAM complex-mediated quiescence by facilitating the Rbl2/p130–PP2A interaction; and in hepatocytes it integrates inflammatory and metabolic signals to regulate lipid accumulation and cytokine production."},"narrative":{"mechanistic_narrative":"CD53 is a leukocyte-restricted tetraspanin that organizes multi-protein membrane complexes to set signaling thresholds across immune cell development, activation, and trafficking [PMID:2258620, PMID:1700763, PMID:8757325]. As a scaffold, it laterally associates with integrin α4β1 [PMID:8757325], MHC class II and other tetraspanins within supramolecular surface clusters [PMID:8119731, PMID:8816400], and stabilizes the membrane residence of key signaling receptors: it sustains IL-7Rα surface expression to drive PI3K and JAK/STAT signaling required for the pro-B to pre-B transition [PMID:31748347], stabilizes CD45 (controlling the CD45RO isoform and membrane mobility) to enable optimal CD45 phosphatase activity and downstream Lck activation in T cells [PMID:35767951], and partners with CXCR4 to support CXCL12-driven signaling, receptor internalization, and bone marrow homing [PMID:38363205]. CD53 also stabilizes L-selectin by restraining ADAM17-dependent shedding, and loss of CD53 impairs lymphocyte homing and neutrophil transendothelial migration through altered α3 integrin expression and cytoskeletal remodeling [PMID:32428859, PMID:32532837]. Antibody ligation of CD53 transduces active signals—mobilizing calcium, translocating PKC, and inducing iNOS-dependent nitric oxide production [PMID:8335905, PMID:7511680]—and engages JNK, ERK, and AKT cascades that variously drive transcription, proliferation, and survival [PMID:11846804, PMID:12606948, PMID:12631118]. Beyond classical leukocyte roles, CD53 promotes DREAM-complex-mediated hematopoietic stem cell quiescence by facilitating the Rbl2/p130–PP2A interaction [PMID:36542833] and integrates inflammatory and metabolic signals in hepatocytes to regulate lipid accumulation and cytokine production [PMID:36581203]. Its scaffolding is conformation- and glycosylation-dependent, with N-glycosylation limiting partner engagement and protein conformation governing nanoscale clustering [PMID:38031400].","teleology":[{"year":1990,"claim":"Established CD53 as a four-transmembrane integral membrane glycoprotein of the tetraspanin family, defining the structural class from which all subsequent function was interpreted.","evidence":"cDNA cloning and sequence analysis with transfection-based immunostaining/immunoprecipitation in NIH3T3/COS cells","pmids":["2258620","1700763"],"confidence":"High","gaps":["Structure inferred from sequence, no experimental 3D structure","No function assigned at this stage"]},{"year":1994,"claim":"Defined CD53 as a signaling-competent receptor by showing that ligation triggers calcium flux, inositol phosphate/DAG generation, PKC translocation, and iNOS-dependent nitric oxide production, independent of GTP-binding proteins.","evidence":"Antibody cross-linking with pharmacological dissection (staurosporine, pertussis/cholera toxins) and biochemical readouts in human and rat myeloid/lymphoid cells","pmids":["8335905","7511680"],"confidence":"Medium","gaps":["Antibody cross-linking is non-physiological; native ligand unknown","Proximal kinase linking CD53 to these effectors not identified"]},{"year":1994,"claim":"Showed CD53 physically assembles into large supramolecular membrane complexes with other tetraspanins and MHC class II, establishing its role as a membrane organizer rather than a solitary receptor.","evidence":"Co-immunoprecipitation with preclearing from human B-cell lysates","pmids":["8119731"],"confidence":"Medium","gaps":["Detergent-based co-IP cannot distinguish direct from indirect association","Stoichiometry and architecture of the complex undefined"]},{"year":1996,"claim":"Demonstrated specific, reciprocal association of CD53 with integrin α4β1 and nanoscale proximity to MHC molecules, linking the tetraspanin scaffold to adhesion machinery.","evidence":"Reciprocal co-IP across multiple cell lines with adhesion-deficient integrin mutants, plus flow cytometric FRET on B cells","pmids":["8757325","8816400"],"confidence":"High","gaps":["Functional consequence of the CD53–α4β1 association not tested in this work","Direct versus tetraspanin-web-mediated contact unresolved"]},{"year":1995,"claim":"Linked CD53 to phosphatase-dependent signaling by showing its immunoprecipitates carry tyrosine phosphatase activity acting on Lck, distinct from CD45, foreshadowing later CD45/Lck regulation.","evidence":"Co-IP plus in vitro phosphatase assay on Lck with depletion controls and phosphatase inhibitor","pmids":["7621882"],"confidence":"Medium","gaps":["Identity of the associated phosphatase not established","Functional relevance in intact cells not shown"]},{"year":2002,"claim":"Connected CD53 ligation to defined intracellular kinase cascades — JNK/Jun transcription, ERK-driven mitogenesis, and AKT-mediated survival — broadening its signaling output beyond calcium/PKC.","evidence":"Kinase activity assays, transcriptional reporters, and pharmacological dissection across lymphoma, mesangial, and renal carcinoma cells","pmids":["11846804","12631118","12606948"],"confidence":"Medium","gaps":["Cascades triggered by antibody ligation, not a physiological ligand","Cell-type specificity of which cascade dominates unexplained"]},{"year":1998,"claim":"Showed CD53 surface levels are dynamically regulated by proteolytic shedding upon neutrophil activation, indicating post-translational control of tetraspanin availability.","evidence":"Flow cytometry, immunoblot, and Northern blot with PMSF protease inhibitor rescue in human neutrophils","pmids":["9620662"],"confidence":"Medium","gaps":["Responsible protease not identified","Functional significance of shedding not tested"]},{"year":2007,"claim":"Placed CD53 within HIV-1 assembly compartments, defining these as internalized plasma-membrane tetraspanin domains rather than endosomes.","evidence":"Immunofluorescence, immunoelectron microscopy, and tracer-accessibility assays in HIV-infected macrophages","pmids":["17438075"],"confidence":"High","gaps":["Whether CD53 contributes functionally to viral assembly versus being a passive marker not resolved"]},{"year":2007,"claim":"Identified EBF1 as a direct transcriptional driver of CD53, placing the gene in the B-cell developmental transcriptional program.","evidence":"EBF1 overexpression with microarray and promoter reporter mapping in BaF/3 cells","pmids":["17429843"],"confidence":"Medium","gaps":["Other regulators of CD53 expression not mapped"]},{"year":2019,"claim":"Established the first in vivo developmental requirement: CD53 sustains IL-7Rα surface expression and PI3K/JAK-STAT signaling needed for B-cell maturation, with direct physical interaction with IL-7R.","evidence":"Cd53-/- mice, bone marrow chimeras, phospho-signaling assays, co-IP and proximity ligation assay","pmids":["31748347"],"confidence":"High","gaps":["Mechanism by which CD53 stabilizes IL-7Rα at the membrane not resolved","Direct versus tetraspanin-web interaction undefined"]},{"year":2020,"claim":"Defined CD53 as a regulator of leukocyte trafficking by stabilizing L-selectin against ADAM17-dependent shedding and controlling α3 integrin and cytoskeletal remodeling required for homing and transmigration.","evidence":"Cd53-/- mice with flow cytometry, ADAM17 inhibition, intravital microscopy, homing and arthritis models","pmids":["32428859","32532837"],"confidence":"High","gaps":["How CD53 mechanistically restrains ADAM17 access to L-selectin not detailed","ADAM17-independent shedding pathway uncharacterized"]},{"year":2022,"claim":"Identified CD45 as an unbiased CD53 interactor and showed CD53 stabilizes CD45, controls the CD45RO isoform, and is required for CD45 phosphatase activity driving Lck activation and T-cell function.","evidence":"Mass spectrometry interactome, Cd53-/- T cells, super-resolution microscopy, phosphatase and Lck assays, tumor rejection model","pmids":["35767951"],"confidence":"High","gaps":["Structural basis of CD53–CD45 interaction unknown","Reconciliation with the earlier CD45-independent phosphatase association not addressed"]},{"year":2022,"claim":"Extended CD53 function beyond leukocytes, showing it integrates metabolic and inflammatory signals in hepatocytes to drive diet-induced dyslipidemia, hepatic inflammation, and lipid accumulation.","evidence":"Cd53-/- mice on Western/NASH diet plus primary hepatocyte siRNA/KO with metabolic and cytokine readouts","pmids":["36581203"],"confidence":"Medium","gaps":["Molecular partner mediating hepatocyte CD53 signaling not identified","Direct versus systemic-immune contribution to phenotype not fully separated"]},{"year":2023,"claim":"Revealed a nuclear/intracellular mechanism: CD53 promotes HSC quiescence by facilitating Rbl2/p130–PP2A interaction to stabilize p130 for DREAM complex assembly.","evidence":"Cd53-/- mice, BioID proximity labeling, confocal microscopy, DREAM co-IP, and HSC functional assays under inflammatory stress","pmids":["36542833"],"confidence":"High","gaps":["How a plasma-membrane tetraspanin influences a nuclear repressor complex mechanistically unresolved","Whether membrane signaling is upstream of the DREAM effect unknown"]},{"year":2024,"claim":"Added CXCR4 to the CD53 interactome, showing CD53 supports CXCL12-driven CXCR4 signaling, internalization, and B-cell bone marrow homing.","evidence":"Proximity ligation assay, migration and internalization assays, and in vivo homing in Cd53-/- mice","pmids":["38363205"],"confidence":"High","gaps":["Whether CD53 directly contacts CXCR4 or acts through the tetraspanin web not resolved"]},{"year":2023,"claim":"Defined the biophysical rules of CD53 partnering, showing N-glycosylation inhibits engagement of CD45, CD20, and CD37 and protein conformation governs nanoscale clustering.","evidence":"Glycosylation and conformational mutants with co-IP and dSTORM super-resolution microscopy","pmids":["38031400"],"confidence":"Medium","gaps":["Physiological regulation of CD53 glycosylation/conformation in vivo not established"]},{"year":2025,"claim":"Implicated CD53 in neutrophil effector function by showing it promotes PI3K/AKT-dependent NET formation in inflammatory disease.","evidence":"Neutralizing antibody, in vitro PMA NET assay with pathway inhibitors, and caerulein-induced pancreatitis mouse model","pmids":["40098997"],"confidence":"Medium","gaps":["Upstream receptor/ligand engaging CD53 in NETosis unknown","Antibody blockade may report on more than physiological CD53 function"]},{"year":null,"claim":"The physiological ligand(s) of CD53 and the structural basis for its selective, conformation-dependent recruitment of partners (CD45, IL-7R, CXCR4, integrins) across diverse cell types remain undefined.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No endogenous CD53 ligand identified","No experimental structure of CD53 or its partner complexes","Unifying mechanism linking membrane scaffolding to the nuclear DREAM-complex role unresolved"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0060090","term_label":"molecular adaptor activity","supporting_discovery_ids":[3,6,18,21,25]},{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[19,21,24]},{"term_id":"GO:0005198","term_label":"structural molecule activity","supporting_discovery_ids":[0,7]}],"localization":[{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[0,6,7,14,24]}],"pathway":[{"term_id":"R-HSA-168256","term_label":"Immune System","supporting_discovery_ids":[4,18,20,21]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[1,2,10,11,12,25]},{"term_id":"R-HSA-1266738","term_label":"Developmental Biology","supporting_discovery_ids":[18,23]}],"complexes":["tetraspanin-enriched microdomain (tetraspanin web)","DREAM complex (regulatory association)"],"partners":["ITGA4","MHC CLASS II (HLA-DR)","IL7R","PTPRC (CD45)","CXCR4","CD37","CD81","RBL2"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"P19397","full_name":"Leukocyte surface antigen CD53","aliases":["Cell surface glycoprotein CD53","Tetraspanin-25","Tspan-25"],"length_aa":219,"mass_kda":24.3,"function":"Structural component of specialized membrane microdomains known as tetraspanin-enriched microdomains (TERMs), which act as platforms for receptor clustering and signaling (PubMed:28487417). Participates thereby in diverse biological functions such as cell signal transduction, adhesion, migration and protein trafficking (PubMed:32974937, PubMed:35767951). Plays a role in the activation of monocytes and B-cells (PubMed:8335905). Acts as an essential regulator of B-cell development by promoting interleukin-7 receptor/IL7R signaling (By similarity). Also promotes, in B-cells, the BCR signaling by recruiting PKC to the plasma membrane in order to phosphorylate its substrates (PubMed:28487417). Plays an essential role in B- and T-cells homing to lymph nodes by stabilizing L-selectin/SELL cell surface expression (By similarity). Also mediates metabolic and inflammatory functions in hepatocytes and adipose tissue by promoting TNF and LPS signaling independent of the immune compartment (By similarity)","subcellular_location":"Cell membrane; Cell junction; Membrane; Synapse","url":"https://www.uniprot.org/uniprotkb/P19397/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/CD53","classification":"Not Classified","n_dependent_lines":0,"n_total_lines":1208,"dependency_fraction":0.0},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/CD53","total_profiled":1310},"omim":[{"mim_id":"614406","title":"SLP ADAPTOR- AND CSK-INTERACTING MEMBRANE PROTEIN; SCIMP","url":"https://www.omim.org/entry/614406"},{"mim_id":"604516","title":"IMMUNOGLOBULIN SUPERFAMILY, MEMBER 2; IGSF2","url":"https://www.omim.org/entry/604516"},{"mim_id":"602380","title":"UROPLAKIN 1B; UPK1B","url":"https://www.omim.org/entry/602380"},{"mim_id":"600623","title":"CD82 ANTIGEN; CD82","url":"https://www.omim.org/entry/600623"},{"mim_id":"181035","title":"TETRASPANIN 31; TSPAN31","url":"https://www.omim.org/entry/181035"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"","locations":[],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in all","driving_tissues":[{"tissue":"lymphoid tissue","ntpm":419.9}],"url":"https://www.proteinatlas.org/search/CD53"},"hgnc":{"alias_symbol":["TSPAN25"],"prev_symbol":["MOX44"]},"alphafold":{"accession":"P19397","domains":[{"cath_id":"-","chopping":"1-219","consensus_level":"medium","plddt":93.3437,"start":1,"end":219}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/P19397","model_url":"https://alphafold.ebi.ac.uk/files/AF-P19397-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-P19397-F1-predicted_aligned_error_v6.png","plddt_mean":93.0},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=CD53","jax_strain_url":"https://www.jax.org/strain/search?query=CD53"},"sequence":{"accession":"P19397","fasta_url":"https://rest.uniprot.org/uniprotkb/P19397.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/P19397/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/P19397"}},"corpus_meta":[{"pmid":"17438075","id":"PMC_17438075","title":"In macrophages, HIV-1 assembles into an intracellular plasma membrane domain containing the tetraspanins CD81, CD9, and CD53.","date":"2007","source":"The Journal of cell biology","url":"https://pubmed.ncbi.nlm.nih.gov/17438075","citation_count":268,"is_preprint":false},{"pmid":"8757325","id":"PMC_8757325","title":"Transmembrane-4 superfamily proteins CD81 (TAPA-1), CD82, CD63, and CD53 specifically associated with integrin alpha 4 beta 1 (CD49d/CD29).","date":"1996","source":"Journal of immunology (Baltimore, Md. : 1950)","url":"https://pubmed.ncbi.nlm.nih.gov/8757325","citation_count":200,"is_preprint":false},{"pmid":"8816400","id":"PMC_8816400","title":"Supramolecular complexes of MHC class I, MHC class II, CD20, and tetraspan molecules (CD53, CD81, and CD82) at the surface of a B cell line JY.","date":"1996","source":"Journal of immunology (Baltimore, Md. : 1950)","url":"https://pubmed.ncbi.nlm.nih.gov/8816400","citation_count":177,"is_preprint":false},{"pmid":"8119731","id":"PMC_8119731","title":"Association of four antigens of the tetraspans family (CD37, CD53, TAPA-1, and R2/C33) with MHC class II glycoproteins.","date":"1994","source":"Immunogenetics","url":"https://pubmed.ncbi.nlm.nih.gov/8119731","citation_count":166,"is_preprint":false},{"pmid":"9514697","id":"PMC_9514697","title":"Functional analysis of four tetraspans, CD9, CD53, CD81, and CD82, suggests a common role in costimulation, cell adhesion, and migration: only CD9 upregulates HB-EGF activity.","date":"1997","source":"Cellular immunology","url":"https://pubmed.ncbi.nlm.nih.gov/9514697","citation_count":128,"is_preprint":false},{"pmid":"1401919","id":"PMC_1401919","title":"C33 antigen recognized by monoclonal antibodies inhibitory to human T cell leukemia virus type 1-induced syncytium formation is a member of a new family of transmembrane proteins including CD9, CD37, CD53, and CD63.","date":"1992","source":"Journal of immunology (Baltimore, Md. : 1950)","url":"https://pubmed.ncbi.nlm.nih.gov/1401919","citation_count":115,"is_preprint":false},{"pmid":"1700763","id":"PMC_1700763","title":"The human leucocyte surface antigen CD53 is a protein structurally similar to the CD37 and MRC OX-44 antigens.","date":"1990","source":"Immunogenetics","url":"https://pubmed.ncbi.nlm.nih.gov/1700763","citation_count":75,"is_preprint":false},{"pmid":"2258620","id":"PMC_2258620","title":"Identification and analysis of cDNA clones encoding CD53. 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Protein sequence was deduced from cDNA cloning and confirmed by immunostaining/immunoprecipitation of transfected cells.\",\n      \"method\": \"cDNA cloning, sequence analysis, immunostaining and immunoprecipitation of transfected NIH3T3/COS cells\",\n      \"journal\": \"Journal of immunology / Immunogenetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — two independent labs (Amiot PMID:2258620; Angelisova PMID:1700763) determined the primary structure by cDNA cloning with functional validation by transfection\",\n      \"pmids\": [\"2258620\", \"1700763\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1993,\n      \"finding\": \"Cross-linking of CD53 on human B cells, monocytes, and granulocytes induces cytoplasmic calcium fluxes; in monocytes it also activates the oxidative burst. The signaling is largely protein kinase C-independent (not blocked by low staurosporine) but sensitive to high staurosporine and not blocked by ADP-ribosylating toxins, suggesting dependence on tyrosine kinases rather than GTP-binding proteins.\",\n      \"method\": \"Cross-linking with F(ab')2 anti-CD53 mAb + secondary antibody; calcium flux measurement; oxidative burst assay; pharmacological inhibitors (staurosporine, pertussis/cholera toxins)\",\n      \"journal\": \"Journal of immunology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — clean functional assay with pharmacological dissection, single lab, multiple readouts\",\n      \"pmids\": [\"8335905\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1994,\n      \"finding\": \"CD53 activation by cross-linking in rat macrophages increases inositol phosphates, diacylglycerol, and Ca2+ mobilization (insensitive to pertussis/cholera toxins), causes PKC translocation to the membrane, and induces nitric oxide release via expression of inducible nitric oxide synthase (iNOS) in a PKC- and protein synthesis-dependent manner.\",\n      \"method\": \"Cross-linking of CD53 with mAb; measurement of inositol phosphates, DAG, Ca2+; PKC translocation assay; NO production assay; iNOS protein synthesis inhibition\",\n      \"journal\": \"The Journal of experimental medicine\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple orthogonal biochemical readouts in a single lab study\",\n      \"pmids\": [\"7511680\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1994,\n      \"finding\": \"CD53, CD37, TAPA-1, and R2/C33 tetraspanins co-precipitate with MHC class II DR antigens from B-cell lysates, forming large multicomponent complexes also containing CD19 and CD21. Shown by coprecipitation and preclearing experiments.\",\n      \"method\": \"Co-immunoprecipitation from mild detergent lysates of human B-cell lines and tonsillar B cells\",\n      \"journal\": \"Immunogenetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Strong — single co-IP method but independently replicated across multiple cell types and confirmed by preclearing\",\n      \"pmids\": [\"8119731\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1994,\n      \"finding\": \"Cross-linking of CD53 on resting human B cells promotes G1 cell cycle entry (increased CD69, RNA synthesis, c-myc, cell volume) and, in cooperation with IL-2 or IL-4, induces DNA synthesis and Ig production, demonstrating a functional role in B cell activation.\",\n      \"method\": \"Anti-CD53 mAb cross-linking; flow cytometry for CD69; RNA synthesis measurement; c-myc Western blot; DNA synthesis (7-AAD binding); Ig ELISA\",\n      \"journal\": \"Journal of immunology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple orthogonal readouts of B cell activation, single lab\",\n      \"pmids\": [\"7963560\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1995,\n      \"finding\": \"Immunoprecipitates of rat CD53 from lymph node and thymoma cell lysates contain tyrosine phosphatase activity capable of dephosphorylating the tyrosine kinase Lck and a synthetic phosphotyrosine substrate in vitro; activity is abrogated by a tyrosine phosphatase inhibitor. The associated phosphatase is not CD45 (shown by depletion experiments).\",\n      \"method\": \"Co-immunoprecipitation; in vitro phosphatase activity assay on Lck and synthetic substrate; depletion experiments; phosphatase inhibitor treatment\",\n      \"journal\": \"European journal of immunology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vitro enzymatic assay with controls and depletion experiments, single lab\",\n      \"pmids\": [\"7621882\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1996,\n      \"finding\": \"CD53, CD63, and CD82 (like CD81/TAPA-1) specifically co-precipitate with integrin α4β1 (CD49d/CD29) from hemopoietic cell lines; the association does not require the α4 cytoplasmic domain or divalent cations, but two α4 adhesion-deficient mutants (D346E, D408E) lack this association.\",\n      \"method\": \"Reciprocal co-immunoprecipitation from multiple α4β1-positive cell lines; confocal microscopy for colocalization; mutant integrin analysis\",\n      \"journal\": \"Journal of immunology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal co-IP across multiple cell lines with mutant integrin controls, replicated within study\",\n      \"pmids\": [\"8757325\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1996,\n      \"finding\": \"CD53, CD81, and CD82 are in close proximity (within 2–10 nm) with MHC class II (DR, DQ), MHC class I, and CD20 at the B cell surface, forming a single large supramolecular complex as determined by FRET analysis.\",\n      \"method\": \"Flow cytometric FRET (fluorescence resonance energy transfer) with labeled mAbs on JY B cells\",\n      \"journal\": \"Journal of immunology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — biophysical proximity measurement (FRET) complementing prior biochemical data, single lab\",\n      \"pmids\": [\"8816400\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1997,\n      \"finding\": \"CD53 ligation induces homotypic adhesion in rat B-cell lymphoma that requires de novo protein synthesis (blocked by cycloheximide/actinomycin D), divalent cations (Ca2+/Mg2+), and is dependent on tyrosine kinases (genistein/piceatannol-sensitive), PI3K (wortmannin-sensitive), and PKC (H7/bisindolylmaleimide-sensitive), but not LFA-1.\",\n      \"method\": \"Anti-CD53 mAb (MRC OX-44) stimulation; pharmacological inhibitors; electron microscopy of cell contact zones\",\n      \"journal\": \"Cellular immunology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple pharmacological pathway probes with single lab, defined mechanistic pathway\",\n      \"pmids\": [\"9225004\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"Physiological activators of neutrophils (TNFα, PAF, fMLP, PMA, ionomycin) cause down-regulation of CD53 from the neutrophil surface without changing CD53 mRNA levels; this down-regulation is blocked by the serine protease inhibitor PMSF, indicating proteolytic shedding.\",\n      \"method\": \"Flow cytometry; immunoblotting; Northern blot; PMSF protease inhibitor treatment of human neutrophils\",\n      \"journal\": \"Journal of leukocyte biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — orthogonal methods (flow cytometry + immunoblot + Northern blot) in a single lab with protease inhibitor rescue\",\n      \"pmids\": [\"9620662\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"CD53 ligation (rat or human) induces a 3–4-fold transient activation of JNK kinase activity (peak 3–5 min) in B-cell and T-cell lymphoma lines, and in renal carcinoma cells transiently transfected with human CD53 cDNA. JNK activation is not mediated by Vav, and CD53 does not cooperate with CD3 for Vav activation. In stable CD53-transfected cells, JNK activation stimulates Jun-dependent transcriptional activity.\",\n      \"method\": \"JNK kinase activity assay on endogenous and transfected cells; transcriptional reporter assay; pharmacological and genetic controls\",\n      \"journal\": \"European journal of biochemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — kinase assay plus reporter gene in multiple cell lines, single lab\",\n      \"pmids\": [\"11846804\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"CD53 ligation on tumor lymphoma cells triggers a survival signal reducing apoptosis by activating AKT (phospho-Ser473), increasing Bcl-xL levels, decreasing Bax levels (changing Bcl-xL/Bax ratio ~24-fold toward survival), and reducing caspase activation and DNA fragmentation.\",\n      \"method\": \"Anti-CD53 mAb ligation; Western blot for phospho-AKT, Bcl-xL, Bax; PARP cleavage assay; DNA fragmentation assay; serum deprivation model\",\n      \"journal\": \"Oncogene\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple orthogonal readouts in single lab, pharmacologically and biochemically defined\",\n      \"pmids\": [\"12606948\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"CD53 ligation on primary rat mesangial cells induces DNA synthesis via ERK1/ERK2 activation; this effect is blocked by the MEK inhibitor PD98059 but not by PI3K, PKC inhibitors, or calcium channel blockers, defining a specific ERK-dependent mitogenic pathway.\",\n      \"method\": \"Thymidine incorporation; ERK phosphorylation by Western blot; pharmacological inhibitors (PD98059, wortmannin, H7, thapsigargin, verapamil); flow cytometry\",\n      \"journal\": \"Kidney international\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple pharmacological dissection with biochemical readout, single lab, primary cells\",\n      \"pmids\": [\"12631118\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"Stable overexpression of CD53 in macrophages increases intracellular glutathione (GSH) and decreases peroxide levels, conferring resistance to H2O2 and UVB irradiation; antisense CD53 has the opposite effect. CD53 is also induced by LPS and nitric oxide (SNAP) in RAW264.7 macrophages.\",\n      \"method\": \"Stable transfection (sense and antisense CD53); GSH measurement; peroxide assay; H2O2 and UVB survival assays; microarray + Northern blot for induction\",\n      \"journal\": \"Molecules and cells\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — gain- and loss-of-function with multiple biochemical readouts, single lab\",\n      \"pmids\": [\"15055538\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"In macrophages, HIV-1 assembles into an intracellular plasma membrane domain that contains tetraspanins CD81, CD9, and CD53 (but not endosome marker CD63). These CD53/CD81/CD9-positive compartments are connected to the cell surface (accessible to HRP/ruthenium red at 4°C), indicating they are an internalized plasma membrane domain, not endosomes. CD63 is secondarily recruited to the virus-containing compartment.\",\n      \"method\": \"Immunofluorescence microscopy; immunoelectron microscopy; horseradish peroxidase/ruthenium red tracer accessibility assays; tetraspanin co-localization in HIV-infected macrophages\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Strong — multiple orthogonal imaging methods (IF, IEM, tracer accessibility) with rigorous controls, high citation study\",\n      \"pmids\": [\"17438075\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"CD53 is a direct transcriptional target of the early B cell factor EBF1; functional EBF1 binding sites were identified in the CD53 promoter and confirmed to respond to EBF1 expression in transient transfection assays.\",\n      \"method\": \"Retroviral EBF1 overexpression in BaF/3 cells + microarray; promoter mapping; transient transfection reporter assay\",\n      \"journal\": \"European journal of immunology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — retroviral overexpression plus reporter assay, single lab\",\n      \"pmids\": [\"17429843\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"siRNA knockdown of CD53 in THP-1 monocytic cells stimulated with house dust mite antigen leads to over-activation of inflammatory cytokine production and increased NF-κB activity, demonstrating that CD53 acts as a suppressor of inflammatory cytokine signaling.\",\n      \"method\": \"siRNA knockdown; cytokine ELISA; NF-κB activity assay; promoter polymorphism functional analysis (EMSA)\",\n      \"journal\": \"Biochimica et biophysica acta\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — siRNA loss-of-function with multiple readouts (cytokines, NF-κB), single lab\",\n      \"pmids\": [\"23313165\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"CD53 ligation on rat NK cells reduces degranulation and IFN-γ response to activating receptors (Ly49s3, NKR-P1A, NKp46), induces LFA-1 activation and homotypic NK cell adhesion, and enhances NK cell proliferation in response to IL-2, indicating CD53 modulates NK cell effector functions by promoting adhesion over cytotoxicity.\",\n      \"method\": \"Anti-CD53 mAb ligation; degranulation assay (CD107a); redirected killing assay; IFN-γ ELISA; LFA-1 activation assay (conformational mAb); proliferation assay\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple functional assays in rat NK cells, single lab\",\n      \"pmids\": [\"24832104\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"CD53 promotes IL-7 receptor (IL-7Rα) surface expression and downstream PI3K and JAK/STAT signaling in prepro- and pro-B cells; CD53-deficient mice have reduced IL-7Rα surface expression, impaired IL-7 signaling, increased apoptosis in developing B cells, and a block at the pro-B to pre-B cell transition. CD53 physically interacts with IL-7R as shown by co-immunoprecipitation and proximity ligation assay.\",\n      \"method\": \"Cd53-/- mouse model; mixed bone marrow chimeras; flow cytometry; phospho-signaling (PI3K, JAK/STAT) assays; co-immunoprecipitation; proximity ligation assay (PLA)\",\n      \"journal\": \"Journal of immunology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — in vivo KO phenotype plus cell-autonomous chimera proof, biochemical interaction by two orthogonal methods (Co-IP + PLA), single rigorous study\",\n      \"pmids\": [\"31748347\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"CD53 stabilizes L-selectin surface expression on lymphocytes and restrains its shedding via ADAM17-dependent and ADAM17-independent mechanisms. Loss of CD53 in mice results in near absence of L-selectin from B cells and reduced L-selectin stability on T cells, causing impaired lymphocyte homing to lymph nodes and defective antigen-dependent immune responses.\",\n      \"method\": \"Cd53-/- mouse model; flow cytometry for L-selectin; ADAM17 inhibitor experiments; adoptive transfer homing assays; intravital microscopy; human lymphocyte analysis\",\n      \"journal\": \"iScience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — KO mouse with in vivo functional rescue, multiple orthogonal assays (flow cytometry, homing assays, ADAM17 inhibition), replicated in human cells\",\n      \"pmids\": [\"32428859\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"CD53 deficiency in mice impairs neutrophil transendothelial migration induced by TNF, CXCL1, and CCL2, reduces leukocyte retention under shear flow, and causes defects in activation-induced cytoskeletal remodeling. CD53-deficient neutrophils show increased α3 integrin expression and near-complete loss of L-selectin, and demonstrate delayed onset of serum-induced arthritis.\",\n      \"method\": \"Cd53-/- mouse model; intravital microscopy; peritoneal recruitment assays; adhesion molecule flow cytometry; cytoskeletal remodeling imaging; serum-induced arthritis model\",\n      \"journal\": \"Journal of immunology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — KO mouse with intravital microscopy, multiple inflammatory models, and molecular characterization of integrin and cytoskeletal changes\",\n      \"pmids\": [\"32532837\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"CD53 is identified by unbiased mass spectrometry as a partner of CD45. CD53 controls CD45RO isoform expression and membrane mobility, stabilizes total CD45 on the membrane, and is required for optimal CD45 phosphatase activity and subsequent Lck activation. CD53-deficient T cells show substantial proliferation defects and impaired tumor rejection.\",\n      \"method\": \"Cd53-/- mouse model; unbiased mass spectrometry interactome; super-resolution microscopy (membrane mobility); phosphatase activity assay; Lck phosphorylation (Western blot); tumor rejection assay; IFN-γ intracellular staining\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Strong — unbiased mass spectrometry identification of CD45 as partner, biochemical phosphatase activity assay, in vivo KO phenotype, multiple orthogonal methods in a single rigorous study\",\n      \"pmids\": [\"35767951\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"CD53 in hepatocytes integrates inflammatory and nutritional signals: high-fat/fructose exposure and inflammatory stimuli induce CD53 expression in liver; CD53 deletion in mice blocks Western diet-induced dyslipidemia, hepatic inflammatory transcriptome activation, adipose inflammation, and liver lipid accumulation. In isolated hepatocytes, CD53 deletion attenuates TNFα- and fatty acid+LPS-induced cytokine expression and triglyceride accumulation.\",\n      \"method\": \"Cd53-/- mouse model on Western/NASH diet; primary hepatocyte cultures with siRNA/KO; triglyceride assays; cytokine gene expression; transcriptomic analysis; glucose transporter 8 KO epistasis\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vivo KO plus primary cell experiments with multiple metabolic/inflammatory readouts, single lab\",\n      \"pmids\": [\"36581203\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"CD53 promotes DREAM transcriptional repressor complex activity in hematopoietic stem cells (HSCs) by facilitating the interaction between Rbl2/p130 and its phosphatase PP2A, stabilizing p130 for DREAM binding and thereby promoting quiescence. Loss of CD53 causes prolonged cycling and reduced HSC function under inflammatory stress.\",\n      \"method\": \"Cd53-/- mouse model; proximity labeling (BioID); confocal fluorescence microscopy; DREAM complex co-immunoprecipitation; cell cycle analysis; HSC functional assays under inflammatory stress\",\n      \"journal\": \"Blood\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — proximity labeling + co-IP for molecular mechanism, KO in vivo phenotype, multiple orthogonal methods in a single rigorous study\",\n      \"pmids\": [\"36542833\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"Glycosylation of CD53 inhibits its interaction with partner proteins CD45, CD20, and CD37 (but not vice versa for CD37-CD53); surface expression of CD53 is unaffected by glycosylation. Conformational mutations show that the nanoscale clustering of CD53 depends on its conformation (closed mutant F44E shows higher clustering fraction).\",\n      \"method\": \"N-glycosylation mutants; surface expression flow cytometry; co-immunoprecipitation; dSTORM super-resolution microscopy\",\n      \"journal\": \"Biophysical journal\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — glycosylation mutants with Co-IP and super-resolution imaging, single lab, multiple partner proteins tested\",\n      \"pmids\": [\"38031400\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"CD53 physically interacts with CXCR4 (the CXCL12 receptor) on B cells as shown by proximity ligation assay. CD53-deficient B cells show reduced CXCL12-induced CXCR4 signaling and receptor internalization, and impaired bone marrow homing in vivo.\",\n      \"method\": \"Proximity ligation assay; in vitro migration assay toward CXCL12; CXCR4 internalization assay; in vivo bone marrow homing assay in Cd53-/- mice\",\n      \"journal\": \"Journal of immunology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — proximity ligation for physical interaction, in vitro signaling/internalization assays, and in vivo homing confirmation, multiple orthogonal methods in single study\",\n      \"pmids\": [\"38363205\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"CD53 promotes neutrophil extracellular trap (NET) formation through the PI3K/AKT pathway; CD53 neutralizing antibody inhibits PMA-induced NETs in vitro and reduces inflammatory injury and NET formation in an acute pancreatitis mouse model.\",\n      \"method\": \"Anti-CD53 neutralizing antibody; in vitro NET model (PMA stimulation); PI3K/AKT pathway inhibitors; caerulein-induced AP mouse model; neutrophil isolation from AP patients\",\n      \"journal\": \"Journal of inflammation research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — functional antibody blockade in vitro plus in vivo mouse model with defined signaling pathway, single lab\",\n      \"pmids\": [\"40098997\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"CD53 is a leukocyte-restricted tetraspanin that organizes multi-protein complexes at the plasma membrane—including associations with integrin α4β1, MHC class II, IL-7R, CD45, and CXCR4—to regulate diverse signaling outcomes: CD53 ligation activates calcium flux, PKC, JNK, ERK, and AKT while triggering iNOS-dependent nitric oxide production; CD53 stabilizes L-selectin surface expression (restraining ADAM17-dependent shedding) and α3 integrin trafficking to promote lymphocyte homing and neutrophil transmigration; CD53 supports B cell development by promoting IL-7Rα surface expression and downstream PI3K/JAK-STAT signaling; it controls T cell immunity by stabilizing the CD45RO isoform on the membrane to enable optimal Lck activation; in HSCs it promotes DREAM complex-mediated quiescence by facilitating the Rbl2/p130–PP2A interaction; and in hepatocytes it integrates inflammatory and metabolic signals to regulate lipid accumulation and cytokine production.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"CD53 is a leukocyte-restricted tetraspanin that organizes multi-protein membrane complexes to set signaling thresholds across immune cell development, activation, and trafficking [#0, #6]. As a scaffold, it laterally associates with integrin \\u03b14\\u03b21 [#6], MHC class II and other tetraspanins within supramolecular surface clusters [#3, #7], and stabilizes the membrane residence of key signaling receptors: it sustains IL-7R\\u03b1 surface expression to drive PI3K and JAK/STAT signaling required for the pro-B to pre-B transition [#18], stabilizes CD45 (controlling the CD45RO isoform and membrane mobility) to enable optimal CD45 phosphatase activity and downstream Lck activation in T cells [#21], and partners with CXCR4 to support CXCL12-driven signaling, receptor internalization, and bone marrow homing [#25]. CD53 also stabilizes L-selectin by restraining ADAM17-dependent shedding, and loss of CD53 impairs lymphocyte homing and neutrophil transendothelial migration through altered \\u03b13 integrin expression and cytoskeletal remodeling [#19, #20]. Antibody ligation of CD53 transduces active signals\\u2014mobilizing calcium, translocating PKC, and inducing iNOS-dependent nitric oxide production [#1, #2]\\u2014and engages JNK, ERK, and AKT cascades that variously drive transcription, proliferation, and survival [#10, #11, #12]. Beyond classical leukocyte roles, CD53 promotes DREAM-complex-mediated hematopoietic stem cell quiescence by facilitating the Rbl2/p130\\u2013PP2A interaction [#23] and integrates inflammatory and metabolic signals in hepatocytes to regulate lipid accumulation and cytokine production [#22]. Its scaffolding is conformation- and glycosylation-dependent, with N-glycosylation limiting partner engagement and protein conformation governing nanoscale clustering [#24].\",\n  \"teleology\": [\n    {\n      \"year\": 1990,\n      \"claim\": \"Established CD53 as a four-transmembrane integral membrane glycoprotein of the tetraspanin family, defining the structural class from which all subsequent function was interpreted.\",\n      \"evidence\": \"cDNA cloning and sequence analysis with transfection-based immunostaining/immunoprecipitation in NIH3T3/COS cells\",\n      \"pmids\": [\"2258620\", \"1700763\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structure inferred from sequence, no experimental 3D structure\", \"No function assigned at this stage\"]\n    },\n    {\n      \"year\": 1994,\n      \"claim\": \"Defined CD53 as a signaling-competent receptor by showing that ligation triggers calcium flux, inositol phosphate/DAG generation, PKC translocation, and iNOS-dependent nitric oxide production, independent of GTP-binding proteins.\",\n      \"evidence\": \"Antibody cross-linking with pharmacological dissection (staurosporine, pertussis/cholera toxins) and biochemical readouts in human and rat myeloid/lymphoid cells\",\n      \"pmids\": [\"8335905\", \"7511680\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Antibody cross-linking is non-physiological; native ligand unknown\", \"Proximal kinase linking CD53 to these effectors not identified\"]\n    },\n    {\n      \"year\": 1994,\n      \"claim\": \"Showed CD53 physically assembles into large supramolecular membrane complexes with other tetraspanins and MHC class II, establishing its role as a membrane organizer rather than a solitary receptor.\",\n      \"evidence\": \"Co-immunoprecipitation with preclearing from human B-cell lysates\",\n      \"pmids\": [\"8119731\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Detergent-based co-IP cannot distinguish direct from indirect association\", \"Stoichiometry and architecture of the complex undefined\"]\n    },\n    {\n      \"year\": 1996,\n      \"claim\": \"Demonstrated specific, reciprocal association of CD53 with integrin \\u03b14\\u03b21 and nanoscale proximity to MHC molecules, linking the tetraspanin scaffold to adhesion machinery.\",\n      \"evidence\": \"Reciprocal co-IP across multiple cell lines with adhesion-deficient integrin mutants, plus flow cytometric FRET on B cells\",\n      \"pmids\": [\"8757325\", \"8816400\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Functional consequence of the CD53\\u2013\\u03b14\\u03b21 association not tested in this work\", \"Direct versus tetraspanin-web-mediated contact unresolved\"]\n    },\n    {\n      \"year\": 1995,\n      \"claim\": \"Linked CD53 to phosphatase-dependent signaling by showing its immunoprecipitates carry tyrosine phosphatase activity acting on Lck, distinct from CD45, foreshadowing later CD45/Lck regulation.\",\n      \"evidence\": \"Co-IP plus in vitro phosphatase assay on Lck with depletion controls and phosphatase inhibitor\",\n      \"pmids\": [\"7621882\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Identity of the associated phosphatase not established\", \"Functional relevance in intact cells not shown\"]\n    },\n    {\n      \"year\": 2002,\n      \"claim\": \"Connected CD53 ligation to defined intracellular kinase cascades \\u2014 JNK/Jun transcription, ERK-driven mitogenesis, and AKT-mediated survival \\u2014 broadening its signaling output beyond calcium/PKC.\",\n      \"evidence\": \"Kinase activity assays, transcriptional reporters, and pharmacological dissection across lymphoma, mesangial, and renal carcinoma cells\",\n      \"pmids\": [\"11846804\", \"12631118\", \"12606948\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Cascades triggered by antibody ligation, not a physiological ligand\", \"Cell-type specificity of which cascade dominates unexplained\"]\n    },\n    {\n      \"year\": 1998,\n      \"claim\": \"Showed CD53 surface levels are dynamically regulated by proteolytic shedding upon neutrophil activation, indicating post-translational control of tetraspanin availability.\",\n      \"evidence\": \"Flow cytometry, immunoblot, and Northern blot with PMSF protease inhibitor rescue in human neutrophils\",\n      \"pmids\": [\"9620662\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Responsible protease not identified\", \"Functional significance of shedding not tested\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Placed CD53 within HIV-1 assembly compartments, defining these as internalized plasma-membrane tetraspanin domains rather than endosomes.\",\n      \"evidence\": \"Immunofluorescence, immunoelectron microscopy, and tracer-accessibility assays in HIV-infected macrophages\",\n      \"pmids\": [\"17438075\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether CD53 contributes functionally to viral assembly versus being a passive marker not resolved\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Identified EBF1 as a direct transcriptional driver of CD53, placing the gene in the B-cell developmental transcriptional program.\",\n      \"evidence\": \"EBF1 overexpression with microarray and promoter reporter mapping in BaF/3 cells\",\n      \"pmids\": [\"17429843\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Other regulators of CD53 expression not mapped\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Established the first in vivo developmental requirement: CD53 sustains IL-7R\\u03b1 surface expression and PI3K/JAK-STAT signaling needed for B-cell maturation, with direct physical interaction with IL-7R.\",\n      \"evidence\": \"Cd53-/- mice, bone marrow chimeras, phospho-signaling assays, co-IP and proximity ligation assay\",\n      \"pmids\": [\"31748347\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism by which CD53 stabilizes IL-7R\\u03b1 at the membrane not resolved\", \"Direct versus tetraspanin-web interaction undefined\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Defined CD53 as a regulator of leukocyte trafficking by stabilizing L-selectin against ADAM17-dependent shedding and controlling \\u03b13 integrin and cytoskeletal remodeling required for homing and transmigration.\",\n      \"evidence\": \"Cd53-/- mice with flow cytometry, ADAM17 inhibition, intravital microscopy, homing and arthritis models\",\n      \"pmids\": [\"32428859\", \"32532837\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How CD53 mechanistically restrains ADAM17 access to L-selectin not detailed\", \"ADAM17-independent shedding pathway uncharacterized\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Identified CD45 as an unbiased CD53 interactor and showed CD53 stabilizes CD45, controls the CD45RO isoform, and is required for CD45 phosphatase activity driving Lck activation and T-cell function.\",\n      \"evidence\": \"Mass spectrometry interactome, Cd53-/- T cells, super-resolution microscopy, phosphatase and Lck assays, tumor rejection model\",\n      \"pmids\": [\"35767951\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis of CD53\\u2013CD45 interaction unknown\", \"Reconciliation with the earlier CD45-independent phosphatase association not addressed\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Extended CD53 function beyond leukocytes, showing it integrates metabolic and inflammatory signals in hepatocytes to drive diet-induced dyslipidemia, hepatic inflammation, and lipid accumulation.\",\n      \"evidence\": \"Cd53-/- mice on Western/NASH diet plus primary hepatocyte siRNA/KO with metabolic and cytokine readouts\",\n      \"pmids\": [\"36581203\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Molecular partner mediating hepatocyte CD53 signaling not identified\", \"Direct versus systemic-immune contribution to phenotype not fully separated\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Revealed a nuclear/intracellular mechanism: CD53 promotes HSC quiescence by facilitating Rbl2/p130\\u2013PP2A interaction to stabilize p130 for DREAM complex assembly.\",\n      \"evidence\": \"Cd53-/- mice, BioID proximity labeling, confocal microscopy, DREAM co-IP, and HSC functional assays under inflammatory stress\",\n      \"pmids\": [\"36542833\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How a plasma-membrane tetraspanin influences a nuclear repressor complex mechanistically unresolved\", \"Whether membrane signaling is upstream of the DREAM effect unknown\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Added CXCR4 to the CD53 interactome, showing CD53 supports CXCL12-driven CXCR4 signaling, internalization, and B-cell bone marrow homing.\",\n      \"evidence\": \"Proximity ligation assay, migration and internalization assays, and in vivo homing in Cd53-/- mice\",\n      \"pmids\": [\"38363205\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether CD53 directly contacts CXCR4 or acts through the tetraspanin web not resolved\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Defined the biophysical rules of CD53 partnering, showing N-glycosylation inhibits engagement of CD45, CD20, and CD37 and protein conformation governs nanoscale clustering.\",\n      \"evidence\": \"Glycosylation and conformational mutants with co-IP and dSTORM super-resolution microscopy\",\n      \"pmids\": [\"38031400\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Physiological regulation of CD53 glycosylation/conformation in vivo not established\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Implicated CD53 in neutrophil effector function by showing it promotes PI3K/AKT-dependent NET formation in inflammatory disease.\",\n      \"evidence\": \"Neutralizing antibody, in vitro PMA NET assay with pathway inhibitors, and caerulein-induced pancreatitis mouse model\",\n      \"pmids\": [\"40098997\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Upstream receptor/ligand engaging CD53 in NETosis unknown\", \"Antibody blockade may report on more than physiological CD53 function\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"The physiological ligand(s) of CD53 and the structural basis for its selective, conformation-dependent recruitment of partners (CD45, IL-7R, CXCR4, integrins) across diverse cell types remain undefined.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No endogenous CD53 ligand identified\", \"No experimental structure of CD53 or its partner complexes\", \"Unifying mechanism linking membrane scaffolding to the nuclear DREAM-complex role unresolved\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [3, 6, 18, 21, 25]},\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [19, 21, 24]},\n      {\"term_id\": \"GO:0005198\", \"supporting_discovery_ids\": [0, 7]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [0, 6, 7, 14, 24]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-168256\", \"supporting_discovery_ids\": [4, 18, 20, 21]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [1, 2, 10, 11, 12, 25]},\n      {\"term_id\": \"R-HSA-1266738\", \"supporting_discovery_ids\": [18, 23]}\n    ],\n    \"complexes\": [\"tetraspanin-enriched microdomain (tetraspanin web)\", \"DREAM complex (regulatory association)\"],\n    \"partners\": [\"ITGA4\", \"MHC class II (HLA-DR)\", \"IL7R\", \"PTPRC (CD45)\", \"CXCR4\", \"CD37\", \"CD81\", \"RBL2\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":6,"faith_total":6,"faith_pct":100.0}}