Affinage

MS4A1

B-lymphocyte antigen CD20 · UniProt P11836

Round 2 corrected
Length
297 aa
Mass
33.1 kDa
Annotated
2026-04-28
130 papers in source corpus 25 papers cited in narrative 25 extracted findings

Mechanistic narrative

Synthesis pass · prose summary of the discoveries below

CD20 (MS4A1) is a non-glycosylated, differentially phosphorylated tetraspan membrane protein that functions as a compact double-barrel dimer in lipid raft microdomains of B lymphocytes, where it regulates store-operated calcium entry and couples to B-cell antigen receptor (BCR) signaling through Syk, Src, and PI3K kinases to promote B-cell activation from G0 to G1 (PMID:7684739, PMID:12920111, PMID:18426802, PMID:2415587). Homozygous loss-of-function mutations in MS4A1 cause selective deficiency of T cell-independent antibody responses while leaving B-cell development intact (PMID:20038800). Cryo-EM structures reveal that Type I anti-CD20 monoclonal antibodies (rituximab, ofatumumab) cross-link CD20 dimers into assemblies that seed complement recruitment, whereas Type II antibodies (obinutuzumab) form terminal complexes that preclude complement activation, explaining their divergent cytotoxic mechanisms (PMID:32079680, PMID:32792392). CD20 protein levels are controlled post-transcriptionally by HDAC6-dependent translational regulation and by alternative 5′-UTR splicing—the V1 isoform contains inhibitory uORFs and a stem-loop that suppress translation, while V3 is the translation-competent form—and transcriptionally by TGF-β/Smad-mediated repression of the MS4A1 promoter (PMID:28830887, PMID:37683180, PMID:22665052).

Mechanistic history

Synthesis pass · year-by-year structured walk · 16 steps
  1. 1985 High

    Establishing that CD20 has a direct role in B-cell activation: antibody cross-linking of CD20 drives resting B cells from G0 to G1, while monovalent Fab fragments are inactive, demonstrating that receptor aggregation is the mechanistic trigger for activation signaling.

    Evidence B-cell proliferation assays with intact antibody versus Fab fragments, cyclosporin A inhibition, and multi-stimulus blocking experiments on tonsillar B cells

    PMID:2415587 PMID:3872456 PMID:3925015

    Open questions at the time
    • Downstream signaling pathway from CD20 aggregation was unknown
    • Whether CD20 functions as an intrinsic signaling receptor or accessory molecule was unresolved
  2. 1988 High

    Molecular cloning and biochemical characterization revealed CD20 as a non-glycosylated phosphoprotein with multiple transmembrane domains and no homology to known proteins, with differential phosphorylation (serine and threonine) correlating with B-cell proliferative state.

    Evidence cDNA cloning from two independent groups, in vitro translation, 32P metabolic labeling, endoglycosidase digestion, tunicamycin treatment, PMA stimulation

    PMID:2448768 PMID:2454914 PMID:2456210 PMID:2467190

    Open questions at the time
    • Identity of kinases phosphorylating CD20 was unknown
    • Functional consequence of individual phosphorylation sites was not mapped
    • Membrane topology was inferred from hydropathy, not experimentally determined
  3. 1993 High

    Reconstitution of CD20 in multiple non-B cell lines demonstrated that CD20 directly increases transmembrane Ca²⁺ conductance, and chemical cross-linking revealed CD20 exists as a multimer consistent with ion channel or channel-regulatory function.

    Evidence Stable cDNA transfection into T cells, pre-B cells, K562, and NIH-3T3; whole-cell patch clamp electrophysiology; chemical cross-linking and immunoprecipitation

    PMID:7684739

    Open questions at the time
    • Whether CD20 itself forms a pore or activates an endogenous channel was unresolved
    • Ion selectivity and single-channel properties were not characterized
  4. 1996 Medium

    FRET analysis revealed CD20 resides within 2–10 nm of MHC class I, MHC class II, and tetraspanins CD53/CD81/CD82, suggesting it participates in supramolecular membrane signaling complexes.

    Evidence Flow cytometric energy transfer with fluorescently labeled antibodies on B cells

    PMID:8816400

    Open questions at the time
    • Proximity data did not confirm direct physical interaction
    • Functional significance of CD20–tetraspanin association was not tested
    • No reciprocal co-immunoprecipitation was performed
  5. 2002 High

    CD20 cross-linking was shown to induce a caspase- and Bcl-2-independent apoptotic pathway, and separately, the ability of anti-CD20 mAbs to activate complement was mechanistically linked to their capacity to translocate CD20 into lipid raft microdomains.

    Evidence Caspase inhibitor and Bcl-2 overexpression experiments in Ramos cells; membrane fractionation and complement lysis assays with Type I and Type II mAb panels; hyper-cross-linking rescue

    PMID:12200688 PMID:12393541

    Open questions at the time
    • Identity of the caspase-independent death effector was unknown
    • Whether raft residency was necessary for all CD20 effector functions beyond complement was untested
  6. 2003 High

    CD20 was established as a component of the BCR-activated store-operated calcium (SOC) entry pathway: ectopic expression in CHO cells introduced SOC activity dependent on a raft-targeting cytoplasmic domain, and siRNA knockdown in B cells reduced BCR-stimulated Ca²⁺ influx. Cholesterol-dependent conformational states of CD20 were also demonstrated.

    Evidence Reconstitution in CHO cells with deletion mutagenesis, siRNA knockdown in B cells, cholesterol depletion/enrichment, Ca²⁺/Sr²⁺ influx assays, CD40-stimulated internalization microscopy

    PMID:12835728 PMID:12920111 PMID:12938216

    Open questions at the time
    • Molecular identity of the SOC channel activated by CD20 was not determined
    • Whether CD20 is the pore-forming subunit or an accessory/regulatory subunit remained open
  7. 2004 High

    CD20-knockout mice confirmed a physiological role for CD20 in transmembrane Ca²⁺ signaling—particularly CD19-induced responses—while revealing that B-cell development and T cell-dependent immunity are largely CD20-independent.

    Evidence CD20⁻/⁻ mouse generation, intracellular calcium flux upon CD19 and IgM cross-linking, flow cytometry phenotyping

    PMID:14688067

    Open questions at the time
    • T cell-independent responses in CD20⁻/⁻ mice were not tested in this study
    • Mechanism linking CD20 to CD19-specific calcium signaling was not identified
  8. 2005 High

    Structural characterization of purified CD20 revealed substantial α-helical content and showed that the rituximab epitope requires a disulfide bond between C167 and C183 in the extracellular loop, with avidity effects on intact B cells suggesting CD20 multimerization on the cell surface.

    Evidence E. coli expression and purification, circular dichroism spectroscopy, surface plasmon resonance, reduction/alkylation mutagenesis

    PMID:16285718

    Open questions at the time
    • No high-resolution structure was yet available
    • Stoichiometry of native CD20 complexes on B cells was unknown
  9. 2008 High

    The mechanism of CD20-induced Ca²⁺ signaling was resolved: Type I mAbs cause direct physical association of CD20 with the BCR (by FRET), activate BLNK/SLP-76 phosphorylation, and require Syk, Src, and PI3K—BCR-negative cells expressing normal CD20 completely fail to signal, demonstrating CD20 Ca²⁺ flux is BCR-dependent rather than intrinsic channel activity.

    Evidence FRET for CD20–BCR proximity, pharmacological kinase inhibitor panel, BCR-negative Ramos variant, Western blot for adaptor phosphorylation

    PMID:18426802

    Open questions at the time
    • How CD20 physically engages the BCR complex was not structurally resolved
    • Whether CD20 directly contacts BCR or requires an intermediary was unknown
  10. 2009 High

    A human loss-of-function mutation in MS4A1 established CD20 as specifically required for T cell-independent antibody responses, the first Mendelian phenotype linked to CD20 deficiency.

    Evidence Homozygous splice-junction mutation in a patient, vaccination response assays for TI antigens, corroboration in CD20⁻/⁻ mice

    PMID:20038800

    Open questions at the time
    • Mechanism by which CD20 specifically enables TI responses was not elucidated
    • Whether the phenotype extends to other TI antigen classes was not fully tested
  11. 2011 High

    X-ray crystallography of the obinutuzumab Fab–CD20 peptide complex revealed that Type I and Type II mAbs bind overlapping epitopes in completely different orientations, explaining their divergent capacities for complement activation and raft redistribution.

    Evidence X-ray crystallography of Fab alone and Fab–cyclopeptide complex, protein tomography, confocal microscopy

    PMID:21444918

    Open questions at the time
    • Structure was of Fab with a cyclopeptide, not full-length membrane-embedded CD20
    • Orientation differences did not explain direct homotypic killing by Type II mAbs
  12. 2012 High

    TGF-β/Smad signaling was shown to directly repress MS4A1 transcription by Smad binding at the promoter, and CD20 knockdown phenocopied TGF-β-induced apoptosis while overexpression conferred resistance, establishing CD20 as a Smad-regulated survival factor.

    Evidence ChIP for Smad at MS4A1 promoter, siRNA knockdown, stable overexpression, apoptosis assays in vitro and in vivo xenograft

    PMID:22665052

    Open questions at the time
    • Whether Smad-mediated CD20 repression operates in normal B cells beyond lymphoma was untested
    • Whether CD20's survival function is calcium-dependent was not determined
  13. 2017 High

    HDAC6 was identified as a post-transcriptional regulator of CD20: HDAC6 inhibition increases CD20 protein without affecting mRNA levels, by enhancing MS4A1 mRNA loading onto polysomes—revealing a translational control mechanism with therapeutic implications for anti-CD20 therapy.

    Evidence Pharmacological and genetic HDAC6 inhibition, polysome fractionation, flow cytometry, in vivo rituximab survival model

    PMID:28830887

    Open questions at the time
    • The HDAC6 substrate mediating translational control of CD20 mRNA was not identified
    • Whether HDAC6 acts via the 5′-UTR splicing mechanism was unknown
  14. 2020 High

    Cryo-EM structures of full-length CD20 in complex with rituximab, ofatumumab, and obinutuzumab at 3.7–4.7 Å resolution defined CD20 as a compact double-barrel dimer and revealed that Type I mAbs cross-link dimers into supramolecular assemblies that seed complement, while Type II mAbs form terminal complexes that preclude complement recruitment.

    Evidence Cryo-EM structure determination with ITC/SPR binding thermodynamics

    PMID:32079680 PMID:32792392

    Open questions at the time
    • No structure of CD20 in its native lipid environment or without mAb was obtained
    • Whether oligomeric assemblies form on live cell membranes at physiological mAb concentrations was not proven
  15. 2023 High

    Alternative 5′-UTR splicing of MS4A1 mRNA was revealed as a major determinant of CD20 protein expression: the abundant V1 isoform contains inhibitory uORFs and a stem-loop that block translation, while V3 is translation-competent, and V1-to-V3 splice-switching enhanced CD20 surface expression and rituximab efficacy.

    Evidence RNA sequencing, ribosome profiling, morpholino splice-switching, CD20-KO reconstitution with V1 or V3, clinical relapse sample analysis

    PMID:37683180

    Open questions at the time
    • Trans-acting factors controlling V1/V3 splice choice were not identified
    • Relationship between HDAC6-mediated translational control and 5′-UTR isoform usage was not tested
  16. 2025 Medium

    Super-resolution imaging localized endogenous CD20 to B-cell microvilli and showed that therapeutic mAbs induce distinct oligomeric states and B-cell polarization, adding a spatial dimension to understanding of mAb mechanism of action.

    Evidence TDI-DNA-PAINT and lattice light-sheet microscopy on live B cells

    PMID:39787234

    Open questions at the time
    • Functional consequence of microvillar CD20 localization for signaling or cytotoxicity was not established
    • Whether microvillar enrichment is constitutive or activation-dependent was not resolved
    • Single-lab methodology awaits independent replication

Open questions

Synthesis pass · forward-looking unresolved questions
  • Key unresolved questions include the molecular identity of the ion conductance pathway regulated by CD20 (intrinsic pore versus activation of a distinct channel), the HDAC6 substrate controlling CD20 mRNA translation, the trans-acting splicing factors governing V1/V3 5′-UTR isoform selection, and the structural basis for CD20's selective requirement in T cell-independent humoral immunity.
  • No structure of apo CD20 dimer without antibody bound
  • No reconstitution of CD20 ion conductance with defined channel identity
  • Mechanism linking CD20 to TI-specific B-cell signaling is uncharacterized

Mechanism profile

Synthesis pass · controlled-vocabulary classification · explore literature graph →
Molecular activity
GO:0005215 transporter activity 3 GO:0098772 molecular function regulator activity 2
Localization
GO:0005886 plasma membrane 8
Pathway
R-HSA-168256 Immune System 4 R-HSA-162582 Signal Transduction 3 R-HSA-5357801 Programmed Cell Death 2
Partners
BCR (IGM)BLNKCD19CD53CD81CD82SLP-76
Complex memberships
CD20 double-barrel homodimer

Evidence

Reading pass · 25 per-paper findings extracted from the source corpus
Year Finding Method Journal Conf PMIDs
1988 Molecular cloning of CD20 (B1/MS4A1) cDNA revealed a predicted protein lacking an N-terminal signal sequence, containing three extensive hydrophobic (transmembrane) regions, a highly charged C-terminal cytoplasmic domain, and no homology to other known proteins. In vitro translation produced a single 33 kDa protein. CD20 was shown to be strongly phosphorylated after CDw40 stimulation. cDNA cloning, in vitro translation, immunoprecipitation, Northern blot The EMBO journal High 2456210
1988 CD20 (B1) cDNA was isolated and its amino acid sequence determined, confirming it is a ~33 kDa phosphoprotein with no signal peptide and three major hydrophobic regions consistent with multiple membrane-spanning domains. Two mRNA species (2.8 and 3.4 kb) arise from alternative splicing. cDNA cloning from tonsillar library, differential hybridization, in vitro translation, limited proteinase digestion peptide mapping Proceedings of the National Academy of Sciences of the United States of America High 2448768
1988 CD20 (B1) is a non-glycosylated phosphoprotein expressed as multiple isoforms (Mr 33,000 and 34,500–36,000). Phosphorylation of B1 is associated with B-cell proliferation: non-proliferating B cells show no 32P incorporation into B1, whereas proliferating/malignant B cells show heavy phosphorylation. Cross-linking B1 on the cell surface with antibody or phorbol ester treatment enhanced phosphorylation. B1(35) contains both phosphoserine and phosphothreonine, while B1(33) contains only phosphoserine, and these isoforms are generated by differential phosphorylation. 32P metabolic labeling, immunoprecipitation, peptide mapping, alkaline phosphatase treatment, PMA stimulation The Journal of biological chemistry High 2454914
1988 CD20 is a non-glycosylated phosphoprotein: endoglycosidase digestion and tunicamycin labeling confirmed neither the 33 kDa nor the 34,500–36,000 Mr forms are glycosylated. PMA treatment selectively increases phosphorylation and abundance of the 34,500–36,000 Mr form, indicating phosphorylation underlies the molecular weight heterogeneity. Biosynthetic labeling with [35S]methionine, endoglycosidase digestion, tunicamycin treatment, PMA stimulation, immunoprecipitation Molecular immunology High 2467190
1993 Stable transfection of CD20 cDNA into non-B cell lines (T lymphoblastoid, pre-B lymphoblastoid, K562 erythroleukemia, NIH-3T3 fibroblasts) specifically increased transmembrane Ca2+ conductance as measured by whole-cell patch clamp. Antibody cross-linking of CD20 on lymphoblastoid cells enhanced the same Ca2+ conductance. Biochemical cross-linking suggested CD20 exists as a multimeric oligomer in the membrane, consistent with ion channel formation. Stable cDNA transfection, whole-cell patch clamp electrophysiology, fluorescence microscopy of cytosolic Ca2+, chemical cross-linking, immunoprecipitation The Journal of cell biology High 7684739
1985 Anti-B1 (anti-CD20) monoclonal antibodies stimulate resting tonsillar B cells to transition from G0 to G1 phase of the cell cycle, inducing RNA synthesis and growth factor responsiveness but not S-phase entry or mitosis. This activation is inhibited by cyclosporin A (I50 ~50 ng/ml), implicating early activation pathways. Both activatory and inhibitory (of Ig secretion) effects of anti-CD20 depend on distinct epitopes. B cell proliferation assays, RNA synthesis measurement (3H-uridine), thymidine incorporation, flow cytometry, cyclosporin A inhibition Journal of immunology High 2415587
1985 Cross-linking of Bp35 (CD20) on the B-cell surface by intact antibody (but not monovalent Fab) is required to trigger B-cell proliferation, indicating that receptor aggregation/multimerization is a mechanistic requirement for CD20-mediated B-cell activation. B-cell proliferation assays with intact antibody vs. Fab fragments, blocking experiments Proceedings of the National Academy of Sciences of the United States of America High 3872456
1985 The B1 (CD20) molecule is a 32 kDa phosphorylated cell surface protein expressed exclusively from mid pre-B to plasma cell stage. Anti-B1 antibody inhibits B-cell proliferation induced by anti-μ, Staphylococcus aureus Cowan 1, activated T cells, and Epstein-Barr virus, but does not activate B cells itself. Inhibition requires continuous presence of antibody and is maximal when added at culture initiation, suggesting CD20 plays a role in regulating early B-cell activation rather than growth factor-dependent proliferation of pre-activated cells. Anti-B1 antibody blocking assays, thymidine incorporation, Ig secretion (pokeweed mitogen), co-culture experiments Journal of immunology High 3925015
2002 CD20 crosslinking (CD20XL) induces apoptosis in Burkitt lymphoma Ramos cells through a pathway that is distinct from CD95 and BCR-mediated apoptosis: it does not require active caspases (broad-spectrum caspase inhibitor zVAD-fmk blocked caspase processing but not cell death) and cannot be blocked by Bcl-2 overexpression (which blocked cytochrome c release but not CD20XL-induced death), demonstrating a caspase- and mitochondria-independent cell death pathway. Caspase inhibitor (zVAD-fmk) treatment, Bcl-2 overexpression, annexin V staining, mitochondrial membrane potential assay, cytochrome c release, flow cytometry Leukemia High 12200688
2002 The ability of anti-CD20 mAbs to activate complement-dependent lysis correlates with their capacity to translocate CD20 into lipid raft (detergent-insoluble) membrane microdomains. mAb B1, which cannot translocate CD20 into rafts, is unable to recruit complement, whereas rituximab and 1F5, which translocate CD20 into rafts, effectively recruit complement. Hyper-cross-linking drove B1 and other mAbs into detergent-insoluble fractions and conferred complement activation ability, directly linking raft residency to complement function. Membrane fractionation (sucrose gradient), complement lysis assays, hyper-cross-linking with F(ab')2 anti-Ig, panel of anti-B-cell mAbs Blood High 12393541
2003 CD20 is resident in lipid raft (detergent-insoluble) membrane domains. CD40 stimulation of normal human B lymphocytes causes rapid, time- and concentration-dependent internalization of CD20 via translocation into lipid rafts and subsequent uptake into cytoplasmic vesicles. This process is inhibited by cytochalasin B and protein kinase C antagonists. Paradoxically, CD20 down-regulation via CD40 activation enhanced calcium signaling upon subsequent CD20 cross-linking, suggesting CD20 engages downstream signaling pathways that modulate calcium homeostasis rather than functioning as a direct calcium channel. Confocal fluorescent microscopy, flow cytometry, cytochalasin B inhibition, PKC antagonists, calcium signaling assays, RT-PCR for mRNA stability European journal of immunology High 12938216
2003 Ectopic expression of CD20 in Chinese hamster ovary cells introduced a novel store-operated cation (SOC) entry pathway permeable to both Ca2+ and Sr2+. Deletion of a cytoplasmic sequence in CD20 essential for raft localization abolished this SOC activity. In B cells, BCR-stimulated Ca2+ influx was significantly reduced by CD20 downregulation (siRNA) and by cholesterol depletion, establishing raft-associated CD20 as a component of the BCR-activated SOC entry pathway. Ectopic expression in CHO cells, domain deletion mutagenesis, Sr2+/Ca2+ influx assays, siRNA knockdown of CD20, cholesterol depletion (methyl-β-cyclodextrin), B-cell receptor stimulation The Journal of biological chemistry High 12920111
2004 In CD20-deficient (CD20−/−) mouse B cells, CD19-induced intracellular calcium responses were significantly reduced compared to wild-type, with a less dramatic effect on IgM-induced responses, establishing a role for CD20 in facilitating transmembrane Ca2+ movement in primary B cells. Immature and mature B-cell IgM expression was ~20–30% lower in CD20−/− mice. B-cell development, tissue localization, signal transduction, proliferation, T cell-dependent antibody responses, and affinity maturation were otherwise normal. CD20−/− mouse generation and analysis, intracellular calcium flux assays (CD19 and IgM cross-linking), flow cytometry panel International immunology High 14688067
2005 Purified human CD20 expressed in E. coli localizes to the cell membrane and has substantial α-helical secondary structure by circular dichroism spectroscopy. Rituximab binds purified CD20 with nanomolar affinity in a manner abolished by reduction and alkylation, with data consistent with the antibody epitope being within the disulfide-bonded loop formed between cysteine residues C167 and C183. Intact rituximab shows much higher affinity for CD20 on B cells than for isolated CD20, suggesting B cells display CD20 such that avidity effects occur through cross-linking of CD20 monomers, possibly into lipid rafts. E. coli expression, detergent purification, circular dichroism spectroscopy, surface plasmon resonance (binding kinetics), reduction/alkylation mutagenesis, reoxidation experiments Biochemistry High 16285718
2008 Type I anti-CD20 mAbs (e.g., rituximab) but not Type II mAbs induce cytosolic Ca2+ flux in B cells, and this requires B-cell antigen receptor (BCR) expression. Type I mAb binding causes direct physical association of CD20 with the BCR (measured by FRET), and phosphorylation of BCR-specific adaptor proteins BLNK and SLP-76. The Ca2+ flux is inhibited by Syk, Src, and PI3K inhibitors but not EGTA, p38, or ERK1/2 inhibitors. BCR-negative Ramos variant cells expressing normal CD20 levels completely fail to flux Ca2+ upon CD20 ligation, demonstrating that CD20-induced Ca2+ signaling is BCR-dependent. FRET analysis, calcium flux assays, pharmacological inhibitor panel (Syk, Src, PI3K, EGTA, p38, ERK1/2), Western blot for BLNK/SLP-76 phosphorylation, BCR-negative Ramos cell variant, Type I vs. Type II mAb comparison The Journal of biological chemistry High 18426802
2009 A patient with homozygous splice-junction mutation in MS4A1 (CD20 gene) resulting in nonfunctional mRNA and absent CD20 protein showed severely impaired T cell-independent (TI) antibody responses after vaccination with TI antigens, while antigen-independent B-cell development was normal. Consistent results were obtained in CD20-deficient mice for TI antipolysaccharide B-cell responses, establishing CD20 as specifically required for TI humoral immunity. Human genetic analysis (homozygous MS4A1 splice mutation), patient immunophenotyping, vaccination response assays, CD20−/− mouse TI antigen challenge The Journal of clinical investigation High 20038800
2011 Epitope mapping and X-ray crystallography of the obinutuzumab (GA101, Type II) Fab fragment alone and in complex with a CD20 cyclopeptide revealed that Type I and Type II antibodies recognize overlapping epitopes on CD20's extracellular loop but bind in completely different orientations. GA101's elbow angle is ~30° wider than Type I antibodies, resulting in different spatial arrangements of the two CD20 molecules bound per antibody. Protein tomography and confocal microscopy showed different CD20 membrane complexes and different membrane compartmentalization for Type I vs. Type II antibodies. X-ray crystallography (Fab alone and Fab-CD20 cyclopeptide complex), epitope fine-mapping, protein tomography, confocal microscopy Blood High 21444918
2012 TGF-β induces apoptosis of B-cell lymphoma Ramos cells through direct transcriptional repression of MS4A1/CD20 by Smad proteins: chromatin immunoprecipitation (ChIP) showed Smad proteins directly bound the MS4A1 promoter upon TGF-β stimulation, reducing CD20 transcription. CD20 knockdown phenocopied TGF-β-induced apoptosis, while stable CD20 overexpression conferred resistance to TGF-β-induced apoptosis, establishing CD20 as a survival factor downstream of TGF-β/Smad signaling. Chromatin immunoprecipitation (ChIP) for Smad at MS4A1 promoter, oligonucleotide microarray, siRNA knockdown, stable overexpression, apoptosis assays in vitro and in vivo xenograft Oncogene High 22665052
2017 HDAC6 regulates CD20 protein levels post-transcriptionally: HDAC6 inhibition significantly increases CD20 protein in B-cell tumor lines and primary malignant cells without affecting MS4A1 mRNA transcription. HDAC6 inhibition enhances CD20 mRNA translation, shown by increased CD20 mRNA in the polysomal fraction, indicating HDAC6 controls CD20 at the level of mRNA translation. Combined HDAC6 inhibition with anti-CD20 mAbs improved in vitro cytotoxicity and mouse survival. Pharmacological HDAC6 inhibition, HDAC6 siRNA/shRNA knockdown, flow cytometry for CD20 surface expression, RT-PCR for MS4A1 mRNA, polysome fractionation, in vivo mouse rituximab survival model Blood High 28830887
2020 Cryo-EM structure of full-length CD20 in complexes with rituximab (Type I) and ofatumumab (Type I) and obinutuzumab (Type II) at 3.7–4.7 Å resolution revealed that CD20 is a compact double-barrel dimer. Two rituximab Fab fragments each engage a composite epitope with an extensive homotypic Fab:Fab interface. Type II mAb obinutuzumab forms terminal complexes preventing recruitment of additional mAbs and complement components, while Type I complexes act as molecular seeds that increase local mAb concentration for efficient complement activation. Ofatumumab complexes display optimal geometry for complement recruitment. Cryo-electron microscopy structure determination, binding thermodynamics (ITC/SPR), structural modeling Science High 32792392
2020 Cryo-EM structure of CD20 in complex with rituximab revealed CD20 as a compact double-barrel dimer bound by two RTX Fab fragments, each engaging a composite epitope with an extensive homotypic Fab:Fab interface. The structure suggests RTX cross-links CD20 into circular assemblies on the B-cell surface and provides a structural model for complement recruitment, explaining the mechanism of complement-dependent cytotoxicity. Cryo-EM structure determination Science High 32079680
1996 Flow cytometric energy transfer (FRET) analysis demonstrated that CD20 at the B-cell surface is in close proximity (within 2–10 nm) to MHC class I, MHC class II (DR, DQ), and tetraspan molecules CD53, CD81, and CD82 in a single supramolecular complex, suggesting CD20 participates in multicomponent membrane assemblies that may be involved in signaling and antigen presentation. Flow cytometric FRET with fluorescently labeled antibodies Journal of immunology Medium 8816400
2003 The FMC7 monoclonal antibody specifically recognizes CD20 expressed in multiple cell lines, and this reactivity is abolished by mutations in the extracellular domain of CD20. The FMC7 epitope on CD20 is exceptionally sensitive to membrane cholesterol: cholesterol depletion profoundly reduces FMC7 epitope expression, while cholesterol enrichment enhances it, indicating that a cholesterol-dependent conformational state of CD20 exists in the plasma membrane. Ectopic CD20 expression in hematopoietic and non-hematopoietic cell lines, extracellular domain mutation analysis, cholesterol depletion (methyl-β-cyclodextrin) and enrichment, flow cytometry Leukemia Medium 12835728
2023 MS4A1/CD20 mRNA is produced as multiple isoforms with distinct 5' UTRs (V1–V4). V1, the most abundant isoform, contains upstream open reading frames (uORFs) and a stem-loop structure that cooperatively inhibit polysome recruitment, rendering V1 translation-deficient. V3 is the translation-competent isoform and correlates with CD20 protein levels in DLBCL. Reconstitution of CD20-knockout cells with V3 mRNA restored CD20 surface expression; V1 reconstitution produced undetectable CD20 protein. Splice-switching morpholino oligomers redirecting splicing from V1 to V3 enhanced CD20 expression and rituximab-mediated cytotoxicity. V3→V1 splicing shift was identified in post-mosunetuzumab relapsed follicular lymphoma samples. RNA sequencing, ribosome profiling/polysome analysis, morpholino splice-switching, CD20-knockout cell reconstitution with V1 or V3 mRNA, flow cytometry, cytotoxicity assays Blood High 37683180
2025 Using TDI-DNA-PAINT combined with lattice light-sheet microscopy on live B cells, endogenous CD20 was found to be abundantly expressed on microvilli. Therapeutic mAbs (rituximab, ofatumumab, obinutuzumab) bind CD20 on microvilli in an antibody concentration-dependent manner, leading to B-cell polarization and stabilization of microvilli protrusions. Different mAbs produced distinct oligomeric states of CD20 on the cell surface. TDI-DNA-PAINT super-resolution microscopy, lattice light-sheet (LLS) microscopy, live B-cell imaging Science Medium 39787234

Source papers

Stage 0 corpus · 130 papers · ranked by NIH iCite citations
Year Title Journal Citations PMID
2002 Generation and initial analysis of more than 15,000 full-length human and mouse cDNA sequences. Proceedings of the National Academy of Sciences of the United States of America 1479 12477932
2014 A proteome-scale map of the human interactome network. Cell 977 25416956
2020 A reference map of the human binary protein interactome. Nature 849 32296183
2011 Phylogenetic-based propagation of functional annotations within the Gene Ontology consortium. Briefings in bioinformatics 656 21873635
1993 Radioimmunotherapy of B-cell lymphoma with [131I]anti-B1 (anti-CD20) antibody. The New England journal of medicine 564 7687326
1994 CD20: a regulator of cell-cycle progression of B lymphocytes. Immunology today 497 7524522
1986 Activation of human B cells mediated through two distinct cell surface differentiation antigens, Bp35 and Bp50. Proceedings of the National Academy of Sciences of the United States of America 496 3487090
1994 Oligo-capping: a simple method to replace the cap structure of eukaryotic mRNAs with oligoribonucleotides. Gene 492 8125298
1987 Flow cytometric analysis of human bone marrow. II. Normal B lymphocyte development. Blood 458 3117132
2004 The status, quality, and expansion of the NIH full-length cDNA project: the Mammalian Gene Collection (MGC). Genome research 438 15489334
2022 OpenCell: Endogenous tagging for the cartography of human cellular organization. Science (New York, N.Y.) 432 35271311
2007 Mechanisms of killing by anti-CD20 monoclonal antibodies. Molecular immunology 415 17768100
2009 Systematic analysis of immune infiltrates in high-grade serous ovarian cancer reveals CD20, FoxP3 and TIA-1 as positive prognostic factors. PloS one 361 19641607
1994 Association between atopy and variants of the beta subunit of the high-affinity immunoglobulin E receptor. Nature genetics 327 7920628
2002 Complement-mediated lysis by anti-CD20 mAb correlates with segregation into lipid rafts. Blood 301 12393541
2009 CD20 deficiency in humans results in impaired T cell-independent antibody responses. The Journal of clinical investigation 276 20038800
2016 Differential Insulitic Profiles Determine the Extent of β-Cell Destruction and the Age at Onset of Type 1 Diabetes. Diabetes 271 26858360
1993 Transfection of the CD20 cell surface molecule into ectopic cell types generates a Ca2+ conductance found constitutively in B lymphocytes. The Journal of cell biology 269 7684739
1988 Molecular cloning of the human B cell CD20 receptor predicts a hydrophobic protein with multiple transmembrane domains. The EMBO journal 267 2456210
2010 B-cell activation influences T-cell polarization and outcome of anti-CD20 B-cell depletion in central nervous system autoimmunity. Annals of neurology 254 20641064
1985 Human B cell development. II. Subpopulations in the human fetus. Journal of immunology (Baltimore, Md. : 1950) 253 3871452
2011 Upregulation of Cyclin B1 by miRNA and its implications in cancer. Nucleic acids research 251 22053081
2005 The biology of CD20 and its potential as a target for mAb therapy. Current directions in autoimmunity 238 15564720
1998 Activation and detoxication of aflatoxin B1. Mutation research 236 9675258
2014 Rituximab efficiently depletes increased CD20-expressing T cells in multiple sclerosis patients. Journal of immunology (Baltimore, Md. : 1950) 226 24928997
2010 MHC class II-associated proteins in B-cell exosomes and potential functional implications for exosome biogenesis. Immunology and cell biology 221 20458337
2009 Down-regulation of CD20 expression in B-cell lymphoma cells after treatment with rituximab-containing combination chemotherapies: its prevalence and clinical significance. Blood 212 19246561
1985 Role of the Bp35 cell surface polypeptide in human B-cell activation. Proceedings of the National Academy of Sciences of the United States of America 211 3872456
1988 Isolation and structure of a cDNA encoding the B1 (CD20) cell-surface antigen of human B lymphocytes. Proceedings of the National Academy of Sciences of the United States of America 207 2448768
2018 CD20-TCB with Obinutuzumab Pretreatment as Next-Generation Treatment of Hematologic Malignancies. Clinical cancer research : an official journal of the American Association for Cancer Research 200 29716920
2011 Next-generation sequencing to generate interactome datasets. Nature methods 200 21516116
1985 The B cell surface molecule B1 is functionally linked with B cell activation and differentiation. Journal of immunology (Baltimore, Md. : 1950) 197 3925015
2004 Mouse CD20 expression and function. International immunology 187 14688067
2011 Flow cytometric study of potential target antigens (CD19, CD20, CD22, CD33) for antibody-based immunotherapy in acute lymphoblastic leukemia: analysis of 552 cases. Leukemia & lymphoma 183 21348573
2011 Epitope characterization and crystal structure of GA101 provide insights into the molecular basis for type I/II distinction of CD20 antibodies. Blood 183 21444918
1996 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. Journal of immunology (Baltimore, Md. : 1950) 177 8816400
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