Affinage

NBEAL2

Neurobeachin-like protein 2 · UniProt Q6ZNJ1

Length
2754 aa
Mass
302.5 kDa
Annotated
2026-06-10
23 papers in source corpus 15 papers cited in narrative 13 extracted findings
Cross-family judge vs UniProt: Affinage preferred faithfulness: 6/7 claims corpus-supported (86%)

Mechanistic narrative

Synthesis pass · prose summary of the discoveries below

NBEAL2 is a large BEACH/ARM/WD40-domain scaffolding protein required for the biogenesis of secretory granules across multiple hematopoietic lineages, most prominently platelet α-granules, whose loss-of-function causes gray platelet syndrome (PMID:21765411, PMID:21765412, PMID:21765413, PMID:23863626, PMID:23861251). In megakaryocytes it acts at a late stage of α-granule maturation, downstream of and independently of the VPS33B/VPS16B complex: it is dispensable for cargo endocytosis but essential for retaining both endocytosed (e.g. fibrinogen) and de novo-synthesized cargo within maturing granules, preventing cargo from passing into RAB11 endosomes and being lost (PMID:23861251, PMID:30354215). NBEAL2 carries out this retention function through direct physical interactions with the granule membrane protein P-selectin and the ER membrane protein SEC22B, and it can engage both simultaneously; SEC22B binding maps to NBEAL2 residues 1798–1903, and GPS-associated missense variants (E1833K, R1839C) abolish this interaction and α-granule production (PMID:30354215, PMID:32384141). NBEAL2 additionally scaffolds Dock7 (and Vac14/Sec16a), and GPS BEACH-domain mutations disrupt Dock7 binding, depleting platelet Dock7 and impairing actin polymerization, platelet activation, and shape change (PMID:29187380). Beyond platelets, NBEAL2 is independently required within leukocytes for neutrophil granule content, monocyte granularity, and NK cell degranulation, with deficiency increasing susceptibility to infection (PMID:28783043, PMID:29930006). In other immune cells NBEAL2 binds CTLA-4 to maintain its expression in conventional T cells, and binds RPS6 in mast cells to restrain p90RSK-dependent RPS6 phosphorylation and mast cell survival (PMID:37349339, PMID:38272677). Its expression in the megakaryocyte lineage is driven by GATA1/GATA2 acting through a long-distance enhancer 31 kb upstream of the gene (PMID:28082341).

Mechanistic history

Synthesis pass · year-by-year structured walk · 13 steps
  1. 2011 High

    Established the disease link and core cellular requirement: that NBEAL2 loss-of-function causes gray platelet syndrome by abolishing platelet α-granule biogenesis, defining a previously unassigned BEACH/ARM/WD40 protein as essential for granule formation.

    Evidence Exome sequencing of GPS patients, subcellular fractionation/proteomics, and zebrafish nbeal2 knockdown

    PMID:21765411 PMID:21765412 PMID:21765413

    Open questions at the time
    • Molecular mechanism of how NBEAL2 promotes granule biogenesis not defined
    • Binding partners and substrates unknown at this stage
  2. 2013 High

    Confirmed causality and dissected the functional consequence in a clean genetic model, showing NBEAL2 is dispensable for megakaryocyte differentiation/proplatelet formation but required for granule-dependent platelet adhesion, aggregation, thrombus formation, and wound healing.

    Evidence Nbeal2 knockout mouse phenotyping with aggregometry, intravital imaging, EM, and wound model

    PMID:23861251 PMID:23863626

    Open questions at the time
    • Molecular partners mediating granule retention not identified
    • Stage of biogenesis at which NBEAL2 acts not pinpointed
  3. 2013 Medium

    Placed NBEAL2 at a late, distinct step of α-granule biogenesis by showing it acts independently of the VPS33B/VPS16B complex, since those proteins are normal in Nbeal2-/- platelets while residual P-selectin is still trafficked and externalized.

    Evidence Flow cytometry and western blot of Nbeal2-/- mouse platelets

    PMID:23861251

    Open questions at the time
    • Direct molecular partners of NBEAL2 at this step not yet identified
    • Single lab
  4. 2017 High

    Identified the first NBEAL2 interactome partners (Dock7, Sec16a, Vac14) and connected them to platelet function, showing GPS BEACH mutations disrupt Dock7/Vac14 binding and that Dock7 loss underlies defective actin polymerization and shape change.

    Evidence Mass spectrometry interactome, reciprocal Co-IP, proximity ligation assay, and actin polymerization assays in megakaryocytes/platelets

    PMID:29187380

    Open questions at the time
    • Whether Dock7 interaction is direct not resolved
    • Mechanism linking cytoplasmic NBEAL2 to membrane/granule Dock7 unclear
  5. 2017 High

    Resolved how NBEAL2 expression is controlled in the megakaryocyte lineage, mapping a GATA1/GATA2-bound long-distance enhancer 31 kb upstream that drives NBEAL2 transcription.

    Evidence ChIP-seq, luciferase reporter with binding-site mutagenesis, and GATA1 knockdown in K562 cells

    PMID:28082341

    Open questions at the time
    • Enhancer-promoter looping not directly demonstrated
    • Lineage-specificity of enhancer beyond erythroleukemia line not tested
  6. 2017 High

    Extended NBEAL2's granule role beyond platelets, establishing it as required for neutrophil granule content and NK degranulation, with a paradoxical respiratory burst increase and heightened infection susceptibility.

    Evidence Nbeal2-/- mouse phenotyping with respiratory burst assays and in vivo S. aureus/CMV infection

    PMID:28783043

    Open questions at the time
    • Whether leukocyte defect is platelet-independent not yet resolved here
    • Molecular mechanism of granule content loss in neutrophils not defined
  7. 2018 Medium

    Showed NBEAL2 acts cell-autonomously in leukocytes, since platelet-specific deficiency by transfusion did not impair leukocyte function, and reduced monocyte granularity, establishing a direct rather than platelet-mediated effect.

    Evidence Platelet-transfusion rescue into thrombocytopenic mice plus functional assays and Klebsiella model

    PMID:29930006

    Open questions at the time
    • Molecular partners in monocytes/neutrophils not identified
    • Single lab
  8. 2018 High

    Defined the mechanistic action of NBEAL2 as cargo retention rather than uptake, showing it is dispensable for fibrinogen endocytosis but required to keep endocytosed and synthesized cargo in maturing granules via interaction with P-selectin.

    Evidence Fluorescent cargo tracking, endogenous Co-IP, and colocalization in human megakaryocytes/proplatelets

    PMID:30354215

    Open questions at the time
    • Whether NBEAL2–P-selectin interaction is direct not established here
    • Structural basis of retention not defined
  9. 2020 High

    Provided a molecular anchor for NBEAL2's granule function by showing direct binding to the ER protein SEC22B, mapping the interface (aa 1798–1903) and demonstrating GPS missense variants abolish binding and α-granule production.

    Evidence Co-IP of tagged and endogenous proteins, CRISPR knockout, and GPS missense mutagenesis in HEK293/imMKCL/primary megakaryocytes

    PMID:32384141

    Open questions at the time
    • Mechanism by which SEC22B stabilizes NBEAL2 protein not defined
    • How ER-localized SEC22B contributes to granule cargo retention not fully explained
  10. 2023 High

    Revealed an immunological role distinct from granule biogenesis, showing NBEAL2 binds CTLA-4 and is required to maintain CTLA-4 expression in conventional but not regulatory T cells.

    Evidence Primary T cell interactome, Co-IP, siRNA knockdown, and flow cytometry of GPS patient T cells

    PMID:37349339

    Open questions at the time
    • Whether NBEAL2–CTLA-4 interaction is direct not established
    • Mechanism by which NBEAL2 controls CTLA-4 levels not defined
    • Role of identified partner LRBA not functionally tested
  11. 2024 Medium

    Identified an NBEAL2 role in mast cell homeostasis through interaction with RPS6, where deficiency causes accumulation of p90RSK-phosphorylated RPS6 and abnormal growth factor-independent survival.

    Evidence Co-IP, CRISPR deletion in MC/9 cells, western blot, and structural prediction

    PMID:38272677

    Open questions at the time
    • Interaction shown by single method (Co-IP) without reciprocal validation
    • Direct vs indirect binding to RPS6 unresolved
  12. 2025 Medium

    Linked NBEAL2 loss in mast cells to Abl1 stabilization and elevated surface ABCB1/MDR1, modulated by IL-33-driven TAK1-IKK2 and Src-family kinase signaling.

    Evidence Nbeal2-/- mast cells, CRISPR deletion, flow cytometry, and pharmacological pathway inhibition

    PMID:41111259

    Open questions at the time
    • Pathway connections partly inferred from inhibitor studies
    • Direct molecular link from NBEAL2 to Abl1/ABCB1 not defined
  13. 2025 Medium

    Demonstrated the physiological consequence of α-granule cargo loss for tissue repair, showing Nbeal2-/- mice have impaired wound healing across inflammation, proliferation, and remodeling phases with altered IL-1β, VEGF, MMP-9, and TIMP-1.

    Evidence Nbeal2-/- mouse excisional wound model with histology and molecular profiling (preprint)

    PMID:bio_10.1101_2025.02.01.636051

    Open questions at the time
    • Preprint not yet peer-reviewed
    • Specific cargo proteins responsible not pinpointed

Open questions

Synthesis pass · forward-looking unresolved questions
  • How a single cytoplasmic scaffold coordinates SEC22B/P-selectin-dependent granule cargo retention while also regulating distinct partners (CTLA-4, RPS6, Dock7) across different cell types remains unresolved at the structural and mechanistic level.
  • No structure of NBEAL2 or its interaction interfaces beyond domain mapping
  • Whether interactions in T cells and mast cells are direct is untested
  • Unified molecular model linking granule biogenesis to immune-cell roles is lacking

Mechanism profile

Synthesis pass · controlled-vocabulary classification · explore literature graph →
Molecular activity
GO:0060090 molecular adaptor activity 4 GO:0098772 molecular function regulator activity 2
Localization
GO:0005783 endoplasmic reticulum 2 GO:0005829 cytosol 1 GO:0031410 cytoplasmic vesicle 1
Pathway
R-HSA-168256 Immune System 3 R-HSA-1852241 Organelle biogenesis and maintenance 3 R-HSA-109582 Hemostasis 2
Partners
CTLA4DOCK7LRBARPS6SEC16ASEC22BSELPVAC14

Evidence

Reading pass · 13 per-paper findings extracted from the source corpus
Year Finding Method Journal Conf PMIDs
2011 Loss-of-function mutations in NBEAL2 cause gray platelet syndrome (GPS), establishing NBEAL2 as required for platelet α-granule biogenesis; NBEAL2 encodes a BEACH/ARM/WD40 domain protein and localizes to the dense tubular system (endoplasmic reticulum) in platelets as determined by proteomic analysis of sucrose-gradient subcellular fractions. Exome sequencing of GPS patients, genomic DNA sequencing, subcellular fractionation/proteomics, zebrafish nbeal2 silencing Nature genetics High 21765411 21765412 21765413
2013 Nbeal2-knockout mice recapitulate GPS with defective α-granule biogenesis in megakaryocytes and absence of α-granules from platelets; Nbeal2 deficiency does not affect megakaryocyte differentiation or proplatelet formation in vitro, nor platelet life span in vivo, but impairs platelet adhesion, aggregation, and coagulant activity, leading to defective arterial thrombus formation and impaired wound healing due to reduced myofibroblast differentiation. Nbeal2 knockout mouse model, flow cytometry, platelet aggregometry, intravital imaging, excisional wound model, electron microscopy The Journal of clinical investigation High 23861251 23863626
2013 In Nbeal2-/- mice, P-selectin (α-granule membrane protein) is expressed at 48% of wild-type levels and is still externalized upon platelet activation, and VPS33B/VPS16B levels are normal, indicating NBEAL2 acts independently of the VPS33B/VPS16B complex at a later stage of α-granule biogenesis. Flow cytometry, western blot, platelet functional assays in Nbeal2-/- mice Blood Medium 23861251
2017 NBEAL2 interacts with Dock7, Sec16a, and Vac14 as identified by interactome analysis with validation by reverse co-immunoprecipitation; GPS-causing BEACH domain mutations disrupt interaction with Dock7 and Vac14; Dock7 is physically proximal to Nbeal2 in human megakaryocytes (proximity ligation assay); NBEAL2 is primarily cytoplasmic while Dock7 localizes to the membrane or within α-granules; platelets from GPS patients and Nbeal2-/- mice are nearly devoid of Dock7, leading to defective actin polymerization, platelet activation, and shape change. Mass spectrometry interactome, reverse co-immunoprecipitation, proximity ligation assay, immunofluorescence, actin polymerization assays Blood High 29187380
2017 The transcription factor GATA1 regulates NBEAL2 expression through a long-distance enhancer located 31 kb upstream of NBEAL2; chromatin immunoprecipitation sequencing identified 5 GATA binding sites in this region marked by H3K4Me1; luciferase reporter assays confirmed enhancer activity, and mutagenesis of GATA1 binding sites reduced enhancer activity; GATA1 and GATA2 physically bind this enhancer region. ChIP-seq, luciferase reporter assay, enhancer mutagenesis, DNA binding studies, siRNA knockdown of GATA1 in K562 cells Haematologica High 28082341
2017 NBEAL2 is required for neutrophil granule content across all granule subsets and for NK cell degranulation; Nbeal2-deficient neutrophils show a paradoxically enhanced phagocyte respiratory burst associated with increased expression of cytosolic NADPH oxidase components; NBEAL2 deficiency increases susceptibility to S. aureus and murine CMV infection in vivo. Nbeal2-/- mouse phenotyping, flow cytometry, respiratory burst assay, western blot, in vivo infection models The Journal of clinical investigation High 28783043
2018 NBEAL2 is not required for fibrinogen (FGN) endocytosis by megakaryocytes but is required for retention of both endocytosed and megakaryocyte-synthesized cargo proteins by maturing α-granules; in NBEAL2-null megakaryocytes, endocytosed FGN passes from the P-selectin compartment to RAB11-associated endosomes before release rather than being retained; NBEAL2 colocalizes with P-selectin in human megakaryocytes, proplatelets, and platelets, and native NBEAL2 and P-selectin are coimmunoprecipitated from platelets and megakaryocytes. Fluorescence microscopy tracking of labeled FGN in WT and NBEAL2-null megakaryocytes, co-immunoprecipitation of endogenous proteins, immunofluorescence colocalization Arteriosclerosis, thrombosis, and vascular biology High 30354215
2020 NBEAL2 directly binds the endoplasmic reticulum membrane protein SEC22B; this interaction was established by co-immunoprecipitation of tagged and endogenous proteins in HEK293, imMKCL, and primary human megakaryocyte cells; NBEAL2 can simultaneously bind SEC22B and P-selectin; SEC22B binding maps to NBEAL2 amino acids 1798–1903; GPS-associated missense variants E1833K and R1839C in this region abolish SEC22B binding; CRISPR/Cas9 knockout of SEC22B reduces NBEAL2 protein levels but not vice versa; loss of either SEC22B or NBEAL2 results in failure of α-granule production in imMKCL cells. Co-immunoprecipitation of tagged and endogenous proteins, CRISPR/Cas9 knockout, immunofluorescence microscopy, active-site/domain mutagenesis (GPS missense variants) Blood High 32384141
2023 NBEAL2 interacts with CTLA-4 in T cells as established by co-immunoprecipitation; NBEAL2 deficiency leads to reduced CTLA-4 expression specifically in effector/conventional T cells (not regulatory T cells) in GPS patients; NBEAL2 knockdown in healthy primary T cells recapitulates low CTLA-4 expression; a comprehensive NBEAL2 interactome in primary T cells identified 74 protein partners including LRBA. Mass spectrometry interactome in primary T cells, co-immunoprecipitation (CTLA-4/NBEAL2), siRNA knockdown, flow cytometry of patient-derived T cells Nature communications High 37349339
2024 NBEAL2 interacts with ribosomal protein RPS6 in mast cells as identified by co-immunoprecipitation; NBEAL2 deficiency leads to accumulation of strongly p90RSK-phosphorylated RPS6, resulting in abnormal mast cell phenotype with prolonged growth factor-independent survival and a pro-inflammatory phenotype. Co-immunoprecipitation, CRISPR/Cas9 deletion of Nbeal2 in MC/9 cells, western blotting, flow cytometry, ELISA, structural prediction (RoseTTAFold) Immunology Medium 38272677
2025 NBEAL2 deficiency in mast cells leads to Abl1 stabilization and increased surface expression of the multi-drug-resistant protein ABCB1 (MDR1); this increased ABCB1 surface expression is antagonized by IL-33-induced TAK1-IKK2 module activation and Src-family kinase activation. Nbeal2-/- mouse-derived mast cells, CRISPR/Cas9 deletion, flow cytometry, western blotting, pharmacological pathway inhibition Immunology Medium 41111259
2018 Nbeal2 deficiency reduces monocyte granularity in addition to neutrophil and platelet granularity; platelet-specific Nbeal2 deficiency does not influence leukocyte functions (demonstrated by platelet transfusion into thrombocytopenic mice), indicating NBEAL2 directly modifies leukocytes rather than acting indirectly through platelets. Nbeal2-/- mice, platelet-specific rescue by transfusion into thrombocytopenic mice, flow cytometry, in vitro phagocytosis and cytokine assays, in vivo Klebsiella pneumonia model Arteriosclerosis, thrombosis, and vascular biology Medium 29930006
2025 Nbeal2-/- (α-granule deficient) mice show delayed and impaired dorsal skin wound healing with reductions in wound collagen content, delayed re-epithelialization, and altered expression of IL-1β, VEGF, MMP-9, and TIMP-1, demonstrating that de novo packaged platelet α-granule cargo is required for the inflammation, proliferation, and tissue remodeling phases of wound healing. Nbeal2-/- mouse dorsal full-thickness excisional wound model, histological/morphometric analysis, molecular profiling of wound extracts bioRxivpreprint Medium bio_10.1101_2025.02.01.636051

Source papers

Stage 0 corpus · 23 papers · ranked by NIH iCite citations
Year Title Journal Citations PMID
2011 Exome sequencing identifies NBEAL2 as the causative gene for gray platelet syndrome. Nature genetics 193 21765411
2011 Mutations in NBEAL2, encoding a BEACH protein, cause gray platelet syndrome. Nature genetics 187 21765413
2011 NBEAL2 is mutated in gray platelet syndrome and is required for biogenesis of platelet α-granules. Nature genetics 175 21765412
2013 Gray platelet syndrome and defective thrombo-inflammation in Nbeal2-deficient mice. The Journal of clinical investigation 146 23863626
2013 Abnormal megakaryocyte development and platelet function in Nbeal2(-/-) mice. Blood 97 23861251
2018 NBEAL2 (Neurobeachin-Like 2) Is Required for Retention of Cargo Proteins by α-Granules During Their Production by Megakaryocytes. Arteriosclerosis, thrombosis, and vascular biology 44 30354215
2012 Correlation between platelet phenotype and NBEAL2 genotype in patients with congenital thrombocytopenia and α-granule deficiency. Haematologica 40 23100277
2017 Nbeal2 interacts with Dock7, Sec16a, and Vac14. Blood 32 29187380
2018 NBEAL2 mutations and bleeding in patients with gray platelet syndrome. Platelets 31 29869935
2013 The Nbeal2(-/-) mouse as a model for the gray platelet syndrome. Rare diseases (Austin, Tex.) 29 25003009
2017 NBEAL2 is required for neutrophil and NK cell function and pathogen defense. The Journal of clinical investigation 26 28783043
2023 NBEAL2 deficiency in humans leads to low CTLA-4 expression in activated conventional T cells. Nature communications 25 37349339
2020 The endoplasmic reticulum protein SEC22B interacts with NBEAL2 and is required for megakaryocyte α-granule biogenesis. Blood 25 32384141
2018 Nbeal2 Deficiency Increases Organ Damage but Does Not Affect Host Defense During Gram-Negative Pneumonia-Derived Sepsis. Arteriosclerosis, thrombosis, and vascular biology 18 29930006
2017 The transcription factor GATA1 regulates NBEAL2 expression through a long-distance enhancer. Haematologica 18 28082341
2017 A novel nonsense NBEAL2 gene mutation causing severe bleeding in a patient with gray platelet syndrome. Platelets 9 28504079
2016 Spontaneous 8bp Deletion in Nbeal2 Recapitulates the Gray Platelet Syndrome in Mice. PloS one 9 26950939
2024 The Neurobeachin-like 2 protein (NBEAL2) controls the homeostatic level of the ribosomal protein RPS6 in mast cells. Immunology 4 38272677
2019 Identification of novel pathogenic F13A1 mutation and novel NBEAL2 gene missense mutation in a pedigree with hereditary congenital factor XIII deficiency. Gene 4 30935919
2023 Gray Platelet Syndrome in a Neonate With VACTERL Association: A Novel Homozygous Pathogenic Variant c.5257C>T in the NBEAL2 Gene. Cureus 3 38060757
2025 Nbeal2 knockout mice are not protected against hypoxia-induced pulmonary vascular remodeling and pulmonary hypertension. Blood advances 2 39693512
2025 Nbeal2 Inactivation Triggers Abl1 Stabilisation and Dysregulated Subcellular Localisation of the Multi-Drug-Resistant Protein MDR1 (ABCB1) in Mast Cells. Immunology 2 41111259
2024 NBEAL2 gene mutations do not always lead to gray platelet syndrome: A case report. Medicine 1 39465716

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