Affinage

MMRN2

Multimerin-2 · UniProt Q9H8L6

Round 2 corrected
Length
949 aa
Mass
104.4 kDa
Annotated
2026-04-28
39 papers in source corpus 14 papers cited in narrative 14 extracted findings

Mechanistic narrative

Synthesis pass · prose summary of the discoveries below

MMRN2 (Multimerin-2) is a pan-endothelial extracellular matrix glycoprotein that orchestrates vascular morphogenesis, stability, and angiogenic signaling through its roles as both a VEGF-A sequestrant and a shared ligand for the group 14 C-type lectins CD93, CLEC14A, and CD248. MMRN2 directly binds VEGF-A (~50 nM Kd), blocking VEGFR1/VEGFR2 activation and suppressing endothelial migration, sprouting angiogenesis, and tumor vascularization (PMID:22020326); loss of MMRN2 derepresses a VEGFR2-Tyr951/Src/VE-cadherin phosphorylation cascade that destabilizes endothelial junctions, increases vascular permeability, and impairs pericyte recruitment, as demonstrated in Mmrn2-knockout mice (PMID:31422156). Through its coiled-coil domain, MMRN2 engages CD93 and CLEC14A on endothelial cells, stabilizing CD93 in filopodia and driving β1 integrin activation, FAK phosphorylation, and fibronectin fibrillogenesis; the CD93–MMRN2–β1-integrin complex is recycled via Rab5c-dependent endosomes (PMID:29763414, PMID:31138217, PMID:28671670). Beyond the vasculature, MMRN2 acts as a CD93 ligand on neural stem cells to activate a β-Catenin/ZFP503 pathway that represses GFAP transcription and suppresses astrogenesis (PMID:32291340).

Mechanistic history

Synthesis pass · year-by-year structured walk · 11 steps
  1. 1994 Medium

    The initial identification of EndoGlyx-1 as a high-molecular-weight endothelial-specific surface glycoprotein complex established the existence of a previously unknown vascular-restricted molecule and set the stage for molecular cloning.

    Evidence Monoclonal antibody generation, immunochemical analysis, and immunohistochemistry on vascular endothelial cells and tissues

    PMID:7933987

    Open questions at the time
    • Molecular identity and gene sequence unknown
    • Relationship of the four subunits (p110–p200) to a single gene product unresolved
  2. 2001 High

    Molecular cloning revealed EndoGlyx-1 to be a 949-amino-acid EMILIN-family protein (MMRN2) with an EMI domain, coiled-coil region, and C1q-like domain, resolving the molecular identity behind the endothelial glycoprotein complex and establishing its domain architecture.

    Evidence cDNA cloning from peptide sequences, bioinformatic domain analysis, and carbohydrate enzyme digestion of cell-surface-expressed subunits

    PMID:11559704

    Open questions at the time
    • Functional role of individual domains uncharacterized
    • Biological ligands unknown
  3. 2002 Medium

    Demonstration that MMRN2 is a secreted, ECM-associated glycoprotein capable of homo- and heteromeric disulfide-bonded assembly clarified its extracellular oligomeric nature.

    Evidence Biochemical characterization including disulfide-bonding assays and developmental expression analysis

    PMID:12221002

    Open questions at the time
    • Oligomeric stoichiometry not definitively resolved
    • ECM binding partners unidentified
  4. 2011 High

    The discovery that MMRN2 directly binds VEGF-A with ~50 nM affinity and thereby blocks VEGFR1/VEGFR2 signaling established MMRN2 as an endogenous anti-angiogenic factor, answering the long-standing question of its biological function.

    Evidence Direct binding affinity measurements, VEGFR phosphorylation assays, endothelial migration and tube formation assays, in vivo tumor xenograft and adenoviral delivery experiments

    PMID:22020326

    Open questions at the time
    • Domain(s) of MMRN2 mediating VEGF-A binding not mapped
    • Relative contribution of VEGF sequestration versus receptor-mediated functions unclear
  5. 2013 Medium

    Quantitative proteomics during endothelial morphogenesis identified CLEC14A as an MMRN2 binding partner in the ECM, revealing a receptor-ligand axis relevant to tumor angiogenesis beyond the VEGF-sequestration mechanism.

    Evidence SILAC quantitative proteomics, ECM protein profiling during tube formation, validation in multistage carcinogenesis models

    PMID:23979707

    Open questions at the time
    • Binding domain on MMRN2 not mapped
    • Functional consequences of CLEC14A–MMRN2 interaction not yet tested by loss-of-function
  6. 2015 High

    Validation that CLEC14A physically engages MMRN2 via its extracellular region and that blocking this interaction with a monoclonal antibody inhibits sprouting angiogenesis and tumor growth demonstrated the functional significance of the CLEC14A–MMRN2 axis in vivo.

    Evidence Reciprocal co-IP, pull-down, spheroid sprouting, aortic ring assay, in vivo sponge assay, Clec14a-KO mice, antibody blocking in tumor models

    PMID:25745997

    Open questions at the time
    • Specific MMRN2 domain required for CLEC14A binding not yet identified
    • Downstream signaling from CLEC14A upon MMRN2 engagement uncharacterized
  7. 2017 High

    Mapping of MMRN2 as a shared ligand for three group 14 C-type lectins—CLEC14A, CD93, and CD248—via its coiled-coil domain (CLEC14A/CD93) and a distinct region (CD248), with mutagenesis of the lectin-domain long-loop region abolishing binding, resolved the multi-receptor logic and molecular geometry of the MMRN2 interactome.

    Evidence Direct binding assays, site-directed mutagenesis of C-type lectin domains, competitive binding, co-localization in pancreatic cancer tissue, recombinant peptide blocking experiments in vitro and in vivo

    PMID:28671670 PMID:28912033

    Open questions at the time
    • Structural basis at atomic resolution lacking
    • Whether CD248–MMRN2 and CLEC14A/CD93–MMRN2 axes serve redundant or distinct functions in vivo unclear
  8. 2018 High

    The discovery that the CD93–MMRN2 complex stabilizes CD93 in filopodia, activates β1 integrin and FAK, and drives fibronectin fibrillogenesis—with in vivo validation in CD93-knockout mice—defined the downstream mechanotransduction pathway linking MMRN2 to ECM assembly.

    Evidence Fluorescence microscopy, proteolytic cleavage assays, β1 integrin activation and FAK phosphorylation assays, fibronectin fibrillogenesis assay, CD93-KO mice, retinal vessel imaging

    PMID:29763414

    Open questions at the time
    • Mechanism by which MMRN2 protects CD93 from cleavage not defined at the molecular level
    • Whether FAK activation is the principal effector or one of several downstream pathways unknown
  9. 2019 High

    Demonstration that MMRN2 loss de-represses VEGFR2-Tyr951/Src/VE-cadherin phosphorylation, causing junctional instability and vascular leakage—validated in Mmrn2-knockout mice showing collapsed tumor vessels and impaired drug delivery—established MMRN2 as a non-redundant vascular barrier gatekeeper and uncovered a separate CD93–MMRN2–β1-integrin endosomal recycling circuit via Rab5c.

    Evidence MMRN2 RNAi, permeability assays, VEGFR2/Src/VE-cadherin phosphorylation, Mmrn2-KO mice, intravital imaging, tumor xenografts; separately, confocal microscopy, Rab5c silencing, chimeric CD93 constructs, flow cytometry

    PMID:31138217 PMID:31422156

    Open questions at the time
    • Whether VEGF-A sequestration and junctional VEGFR2 suppression are mechanistically coupled or independent functions of MMRN2 is unresolved
    • Rab5c-dependent recycling characterized only in cultured endothelial cells
  10. 2020 High

    Extension of the CD93–MMRN2 axis to neural stem cells revealed a non-vascular function: MMRN2 engagement of CD93 activates β-Catenin, which induces ZFP503-mediated repression of GFAP to suppress astrogenesis, broadening MMRN2 biology beyond the endothelium.

    Evidence Cd93-KO mice, neural stem cell differentiation assays, β-Catenin nuclear translocation, ChIP on Gfap promoter, behavioral testing

    PMID:32291340

    Open questions at the time
    • Whether MMRN2 is expressed by neural cells or supplied extrinsically not fully delineated
    • Relevance to human neurodevelopmental conditions not established
  11. 2023 High

    Identification of miR-1910-5p as a direct post-transcriptional repressor of MMRN2 via its 3' UTR, downstream of CXCR4 signaling, revealed a regulatory input controlling MMRN2 levels and vascular barrier function in corneal neovascularization.

    Evidence Luciferase 3' UTR reporter, antagomir rescue in murine alkali-burn corneal neovascularization model, Western blotting, cell migration and tube formation assays

    PMID:37040097

    Open questions at the time
    • Additional miRNAs or transcription factors controlling MMRN2 expression not explored
    • Whether CXCR4–miR-1910-5p–MMRN2 axis operates in tumor vasculature unknown

Open questions

Synthesis pass · forward-looking unresolved questions
  • Key open questions include: (1) which MMRN2 domain mediates VEGF-A binding and whether VEGF sequestration and junctional barrier functions are mechanistically separable; (2) the atomic-resolution structure of MMRN2 and its receptor complexes; and (3) the in vivo significance of the CD248–MMRN2 interaction at the pericyte–endothelial interface.
  • No crystal or cryo-EM structure for MMRN2 or its complexes
  • Relative contributions of VEGF-sequestration versus receptor-engagement pathways not dissected genetically
  • CD248–MMRN2 axis lacks in vivo loss-of-function validation

Mechanism profile

Synthesis pass · controlled-vocabulary classification · explore literature graph →
Molecular activity
GO:0048018 receptor ligand activity 5 GO:0098631 cell adhesion mediator activity 2 GO:0140313 molecular sequestering activity 1
Localization
GO:0031012 extracellular matrix 3 GO:0005576 extracellular region 2 GO:0005886 plasma membrane 2
Pathway
R-HSA-162582 Signal Transduction 3 R-HSA-1474244 Extracellular matrix organization 2 R-HSA-1266738 Developmental Biology 1
Partners
CD248CD93CLEC14AITGB1RAB5CVEGFA
Complex memberships
CD93–MMRN2–β1-integrin complex

Evidence

Reading pass · 14 per-paper findings extracted from the source corpus
Year Finding Method Journal Conf PMIDs
1994 EndoGlyx-1 (later identified as MMRN2) was characterized as a high molecular weight (~500 kDa) glycoprotein complex on the surface of vascular endothelial cells, composed of four disulfide-bonded subunits of apparent molecular weight 190, 140, 125, and 110 kDa. It is expressed exclusively on endothelial cells of normal and tumor blood vessels, with no expression in non-endothelial cell types. Monoclonal antibody generation, immunochemical analysis of endothelial cell extracts, immunohistochemistry Laboratory investigation Medium 7933987
2001 EndoGlyx-1/MMRN2 was molecularly cloned and characterized as an EMILIN-like protein of 949 amino acids (~105 kDa) with an N-terminal EMI domain, a central coiled-coil-rich region, and a C-terminal C1q-like domain. The four subunits (p110, p125, p140, p200) are all cell-surface exposed and share similar patterns of N-linked and O-linked carbohydrates as shown by enzyme digestion. Peptide purification, cDNA cloning, bioinformatic domain analysis, enzyme digestion of carbohydrates, cell surface expression assays The Journal of biological chemistry High 11559704
2002 Multimerin-2 (MMRN2) is a secreted glycoprotein of the EMI domain family capable of forming homo- and heteromers via disulfide bonding, and is attached to the extracellular matrix. Its structural organization includes an N-terminal EMI domain, an interrupted collagen stretch, and a conserved C-terminal domain. Developmental expression analysis, biochemical characterization, disulfide bonding assays Developmental biology Medium 12221002
2011 MMRN2 directly binds VEGF-A with an affinity of ~50 nM (Kd), thereby sequestering VEGF-A and impairing its binding to VEGFR1 and VEGFR2, leading to inhibition of endothelial cell migration, vessel network organization, and tumor growth in vivo. MMRN2 overexpression in tumor cells impaired tumor vascularization, and adenoviral delivery of MMRN2 to established tumors similarly reduced growth. Multiple binding assays (affinity measurement), VEGFR phosphorylation assays, endothelial migration and tube formation assays, in vivo tumor xenograft models, adenoviral construct delivery Oncogene High 22020326
2012 MMRN2 (Multimerin-2) is a homotrimeric glycoprotein that assembles into high molecular weight multimers, functions through its gC1q domain, and contributes to vascular biology including pro-angiogenic functions and potential roles in hemostasis. The gC1q domain mediates ligand-receptor interactions. Biochemical analysis, structural studies of family members, review with mechanistic synthesis Frontiers in immunology Medium 22566882
2013 CLEC14A was identified as a matrix component that binds to MMRN2 in endothelial cells undergoing morphogenesis. This interaction was detected by quantitative proteomics during endothelial cell tube formation on matrigel, and deregulated levels of both proteins were verified during tumor angiogenesis in multistage carcinogenesis models. SILAC quantitative proteomics, extracellular matrix protein profiling, in vitro morphogenesis assay Molecular & cellular proteomics : MCP Medium 23979707
2015 MMRN2 binds to the extracellular region of CLEC14A (confirmed by pull-down and co-immunoprecipitation), and this interaction is required for sprouting angiogenesis. A monoclonal antibody (clone C4) that blocks CLEC14A-MMRN2 binding inhibits tube formation, endothelial sprouting in vitro and in vivo, and impairs tumor growth and vascular density in treated animals. Pull-down assays, co-immunoprecipitation, spheroid sprouting assay, aortic ring assay, in vivo sponge assay, clec14a knockout mice, antibody blocking experiments, tumor growth assays Oncogene High 25745997
2017 MMRN2 is a ligand for the group 14 C-type lectins CLEC14A, CD93, and CD248 (endosialin/TEM-1). Binding to MMRN2 depends on a predicted long-loop region in the C-type lectin domain and is abrogated by mutation within this domain. CLEC14A and CD93 both bind the same non-glycosylated coiled-coil region of MMRN2, while CD248 binds a distinct, non-competing region. CLEC14A and CD248 can bind MMRN2 simultaneously, spanning the endothelial-pericyte interface in human pancreatic cancer. A recombinant MMRN2 peptide spanning the CLEC14A/CD93 binding region blocks CLEC14A binding to the endothelial cell surface, increases cell adhesion, and is anti-angiogenic in vitro and in vivo. Direct binding assays, site-directed mutagenesis of C-type lectin domain, competitive binding assays, co-localization in tumor tissue, recombinant peptide functional assays, in vivo tumor growth assays Oncogene High 28671670
2017 MMRN2 was identified as a specific ligand for CD93 in endothelial cells. The CD93-MMRN2 interaction mediates endothelial cell adhesion and migration, and disruption of this interaction reduces both processes. Site-directed mutagenesis identified F238 of CD93 as a key residue for the interaction, with the coiled-coil domain of MMRN2 engaged by CD93. Both proteins are co-expressed in blood vessels of human tumors. Co-immunoprecipitation, site-directed mutagenesis, molecular docking, cell adhesion and migration assays, co-expression analysis in tumor vessels Matrix biology High 28912033
2018 In endothelial cells, CD93 localizes to filopodia and promotes filopodia formation. The interaction of CD93 with MMRN2 stabilizes CD93 in filopodia by inhibiting its proteolytic cleavage. The CD93-MMRN2 complex is required for activation of β1 integrin, phosphorylation of focal adhesion kinase (FAK), and fibronectin fibrillogenesis. In CD93-deficient mice, tumor vessels show diminished β1 integrin activation and lack fibronectin fibrillar organization. Fluorescence microscopy, co-localization, proteolytic cleavage assays, β1 integrin activation assays, FAK phosphorylation assays, fibronectin fibrillogenesis assay, CD93-knockout mice, mouse retina imaging The Journal of clinical investigation High 29763414
2019 MMRN2 is required for vascular stability and permeability. RNAi knockdown of MMRN2 in endothelial cells causes cell-cell junctional instability and increased permeability through phosphorylation of VEGFR2 at Tyr951, activation of Src, and phosphorylation of VE-cadherin. Mmrn2-/- mice show endothelial junctional defects, impaired pericyte recruitment, and increased vascular leakage. Tumor vessels in Mmrn2-/- mice have increased collapsed vessels, reduced pericyte coverage, and are leakier, leading to increased tumor hypoxia and impaired chemotherapy efficacy. RNAi knockdown, permeability assays, VEGFR2/Src/VE-cadherin phosphorylation analysis, Mmrn2 knockout mouse generation, intravital imaging, pericyte recruitment assay, tumor xenograft models, chemotherapy efficacy assessment Matrix biology High 31422156
2019 CD93 is recycled to the endothelial cell surface via a Rab5c-dependent endosomal pathway. After endocytosis, CD93 forms a complex with MMRN2 and active β1 integrin in the Rab5c endosomal compartment, and this complex is recycled back to the basolaterally-polarized cell surface by clathrin-independent endocytosis. The cytoplasmic domain of CD93 interacts with Moesin and F-actin to facilitate retrieval during adhesion and migration. Fluorescence confocal microscopy, drug treatments, chimeric CD93 constructs (wild type and mutant), scratch migration assay, gene silencing (Rab5c), flow cytometry, co-localization studies Cell communication and signaling High 31138217
2020 MMRN2 acts as an extracellular ligand for CD93 on neural stem cells to trigger repression of astrogenesis. MMRN2 engagement of CD93 activates a phosphorylation cascade that stabilizes β-Catenin, which translocates to the nucleus to activate Zfp503 transcription. The transcriptional repressor ZFP503 then inhibits Gfap transcription by binding to the Gfap promoter with the assistance of Grg5, thereby suppressing astrocyte differentiation. Cd93 knockout mice, neural stem cell differentiation assays, phosphorylation cascade analysis, β-Catenin nuclear translocation assays, Zfp503 transcriptional activity assays, ChIP (Gfap promoter binding), behavioral testing (autism-like behaviors) Proceedings of the National Academy of Sciences of the United States of America High 32291340
2023 miR-1910-5p directly targets the 3' UTR of MMRN2 mRNA to suppress its expression, causing extracellular junctional defects in endothelial cells and promoting vascular leakage and angiogenesis in corneal neovascularization. miR-1910-5p antagomir treatment increased MMRN2 levels and decreased vascular leakage and CNV in a murine alkali-burn model. This pathway is downstream of CXCR4 signaling. Luciferase reporter assay (3' UTR targeting), gene interference, cell migration/tube formation/aortic ring assays, miR-1910-5p antagomir in vivo, murine alkali-burn CNV model, Western blotting Investigative ophthalmology & visual science High 37040097

Source papers

Stage 0 corpus · 39 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
2020 A reference map of the human binary protein interactome. Nature 849 32296183
2003 Complete sequencing and characterization of 21,243 full-length human cDNAs. Nature genetics 754 14702039
2011 Phylogenetic-based propagation of functional annotations within the Gene Ontology consortium. Briefings in bioinformatics 656 21873635
2008 Large-scale proteomics and phosphoproteomics of urinary exosomes. Journal of the American Society of Nephrology : JASN 607 19056867
2004 The status, quality, and expansion of the NIH full-length cDNA project: the Mammalian Gene Collection (MGC). Genome research 438 15489334
1996 Normalization and subtraction: two approaches to facilitate gene discovery. Genome research 401 8889548
2005 Human plasma N-glycoproteome analysis by immunoaffinity subtraction, hydrazide chemistry, and mass spectrometry. Journal of proteome research 350 16335952
2011 Toward an understanding of the protein interaction network of the human liver. Molecular systems biology 207 21988832
2017 Characterization of the Extracellular Matrix of Normal and Diseased Tissues Using Proteomics. Journal of proteome research 185 28675934
2013 In-depth proteomic analyses of exosomes isolated from expressed prostatic secretions in urine. Proteomics 138 23533145
2013 Proteomic analysis of podocyte exosome-enriched fraction from normal human urine. Journal of proteomics 126 23376485
2018 CD93 promotes β1 integrin activation and fibronectin fibrillogenesis during tumor angiogenesis. The Journal of clinical investigation 111 29763414
2012 The EMILIN/Multimerin family. Frontiers in immunology 93 22566882
2011 MULTIMERIN2 impairs tumor angiogenesis and growth by interfering with VEGF-A/VEGFR2 pathway. Oncogene 77 22020326
2020 N-Terminomics for the Identification of In Vitro Substrates and Cleavage Site Specificity of the SARS-CoV-2 Main Protease. Proteomics 70 33111431
2017 Multimerin-2 is a ligand for group 14 family C-type lectins CLEC14A, CD93 and CD248 spanning the endothelial pericyte interface. Oncogene 68 28671670
2017 Dissecting the CD93-Multimerin 2 interaction involved in cell adhesion and migration of the activated endothelium. Matrix biology : journal of the International Society for Matrix Biology 66 28912033
2013 SILAC-based proteomics of human primary endothelial cell morphogenesis unveils tumor angiogenic markers. Molecular & cellular proteomics : MCP 57 23979707
2006 Expression of stromal cell markers in distinct compartments of human skin cancers. Journal of cutaneous pathology 55 16420310
2001 Molecular cloning and characterization of EndoGlyx-1, an EMILIN-like multisubunit glycoprotein of vascular endothelium. The Journal of biological chemistry 49 11559704
2008 N-glycoprotein profiling of lung adenocarcinoma pleural effusions by shotgun proteomics. Cancer 46 18327805
2015 Blocking CLEC14A-MMRN2 binding inhibits sprouting angiogenesis and tumour growth. Oncogene 45 25745997
2019 Multimerin-2 maintains vascular stability and permeability. Matrix biology : journal of the International Society for Matrix Biology 42 31422156
2002 Developmental expression and biochemical characterization of Emu family members. Developmental biology 42 12221002
2012 EMILIN-3, peculiar member of elastin microfibril interface-located protein (EMILIN) family, has distinct expression pattern, forms oligomeric assemblies, and serves as transforming growth factor β (TGF-β) antagonist. The Journal of biological chemistry 40 22334695
2013 Emilin3 is required for notochord sheath integrity and interacts with Scube2 to regulate notochord-derived Hedgehog signals. Development (Cambridge, England) 37 24131633
2019 The small GTPase Rab5c is a key regulator of trafficking of the CD93/Multimerin-2/β1 integrin complex in endothelial cell adhesion and migration. Cell communication and signaling : CCS 35 31138217
2020 SUMOylation of DDX39A Alters Binding and Export of Antiviral Transcripts to Control Innate Immunity. Journal of immunology (Baltimore, Md. : 1950) 27 32393512
2020 CD93 negatively regulates astrogenesis in response to MMRN2 through the transcriptional repressor ZFP503 in the developing brain. Proceedings of the National Academy of Sciences of the United States of America 25 32291340
2018 Loss of Multimerin-2 and EMILIN-2 Expression in Gastric Cancer Associate with Altered Angiogenesis. International journal of molecular sciences 24 30544909
1994 Identification of a high molecular weight endothelial cell surface glycoprotein, endoGlyx-1, in normal and tumor blood vessels. Laboratory investigation; a journal of technical methods and pathology 18 7933987
2024 Ultrasound Imaging of Tumor Vascular CD93 with MMRN2 Modified Microbubbles for Immune Microenvironment Prediction. Advanced materials (Deerfield Beach, Fla.) 17 38270289
2023 TRIM21 ameliorates hepatic glucose and lipid metabolic disorders in type 2 diabetes mellitus by ubiquitination of PEPCK1 and FASN. Cellular and molecular life sciences : CMLS 17 37249651
2023 Angiogenesis modulated by CD93 and its natural ligands IGFBP7 and MMRN2: a new target to facilitate solid tumor therapy by vasculature normalization. Cancer cell international 16 37660019
2012 Identification of ovarian cancer-associated proteins in symptomatic women: A novel method for semi-quantitative plasma proteomics. Proteomics. Clinical applications 16 22532453
2017 EMILIN3, an extracellular matrix molecule with restricted distribution in skin. Experimental dermatology 8 27892605
2023 The CXCR4/miR-1910-5p/MMRN2 Axis Is Involved in Corneal Neovascularization by Affecting Vascular Permeability. Investigative ophthalmology & visual science 6 37040097
2024 The Potential Significance of the EMILIN3 Gene in Augmenting the Aggressiveness of Low-Grade Gliomas is Noteworthy. Cancer management and research 3 38952353