MMP17

MMP17 (MT4-MMP) is a GPI-anchored membrane-type matrix metalloproteinase that functions in vascular smooth muscle cell maturation, intestinal epithelial repair, and immune cell regulation, with additional non-proteolytic roles in cancer cell signaling. As the only GPI-anchored MMP family member, it is processed by furin in the Golgi, N-glycosylated at Asn318, and trafficked to the plasma membrane where it forms homophilic complexes and is internalized via the CDC42/RhoA-dependent CLIC/GEEC pathway (PMID:10567400, PMID:28531887, PMID:26663028). Its proteolytic substrates include osteopontin—whose MMP17-generated N-terminal fragment activates JNK signaling to drive vascular smooth muscle cell maturation and protect against aortic aneurysm—PERIOSTIN in intestinal epithelial regeneration, pro-TNFα, fibrinogen/fibrin, and ADAMTS4 (PMID:25963716, PMID:34795242, PMID:10799478, PMID:15780640). Independent of its catalytic activity, MMP17 associates with EGFR to enhance receptor phosphorylation and downstream CDK4/Rb signaling, and binds Tks5/PDGFRα to activate Src and promote invadopodia formation (PMID:25320013, PMID:31813546).

1. 1999 High

   Establishing MMP17 as the first GPI-anchored MMP resolved how a membrane metalloproteinase could be tethered without a transmembrane domain, revealing a novel mode of surface presentation and shedding.

   Evidence [3H]ethanolamine radiolabeling and PI-PLC release from cell surface

   PMID:10567400

   Open questions at the time

   • Identity of the endogenous metalloproteinase responsible for MMP17 shedding was not determined
   • Functional consequences of GPI anchoring versus transmembrane anchoring were not compared
2. 2000 High

   Defining the substrate profile revealed that MMP17 is a poor ECM protease but an efficient pro-TNFα sheddase and fibrinogen/fibrin protease, distinguishing it functionally from transmembrane MT-MMPs that activate pro-MMP2.

   Evidence Recombinant catalytic domain assays against ECM substrates, GST-pro-TNFα cleavage, and COS-7 co-transfection shedding assay

   PMID:10799478

   Open questions at the time

   • In vivo relevance of TNFα shedding by MMP17 was not tested
   • Full substrate repertoire remained uncharacterized
3. 2005 Medium

   Linking MMP17 to cartilage aggrecanolysis via ADAMTS4 processing revealed a new indirect mechanism by which a GPI-anchored MMP can regulate ECM turnover.

   Evidence IL-1-treated bovine cartilage explants with mannosamine inhibition of GPI anchor synthesis, Western blot of ADAMTS4 processing

   PMID:15780640

   Open questions at the time

   • Evidence for MMP17 as the responsible GPI-anchored protease is indirect (pharmacological inhibitor affects all GPI-anchored proteins)
   • Direct cleavage of ADAMTS4 by MMP17 was not reconstituted in vitro
4. 2006 High

   Domain-swap experiments showed that the hemopexin domain of MMP17 prevents ER-to-surface maturation when placed in MT1-MMP, explaining why MMP17 cannot activate pro-MMP2 and establishing that domain-specific features dictate its trafficking fate.

   Evidence MT1-MMP/MT4-MMP hemopexin domain chimeras assayed for surface biotinylation, propeptide processing, and pro-MMP2 activation

   PMID:16686598

   Open questions at the time

   • Structural basis for ER retention by the MMP17 hemopexin domain was not resolved
   • Whether hemopexin domain also governs substrate selectivity was not tested
5. 2007 High

   Generation of MMP17-null mice revealed its tissue expression pattern (neurons, smooth muscle, macrophages) and showed that it is dispensable for TNFα shedding in macrophages, redirecting the search for its physiological substrates.

   Evidence LacZ knock-in reporter mouse, LPS-stimulated macrophage TNFα release assay

   PMID:17825051

   Open questions at the time

   • Physiological substrates in smooth muscle and neurons remained unidentified
   • Compensatory mechanisms by other sheddases were not excluded
6. 2009 Medium

   Demonstrating that MMP17 promotes lung metastasis by increasing tumor vascular permeability and mural cell detachment identified a specific pro-metastatic mechanism distinct from direct ECM degradation.

   Evidence Spontaneous and experimental lung metastasis models with ultrastructural vessel analysis

   PMID:19426156

   Open questions at the time

   • Molecular substrate responsible for mural cell detachment was not identified
   • Contribution of proteolytic versus non-proteolytic activity was not distinguished
7. 2012 High

   Active-site mutagenesis (E249A) established that proteolytic activity is required for MMP17-driven angiogenesis and metastasis, and host-derived MMP17 is dispensable, pinpointing tumor-cell-intrinsic catalysis as the driver.

   Evidence E249A catalytic-dead mutant in subcutaneous tumor models and MMP17-deficient hosts (RAG1−/− mice)

   PMID:22262494

   Open questions at the time

   • The pro-angiogenic substrate cleaved by tumor-derived MMP17 was not identified
   • Whether the non-proteolytic EGFR mechanism contributes to angiogenesis was not tested
8. 2014 Medium

   Discovery that MMP17 associates with EGFR and enhances its phosphorylation independently of catalytic activity revealed a non-proteolytic signaling function, expanding MMP17's role beyond substrate cleavage.

   Evidence Co-immunoprecipitation of MMP17–EGFR, proliferation and CDK4/Rb pathway analysis with catalytically inactive mutant

   PMID:25320013

   Open questions at the time

   • Structural basis of MMP17–EGFR interaction is unknown
   • Whether GPI-anchor microdomain co-localization drives the interaction was not tested
   • In vivo relevance of non-proteolytic EGFR activation was not assessed
9. 2015 High

   Identification of osteopontin as a physiological MMP17 substrate whose N-terminal cleavage fragment activates JNK signaling resolved the mechanism by which MMP17 regulates vascular smooth muscle cell maturation and protects against aortic aneurysm.

   Evidence Mmp17 KO mouse, angiotensin-II aneurysm model, lentiviral re-expression of catalytically active MMP17 and OPN N-terminal fragment, mass spectrometry, human R373H mutation analysis

   PMID:25963716

   Open questions at the time

   • How the OPN N-terminal fragment specifically activates JNK is mechanistically unresolved
   • Whether the human R373H variant causes clinical aortic disease was not established in a family study
10. 2016 High

    Elucidating MMP17 homophilic complex formation and CLIC/GEEC-mediated internalization dependent on CDC42/RhoA defined the trafficking itinerary of this GPI-anchored protease and explained how surface levels are regulated.

    Evidence Co-IP of tagged MMP17 constructs, antibody-feeding internalization assay, siRNA knockdown of CDC42/RhoA/caveolin-1

    PMID:26663028

    Open questions at the time

    • Functional consequence of homophilic oligomerization for catalytic activity was not determined
    • Whether oligomerization state governs internalization rate is unknown
11. 2017 Medium

    Mapping the biosynthetic pathway showed furin-dependent Golgi processing of the 69 kDa precursor to the 58 kDa mature form, with Asn318 as the sole N-glycosylation site, clarifying MMP17 maturation steps.

    Evidence Organelle fractionation, glycosidase treatment, N-glycosylation site mutagenesis in melanoma cells

    PMID:28531887

    Open questions at the time

    • Role of N-glycosylation at Asn318 in folding, trafficking, or catalysis was not functionally tested
    • Identity of the 45 kDa species (degradation product vs. alternatively processed form) was not resolved
12. 2018 High

    MMP17 deficiency enhanced patrolling monocyte recruitment and Mafb+AIM+ macrophage accumulation at atherosclerotic lesions, identifying MMP17 as a regulator of myeloid cell adhesion and atherogenesis.

    Evidence MMP17-KO mice crossed to atherosclerosis model, intravital microscopy, flow cytometry, CCR5 inhibitor rescue

    PMID:29500407

    Open questions at the time

    • The substrate cleaved by MMP17 to regulate monocyte/macrophage adhesion is unknown
    • Whether macrophage-intrinsic or smooth-muscle-derived MMP17 is responsible was not resolved
13. 2019 Medium

    MMP17 was shown to form complexes with Tks5 and PDGFRα to activate Src, promoting invadopodia and amoeboid movement, revealing a second non-proteolytic scaffolding function in cancer invasion.

    Evidence Co-IP of MMP17 with Tks5/PDGFRα, 3D invadopodia and collagen gel motility assays in FaDu head and neck cancer cells

    PMID:31813546

    Open questions at the time

    • Whether this scaffolding function requires the GPI anchor or hemopexin domain is untested
    • Single lab finding without independent replication
    • Contribution of proteolytic versus scaffolding activity was not separated
14. 2021 High

    Identification of PERIOSTIN as an MMP17 substrate in intestinal smooth muscle cells established a paracrine mechanism by which mesenchymal cells regulate epithelial regeneration and YAP activity after injury.

    Evidence Mmp17 KO mice with colitis and irradiation injury models, proteomics, organoid culture, single-cell RNA-seq

    PMID:34795242

    Open questions at the time

    • Direct cleavage site on PERIOSTIN and identity of active fragments were not fully characterized
    • Whether other diffusible substrates contribute to the epithelial phenotype is unresolved
15. 2023 Medium

    MMP17 was found to extrinsically regulate goblet cell maturation, with knockout mice showing enhanced goblet cell effector expression and helminth resistance, extending MMP17's intestinal role beyond epithelial repair to mucosal immunity.

    Evidence Mmp17 KO mice with Trichuris muris and Citrobacter rodentium infection models, gene/protein expression, single-cell RNA-seq

    PMID:37869014

    Open questions at the time

    • Molecular target through which MMP17 regulates goblet cell maturation is unidentified
    • Whether the phenotype is a direct consequence of PERIOSTIN cleavage or involves distinct substrates is unknown

• Key unresolved questions include the structural basis for MMP17's non-proteolytic signaling interactions (EGFR, Tks5/PDGFRα), the substrates responsible for its roles in atherosclerosis and goblet cell regulation, and whether its proteolytic and scaffolding functions are segregated by tissue or context.
• No crystal or cryo-EM structure of MMP17 exists
• Substrate responsible for myeloid/vascular adhesion phenotype is unknown
• Relative in vivo contributions of proteolytic versus non-proteolytic functions remain unseparated