HECW2

HECW2 is a HECT-domain E3 ligase with dual ubiquitin and Nedd8 ligase activities that controls the stability of diverse nuclear and cytoplasmic substrates while also functioning as a signaling scaffold. It catalyzes K63-linked ubiquitination of AMOTL1 to stabilize endothelial junctions and sequester YAP in the cytoplasm, and non-degradative ubiquitination of p73 to enhance its transcriptional activity, whereas it targets PCNA, lamin B1, HP1α/β, and ALKBH5 for proteasomal degradation (PMID:12890487, PMID:27498087, PMID:29753763, PMID:30208514, PMID:40520873). Its Nedd8 ligase activity, dependent on catalytic cysteine C1341, is specifically required for GDNF-stimulated Akt activation and enteric nervous system development, where it scaffolds SHC, Grb2, PI3K, PDK1, and Akt; HECW2-deficient mice accordingly develop intestinal aganglionosis (PMID:27119228, PMID:25555806). HECW2 itself is a substrate of APC/C-Cdh1, which degrades it during mitotic exit via a destruction box motif, and its depletion prolongs metaphase while its overexpression causes chromosome lagging (PMID:24163370).

1. 2003 High

   Establishing HECW2 as a HECT-domain E3 ligase that paradoxically stabilizes rather than degrades its substrate p73 answered how a ubiquitin ligase could function as a transcriptional co-activator.

   Evidence Reciprocal co-IP, in vitro ubiquitination, and transcriptional reporter assays in mammalian cells

   PMID:12890487

   Open questions at the time

   • Ubiquitin chain linkage type on p73 not determined
   • In vivo relevance to p73-dependent apoptosis or differentiation not tested
   • No structural basis for WW–PY interaction
2. 2013 High

   Identifying HECW2 as an APC/C-Cdh1 substrate that peaks in mitosis and localizes to spindles revealed cell-cycle-dependent regulation and a mitotic function for this ligase.

   Evidence IP-MS identification, destruction box mutagenesis, Cdh1 knockdown/overexpression, immunofluorescence, and mitotic timing assays

   PMID:24163370

   Open questions at the time

   • Mitotic substrates of HECW2 at the spindle not identified
   • Mechanism by which overexpression causes chromosome lagging unknown
   • Functional consequence of destruction box mutation in vivo untested
3. 2014 High

   Demonstrating that HECW2-deficient mice develop intestinal aganglionosis via defective GDNF/Akt signaling established a non-redundant developmental role in the enteric nervous system.

   Evidence Knockout mouse model with bowel motility, histology, and Akt signaling pathway analysis

   PMID:25555806

   Open questions at the time

   • Whether the ENS phenotype depends on ubiquitin or Nedd8 ligase activity was unresolved at this point
   • Cell-autonomous versus non-cell-autonomous contributions not dissected
4. 2016 High

   Distinguishing HECW2's Nedd8 ligase activity (C1341-dependent) from its ubiquitin ligase activity, and showing only the former is required for GDNF/Akt signaling and ENS/kidney development, redefined HECW2 as a dual-function ligase with separable catalytic outputs.

   Evidence Active-site mutagenesis, double KO mice, scaffold complex reconstitution with SHC/Grb2/PI3K/PDK1/Akt

   PMID:27119228

   Open questions at the time

   • Nedd8 substrate(s) in the GDNF pathway not identified
   • Whether Nedd8 ligase activity is relevant beyond ENS/kidney contexts unknown
   • Structural basis for dual specificity not established
5. 2016 High

   Showing that HECW2 K63-ubiquitinates AMOTL1 to stabilize it and retain YAP in the cytoplasm connected HECW2 to Hippo pathway regulation and endothelial junction integrity.

   Evidence Co-IP, K63-linkage-specific ubiquitination assay, siRNA knockdown, YAP subcellular fractionation, angiogenic sprouting assay

   PMID:27498087

   Open questions at the time

   • Whether HECW2-AMOTL1 axis operates in non-endothelial tissues untested
   • Upstream signals controlling HECW2 activity in endothelial cells unknown
6. 2018 High

   Identifying PCNA and lamin B1 as degradative substrates of HECW2, and linking altered HECW2–lamin A interaction to laminopathy-causing mutations, expanded the substrate repertoire to nuclear envelope and DNA replication machinery.

   Evidence Co-IP, in vitro ubiquitination, PIP motif identification, proteasome inhibitor experiments, lamin A mutant cell lines

   PMID:29753763

   Open questions at the time

   • Functional consequence of PCNA degradation for DNA replication or repair not assessed
   • Whether lamin B1 degradation contributes to laminopathy pathology remains unclear
7. 2018 Medium

   Demonstrating selective ubiquitination and degradation of HP1α and HP1β (but not HP1γ) by HECW2 implicated it in heterochromatin regulation with isoform specificity.

   Evidence Co-IP, ubiquitination assay, HECW2 overexpression/knockdown with proteasome inhibitor treatment

   PMID:30208514

   Open questions at the time

   • Functional impact on heterochromatin spreading or gene silencing not tested
   • Basis for HP1 isoform selectivity unknown
   • Single-lab finding awaits independent confirmation
8. 2021 Medium

   Localization of HECW2 to nuclear foci in oocytes and zygotes, and its requirement for sperm DNA decondensation and pronucleus formation, established a role in the earliest events of mammalian development.

   Evidence Immunofluorescence in oocytes/zygotes, antibody microinjection into oocytes before IVF

   PMID:33030211

   Open questions at the time

   • Substrate(s) mediating sperm decondensation not identified
   • Antibody inhibition approach does not distinguish catalytic from scaffolding functions
   • Single study with no genetic confirmation
9. 2023 Medium

   Connecting HECW2-mediated lamin B1 degradation to AKT/mTOR activation in colorectal cancer provided a disease-relevant downstream pathway for a previously identified substrate.

   Evidence HECW2 knockdown/overexpression, ubiquitination assay, AKT/mTOR pathway analysis, CRC proliferation and chemoresistance assays

   PMID:37781079

   Open questions at the time

   • Mechanism linking lamin B1 loss to AKT/mTOR activation not delineated
   • In vivo tumor model confirmation limited
   • Independent replication needed
10. 2025 Medium

    Identification of ALKBH5 as a HECW2 substrate linked ubiquitin-mediated regulation to m6A RNA modification and glycolysis in hemangioma, revealing an epitranscriptomic arm of HECW2 function.

    Evidence Ubiquitination assay, glycolysis assays, LDHA rescue, in vivo xenograft model in hemangioma endothelial cells

    PMID:40520873

    Open questions at the time

    • Ubiquitin chain linkage type on ALKBH5 not determined
    • Whether this pathway operates in normal endothelial physiology unknown
    • Single-lab finding

• Major open questions include the identity of HECW2's Nedd8 substrate(s) in GDNF signaling, the structural basis for its dual ubiquitin/Nedd8 specificity, how its numerous degradative and non-degradative substrates are prioritized in different cell types, and whether its mitotic spindle association reflects a direct mitotic substrate.
• Nedd8 substrate in GDNF/Akt pathway unidentified
• No structural model of HECW2 HECT domain or WW domains
• Context-dependent substrate selection mechanism unknown