HECW1

HECW1 (also called NEDL1) is a neuronal HECT-domain E3 ubiquitin ligase that targets a broad range of substrates for proteasomal degradation, thereby modulating signaling pathways in both neural and epithelial contexts. Identified substrates include mutant SOD1, DVL1/Dishevelled-1, Smad4, Scribble, TTF1 (at K151), HIPK2, and NRG2 (at K223), through which HECW1 regulates Wnt/β-catenin signaling, TGF-β/Smad signaling, cell polarity, and autophagy (PMID:14684739, PMID:38266865, PMID:33529121, PMID:31616916, PMID:30849519, PMID:39615883, PMID:41193668). Independent of its catalytic activity, HECW1 binds the C-terminal region of p53 and enhances p53-dependent transcription and apoptosis (PMID:18223681). In neurons, HECW1 is required for normal spatial learning and memory, its overexpression causes TDP-43 cytoplasmic mislocalization and motor neuron degeneration, and in C. elegans the ortholog HECW-1 acts upstream of the neuropeptide receptor NPR-1 in sensory neurons to regulate innate behavior (PMID:39424023, PMID:36674783, PMID:20976258, PMID:22089131).

1. 2003 High

   Discovery of HECW1 as a HECT-type E3 ligase that selectively ubiquitinates ALS-linked mutant SOD1 and co-localizes with it in motor neuron inclusions established the gene's founding connection to neurodegeneration and defined its enzymatic activity.

   Evidence Yeast two-hybrid, Co-IP, in vitro ubiquitination, and immunohistochemistry in FALS patient/mouse tissue

   PMID:14684739

   Open questions at the time

   • Whether ubiquitination of mutant SOD1 is protective or pathogenic was not resolved
   • Structural basis for selective recognition of mutant over wild-type SOD1 is unknown
   • Whether TRAP-delta interaction is functionally relevant remains untested
2. 2008 High

   Demonstrating that HECW1 binds p53 and enhances p53-dependent apoptosis independently of its E3 ligase activity revealed a non-catalytic scaffold function, expanding the gene's mechanistic repertoire beyond ubiquitination.

   Evidence Co-IP, in vitro binding, luciferase reporter, siRNA knockdown, colony formation, and sub-G1 analysis

   PMID:18223681

   Open questions at the time

   • The domain within HECW1 responsible for p53 binding was not mapped
   • Whether endogenous p53 stabilization occurs under physiological conditions is unclear
   • The interaction with RNF43 (PMID:21108931) and its functional significance for p53 regulation need independent validation
3. 2010 Medium

   Transgenic overexpression of HECW1 in mice caused motor dysfunction, spinal cord neuron loss, and microglial activation, providing in vivo evidence that elevated HECW1 is sufficient to drive motor neuron disease.

   Evidence Human HECW1 transgenic mouse model with behavioral, histological, and immunostaining analyses

   PMID:20976258

   Open questions at the time

   • The specific substrate(s) responsible for motor neuron toxicity upon overexpression were not identified
   • Whether endogenous HECW1 levels are elevated in sporadic ALS patients was not tested
   • Single transgenic model without independent replication
4. 2011 High

   Genetic dissection in C. elegans placed HECW-1 upstream of the neuropeptide receptor NPR-1 in a defined sensory neuron pair, establishing a conserved neuronal signaling role and demonstrating cell-type specificity of its function.

   Evidence Neuron-specific rescue, neuronal ablation, and genetic epistasis analysis for pathogen avoidance behavior

   PMID:22089131

   Open questions at the time

   • The direct substrate of HECW-1 in this pathway was not identified
   • Whether this NPR-1-related function is conserved in mammals remains unknown
5. 2019 High

   Identification of TTF1/NKX2.1 K151 as a specific HECW1 ubiquitination site, with a K151R mutant resisting degradation, demonstrated site-resolved substrate targeting and linked HECW1 to thyroid cell biology and cancer.

   Evidence Site-directed mutagenesis, ubiquitination assay, cycloheximide chase, and functional assays in normal thyroid versus carcinoma cells

   PMID:30849519 PMID:31238008

   Open questions at the time

   • Why HECW1 fails to ubiquitinate TTF1 in follicular thyroid carcinoma cells is mechanistically unresolved
   • Whether other E3 ligases also target TTF1 was not addressed
6. 2020 Medium

   Showing that HECW1 ubiquitinates and degrades the polarity protein Scribble under estrogen stimulation extended the ligase's role to epithelial polarity regulation and uterine receptivity.

   Evidence 3D primary endometrial cell culture, ubiquitination assay, siRNA/overexpression, and in vivo tissue correlation

   PMID:31616916

   Open questions at the time

   • Single study without independent replication
   • The ubiquitin chain type and acceptor lysine on Scribble were not determined
7. 2021 Medium

   HECW1-mediated ubiquitination and degradation of Smad4 in NSCLC cells linked the ligase to TGF-β pathway suppression and pro-tumorigenic phenotypes, broadening its substrate repertoire to a major tumor suppressor.

   Evidence Overexpression/knockdown, Co-IP, ubiquitination assay, MG-132 rescue, migration/invasion assays in NSCLC lines

   PMID:33529121

   Open questions at the time

   • Single study without independent confirmation
   • The specific lysine site(s) on Smad4 targeted by HECW1 were not mapped
8. 2023 Medium

   Demonstrating that HECW1 overexpression causes cytoplasmic mislocalization of TDP-43 and neuronal death linked the ligase mechanistically to TDP-43 proteinopathy, a hallmark of ALS/FTD.

   Evidence Immunofluorescence and overexpression with TDP-43 localization and cell death readouts in neurons

   PMID:36674783

   Open questions at the time

   • Whether TDP-43 is a direct ubiquitination substrate of HECW1 was not tested
   • The causal chain between HECW1 overexpression and TDP-43 mislocalization is undefined
   • Single study without independent replication
9. 2024 Medium

   Multiple substrate discoveries in 2024 (DVL1 driving Wnt suppression; HIPK2 driving AKT/EMT activation) and a knockout mouse revealing learning/memory deficits and astrocyte expansion consolidated HECW1's roles as a multi-pathway signaling regulator in both cancer and neuronal function.

   Evidence Co-IP/ubiquitination assays with in vivo xenograft (DVL1, HIPK2); Nedl1 KO mouse with Barnes maze, histology, metabolomics

   PMID:38266865 PMID:39424023 PMID:39615883

   Open questions at the time

   • How HECW1 achieves substrate selectivity among its many targets is structurally unresolved
   • Whether learning deficits in KO mice result from loss of a specific substrate or cumulative pathway dysregulation is unknown
   • The significance of altered amino acid metabolism (proline/tryptophan) in the KO brain is mechanistically unexplained
10. 2025 Medium

    Site-specific ubiquitination of NRG2 at K223 by HECW1, facilitated by NDRG1, and suppression of autophagy-mediated EGFR TKI resistance demonstrated a new role in drug resistance through receptor tyrosine kinase signaling.

    Evidence Co-IP, ubiquitination assay with lysine-site identification, RNA-seq, and in vivo PDX model in NSCLC

    PMID:41193668

    Open questions at the time

    • Single study; independent validation needed
    • Whether NDRG1 acts as a scaffold or modifies HECW1 activity is not resolved

• A structural model of HECW1's HECT domain and its substrate-recognition determinants is lacking, leaving the basis for its unusually broad substrate specificity unresolved.
• No crystal or cryo-EM structure of HECW1 exists
• Ubiquitin chain-type preference (K48 vs K63 vs other) has not been systematically characterized across substrates
• Physiological regulation of HECW1 expression and activity (post-translational modifications, interacting E2s) is largely undefined