ENO3

ENO3 (β-enolase) is a muscle-enriched glycolytic enzyme whose expression and activity drive glycolytic flux across multiple metabolic and oncologic contexts (PMID:35477821). Its skeletal-muscle transcription is governed by an intronic enhancer (intron 1, +504 to +637) in which MEF-2 binds an A/T-rich box and a ubiquitous factor binds a G-rich box, with both elements required for full enhancer activity (PMID:7565752). ENO3 abundance is set by layered post-transcriptional and post-translational control: NSUN5-dependent m5C modification stabilizes ENO3 mRNA to support the Warburg effect in renal carcinoma (PMID:36915728), miR-34a directly targets ENO3 mRNA to suppress it and impair hepatic insulin signaling (PMID:37960269), and CSN5 stabilizes ENO3 protein by limiting its ubiquitin-mediated proteasomal degradation (PMID:41524948). Functionally, ENO3 enhances glycolysis to promote colorectal cancer proliferation and migration (PMID:35477821) and mediates the pro-glycolytic, anti-EMT oncogenic program downstream of CSN5 (PMID:41524948), yet in hepatocellular carcinoma it suppresses proliferation, migration, and invasion by inhibiting Wnt/β-catenin signaling (PMID:35004693). In hepatic lipid disease, ENO3 negatively regulates ferroptosis—elevating GPX4 and SLC7A11—and promotes lipid accumulation, partly through a physical interaction with PKM2 (PMID:33987359, PMID:40400308). A lower-confidence finding links ENO3 to iron homeostasis via an ENO3–IRP1 axis in colonic epithelium (PMID:37006994).

1. 1995 High

   Established how ENO3 achieves muscle-specific transcription, resolving the cis-regulatory and trans-acting basis of its tissue-restricted expression.

   Evidence Deletion/CAT reporter assays, EMSA, DNase I footprinting, and site-directed mutagenesis in C2C12 myogenic cells

   PMID:7565752

   Open questions at the time

   • Identity of the ubiquitous G-box-binding factor not determined
   • Does not connect transcriptional control to enzymatic or metabolic output
2. 2021 Medium

   Showed ENO3 acts beyond glycolysis as a negative regulator of ferroptosis and a promoter of lipid accumulation in fatty liver disease, linking it to GPX4.

   Evidence Gain/loss-of-function in MCD-diet NASH mice and HFFA-treated L02 hepatocytes with ferroptosis and Oil Red O readouts

   PMID:33987359

   Open questions at the time

   • Mechanism connecting ENO3 to GPX4 not defined
   • Whether the effect requires enolase catalytic activity untested
3. 2021 Medium

   Revealed a context-dependent tumor-suppressive role for ENO3 in HCC via Wnt/β-catenin inhibition, contrasting with its pro-glycolytic oncogenic roles elsewhere.

   Evidence Gain/loss-of-function in HCC cell lines with proliferation/migration/invasion assays, xenografts, and Wnt/EMT Western blots

   PMID:35004693

   Open questions at the time

   • Molecular link between ENO3 and Wnt/β-catenin components unresolved
   • Reconciliation with pro-tumor glycolytic roles in other cancers not addressed
4. 2022 Medium

   Demonstrated that ENO3's pro-tumor effect operates through enhanced glycolytic flux, anchoring its oncogenic function to its metabolic activity.

   Evidence Gain/loss-of-function in CRC cell lines with RNA-seq, ATP, and lactate assays

   PMID:35477821

   Open questions at the time

   • Does not identify upstream regulators of ENO3 in CRC
   • Direct enzymatic contribution versus indirect transcriptional effect not separated
5. 2023 Medium

   Identified two opposing modes of ENO3 expression control—NSUN5-mediated m5C mRNA stabilization and miR-34a-mediated repression—defining post-transcriptional setpoints for ENO3 in cancer and metabolic disease.

   Evidence NSUN5 and miR-34a perturbation with metabolic/insulin readouts; ENO3 rescue and NAFLD patient tissue validation

   PMID:36915728 PMID:37960269

   Open questions at the time

   • Direct m5C mapping on ENO3 transcript not shown
   • Whether both regulators act in the same tissues unknown
6. 2023 Low

   Proposed an ENO3–IRP1 axis controlling cellular iron levels and ferroptosis in colonic epithelium, extending ENO3 function into iron homeostasis.

   Evidence DSS colitis model, RNA-seq, pharmacological modulation by kumatakenin, and molecular docking

   PMID:37006994

   Open questions at the time

   • ENO3–IRP1 physical interaction not directly validated
   • Docking predictions (Thr208/Val206/Pro203) computational only
   • Causality of the axis not established by direct perturbation of IRP1
7. 2025 Medium

   Provided direct physical evidence for an ENO3–PKM2 complex driving ferroptosis suppression and lipid accumulation in hepatocytes, mechanistically linking ENO3 to a second glycolytic enzyme.

   Evidence Reciprocal Co-IP, immunofluorescence co-localization, and PKM2 siRNA rescue in FFA-treated THLE-2 cells and MASLD rat liver

   PMID:40400308

   Open questions at the time

   • Interaction interface and stoichiometry undefined
   • Whether the complex alters enzymatic activity of either partner untested
8. 2026 Medium

   Established post-translational stabilization of ENO3 by CSN5 against ubiquitin-mediated degradation as a mechanism placing ENO3 downstream of an oncogenic regulator.

   Evidence Proteomic profiling, ubiquitination/stability analysis, and ENO3-silencing rescue of CSN5 phenotype in cervical cancer in vitro and in vivo

   PMID:41524948

   Open questions at the time

   • E3 ligase targeting ENO3 not identified
   • Whether CSN5 acts directly or via deneddylation/CSN complex unclear

• How ENO3's canonical enolase catalysis is mechanistically coupled to its disparate non-glycolytic roles (ferroptosis, Wnt signaling, iron homeostasis) across tissues remains unresolved.
• No structural model linking catalytic and moonlighting functions
• Context-dependence (tumor-suppressive in HCC vs pro-tumor in CRC) not mechanistically explained
• Direct demonstration that catalytic activity is dispensable for ferroptosis/Wnt effects is absent