ALDH1B1

ALDH1B1 is a mitochondrial NAD+-dependent aldehyde dehydrogenase that detoxifies reactive aldehydes and serves as a determinant of progenitor cell identity, antiviral immunity, and tumorigenesis (PMID:7779080, PMID:31548432, PMID:38194477). The enzyme oxidizes short-chain aldehydes including acetaldehyde and propionaldehyde, and purified recombinant protein also metabolizes nitroglycerin, all-trans retinaldehyde, and the lipid-peroxidation product 4-hydroxynonenal; naturally occurring human variants differ in catalytic competence, with the A86V (ALDH1B1*2) substitution abolishing activity by impairing NAD+ binding (PMID:7779080, PMID:25413692). In vivo, ALDH1B1-mediated acetaldehyde clearance protects epithelial tissue: Aldh1b1-knockout mice accumulate blood and plasma acetaldehyde after ethanol exposure and develop aggravated intestinal hyperproliferation and tumor features, and combined loss with mismatch-repair deficiency drives colonic adenoma formation, establishing the enzyme as a barrier against acetaldehyde-induced DNA damage (PMID:26086111, PMID:28026023, PMID:37395714). ALDH1B1 marks self-renewing centroacinar pancreatic progenitors and is genetically required for both progenitor maintenance and KrasG12D-driven pancreatic oncogenesis, and its support of colon cancer spheroid and xenograft growth is accompanied by activation of Wnt/β-catenin, Notch, and PI3K/Akt signaling (PMID:25950950, PMID:31548432, PMID:23142317). In innate immunity, ALDH1B1 is an interferon-stimulated gene that interacts with the MAVS transmembrane domain to promote MAVS prion-like aggregation and IFN-β production, restricting RNA virus replication (PMID:38194477). Its abundance and activity are controlled at multiple levels: transcriptionally by NR5A2 (loss of which elevates ROS and triggers pyroptosis), post-translationally by AMBRA1/TRAF6-mediated K27/K33-linked noncanonical ubiquitination that constrains its oligomerization, and translation-independently by EIF4E, whose repression of ALDH1B1 in mitochondria sensitizes cells to ferroptosis by permitting 4-HNE accumulation (PMID:36274088, PMID:34769507, PMID:39438459).

1. 1995 Medium

   Established that ALDH1B1 (ALDH5) is a catalytically active, mitochondrially enriched enzyme distinct in cofactor and inhibitor profile, answering whether the gene encodes a functional aldehyde dehydrogenase.

   Evidence Enzymatic assays, subcellular fractionation, and cofactor/inhibitor testing in HuH7 hepatoma extracts

   PMID:7779080

   Open questions at the time

   • Substrate range tested only for short-chain aldehydes
   • No recombinant protein or structural data
2. 2012 Medium

   Defined the developmental context of ALDH1B1 by showing its expression in multipotent pancreatic progenitors under Pdx1 and Ngn3 control and that ALDH activity is needed for progenitor maintenance.

   Evidence ISH, immunofluorescence, and explant culture with ALDH inhibitor in developing pancreas

   PMID:23142317

   Open questions at the time

   • Pharmacological inhibitor not ALDH1B1-selective
   • Mechanism linking enzyme activity to progenitor state unknown
3. 2012 Low

   Raised the possibility that ALDH1B1 activity is modulated by heterotetramerization with ALDH2, offering an explanation for absent compensatory activity in ALDH2*2 individuals.

   Evidence Computational protein-protein interaction modeling and sequence analysis

   PMID:23247008

   Open questions at the time

   • Computational prediction only; heterotetramer formation not experimentally validated
   • No functional dominant-negative data
4. 2014 High

   Defined the substrate and variant landscape by showing recombinant ALDH1B1 metabolizes nitroglycerin, retinaldehyde, and 4-HNE, and that polymorphic variants differ in catalytic competence.

   Evidence In vitro assays with purified recombinant protein and polymorphic variants plus molecular modeling

   PMID:25413692

   Open questions at the time

   • Physiological relevance of each substrate not established in vivo
   • No crystal structure to confirm modeled binding modes
5. 2015 High

   Demonstrated in vivo that ALDH1B1 metabolizes acetaldehyde and links it to glucose homeostasis, moving beyond in vitro activity to organismal function.

   Evidence Global Aldh1b1 knockout mice with ethanol pharmacokinetics and fasting glucose measurement

   PMID:26086111

   Open questions at the time

   • Mechanism connecting ALDH1B1 to glucose regulation unresolved
   • Tissue responsible for acetaldehyde clearance not pinpointed
6. 2015 Medium

   Established a pro-tumorigenic role in colon cancer, showing ALDH1B1 knockdown reduces tumor growth and downregulates Wnt/β-catenin, Notch, and PI3K/Akt signaling.

   Evidence shRNA knockdown, spheroid and xenograft assays, signaling pathway and promoter reporter analysis in SW480 cells

   PMID:25950950

   Open questions at the time

   • Whether catalytic activity drives signaling not addressed
   • Direct molecular link between enzyme and Wnt/Notch/PI3K unknown
7. 2017 High

   Showed that ALDH1B1-mediated acetaldehyde detoxification protects the intestinal epithelium, as its loss aggravates ethanol-induced hyperproliferation and tumor features.

   Evidence Long-term ethanol drinking model in Aldh1b1-knockout mice with histopathology and DNA damage quantification

   PMID:28026023

   Open questions at the time

   • Cooperating genetic events not yet defined in this study
   • Cell-of-origin within the epithelium not resolved
8. 2019 High

   Provided genetic proof that Aldh1b1-expressing centroacinar cells are pancreatic progenitors and that ALDH1B1 is required for KrasG12D-driven pancreatic oncogenesis.

   Evidence Lineage tracing, Aldh1b1 KO crossed to KrasG12D model, scRNA-seq, and organoid assays

   PMID:31548432

   Open questions at the time

   • Mechanism by which ALDH1B1 enables Kras transformation not defined
   • Role of catalytic activity versus protein presence unclear
9. 2019 Medium

   Connected methyltransferase signaling to ALDH1B1 in endocrine differentiation, showing Aldh1b1 is required for methyltransferase-inhibitor effects on Ngn3 and endocrine specification.

   Evidence Reporter-based small-molecule screen, pancreas explant culture, and Aldh1b1-null genetic epistasis

   PMID:30681750

   Open questions at the time

   • Methyltransferase target acting upstream unidentified
   • Molecular link between ALDH1B1 and Ngn3 regulation unknown
10. 2021 Medium

    Identified post-translational control of ALDH1B1 via AMBRA1/TRAF6-mediated noncanonical ubiquitination that limits its oligomerization and downstream PTEN/β-catenin signaling.

    Evidence Co-IP, ubiquitination site mutagenesis, self-association assays, and gene expression analysis

    PMID:34769507

    Open questions at the time

    • Functional consequence of altered oligomerization on enzymatic activity not measured
    • Single-lab Co-IP; in vivo relevance untested
11. 2022 High

    Revealed EIF4E as a translation-independent mitochondrial repressor of ALDH1B1 that, by limiting 4-HNE clearance, controls ferroptotic sensitivity.

    Evidence MS-based interactomics, reciprocal Co-IP, genetic KO/overexpression, and ferroptosis assays in vitro and in vivo

    PMID:36274088

    Open questions at the time

    • Mechanism of EIF4E mitochondrial localization to ALDH1B1 unresolved
    • Quantitative contribution of ALDH1B1 to lipid-peroxide pool not defined
12. 2022 High

    Delivered active-site-directed selective inhibitors confirming ALDH1B1 is a druggable cancer dependency and linked its activity to mitochondrial metabolism and ribosomal gene programs.

    Evidence Active-site inhibitor development, proteome-wide selectivity profiling, spheroid/organoid assays, and transcriptomics

    PMID:35788181

    Open questions at the time

    • Direct substrates underlying the dependent transcriptome not identified
    • How enzyme activity shapes ribosomal/metabolic genes unknown
13. 2023 High

    Showed ALDH1B1 acetaldehyde detoxification cooperates with mismatch-repair status, as its loss with Msh2 inactivation and ethanol drives colonic tumorigenesis.

    Evidence Aldh1b1/Msh2 double-knockout mice with ethanol exposure, plasma acetaldehyde measurement, and adenoma quantification

    PMID:37395714

    Open questions at the time

    • Molecular nature of acetaldehyde-induced lesions cooperating with dMMR not detailed
    • Human relevance of the genetic interaction untested
14. 2024 High

    Defined a non-detoxification antiviral function, with ALDH1B1 binding the MAVS transmembrane domain to promote MAVS aggregation and IFN-β signaling that restricts RNA viruses.

    Evidence KO/overexpression, mitochondrial fractionation/imaging, reciprocal Co-IP, MAVS aggregation and IFN-β reporter assays, and in vivo influenza infection

    PMID:38194477

    Open questions at the time

    • Whether catalytic activity is required for MAVS aggregation unresolved
    • Structural basis of the ALDH1B1–MAVS interaction unknown
15. 2024 Medium

    Established transcriptional control of ALDH1B1 by NR5A2 governing ROS levels and pyroptosis in hepatocytes.

    Evidence Hepatocyte-specific Nr5a2 KO mice, isoform reintroduction rescue, ROS and pyroptosis assays, and NF-κB analysis

    PMID:39438459

    Open questions at the time

    • Direct NR5A2 binding at the ALDH1B1 locus not confirmed in this study
    • Substrate basis of ALDH1B1-dependent ROS modulation undefined

• Whether the diverse roles of ALDH1B1 (acetaldehyde detoxification, ferroptosis control, oncogenic signaling, MAVS-dependent antiviral immunity) all depend on its catalytic activity, and what its physiological substrates are in each context, remains unresolved.
• No structure of ALDH1B1 alone or in complex
• Catalysis-versus-scaffold contributions to antiviral and oncogenic roles not dissected
• Endogenous substrate spectrum in each tissue context undefined