Affinage

DDHD2

Triacylglycerol hydrolase DDHD2 · UniProt O94830

Length
711 aa
Mass
81.0 kDa
Annotated
2026-06-09
26 papers in source corpus 16 papers cited in narrative 16 extracted findings
Cross-family judge vs UniProt: Affinage preferred faithfulness: 6/7 claims corpus-supported (86%)

Mechanistic narrative

Synthesis pass · prose summary of the discoveries below

DDHD2 is a brain-enriched serine lipase that serves as the principal neuronal triacylglycerol and diacylglycerol hydrolase, coupling lipid droplet catabolism to neuronal energy metabolism and synaptic function (PMID:25267624, PMID:27198176, PMID:41028912). Genetic ablation in mice causes CNS-selective accumulation of triglycerides and neuronal lipid droplets, and recombinant enzyme directly hydrolyzes TAG; a selective inhibitor reproduces the brain lipid phenotype in wild-type animals (PMID:25267624). Beyond TAG, DDHD2 preferentially acts on diacylglycerol with polyunsaturated sn-2 chains, generating 2-arachidonoylglycerol, and exhibits transacylase activity that remodels TAG acyl chains, an activity dependent on an amphipathic helix required for lipid droplet binding (PMID:27198176, PMID:41264248). The activity-dependent release of long-chain saturated free fatty acids by DDHD2 fuels mitochondrial β-oxidation and ATP synthesis, and saturated fatty acyl-CoA supplementation rescues the respiratory, trafficking, and synaptic defects of DDHD2-null neurons (PMID:41028912). DDHD2 promotes lipophagy through two LIR motifs that bind LC3 and GABARAP ATG8-family proteins, enhancing colocalization of LC3B with lipid droplets (PMID:38332048), and its binding to STXBP1 directs plasma-membrane targeting and saturated FFA generation required for memory (PMID:38316990). Loss of lipase activity decreases cardiolipin, raises reactive oxygen species, and triggers age-dependent motor neuron apoptosis, with catalytically dead and disease mutants failing to rescue (PMID:30038238). DDHD2 additionally mediates a COPI- and Rab6-independent Golgi-to-ER retrograde transport pathway (PMID:19632984), and disease-associated mutations that disrupt its DDHD/SAM domains and phospholipase activity cause the SPG54 form of hereditary spastic paraplegia (PMID:23176823, PMID:25417924, PMID:29278326).

Mechanistic history

Synthesis pass · year-by-year structured walk · 14 steps
  1. 2009 High

    Established the first cellular function for DDHD2 by showing it operates in a defined membrane-trafficking route, before any lipase role was known.

    Evidence RNAi knockdown with live imaging and orthogonal retrograde/anterograde transport assays in cultured cells

    PMID:19632984

    Open questions at the time
    • Did not connect transport function to lipase activity
    • Mechanism of how DDHD2 drives retrograde transport unresolved
    • No substrate identified at this stage
  2. 2012 Medium

    Linked DDHD2 to human disease and synaptic function by tying DDHD-domain mutations to SPG54 and showing ortholog loss reduces synaptic active zones.

    Evidence Human mutation identification plus Drosophila ortholog RNAi with synapse morphology analysis

    PMID:23176823

    Open questions at the time
    • No biochemical reconstitution of mutant enzyme activity
    • Connection between synaptic phenotype and lipid metabolism unestablished
  3. 2014 High

    Defined DDHD2's core enzymatic identity as the principal brain TAG hydrolase, explaining the CNS-selective lipid accumulation in disease.

    Evidence DDHD2 KO mice, lipidomics, recombinant TAG hydrolase assay, and selective inhibitor pharmacology

    PMID:25267624 PMID:25417924

    Open questions at the time
    • Did not resolve preferred physiological substrate (TAG vs DAG)
    • Downstream metabolic consequence of accumulation not yet defined
  4. 2016 High

    Refined substrate specificity, showing DDHD2 acts preferentially as a diacylglycerol lipase generating the endocannabinoid 2-AG, not solely a TAG hydrolase.

    Evidence Purified recombinant enzyme kinetics, LC-MS substrate profiling, and 2-AG quantification in transfected cells

    PMID:27198176

    Open questions at the time
    • Reconciliation with TAG-hydrolase role in vivo incomplete
    • Physiological relevance of 2-AG production in neurons untested here
  5. 2017 High

    Connected disease mutations mechanistically to enzyme dysfunction and lipid droplet protection, and catalogued the protein content of pathological LDs.

    Evidence In vitro TAG hydrolase assays of HSP mutants, cell-based LD accumulation assays, and KO brain LD proteomics

    PMID:29278326

    Open questions at the time
    • Functional role of CNS-enriched LD-associated proteins unexplored
    • Mechanism of LD targeting not defined
  6. 2018 High

    Demonstrated that DDHD2 lipase activity protects mitochondria and motor neurons, linking lipid hydrolysis to redox/cardiolipin homeostasis and cell survival.

    Evidence KO mice with ROS and cardiolipin measurements and rescue by wild-type versus catalytically dead/HSP-mutant DDHD2

    PMID:30038238

    Open questions at the time
    • Mechanistic link from lipase activity to cardiolipin content unresolved
    • Whether ROS rise is cause or consequence of LD accumulation unclear
  7. 2020 Medium

    Revealed a non-redundant, paralog-distinct role for DDHD2 in neurite outgrowth, separating it functionally from DDHD1.

    Evidence siRNA depletion with neurite length measurement in SH-SY5Y and PC12 cells

    PMID:32850804

    Open questions at the time
    • Molecular basis of neurite phenotype not defined
    • Single readout per condition
  8. 2023 Medium

    Showed DDHD2's lipolytic role is cell-type-specific, acting as a dual TAG/DAG hydrolase in neurons but only downstream of ATGL on DAG in neuroblastoma cells.

    Evidence In vitro acylglycerol hydrolase assays and ATGL/DDHD2 modulation in primary neurons and neuroblastoma cells

    PMID:37832604

    Open questions at the time
    • Determinants of lipolysome configuration unknown
    • In vivo relevance of cell-type differences untested
  9. 2024 High

    Identified the lipophagy arm of DDHD2 function through direct LIR-mediated binding to ATG8 proteins, complementing its direct hydrolase activity in LD elimination.

    Evidence AP-MS, LIR motif mutagenesis, and LC3B/LD colocalization with LD quantification

    PMID:38332048

    Open questions at the time
    • Relative contribution of direct hydrolysis versus lipophagy in vivo unquantified
    • Regulation of LIR-mediated recruitment unknown
  10. 2024 High

    Established a synaptic-protein partner (STXBP1) that controls DDHD2 plasma-membrane targeting and links its saturated FFA output to memory.

    Evidence Pulldown-MS, STXBP1 KO and haploinsufficient models, DDHD2 KO mice, lipidomics, and behavioral memory assays

    PMID:38316990

    Open questions at the time
    • Structural basis of DDHD2-STXBP1 interaction undefined
    • How plasma-membrane targeting alters FFA release mechanism unclear
  11. 2024 Medium

    Tested whether DDHD2-driven LD accumulation engages alpha-synuclein pathology, returning an informative negative result.

    Evidence Pharmacological DDHD2 inhibition in primary rat cortical neurons with alpha-synuclein blots, solubility, and colocalization

    PMID:39853540

    Open questions at the time
    • Negative result limited to acute inhibition
    • Does not exclude chronic or in vivo synuclein effects
  12. 2024 Low

    Proposed a link between DDHD2 and the Nrf2/GPX4 ferroptosis-protective pathway in endothelial cells.

    Evidence siRNA knockdown, single co-immunoprecipitation, GPX4/Nrf2 western blots, and lipid peroxidation assay

    PMID:39062593

    Open questions at the time
    • Single Co-IP without reciprocal validation
    • No demonstration of direct binding or mechanism
    • Relevance outside endothelial cells untested
  13. 2025 High

    Mechanistically completed the metabolic picture: DDHD2 releases long-chain saturated FFAs to fuel mitochondrial beta-oxidation and ATP synthesis, with acyl-CoA rescue restoring multiple neuronal defects.

    Evidence KO neurons with Seahorse respiration, ATP and glycolysis assays, mitochondrial import inhibition, and saturated fatty acyl-CoA rescue

    PMID:41028912

    Open questions at the time
    • How activity-dependent FFA release is triggered remains unresolved
    • Coupling between LD pool and mitochondrial import undefined
  14. 2025 High

    Resolved substrate preference and added a transacylase activity for human DDHD2, and identified an amphipathic helix required for LD binding and full activity.

    Evidence Purified recombinant human enzyme assays, substrate profiling, transacylase assays, and amphipathic-helix deletion mutagenesis

    PMID:41264248

    Open questions at the time
    • Structure of the LD-bound enzyme unsolved
    • Physiological role of transacylase remodeling in vivo untested

Open questions

Synthesis pass · forward-looking unresolved questions
  • How DDHD2's distinct activities — Golgi-to-ER transport, direct acylglycerol hydrolysis, transacylation, lipophagy, and STXBP1-dependent membrane targeting — are integrated and regulated within a single neuron remains unresolved.
  • No structural model of the full-length enzyme on membranes
  • Regulatory triggers for activity-dependent FFA release unknown
  • Mechanistic relationship between transport and lipase functions undefined

Mechanism profile

Synthesis pass · controlled-vocabulary classification · explore literature graph →
Molecular activity
GO:0016787 hydrolase activity 3 GO:0008289 lipid binding 1 GO:0016740 transferase activity 1
Localization
GO:0005811 lipid droplet 3 GO:0005794 Golgi apparatus 1 GO:0005829 cytosol 1 GO:0005886 plasma membrane 1
Pathway
R-HSA-1430728 Metabolism 3 R-HSA-1643685 Disease 2 R-HSA-5653656 Vesicle-mediated transport 1 R-HSA-9612973 Autophagy 1
Partners
GABARAPMAP1LC3BSTXBP1

Evidence

Reading pass · 16 per-paper findings extracted from the source corpus
Year Finding Method Journal Conf PMIDs
2009 iPLA1γ/DDHD2 localizes to the cytosol, cis-Golgi, and ERGIC, and mediates a COPI- and Rab6-independent retrograde membrane transport pathway from the Golgi complex to the ER; RNAi knockdown delayed BFA-induced Golgi-to-ER transfer and cholera toxin B retrograde transport without affecting anterograde VSVGts045 transport or ERGIC-53/Shiga toxin recycling. RNAi knockdown, time-lapse microscopy, GFP-fusion localization, BFA assay, cholera toxin B retrograde transport assay The Journal of biological chemistry High 19632984
2012 Mutations in DDHD2 that affect the DDHD domain (required for phospholipase activity) cause SPG54; knockdown of the Drosophila ortholog reduced active zones at synaptic terminals, implicating DDHD2 in synaptic function. Drosophila Ddhd RNAi knockdown with synapse morphology analysis; human genetics (mutation identification) American journal of human genetics Medium 23176823
2014 DDHD2 is the principal triglyceride (triacylglycerol/TAG) hydrolase in the brain; DDHD2−/− mice accumulate TAGs selectively in the CNS (not peripheral tissues), with lipid droplets localizing to neuronal intracellular compartments; recombinant DDHD2 displays TAG hydrolase activity in vitro; a selective in vivo DDHD2 inhibitor also causes brain TAG accumulation in wild-type mice. DDHD2−/− mouse generation, mass spectrometry-based lipidomics, in vitro TAG hydrolase assay with recombinant enzyme, selective inhibitor pharmacology, electron microscopy Proceedings of the National Academy of Sciences of the United States of America High 25267624
2015 A truncating mutation (p.R287X) in DDHD2 removes the SAM and DDHD domains, which are crucial for phosphoinositide binding and phospholipase activity, confirming these domains are essential for DDHD2 function. Exome sequencing, homozygosity mapping, domain analysis of truncated protein BMC research notes Low 26113134
2014 A DDHD2 missense mutation (identified in late-onset spastic ataxia patients) caused a marked reduction in phospholipase A1 activity, and patients showed abnormal lipid peak on MRS consistent with lipid accumulation. Phospholipase A1 activity assay of mutant DDHD2, patient MR spectroscopy Scientific reports Medium 25417924
2016 Recombinant rat DDHD2 functions preferentially as a diacylglycerol (DG) lipase; kcat/Km for DG(18:0/20:4) was much higher than for TAG or phosphatidic acid; DDHD2 shows preference for DG substrates with polyunsaturated fatty acids at the sn-2 position; DDHD2-expressing CHO cells showed elevated 2-arachidonoylglycerol (2-AG) levels, supporting a DG lipase role in vivo. Enzymatic assay with purified recombinant protein, LC-MS substrate specificity profiling, GC-MS/MS quantification of 2-AG in transfected CHO cells Journal of biochemistry High 27198176
2017 HSP-related mutations in DDHD2 disrupt its triglyceride hydrolase activity in vitro and impair DDHD2's capacity to protect cells from lipid droplet accumulation upon free fatty acid exposure; lipid droplets in DDHD2−/− brains contain both known LD-associated proteins and CNS-enriched proteins including several with links to neurological disease. In vitro TAG hydrolase assay of HSP mutants, cell-based LD accumulation assay with free fatty acid treatment, DDHD2 inhibitor, LD proteomics from KO brain tissue Biochemistry High 29278326
2018 DDHD2 ablation causes age-dependent apoptosis of motor neurons in mouse spinal cord; DDHD2 KO cells show decreased cardiolipin content and increased reactive oxygen species (ROS); ROS increase was reversed by wild-type DDHD2 re-expression but not by catalytically inactive DDHD2, HSP-associated DDHD2 mutants, or DDHD1, establishing that DDHD2 lipase activity is required for mitochondrial protection. DDHD2−/− mice, ROS measurement (chemical and probe-based), cardiolipin quantification, rescue by wild-type vs. active-site or HSP mutant DDHD2 re-expression, apoptosis assays Cell death & disease High 30038238
2020 DDHD2 depletion prevents neurite elongation in SH-SY5Y and PC12 cells (opposite to DDHD1 depletion, which promotes elongation), indicating a distinct and non-redundant role for DDHD2 in neurite outgrowth regulation. siRNA depletion, neurite length measurement in SH-SY5Y and PC12 cells Frontiers in cell and developmental biology Medium 32850804
2023 In primary cortical neurons, DDHD2 functions as a dual TAG/DAG hydrolase and complements ATGL-dependent TAG hydrolysis; in neuroblastoma cells, DDHD2 acts exclusively downstream of ATGL on DAG isomers but is dispensable for TAG hydrolysis, revealing cell-type-specific lipolysome configurations. In vitro acylglycerol hydrolase assays, neutral lipid hydrolase activity measurements in neuroblastoma cells and brain tissue, primary cortical neuron studies with DDHD2 and ATGL modulation Journal of lipid research Medium 37832604
2024 DDHD2 interacts with multiple ATG8-family proteins (LC3s and GABARAPs) via two authentic LIR motifs; this interaction promotes lipophagy, as DDHD2 enhances colocalization of LC3B with lipid droplets; LC3/GABARAP-binding capacity and canonical autophagy both contribute to DDHD2's LD-eliminating activity. Affinity purification-mass spectrometry (AP-MS), mutational analysis of LIR motifs, LC3B/LD colocalization assays, LD quantification upon DDHD2 overexpression/deficiency, LD·ATTEC compound rescue Cell death and differentiation High 38332048
2024 DDHD2 binds the synaptic protein STXBP1 (identified by pulldown-mass spectrometry); STXBP1 controls targeting of DDHD2 to the plasma membrane and generation of saturated free fatty acids in the brain; genetic ablation of DDHD2 dramatically reduces saturated FFA responses to memory acquisition and impairs reward-based and spatial memory performance. Pulldown-mass spectrometry, STXBP1/2 KO neurosecretory cells, haploinsufficient STXBP1+/− mouse model, DDHD2 KO mice, lipidomics, behavioral memory assays The EMBO journal High 38316990
2024 DDHD2 knockdown in human artery endothelial cells reduces GPX4 and Nrf2 protein levels and increases lipid peroxidation; co-immunoprecipitation indicates a physical interaction between DDHD2 and Nrf2, suggesting DDHD2 regulates the Nrf2/GPX4 ferroptosis-protective pathway. DDHD2 siRNA knockdown, co-immunoprecipitation, western blot for GPX4/Nrf2, lipid peroxidation assay Biomolecules Low 39062593
2025 Recombinant human DDHD2 preferentially hydrolyzes DAG over phospholipids and shows slight preference for DAG over TAG; DDHD2 also exhibits transacylase activity, transferring acyl chains from TAGs to DAGs and monoacylglycerols to remodel TAG acyl chains; a predicted hydrophobic amphipathic helix is essential for lipid droplet binding in vitro and in cells and is required for full enzymatic activity and TAG acyl-chain remodeling. In vitro enzyme assays with recombinant human DDHD2, substrate specificity profiling, transacylase activity assay, amphipathic helix deletion mutagenesis, in vitro LD-binding assay, cell-based LD localization Proceedings of the National Academy of Sciences of the United States of America High 41264248
2025 DDHD2-dependent release of long-chain saturated free fatty acids (myristic, palmitic, stearic acids) in an activity-dependent manner supports mitochondrial β-oxidation and ATP synthesis in neurons; genetic ablation of Ddhd2 impairs mitochondrial respiration and ATP production despite increased glycolysis; saturated fatty acyl-CoA supplementation rescues mitochondrial energy production, membrane trafficking, synaptic function, and protein homeostasis defects in Ddhd2 KO neurons. Ddhd2 KO neurons, Seahorse mitochondrial respiration assay, ATP measurement, glycolysis assay, mitochondrial fatty acid import inhibition, saturated fatty acyl-CoA rescue experiments Nature metabolism High 41028912
2025 Acute DDHD2 inhibition (by compound KLH45) causing lipid droplet accumulation in primary rat cortical neurons did not affect total α-synuclein levels, phosphoserine-129 status, or solubility, and no colocalization between LDs and α-synuclein was detected. DDHD2 inhibitor KLH45 in primary rat cortical neurons, western blot for α-synuclein and pSer129, detergent solubility fractionation, immunofluorescence colocalization Metabolic brain disease Medium 39853540

Source papers

Stage 0 corpus · 26 papers · ranked by NIH iCite citations
Year Title Journal Citations PMID
2012 Mutations in DDHD2, encoding an intracellular phospholipase A(1), cause a recessive form of complex hereditary spastic paraplegia. American journal of human genetics 150 23176823
2014 The hereditary spastic paraplegia-related enzyme DDHD2 is a principal brain triglyceride lipase. Proceedings of the National Academy of Sciences of the United States of America 146 25267624
2020 Common genetic risk variants identified in the SPARK cohort support DDHD2 as a candidate risk gene for autism. Translational psychiatry 73 32747698
2013 Mutations in phospholipase DDHD2 cause autosomal recessive hereditary spastic paraplegia (SPG54). European journal of human genetics : EJHG 62 23486545
2013 Mutations in CYP2U1, DDHD2 and GBA2 genes are rare causes of complicated forms of hereditary spastic paraparesis. Journal of neurology 61 24337409
2017 Functional Contribution of the Spastic Paraplegia-Related Triglyceride Hydrolase DDHD2 to the Formation and Content of Lipid Droplets. Biochemistry 47 29278326
2009 Intracellular phospholipase A1gamma (iPLA1gamma) is a novel factor involved in coat protein complex I- and Rab6-independent retrograde transport between the endoplasmic reticulum and the Golgi complex. The Journal of biological chemistry 42 19632984
2021 Circular RNA circRUNX1 promotes papillary thyroid cancer progression and metastasis by sponging MiR-296-3p and regulating DDHD2 expression. Cell death & disease 39 33479208
2018 Loss of DDHD2, whose mutation causes spastic paraplegia, promotes reactive oxygen species generation and apoptosis. Cell death & disease 31 30038238
2014 Late-onset spastic ataxia phenotype in a patient with a homozygous DDHD2 mutation. Scientific reports 28 25417924
2024 The DDHD2-STXBP1 interaction mediates long-term memory via generation of saturated free fatty acids. The EMBO journal 22 38316990
2015 miR-503 represses human cell proliferation and directly targets the oncogene DDHD2 by non-canonical target pairing. BMC genomics 20 25653011
2015 Truncating mutation in intracellular phospholipase A₁ gene (DDHD2) in hereditary spastic paraplegia with intellectual disability (SPG54). BMC research notes 19 26113134
2025 DDHD2 provides a flux of saturated fatty acids for neuronal energy and function. Nature metabolism 18 41028912
2024 DDHD2, whose mutations cause spastic paraplegia type 54, enhances lipophagy via engaging ATG8 family proteins. Cell death and differentiation 16 38332048
2016 Enzymatic characterization of recombinant rat DDHD2: a soluble diacylglycerol lipase. Journal of biochemistry 16 27198176
2023 Cooperative lipolytic control of neuronal triacylglycerol by spastic paraplegia-associated enzyme DDHD2 and ATGL. Journal of lipid research 13 37832604
2024 Radiation-Induced Endothelial Ferroptosis Accelerates Atherosclerosis via the DDHD2-Mediated Nrf2/GPX4 Pathway. Biomolecules 10 39062593
2023 Biallelic DDHD2 mutations in patients with adult-onset complex hereditary spastic paraplegia. Annals of clinical and translational neurology 6 37420318
2020 DDHD1, but Not DDHD2, Suppresses Neurite Outgrowth in SH-SY5Y and PC12 Cells by Regulating Protein Transport From Recycling Endosomes. Frontiers in cell and developmental biology 5 32850804
2024 DDHD2 promotes lipid droplet catabolism by acting as a TAG lipase and a cargo receptor for lipophagy. Autophagy 4 38909316
2025 DDHD2 possesses both lipase and transacylase capacities that remodel triglyceride acyl chains. Proceedings of the National Academy of Sciences of the United States of America 3 41264248
2022 Case report: Novel compound heterozygous missense mutations in the DDHD2 gene in a Chinese patient associated with spastic paraplegia type 54. Frontiers in pediatrics 3 36090575
2020 Coinheritance of novel mutations in NAGLU causing mucopolysaccharidosis type IIIB and in DDHD2 causing spastic paraplegia54 in a Turkish family. Journal of clinical neuroscience : official journal of the Neurosurgical Society of Australasia 2 33246910
2025 Acute lipid droplet accumulation induced by the inhibition of the phospholipase DDHD2 does not affect the level, solubility, or phosphoserine-129 status of α-synuclein. Metabolic brain disease 0 39853540
2025 DDHD2 possesses both lipase and transacylase capacities that remodel triglyceride acyl chains. bioRxiv : the preprint server for biology 0 41040251

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