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Showing GPAT4 — AGPAT6 is a alias.

GPAT4

Glycerol-3-phosphate acyltransferase 4 · UniProt Q86UL3

Length
456 aa
Mass
52.1 kDa
Annotated
2026-06-10
22 papers in source corpus 13 papers cited in narrative 13 extracted findings
Cross-family judge vs UniProt: Affinage preferred faithfulness: 5/6 claims corpus-supported (83%)

Mechanistic narrative

Synthesis pass · prose summary of the discoveries below

GPAT4 (originally misnamed AGPAT6) is an N-ethylmaleimide-sensitive, endoplasmic reticulum-resident glycerol-3-phosphate acyltransferase that catalyzes the first committed step of de novo glycerolipid synthesis, acylating glycerol-3-phosphate with saturated or unsaturated long-chain acyl-CoAs to generate lysophosphatidic acid and, downstream, phosphatidic acid (PMID:18238778, PMID:18192653, PMID:16449762). Enzymatic activity requires the N-myristoylated adaptor CHP1, which binds and activates GPAT4 at the ER, and is further enhanced by insulin-stimulated Ser/Thr phosphorylation in a PI3K-dependent manner (PMID:30846317, PMID:20181984). The lipid intermediates GPAT4 produces define a metabolic pool distinct from that of GPAT1: GPAT4 governs acylation of exogenous fatty acids in brown adipocytes, such that its loss diverts fatty acids from triacylglycerol storage into β-oxidation, whereas GPAT1 handles de novo synthesized fatty acids in liver (PMID:25918168, PMID:23908354). The phosphatidic acid generated by GPAT4 acts as a signaling lipid that activates mTORC1 (PMID:36398416). GPAT4 transcription is positively controlled by PPARγ and repressed by FXR, coupling its expression to lipid-droplet accumulation in hepatic and secretory cells (PMID:36398416, PMID:41530783). Beyond catalysis, GPAT4 maintains ER homeostasis: its deficiency in endocardial cells provokes ER stress, enhanced ER–mitochondria contact, mtDNA escape, and cGAS-STING-driven type-I interferon signaling that impairs heart development, a defect rescued by ablating cGAS-STING signaling (PMID:40199910). GPAT4 also traffics from the ER to lipid droplets through seipin-containing ER-LD bridges [PMID:bio_10.1101_2024.08.27.610018].

Mechanistic history

Synthesis pass · year-by-year structured walk · 11 steps
  1. 2006 High

    Before its enzymatic identity was known, knockout phenotyping established that this ER-localized protein is essential for milk fat production, pinpointing a physiological role in glycerolipid synthesis.

    Evidence Gene-trap knockout mice with mammary histology, milk lipid analysis, and ER marker co-localization

    PMID:16449762

    Open questions at the time
    • Did not define the biochemical reaction catalyzed
    • Mechanism of lipid-droplet loss in mammary epithelium not resolved
  2. 2008 High

    Resolved the long-standing misannotation by demonstrating the enzyme is a GPAT, not an AGPAT, fixing the first committed step of de novo glycerolipid synthesis as its function.

    Evidence In vitro GPAT/AGPAT assays with purified protein and overexpression, isotope labeling/MS, NEM sensitivity, and KO mouse tissue activity in HEK293/Cos-7 systems

    PMID:18192653 PMID:18238778

    Open questions at the time
    • How GPAT4-initiated intermediates are channeled to distinct cellular pools not yet defined
    • Regulatory inputs unknown
  3. 2010 Medium

    Connected GPAT4 activity to hormonal control by showing insulin stimulates its phosphorylation and activity via PI3K.

    Evidence Phosphorylation assays with insulin/wortmannin and GPAT activity measurement in adipocytes and overexpression systems

    PMID:20181984

    Open questions at the time
    • Specific kinase and phosphosites not identified
    • GPAT4 knockdown alone did not reduce adipocyte GPAT activity, leaving its quantitative contribution to adipogenesis unclear
  4. 2013 High

    Established functional non-redundancy between GPAT isoforms by showing GPAT4, unlike GPAT1, does not channel de novo fatty acids into TAG in liver.

    Evidence Primary hepatocytes from Gpat1-/- and Gpat4-/- mice with de novo and exogenous fatty acid labeling plus in vivo acylcarnitine measurement

    PMID:23908354

    Open questions at the time
    • Structural basis for substrate-pool selectivity unknown
  5. 2015 High

    Defined GPAT4's tissue-specific substrate preference by showing it limits oxidation of exogenous fatty acids in brown adipocytes, complementing the liver finding.

    Evidence Gpat4-/- brown adipocytes with fatty acid incorporation/oxidation assays and metabolic rate measurements

    PMID:25918168

    Open questions at the time
    • How exogenous vs de novo fatty acids are physically segregated to GPAT4 not resolved
  6. 2019 High

    Identified the activating partner of GPAT4, showing N-myristoylated CHP1 binds and is required to drive ER lipid synthesis.

    Evidence CRISPR screens, Co-IP, CHP1 N-myristoylation mutants, lipidomics, and invertebrate validation

    PMID:30846317

    Open questions at the time
    • Structural detail of the CHP1-GPAT4 interface not solved
    • How CHP1 binding alters catalysis mechanistically unclear
  7. 2020 Medium

    Linked GPAT4-produced saturated LPAs at omegasome/MAM contact sites to autophagy regulation, extending its role beyond bulk lipid storage.

    Evidence SCD-knockout VSMC model with lipid metabolite analysis, omegasome imaging, and autophagic flux assays

    PMID:32408172

    Open questions at the time
    • GPAT4 not directly perturbed to confirm causality
    • Single lab; effect on autophagy not validated in other cell types
  8. 2022 Medium

    Defined transcriptional and signaling outputs by showing PPARγ drives GPAT4 expression and that its phosphatidic acid product activates mTORC1.

    Evidence Luciferase reporter promoter mapping, siRNA knockdown, and PA rescue with mTORC1 western blots

    PMID:36398416

    Open questions at the time
    • Direct binding of GPAT4-derived PA to mTORC1 components not shown
    • Single cell context
  9. 2025 High

    Revealed a homeostatic role beyond metabolism by showing GPAT4 loss triggers ER stress, mtDNA escape, and cGAS-STING-driven interferon signaling that disrupts heart development.

    Evidence Gpat4 global and tissue-specific KO mice with ER stress markers, ER-mito contact imaging, mtDNA escape assays, and genetic cGAS-STING rescue

    PMID:40199910

    Open questions at the time
    • How loss of GPAT4 catalysis specifically alters ER membrane lipid composition to provoke stress not defined
    • Whether this pathway operates in non-cardiac tissues unknown
  10. 2025 Low

    Implicated GPAT4-dependent glycerophospholipid accumulation in autophagosome maturation downstream of CPT2 loss in colorectal cancer.

    Evidence CPT2 knockdown with metabolite/transcriptomic analysis and proliferation assays

    PMID:41107458

    Open questions at the time
    • GPAT4 not directly manipulated; role inferred from metabolite changes
    • Causal contribution to autophagy not established
  11. 2026 Medium

    Added a second transcriptional regulator by showing FXR represses GPAT4 to limit hepatic lipid-droplet accumulation.

    Evidence Dual-luciferase reporter, siRNA knockdown, and HFD mouse/HepG2 lipid phenotyping

    PMID:41530783

    Open questions at the time
    • Direct FXR binding element on the GPAT4 promoter not mapped
    • Single lab

Open questions

Synthesis pass · forward-looking unresolved questions
  • The structural basis of GPAT4 catalysis and its activation by CHP1, and the mechanism by which it selectively partitions distinct fatty acid pools across tissues, remain unresolved.
  • No high-resolution structure of GPAT4 or the CHP1-GPAT4 complex
  • Molecular basis for de novo vs exogenous fatty acid channeling unknown
  • Direct mechanism coupling GPAT4 activity to ER membrane homeostasis undefined

Mechanism profile

Synthesis pass · controlled-vocabulary classification · explore literature graph →
Molecular activity
GO:0016740 transferase activity 3
Localization
GO:0005783 endoplasmic reticulum 2 GO:0005811 lipid droplet 1
Partners
CHP1

Evidence

Reading pass · 13 per-paper findings extracted from the source corpus
Year Finding Method Journal Conf PMIDs
2008 AGPAT6 (GPAT4) is a microsomal glycerol-3-phosphate acyltransferase (GPAT), not an AGPAT. Membranes from HEK293 cells overexpressing human AGPAT6 showed higher GPAT activity but not AGPAT activity. Purified AGPAT6 protein possessed GPAT activity. The enzyme is sensitive to N-ethylmaleimide (a sulfhydryl-modifying reagent), is active against both saturated and unsaturated long-chain fatty acyl-CoAs, and overexpression increased lysophosphatidic acid and phosphatidic acid levels. Mammary epithelial cell membranes from Agpat6-deficient mice showed markedly reduced GPAT activity. In vitro GPAT/AGPAT activity assays with purified protein and overexpression in HEK293 cells; siRNA knockdown; [13C7]oleic acid labeling with mass spectrometry; NEM sensitivity assay The Journal of biological chemistry High 18238778
2008 GPAT4 (misnamed Agpat6) encodes an NEM-sensitive GPAT, not an AGPAT. In liver and brown adipose tissue from Agpat6-/- mice, NEM-sensitive GPAT specific activity was 65% lower than in wild-type mice, but AGPAT specific activity was unchanged. Overexpression of Agpat6 in Cos-7 cells increased NEM-sensitive GPAT activity but not AGPAT activity. Lipid intermediates (LPA, PA, DAG) initiated by GPAT4 lie in different cellular pools than those initiated by GPAT1. GPAT/AGPAT activity assays in tissues from knockout mice and overexpressing cells; [14C]oleate incorporation into lipid intermediates in Cos-7 cells Journal of lipid research High 18192653
2006 AGPAT6 (GPAT4) localizes exclusively to the endoplasmic reticulum in mammalian cells. Agpat6-/- mice show defective lactation with dramatically reduced lipid droplets in mammary epithelial cells and milk depleted of diacylglycerols and triacylglycerols, establishing its essential role in milk fat production. Gene-trap knockout mice; histology of mammary glands; northern blot; lipid analysis of milk; subcellular localization by ER marker co-localization Journal of lipid research High 16449762
2010 GPAT3 and GPAT4 are both phosphorylated by insulin at Ser and Thr residues, leading to increased GPAT activity that is sensitive to the PI3K inhibitor wortmannin, linking insulin signaling to microsomal GPAT activity. Knockdown of GPAT3 but not GPAT4 in 3T3-L1 adipocytes significantly decreased GPAT activity and inhibited lipid accumulation and adipogenic marker expression during differentiation. shRNA knockdown in 3T3-L1 adipocytes; overexpression in insect and mammalian cells; phosphorylation assays with insulin treatment and wortmannin inhibition; GPAT activity assays; lipid accumulation and gene expression analysis Journal of lipid research Medium 20181984
2013 GPAT1, but not GPAT4, is required to incorporate de novo synthesized fatty acids into triacylglycerol and to divert them away from β-oxidation. In primary hepatocytes from Gpat4-/- mice, incorporation of de novo synthesized fatty acid into TAG was similar to wild-type, but Gpat1-/- hepatocytes showed doubled fatty acid oxidation. This establishes that GPAT1 and GPAT4 metabolize distinct fatty acid pools in liver. Primary hepatocytes from Gpat1-/-, Gpat4-/-, and control mice; de novo fatty acid synthesis labeling; exogenous fatty acid incorporation assays; acylcarnitine measurements in vivo (fasting/refeeding protocol) The Journal of biological chemistry High 23908354
2015 GPAT4 limits oxidation of exogenous fatty acids in brown adipocytes. Gpat4-/- brown adipocytes incorporated 33% less fatty acid into triacylglycerol and 46% more into β-oxidation pathway, specifically through increased oxidation of exogenous (not de novo) fatty acids. GPAT4 comprises ~65% of total GPAT activity in brown adipose tissue. Gpat4-/- mice; metabolic rate measurements; neonatal BAT preadipocytes differentiated to adipocytes; fatty acid incorporation and oxidation assays; GPAT activity measurements; gene expression analysis The Journal of biological chemistry High 25918168
2019 CHP1 (calcineurin B homologous protein 1) binds and activates GPAT4. CHP1 must be N-myristoylated to activate GPAT4, forming a key molecular interface. Loss of CHP1 severely reduces fatty acid incorporation into glycerolipids in mammalian cells and invertebrates. Upon CHP1 loss, the peroxisomal enzyme GNPAT partially compensates for reduced ER lipid synthesis. CRISPR-based genetic screens; unbiased lipidomics; Co-IP/binding assays; CHP1 N-myristoylation mutants; fatty acid incorporation assays; invertebrate model validation Molecular cell High 30846317
2020 GPAT4 synthesizes saturated lysophosphatidic acids (e.g., 1-stearoyl-LPA) at the contact site between omegasomes and the mitochondria-associated membrane (MAM). Accumulation of these saturated LPAs causes abnormal omegasome formation, leading to accumulation of autophagosomal precursor isolation membranes and inhibition of autophagic flux, contributing to vascular calcification and apoptosis in vascular smooth muscle cells. SCD-knockout VSMC model; lipid metabolite analysis; autophagic flux assays; omegasome imaging; GPAT4 functional studies in VSMCs iScience Medium 32408172
2022 PPARγ acts as a transcription factor for AGPAT6 (GPAT4) via an RXRα binding site at -96 bp of the AGPAT6 promoter. Acetate stimulation increases the interaction between PPARγ and AGPAT6 promoter. AGPAT6 knockdown decreased acetate-induced mTORC1 signaling phosphorylation and intracellular TAG content; this was rescued by exogenous 16:0,18:1-phosphatidic acid, demonstrating that AGPAT6 activates mTORC1 by generating PA. Luciferase reporter assay with promoter deletions/mutations; siRNA knockdown; phosphatidic acid rescue experiment; western blot for mTORC1 signaling The Journal of dairy research Medium 36398416
2025 GPAT4 deficiency in endocardial cells provokes ER stress and enhances ER-mitochondria (ER-mito) communications, leading to mitochondrial DNA (mtDNA) escape. The escaped mtDNA activates the cGAS-STING pathway to stimulate type-I interferon response, which impairs heart development. Abolishment of cGAS-STING-type-I-interferon signaling rescued heart defects in Gpat4 deletion mice. Gpat4 global and tissue-specific knockout mice; ER stress markers; ER-mitochondria contact site imaging; mtDNA escape assay; cGAS-STING pathway analysis; genetic rescue with cGAS-STING pathway ablation Nature communications High 40199910
2025 CPT2 knockdown in colorectal cancer cells induces GPAT4-dependent accumulation of glycerophospholipids (primarily phosphatidylcholine and phosphatidylethanolamine), which promote autophagosome maturation and selective autophagy (lipophagy). CPT2 knockdown; metabolite analysis; transcriptomic analysis; in vitro and in vivo proliferation assays Communications biology Low 41107458
2024 GPAT4 diffuses in the ER membrane and translocates to lipid droplets (LDs) via seipin-containing ER-LD bridges (lateral transfer at membrane contact sites). Upon reaching the LD surface, GPAT4 becomes nano-confined, consistent with selective partitioning into nanoscale membrane domains that concentrate it at the LD surface. MINFLUX and HILO single-molecule tracking with machine learning; comparison with HSD17B13 and LiveDrop model cargo; seipin-containing bridge identification bioRxivpreprint Medium bio_10.1101_2024.08.27.610018
2026 FXR (farnesoid X receptor) transcriptionally inhibits GPAT4 expression. Dual-luciferase reporter assay confirmed FXR as a transcriptional repressor of GPAT4. FXR activation reduced lipid droplet accumulation by inhibiting GPAT4 in hepatic cell models. Dual-luciferase reporter assay; siRNA knockdown; western blot; HFD mouse model and oleic acid-induced HepG2 cell model Chinese medicine Medium 41530783

Source papers

Stage 0 corpus · 22 papers · ranked by NIH iCite citations
Year Title Journal Citations PMID
2008 ACSL1, AGPAT6, FABP3, LPIN1, and SLC27A6 are the most abundant isoforms in bovine mammary tissue and their expression is affected by stage of lactation. The Journal of nutrition 183 18492828
2008 AGPAT6 is a novel microsomal glycerol-3-phosphate acyltransferase. The Journal of biological chemistry 116 18238778
2008 Identification of a novel sn-glycerol-3-phosphate acyltransferase isoform, GPAT4, as the enzyme deficient in Agpat6-/- mice. Journal of lipid research 104 18192653
2006 Agpat6--a novel lipid biosynthetic gene required for triacylglycerol production in mammary epithelium. Journal of lipid research 101 16449762
2010 GPAT3 and GPAT4 are regulated by insulin-stimulated phosphorylation and play distinct roles in adipogenesis. Journal of lipid research 94 20181984
2019 CHP1 Regulates Compartmentalized Glycerolipid Synthesis by Activating GPAT4. Molecular cell 85 30846317
2013 Glycerol-3-phosphate acyltransferase (GPAT)-1, but not GPAT4, incorporates newly synthesized fatty acids into triacylglycerol and diminishes fatty acid oxidation. The Journal of biological chemistry 70 23908354
2003 Cloning and identification of the human LPAAT-zeta gene, a novel member of the lysophosphatidic acid acyltransferase family. Journal of human genetics 49 12938015
2014 Expression variants of the lipogenic AGPAT6 gene affect diverse milk composition phenotypes in Bos taurus. PloS one 48 24465687
2015 Glycerol-3-phosphate Acyltransferase Isoform-4 (GPAT4) Limits Oxidation of Exogenous Fatty Acids in Brown Adipocytes. The Journal of biological chemistry 26 25918168
2020 GPAT4-Generated Saturated LPAs Induce Lipotoxicity through Inhibition of Autophagy by Abnormal Formation of Omegasomes. iScience 22 32408172
2011 AGPAT6 polymorphism and its association with milk traits of dairy goats. Genetics and molecular research : GMR 12 22095600
2022 Functional roles for AGPAT6 in milk fat synthesis of buffalo mammary epithelial cells. Animal biotechnology 9 35649414
2022 PPARγ-AGPAT6 signaling mediates acetate-induced mTORC1 activation and milk fat synthesis in mammary epithelial cells of dairy cows. The Journal of dairy research 6 36398416
2025 GPAT4 sustains endoplasmic reticulum homeostasis in endocardial cells and safeguards heart development. Nature communications 5 40199910
2022 Development of TaqMan PCR assay for genotyping SNP rs211250281 of the bovine agpat6 gene. Animal biotechnology 4 35635030
2025 CPT2 inhibition enhances selective autophagy and proliferation in colorectal cancer via GPAT4-dependent glycerophospholipid biosynthesis. Communications biology 3 41107458
2019 Detection of Single-Nucleotide Polymorphism in AGPAT6 Gene, Associated with Milk Fat Content, using Tetra-Primer ARMS PCR-Based Assay, in Karan Fries Breeding Bulls. Iranian journal of biotechnology 3 32671121
2013 Studies of association of AGPAT6 variants with type 2 diabetes and related metabolic phenotypes in 12,068 Danes. BMC medical genetics 2 24156295
2006 Molecular cloning and preliminary function study of a novel human gene, TSARG7, related to spermatogenesis. Yi chuan xue bao = Acta genetica Sinica 1 16625827
2026 Si-Ni-San improves the deposition of lipid droplets in MAFLD through modulating the FXR-GPAT4 axis. Chinese medicine 0 41530783
2023 Functional analysis of the GPAT4 gene mutation predicted to affect splicing. Animal biotechnology 0 37906284

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