GO:1901751 leukotriene A4 metabolic process: Pathway, Genes, Functions and Research Methods
Research-grade guide for scientists and biopharma professionals
Key Takeaways
• GO:1901751 (leukotriene A4 metabolic process) describes the chemical reactions and pathways involving leukotriene A4 (LTA4), a key unstable intermediate in leukotriene biosynthesis.
• LTA4 is produced from arachidonic acid by 5-lipoxygenase (ALOX5) and is rapidly converted to leukotriene B4 (LTB4) by LTA4 hydrolase (LTA4H) or to leukotriene C4 (LTC4) by LTC4 synthase (LTC4S).
• The process is central to inflammation, immune cell chemotaxis, and has been implicated in cancer, asthma, and cardiovascular diseases.
• Key enzymes include ALOX5, ALOX5AP, LTA4H, LTC4S, and transporters such as ABCC1, which determine the metabolic fate of LTA4.
• Dysregulation of LTA4 metabolism contributes to tumor progression and chronic inflammatory disorders, making it a target for therapeutic intervention.
• CRISPR-based models (knockout, point mutation, knock-in, overexpression) enable precise dissection of LTA4 metabolic pathways in human cells.
Description
Leukotriene A4 (LTA4) is a chemically unstable epoxide intermediate generated from arachidonic acid through the 5-lipoxygenase (5-LO) pathway. The metabolic process involving LTA4, formally annotated as GO:1901751, encompasses the enzymatic reactions that produce, transform, and eliminate this pivotal lipid mediator. Because LTA4 sits at the branch point between the pro-inflammatory chemoattractant leukotriene B4 (LTB4) and the cysteinyl leukotrienes (including LTC4, LTD4, LTE4), its metabolism is a critical determinant of inflammatory responses. Understanding this process is essential for researchers studying asthma, arthritis, cancer, and cardiovascular diseases, where leukotriene overproduction is often observed. The short half-life of LTA4 in aqueous environments necessitates rapid enzymatic conversion or non-enzymatic hydrolysis, making the regulation of its metabolic enzymes a focal point of biomedical research. This article provides a comprehensive overview of GO:1901751, integrating authoritative QuickGO annotations with verified PubMed literature to support research design and therapeutic targeting.
leukotriene A4 metabolic process At A Glance
| GO ID | GO:1901751 |
|---|---|
| GO term | leukotriene A4 metabolic process |
| Ontology | biological_process |
| Synonym | leukotriene A4 metabolism |
| Major function | Metabolism of the unstable epoxide intermediate LTA4, leading to production of LTB4 and cysteinyl leukotrienes. |
| Key enzymes | ALOX5, ALOX5AP, LTA4H, LTC4S, ABCC1 |
| Substrates | Arachidonic acid, 5-HPETE, LTA4 |
| Products | Leukotriene B4, leukotriene C4, leukotriene D4, leukotriene E4 |
| Related pathways | Arachidonic acid metabolism, inflammatory mediator synthesis |
What Is GO:1901751?
According to the Gene Ontology, GO:1901751 (leukotriene A4 metabolic process) is defined as the chemical reactions and pathways involving leukotriene A4. This biological process includes the biosynthesis of LTA4 from arachidonic acid, its enzymatic conversion to downstream leukotrienes such as LTB4 and LTC4, and its non-enzymatic degradation. The term is synonymous with leukotriene A4 metabolism and is a child of the broader leukotriene metabolic process.
Why Is leukotriene A4 metabolic process Important in Cell Biology?
The leukotriene A4 metabolic process is a central node in inflammatory signaling and lipid mediator biosynthesis. LTA4 itself is highly reactive and serves as the precursor for potent bioactive lipids that drive chemotaxis, vascular permeability, and bronchoconstriction. Dysregulated LTA4 metabolism is implicated in the pathogenesis of asthma, rheumatoid arthritis, inflammatory bowel disease, and several cancers. Moreover, LTA4H has emerged as a target for chemoprevention and chemotherapy, with natural products and synthetic inhibitors showing efficacy in preclinical models. Therefore, precise understanding of GO:1901751 is critical for developing novel anti-inflammatory and anticancer therapeutics.
• LTA4 is the pivotal intermediate in leukotriene biosynthesis, linking 5-lipoxygenase activity to downstream inflammatory mediators.
• LTA4H converts LTA4 to LTB4, a potent neutrophil chemoattractant involved in innate immunity and tissue damage.
• LTC4S conjugates LTA4 with glutathione to form LTC4, a cysteinyl leukotriene that mediates bronchoconstriction and vascular permeability.
• The balance between LTA4H and LTC4S activities determines the profile of leukotriene products and the nature of inflammatory responses.
• LTA4 metabolism is implicated in cancer progression, where LTB4 promotes tumor cell proliferation and survival.
• Genetic variants in ALOX5, ALOX5AP, and LTA4H are associated with asthma and cardiovascular disease risk.
• LTA4 can be released from cells and taken up by neighboring cells, a process termed transcellular biosynthesis, which amplifies leukotriene production.
• Inhibitors of LTA4H and LTC4S are under investigation for treating inflammatory diseases and cancer.
• CRISPR screens can identify novel regulators of LTA4 metabolic enzymes, offering new therapeutic targets.
• Studying GO:1901751 helps elucidate the role of lipid mediators in health and disease, guiding biomarker discovery.
What Happens During leukotriene A4 metabolic process?
Biosynthesis of LTA4 from arachidonic acid
In simple terms: First, arachidonic acid is converted into an unstable intermediate called LTA4.
The leukotriene A4 metabolic process begins with the release of arachidonic acid from membrane phospholipids by cytosolic phospholipase A2 (cPLA2). Arachidonic acid is then presented to 5-lipoxygenase (ALOX5) by the 5-lipoxygenase-activating protein (ALOX5AP, also known as FLAP). ALOX5 catalyzes the oxygenation of arachidonic acid to 5-hydroperoxyeicosatetraenoic acid (5-HPETE), which is subsequently dehydrated to form the unstable epoxide leukotriene A4 (LTA4). This reaction requires calcium and ATP and occurs at the nuclear envelope. The biosynthesis of LTA4 is the rate-limiting step in leukotriene production and is tightly regulated.
Enzymatic conversion of LTA4 to LTB4
In simple terms: LTA4 can be converted into LTB4, a molecule that attracts immune cells.
Leukotriene A4 hydrolase (LTA4H) is a bifunctional zinc metalloenzyme that catalyzes the hydrolysis of LTA4 to leukotriene B4 (LTB4). This reaction involves the addition of water to the epoxide moiety of LTA4, forming a diol. LTB4 is a potent chemoattractant for neutrophils and macrophages, playing a key role in inflammation and host defense. LTA4H is widely expressed in various tissues and is considered a major determinant of LTB4 levels. The enzyme also possesses aminopeptidase activity, which can degrade pro-inflammatory peptides, but its role in LTA4 metabolism is predominant.
Conversion of LTA4 to cysteinyl leukotrienes
In simple terms: Alternatively, LTA4 can be turned into cysteinyl leukotrienes like LTC4, which cause airway constriction.
Leukotriene C4 synthase (LTC4S) conjugates LTA4 with reduced glutathione to form leukotriene C4 (LTC4). This reaction is the committed step in the biosynthesis of cysteinyl leukotrienes (LTC4, LTD4, LTE4), which are mediators of bronchoconstriction, mucus secretion, and vascular permeability. LTC4S is a membrane-bound enzyme localized to the nuclear envelope and is highly expressed in eosinophils, mast cells, and macrophages. The product LTC4 is actively transported out of cells by multidrug resistance-associated protein 1 (MRP1/ABCC1) and then converted to LTD4 and LTE4 by extracellular peptidases.
Non-enzymatic degradation and transcellular metabolism
In simple terms: LTA4 can also break down spontaneously or be passed to other cells to make leukotrienes.
In the absence of enzymatic conversion, LTA4 undergoes non-enzymatic hydrolysis to 6-trans-LTB4 diastereomers and other inactive products. Additionally, LTA4 can be released from the producing cell and taken up by neighboring cells, such as endothelial cells or platelets, which lack ALOX5 but express LTA4H or LTC4S. This transcellular biosynthesis amplifies leukotriene production and diversifies the types of leukotrienes generated in a tissue microenvironment. The release of LTA4 versus LTB4 from human polymorphonuclear leukocytes has been demonstrated, highlighting the importance of cellular context in determining the metabolic fate of LTA4.
Key Genes Involved in GO:1901751 leukotriene A4 metabolic process
The following genes encode enzymes, transporters, and accessory proteins that directly participate in or regulate the leukotriene A4 metabolic process.
| Gene | Major Role | Research Relevance |
|---|---|---|
| ALOX5 | Catalyzes the conversion of arachidonic acid to 5-HPETE and then to LTA4 | Rate-limiting enzyme; target for anti-leukotriene drugs; knockout models show reduced inflammation |
| ALOX5AP | Activates ALOX5 and presents arachidonic acid | Essential for LTA4 biosynthesis; genetic variants linked to asthma and cardiovascular disease |
| LTA4H | Hydrolyzes LTA4 to LTB4 | Bifunctional enzyme; target for cancer chemoprevention; knockout reduces LTB4 and inflammation |
| LTC4S | Conjugates LTA4 with glutathione to form LTC4 | Determines cysteinyl leukotriene production; knockout abolishes LTC4 synthesis |
| ABCC1 | Transports LTC4 out of cells | Multidrug resistance protein; modulates extracellular leukotriene levels |
| PLA2G4A | Releases arachidonic acid from membrane phospholipids | Upstream regulator of LTA4 synthesis; knockout impairs leukotriene production |
| GGT1 | Converts LTC4 to LTD4 | Extracellular processing of cysteinyl leukotrienes |
| DPEP1 | Converts LTD4 to LTE4 | Terminal step in cysteinyl leukotriene metabolism |
| ALOX15 | May modulate leukotriene synthesis through alternative lipoxygenation | Cross-talk with 5-LO pathway; potential regulatory role |
| PTGS2 | Prostaglandin-endoperoxide synthase 2; can influence arachidonic acid availability | Cross-talk between prostaglandin and leukotriene pathways |
| MGST2 | Microsomal glutathione S-transferase 2; alternative LTC4 synthase | Backup pathway for LTC4 production |
| MGST3 | Microsomal glutathione S-transferase 3; alternative LTC4 synthase | Contributes to cysteinyl leukotriene synthesis |
| CYP4F3 | Omega-hydroxylase that inactivates LTB4 | Regulates LTB4 degradation; knockout increases LTB4 levels |
| SLC22A4 | Transporter for LTB4 and other organic cations | Modulates leukotriene bioavailability; associated with inflammatory diseases |
| SLC22A5 | Transporter for LTB4 and carnitine | Potential role in leukotriene transport |
| NFKB1 | Transcription factor regulating inflammatory gene expression | Controls expression of ALOX5, LTA4H, and other leukotriene enzymes |
| STAT3 | Transcription factor involved in inflammation and cancer | Regulates LTA4H expression; linked to tumor progression |
| CEBPB | Transcription factor regulating immune cell differentiation | Modulates LTC4S and LTA4H expression |
How Is leukotriene A4 metabolic process Regulated?
The leukotriene A4 metabolic process is regulated at multiple levels. Transcriptionally, inflammatory stimuli such as lipopolysaccharide and cytokines (e.g., IL-4, IL-13) induce the expression of ALOX5, ALOX5AP, LTA4H, and LTC4S through transcription factors including NF-κB and STAT3. Post-translationally, ALOX5 activity is regulated by calcium, ATP, and phosphorylation by MAPKAPK2 and ERK. LTA4H activity can be modulated by zinc availability and oxidative stress. Additionally, the subcellular localization of enzymes to the nuclear envelope facilitates efficient substrate channeling. The balance between LTA4H and LTC4S is influenced by cell type and activation state, determining whether LTB4 or cysteinyl leukotrienes predominate. Non-enzymatic degradation and transcellular transport further regulate the effective concentration of LTA4.
leukotriene A4 metabolic process and Human Disease
| Gene | Disease / Biology | Potential Experimental Model |
|---|---|---|
| ALOX5 | Asthma, allergic rhinitis | Knockout mice or human airway epithelial cells with ALOX5 KO to study leukotriene production |
| LTA4H | Cancer (colon, lung), inflammation | LTA4H knockout cancer cell lines (e.g., HCT116) to assess proliferation and migration |
| LTC4S | Asthma, cardiovascular disease | LTC4S knockout mast cells or eosinophils to measure cysteinyl leukotriene release |
| ALOX5AP | Asthma, myocardial infarction | ALOX5AP knockout macrophages to study LTA4 synthesis and inflammatory cytokine release |
| ABCC1 | Drug resistance, inflammation | ABCC1 knockout cell lines to assess LTC4 transport and extracellular leukotriene levels |
Leukotriene A4 metabolism in inflammation and asthma
Leukotrienes are key mediators of allergic inflammation and asthma. LTC4, LTD4, and LTE4 cause bronchoconstriction, mucus hypersecretion, and airway edema. LTB4 recruits neutrophils and eosinophils, contributing to chronic airway inflammation. Genetic variants in ALOX5, ALOX5AP, and LTC4S are associated with asthma susceptibility and response to leukotriene receptor antagonists. Inhibitors of 5-lipoxygenase (e.g., zileuton) and LTA4H are used or investigated for asthma treatment.
Leukotriene A4 metabolism in cancer
Chronic inflammation is a hallmark of cancer, and leukotrienes contribute to tumorigenesis. LTB4 promotes cancer cell proliferation, survival, and migration, and stimulates angiogenesis. LTA4H is overexpressed in several cancers, including colon, lung, and prostate cancer, and its inhibition reduces tumor growth in preclinical models. LTC4 and other cysteinyl leukotrienes can also promote tumor progression by modulating the tumor microenvironment. Therefore, targeting LTA4 metabolic enzymes is a promising chemopreventive and therapeutic strategy.
Leukotriene A4 metabolism in cardiovascular and other diseases
Leukotrienes are implicated in atherosclerosis, myocardial infarction, and stroke. LTB4 promotes monocyte recruitment and foam cell formation, while cysteinyl leukotrienes increase vascular permeability and vasoconstriction. LTA4H polymorphisms have been linked to increased risk of cardiovascular events. Additionally, leukotrienes play roles in inflammatory bowel disease, rheumatoid arthritis, and psoriasis. Targeting LTA4 metabolism may offer therapeutic benefits beyond asthma and cancer.
From leukotriene A4 metabolic process-Related Genes to Experimental Models
| Research Question | Suitable Model |
|---|---|
| Does LTA4H loss reduce LTB4 production and inflammation? | LTA4H knockout in human myeloid cells (e.g., HL-60, THP-1) using CRISPR-Cas9 |
| What is the effect of a specific LTA4H polymorphism on enzyme activity? | Point mutation knock-in of the variant in HEK293 cells, followed by enzymatic assay |
| Can a tagged LTA4H be used to study subcellular localization? | Knock-in of FLAG- or GFP-tagged LTA4H at the endogenous locus in A549 cells |
| Does LTC4S overexpression increase cysteinyl leukotriene production? | Overexpression of LTC4S in HEK293 or COS-7 cells, measured by ELISA |
| Which genes regulate LTA4 metabolic flux? | Genome-wide CRISPR knockout library screening in a leukotriene-producing cell line |
| Can we model transcellular LTA4 metabolism? | Co-culture of ALOX5-expressing cells (neutrophils) with LTA4H- or LTC4S-expressing endothelial cells |
How to Study the leukotriene A4 metabolic process Process
| Method | What It Measures | Typical Application |
|---|---|---|
| LC-MS/MS | Quantification of leukotrienes (LTA4, LTB4, LTC4, etc.) | Profiling lipid mediator production in cells and tissues |
| Enzyme activity assay | Catalytic activity of LTA4H or LTC4S | Characterizing wild-type and mutant enzymes |
| ELISA | Concentration of specific leukotrienes in supernatants | High-throughput screening of inhibitors or CRISPR clones |
| CRISPR knockout screening | Genes affecting leukotriene production | Discovery of novel regulators of LTA4 metabolism |
| Fluorescence microscopy | Subcellular localization of enzymes | Studying nuclear envelope targeting and complex formation |
| Western blot | Protein expression levels of ALOX5, LTA4H, LTC4S | Validating knockout or overexpression efficiency |
| qRT-PCR | mRNA expression of leukotriene enzymes | Assessing transcriptional regulation |
| Transcellular co-culture | Leukotriene production from multiple cell types | Modeling in vivo inflammatory microenvironments |
Enzyme activity assays for LTA4 metabolic enzymes
LTA4H activity can be measured using a spectrophotometric assay with LTA4 as substrate, monitoring the formation of LTB4 at 270 nm. LTC4S activity is typically assayed by incubating LTA4 with glutathione and microsomal fractions, followed by detection of LTC4 by ELISA or mass spectrometry. These assays are essential for characterizing the kinetic properties of wild-type and mutant enzymes.
Lipid mediator quantification by mass spectrometry
Liquid chromatography-tandem mass spectrometry (LC-MS/MS) allows sensitive and specific quantification of LTA4, LTB4, LTC4, LTD4, and LTE4 in biological samples. This method is crucial for profiling leukotriene production in cells and tissues, and for validating CRISPR knockout or overexpression models.
CRISPR screening for regulators of LTA4 metabolism
Genome-wide CRISPR knockout or activation screens can identify genes that modulate LTA4 metabolic flux. For example, a reporter cell line expressing a leukotriene-responsive fluorescent sensor can be used to isolate regulators. Hits can be validated by targeted knockout and lipidomics. This approach is powerful for discovering novel therapeutic targets in the leukotriene pathway.
Imaging and subcellular localization studies
Fluorescence microscopy of GFP- or immuno-tagged LTA4H, LTC4S, and ALOX5 can reveal their subcellular distribution, particularly at the nuclear envelope. Live-cell imaging with fluorescent LTA4 analogs can track its trafficking and metabolism. These methods help elucidate the spatial organization of the leukotriene biosynthetic machinery.
How CRISPR Can Be Used to Study GO:1901751 leukotriene A4 metabolic process
Knockout
CRISPR-Cas9 knockout of LTA4H, LTC4S, ALOX5, or ALOX5AP in human cell lines (e.g., THP-1, HL-60, A549) abolishes or reduces specific leukotriene products, enabling assignment of enzyme function. Knockout models are essential for validating metabolic pathways and for identifying compensatory mechanisms.
Point Mutation
Point mutations in LTA4H (e.g., E271Q, R563A) can be introduced via CRISPR base editing or homology-directed repair to dissect catalytic residues or disease-associated variants. Such models help determine the impact of single-nucleotide polymorphisms on enzyme activity and leukotriene production.
Knock-in
Knock-in of epitope tags (e.g., FLAG, HA) or fluorescent proteins (e.g., GFP) at the endogenous LTA4H or LTC4S locus allows real-time tracking of protein localization and interaction without overexpression artifacts. Knock-in of reporter genes under the control of leukotriene enzyme promoters can monitor transcriptional regulation.
Overexpression
CRISPR activation (CRISPRa) or lentiviral overexpression of LTA4H, LTC4S, or ALOX5 in cell lines increases leukotriene production, facilitating biochemical studies and drug screening. Overexpression models are useful for studying the effects of elevated enzyme levels on inflammation and cancer cell phenotypes.
How EDITGENE Supports leukotriene A4 metabolic process Research
Researchers studying leukotriene A4 metabolic process-related genes often need to determine whether a candidate gene is causally involved in leukotriene production, inflammatory signaling, or disease progression. EDITGENE provides a comprehensive suite of CRISPR-based services to generate precisely engineered cell models, enabling functional validation and therapeutic target discovery.
Contact EDITGENE today to design your custom CRISPR model for leukotriene A4 metabolic process research.
Frequently Asked Questions About leukotriene A4 metabolic process
What is leukotriene A4 metabolic process?
Leukotriene A4 metabolic process (GO:1901751) is the set of chemical reactions and pathways involving leukotriene A4 (LTA4), an unstable intermediate in leukotriene biosynthesis that is converted to LTB4 or cysteinyl leukotrienes.
What genes are involved in leukotriene A4 metabolic process?
Key genes include ALOX5, ALOX5AP, LTA4H, LTC4S, ABCC1, and PLA2G4A, which encode enzymes and transporters that produce, convert, or transport LTA4 and its products.
What is the function of LTA4H in leukotriene A4 metabolism?
LTA4H (leukotriene A4 hydrolase) catalyzes the hydrolysis of LTA4 to leukotriene B4 (LTB4), a potent chemoattractant involved in inflammation.
How is leukotriene A4 metabolized to leukotriene C4?
LTC4 synthase (LTC4S) conjugates LTA4 with glutathione to form leukotriene C4 (LTC4), a cysteinyl leukotriene that mediates bronchoconstriction and vascular permeability.
What diseases are associated with leukotriene A4 metabolic process?
Dysregulation of LTA4 metabolism is linked to asthma, allergic rhinitis, rheumatoid arthritis, inflammatory bowel disease, atherosclerosis, and several cancers.
Can CRISPR be used to study leukotriene A4 metabolism?
Yes, CRISPR-Cas9 knockout, point mutation, knock-in, and overexpression models enable precise dissection of gene function in leukotriene A4 metabolic pathways.
What are the substrates and products of leukotriene A4 metabolic process?
The main substrate is arachidonic acid, which is converted to LTA4; products include LTB4, LTC4, LTD4, and LTE4, depending on the enzymes present.
How is leukotriene A4 metabolic process regulated?
It is regulated transcriptionally by inflammatory stimuli (e.g., NF-κB, STAT3), post-translationally by phosphorylation and calcium, and spatially by enzyme localization to the nuclear envelope.
What methods are used to study leukotriene A4 metabolism?
Common methods include LC-MS/MS for leukotriene quantification, enzyme activity assays, ELISA, CRISPR screening, and fluorescence microscopy.
Why is leukotriene A4 metabolism important for cancer research?
LTB4 and cysteinyl leukotrienes promote tumor cell proliferation, survival, and angiogenesis, making LTA4 metabolic enzymes potential targets for cancer therapy.
Conclusion
The leukotriene A4 metabolic process (GO:1901751) is a critical biological pathway that governs the production of potent lipid mediators of inflammation and cancer. The balance between LTA4H and LTC4S activities determines whether LTA4 is converted to LTB4 or cysteinyl leukotrienes, influencing diverse physiological and pathological outcomes. Advances in CRISPR-based gene editing and lipidomics have enabled precise interrogation of this pathway, revealing new therapeutic opportunities. Continued research into the regulation and dysregulation of LTA4 metabolism will likely yield novel treatments for asthma, inflammatory diseases, and cancer.
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