Recombinant Mouse Bile acyl-CoA synthetase (Slc27a5)

What is SLC27A5 and what are its primary functions in mouse models?

SLC27A5, also known as FATP5 (Fatty Acid Transport Protein 5) or bile acyl-CoA synthetase, is a protein primarily expressed in the liver that serves multiple metabolic functions. It is primarily involved in:

• Bile acid metabolism, specifically the conjugation of bile acids

• Fatty acid uptake and metabolism in hepatocytes

• Maintenance of glutathione (GSH) homeostasis

• Regulation of lipid peroxidation processes

This enzyme is localized in the endoplasmic reticulum lumen and plays a crucial role in maintaining normal liver function . Recent studies have expanded our understanding of SLC27A5 beyond its classical metabolic roles, revealing its involvement in processes such as ferroptosis regulation, hepatocellular carcinoma progression, and liver fibrosis development .

What is the molecular structure and characterization of recombinant SLC27A5?

The recombinant mouse SLC27A5 protein:

• Consists of residues Glu471~Leu689 (when produced in prokaryotic expression systems)

• Contains an N-terminal His Tag for purification and detection purposes

• Has a predicted molecular mass of 25.9kDa (isoelectric point: 6.5)

• Shows an actual molecular mass of approximately 28kDa when analyzed by SDS-PAGE under reducing conditions

For research applications, recombinant SLC27A5 is typically produced as a freeze-dried powder with high purity (>95%) and can be reconstituted in PBS (pH 7.4) to concentrations between 0.1-1.0 mg/mL . The stability of properly stored recombinant protein is excellent, with less than 5% loss rate when subjected to accelerated thermal degradation tests at 37°C for 48 hours .

How is SLC27A5 expression regulated in normal and pathological conditions?

SLC27A5 expression is dynamically regulated and often dysregulated in disease states:

• In normal liver, SLC27A5 is constitutively expressed and helps maintain bile acid homeostasis

• In liver cirrhosis and fibrosis, SLC27A5 is substantially downregulated in both human patients and mouse models

• The downregulation of SLC27A5 is mediated by RUNX2 (RUNX family transcription factor 2), which acts as a transcriptional repressor

• In hepatocellular carcinoma (HCC), SLC27A5 shows significantly decreased expression at both transcriptional and protein levels compared to normal tissues

• In sorafenib-resistant HCC, SLC27A5 levels are particularly reduced, suggesting its involvement in therapy response

This differential expression pattern makes SLC27A5 a potentially valuable biomarker for liver disease progression and treatment response.

What role does SLC27A5 play in sorafenib resistance in hepatocellular carcinoma?

Recent research has revealed that SLC27A5 functions as a suppressor of sorafenib resistance in hepatocellular carcinoma through regulation of ferroptosis:

• SLC27A5 deficiency facilitates resistance towards sorafenib in HCC cells by suppressing ferroptosis

• Mechanistically, loss of SLC27A5 enhances glutathione reductase (GSR) expression through a nuclear factor erythroid 2-related factor 2 (NRF2)-dependent pathway

• Enhanced GSR expression maintains glutathione (GSH) homeostasis, rendering cells less sensitive to sorafenib-induced ferroptosis

• SLC27A5 negatively correlates with GSR expression in HCC tissues

• Genetic or pharmacological inhibition of GSR can restore sorafenib sensitivity in SLC27A5-deficient HCC cells through GSH depletion and accumulation of lipid peroxide products

• Combination therapy with sorafenib and carmustine (BCNU), a selective GSR inhibitor, shows remarkable inhibition of tumor growth by enhancing ferroptotic cell death in vivo

These findings suggest that assessment of SLC27A5 levels might help predict sorafenib response in HCC patients and that targeting the SLC27A5/NRF2/GSR axis represents a promising strategy to overcome sorafenib resistance.

How does SLC27A5 deficiency influence liver fibrosis development?

SLC27A5 deficiency promotes liver fibrosis through several interconnected mechanisms:

• SLC27A5 knockout (Slc27a5^-/-) mice display spontaneous liver fibrosis as they age

• SLC27A5 deficiency aggravates liver fibrosis induced by carbon tetrachloride (CCl₄) and thioacetamide (TAA)

• Mechanistically, SLC27A5 deficiency results in accumulation of unconjugated bile acids, particularly cholic acid (CA), in the liver

• This accumulation activates hepatic stellate cells (HSCs) by upregulating the expression of early growth response genes

• Re-expression of hepatic SLC27A5 using adeno-associated virus vectors ameliorates liver fibrosis in Slc27a5^-/- mice

• Reduction of CA levels in the liver using A4250, an apical sodium-dependent bile acid transporter (ASBT) inhibitor, also improves liver fibrosis in these knockout models

These findings highlight SLC27A5 as a potential therapeutic target for liver fibrosis and suggest that strategies aimed at restoring its expression or counteracting the effects of its deficiency could have clinical value.

What is the relationship between SLC27A5 and cuproptosis in hepatocellular carcinoma?

SLC27A5 has been identified as a potential regulator of cuproptosis (copper-dependent cell death) in HCC:

These findings suggest that SLC27A5 may promote cuproptosis in HCC by upregulating FDX1 and modulating GSH levels, identifying it as a potential therapeutic target.

What are the optimal conditions for using recombinant SLC27A5 in laboratory experiments?

For optimal experimental results with recombinant SLC27A5:

• Reconstitution: Use 10mM PBS (pH 7.4) to a concentration of 0.1-1.0 mg/mL, avoiding vortexing to maintain protein structure integrity

• Storage: For short-term use, store at 2-8°C for up to one month; for long-term storage, aliquot and maintain at -80°C for up to 12 months

• Stability: Minimize freeze/thaw cycles as protein stability decreases with repeated temperature fluctuations

• Applications: Recombinant SLC27A5 is suitable for use as a positive control, immunogen, and in techniques such as SDS-PAGE and Western blotting

• Buffer conditions: The protein is typically formulated in PBS (pH 7.4) containing 0.01% SKL and 5% Trehalose for stability

Researchers should validate protein activity for specific applications, as recombinant proteins may require optimization for different experimental systems.

How can SLC27A5 expression or activity be experimentally manipulated in mouse models?

Several approaches can be used to modulate SLC27A5 in experimental systems:

• Genetic knockout: Slc27a5^-/- mice display altered bile acid profiles, changes in lipid metabolism, and increased susceptibility to liver fibrosis

• Viral vectors: Adeno-associated virus (AAV) vectors expressing SLC27A5 can be used to restore or increase expression in mouse models, with demonstrated efficacy in ameliorating liver fibrosis in Slc27a5^-/- mice

• Pharmacological intervention: Indirect modulation of SLC27A5-dependent pathways can be achieved using compounds like A4250 (an ASBT inhibitor) that alter bile acid levels

• Cell culture models: Overexpression or knockdown of SLC27A5 in cell lines such as HepG2 and LM-3 can be used to study its functions in vitro

• CRISPR-Cas9 genome editing: For targeted modification of SLC27A5 in various experimental systems

When designing experiments, researchers should consider that SLC27A5 manipulation often leads to complex metabolic changes that can influence multiple pathways simultaneously.

What phenotypic changes are observed in SLC27A5 knockout mice?

SLC27A5 knockout mice exhibit several characteristic phenotypes that evolve with age:

• Early development effects: Knockout mice are underweight after weaning but demonstrate catch-up growth

• Metabolic alterations at 3 weeks of age:

  • Increased phospholipid excretion

  • Decreased subcutaneous fat pad mass

  • Reduced glycogen staining in hepatocytes

  • Diminished vitamin A stores in the liver

• Bile acid profile changes: Highly altered bile acid pool throughout the first 8 weeks of life

  • 27-fold lower amounts of taurine-conjugated bile acids in the liver compared to wildtype

  • Similar concentrations of glycine-conjugated bile acids

  • Higher levels of microbially-conjugated bile acids

  • Enrichment of unusual bile acids, including those derived from cysteamine conjugation

• Microbiome alterations: Most pronounced in the first 3 weeks, indicating bile acid conjugation is important for proper microbiome development

• Liver pathology: Development of spontaneous liver fibrosis with age

• Response to challenges: Increased susceptibility to chemically-induced liver fibrosis (CCl₄ and TAA models)

These phenotypic changes highlight the multifaceted roles of SLC27A5 in liver physiology and development.

What are the current limitations in SLC27A5 research and potential solutions?

Several challenges currently exist in SLC27A5 research:

• Complexity of bile acid metabolism: SLC27A5 functions within a complex network of bile acid metabolism enzymes and transporters, making it difficult to isolate its specific effects

  • Solution: Use of multi-omics approaches and systems biology to map interaction networks

• Compensatory mechanisms: Loss of SLC27A5 activates compensatory pathways (e.g., ACNAT1 and ACNAT2) that can mask phenotypic effects

  • Solution: Development of inducible and tissue-specific knockout models to minimize adaptive responses

• Translational barriers: Differences between mouse and human bile acid metabolism limit direct translation of findings

  • Solution: Complementary studies in humanized mouse models and human liver organoids

• Analytical challenges: Accurate profiling of the complex array of bile acid species requires sophisticated analytical techniques

  • Solution: Advanced targeted and untargeted metabolomics approaches with improved sensitivity and specificity

Addressing these limitations will require interdisciplinary collaboration and continued technological innovation in the field.

How might SLC27A5-focused research contribute to therapeutic strategies for liver diseases?

Research on SLC27A5 holds significant potential for developing novel therapeutic approaches:

• Overcoming sorafenib resistance in HCC:

  • Combination therapy of sorafenib with GSR inhibitors (like carmustine) shows promise in SLC27A5-deficient tumors

  • SLC27A5 expression levels could serve as a biomarker for predicting treatment response

• Liver fibrosis treatment:

  • AAV-mediated SLC27A5 gene therapy has shown efficacy in reducing fibrosis in mouse models

  • ASBT inhibitors like A4250, which reduce unconjugated bile acid levels, represent another therapeutic strategy

• Cuproptosis-based cancer therapies:

  • SLC27A5's ability to promote cuproptosis via FDX1 upregulation could be exploited for cancer treatment

  • Strategies to increase SLC27A5 expression or activity might enhance sensitivity to copper-based therapies

• Metabolic liver disease management:

  • Understanding SLC27A5's role in bile acid metabolism could inform treatments for cholestatic disorders

  • Modulation of SLC27A5 might help address lipid metabolism disorders

Future therapeutic development will likely focus on targeted approaches to modulate specific SLC27A5-dependent pathways while minimizing off-target effects.

How should researchers interpret contradictory findings regarding SLC27A5 function?

When faced with contradictory results in SLC27A5 research, consider the following analytical framework:

• Experimental context differences:

  • Cell type specificity: SLC27A5 functions differently in various cell types (hepatocytes vs. hepatic stellate cells)

  • Disease stage variation: Effects may differ between early and advanced stages of liver diseases

  • Model system variations: Results from cell lines, primary cultures, and in vivo models may not align perfectly

• Methodological considerations:

  • Knockout strategies: Complete knockout vs. conditional or tissue-specific deletion can yield different phenotypes

  • Analytical techniques: Different assays for measuring bile acids or protein function have varying sensitivities

  • Timing of analysis: SLC27A5 effects evolve with age, so timing of experiments is critical

• Biological complexity:

  • Compensatory mechanisms: Other enzymes (ACNAT1, ACNAT2) may compensate for SLC27A5 loss

  • Pathway redundancy: Multiple pathways regulate bile acid metabolism and ferroptosis

  • Species differences: Mouse and human SLC27A5 may have subtle functional differences

Resolving contradictions often requires detailed comparison of experimental methods and biological contexts, along with replication studies using standardized protocols.

What are the key considerations for designing experiments to study SLC27A5 in liver disease models?

When designing experiments to investigate SLC27A5 in liver disease, researchers should address:

• Model selection:

  • Choose models relevant to the specific liver pathology (fibrosis, HCC, cholestasis)

  • Consider both genetic models (Slc27a5^-/- mice) and induced disease models (CCl₄, TAA)

  • Include appropriate age-matched controls as SLC27A5 effects vary with development

• Comprehensive phenotyping:

  • Analyze bile acid profiles using LC-MS/MS for detailed characterization

  • Examine both hepatic and serum parameters for complete assessment

  • Include histological evaluation for structural changes and immunohistochemistry for protein localization

• Pathway analysis:

  • Assess known SLC27A5-dependent pathways (NRF2/GSR for ferroptosis, FDX1 for cuproptosis)

  • Monitor compensatory mechanisms (ACNAT1/2, BAAT)

  • Evaluate microbiome changes when relevant

• Intervention testing:

  • Include both genetic interventions (overexpression, knockdown) and pharmacological approaches

  • Test combination therapies (e.g., sorafenib + GSR inhibitors)

  • Consider timing of interventions (preventive vs. therapeutic)