FABP1 Human, His

What are the primary cellular locations and functions of human FABP1?

Human FABP1 is predominantly cytoplasmic in hepatocytes but also found in the nucleus and outer mitochondrial membrane . It serves multiple functions including:

• Fatty acid uptake and intracellular transport

• Regulation of lipid metabolism

• Binding of various ligands (fatty acids, heme, metalloporphyrins)

• Protection from oxidative stress

• Targeting fatty acids to oxidative organelles for oxidation

• Facilitating ligand activation of nuclear receptors (PPARα and HNF4α)

FABP1 is also critical during intracellular bacterial/viral infections by reducing inflammation and adverse effects of energy deficiency .

How does human FABP1 interact with endocannabinoids and other signaling molecules?

Human FABP1 has high affinity for arachidonic acid (ARA, C20:4n-6), the precursor of endocannabinoids AEA and 2-AG . Both human and rat FABP1 bind ARA with higher affinity than saturated and monounsaturated fatty acids . FABP1 enhances uptake of the endocannabinoid precursor arachidonic acid, and studies suggest that endocannabinoids and phytocannabinoids bind to FABP1 . Although FABP1 is not detectable in brain, FABP1 ablation impacts brain endocannabinoids, demonstrating its systemic importance in endocannabinoid metabolism .

What experimental considerations should researchers make when studying human FABP1 versus rodent models?

Researchers must recognize that findings from rodent FABP1 studies may not directly translate to human FABP1 functions due to significant structural and functional differences . Critical methodological considerations include:

• While both mouse and human FABP1 mediate ligand induction of PPARα, they differ markedly in the pattern of genes induced

• Fibrate and other PPARα activators induce different target genes in human compared to mouse primary hepatocytes, with only about half of ligand-induced PPARα target genes overlapping between species

• FABP1's binding cavity differences affect ligand interactions, requiring careful validation of binding studies across species

Researchers should ideally conduct parallel experiments in both human and rodent systems when investigating translational mechanisms.

How should researchers account for the FABP1 T94A variant in experimental design?

The human FABP1 T94A variant (26-38% minor allele frequency, 8.3±1.9% homozygous) significantly impacts experimental design and interpretation . Methodological approaches should include:

• Genotyping study populations for the T94A variant

• Stratifying data analysis based on T94A status

• Considering how this variant might interact with dietary or pharmacological interventions

• Developing separate experimental protocols for wild-type and T94A variant protein studies

This variant is associated with altered BMI, dyslipidemias, atherothrombotic cerebral infarction, and NAFLD, potentially confounding research results if not properly accounted for .

What cellular models are most appropriate for studying human FABP1 function?

Research findings differ significantly between primary hepatocytes, liver tissue in vivo, and transformed cell lines . For example:

Primary human hepatocytes generally provide more physiologically relevant results, though they present greater technical challenges than cell lines.

How is FABP1 expression altered in human tumors and what is its diagnostic utility?

FABP1 expression analysis by immunohistochemistry has significant diagnostic utility due to its tissue specificity . Methodological findings include:

In hepatocellular carcinomas, reduced FABP1 expression correlates with advanced stage, lymph node metastasis, and female gender . In colorectal cancer, reduced FABP1 expression associates with high-grade histology, microsatellite instability-high (MSI) status, and absence of BRAF V600E mutations .

What mechanisms link FABP1 to non-alcoholic fatty liver disease (NAFLD)?

The human FABP1 T94A variant is associated with NAFLD through several mechanisms :

• FABP1 mediates fatty acid β-oxidation, with gene ablation inhibiting this process

• FABP1 facilitates ligand activation of PPARα, a key regulator of genes involved in fatty acid metabolism

• FABP1 influences biliary secretion of HDL-derived cholesterol and alters bile acid profiles

• FABP1 gene ablation decreases hepatic bile acid concentration while increasing biliary bile acid hydrophobicity

• FABP1 affects VLDL clearance by lipoprotein lipase (LPL)

Research approaches should examine these pathways in human hepatocytes with wild-type and T94A variant FABP1 to understand the molecular mechanisms underlying NAFLD development.

What expression systems optimize recombinant human FABP1-His production?

When producing His-tagged human FABP1, researchers should consider:

• E. coli expression systems typically yield sufficient quantities of FABP1 for structural and biochemical studies

• Expression constructs should be designed to prevent the His-tag from interfering with the binding cavity

• Codon optimization for E. coli expression may improve yield

• Expression conditions should minimize endogenous lipid binding during production

• Purification protocols must account for FABP1's propensity to bind bacterial lipids

How does His-tag placement affect human FABP1 ligand binding properties?

The His-tag location significantly impacts FABP1 function:

• N-terminal His-tags may interfere less with ligand binding than C-terminal tags since FABP1's binding pocket is formed by β-sheets toward the C-terminus

• Researchers should validate that His-tagged FABP1 retains binding affinities comparable to native protein

• Given FABP1's large binding cavity that accommodates up to two lipophilic ligands, His-tag interference may be ligand-specific

• Circular dichroism spectroscopy and thermal stability assays should be conducted to verify proper folding of His-tagged protein

• For functional studies, cleavable His-tags with appropriate protease sites may be optimal

What methodological approaches best assess FABP1-ligand interactions in vitro?

Several techniques yield complementary data on FABP1-ligand interactions:

• ANS fluorescence displacement assays effectively measure ligand binding to FABP1

• The cis-parinaroyl-CoA displacement assay provides sensitive detection of FABP1 binding to various ligands including endocannabinoids

• Isothermal titration calorimetry (ITC) offers thermodynamic binding parameters

• Nuclear magnetic resonance (NMR) studies provide structural insights into FABP1-ligand interactions

• X-ray crystallography of FABP1-ligand complexes reveals binding modes and structural adaptations

When comparing human and rodent FABP1, these methods should be applied consistently to identify species-specific differences in ligand interactions.

What are the most promising therapeutic targets related to human FABP1?

Therapeutic targeting of FABP1 is of active interest due to its ability to bind fibrates and various xenobiotics . Potential research approaches include:

• Developing small molecules that modulate FABP1's interaction with PPARα

• Investigating the role of FABP1 in the endocannabinoid system and its impact on hepatic lipid accumulation

• Exploring FABP1-targeted interventions for NAFLD, particularly in patients with the T94A variant

• Examining the protective role of FABP1 against oxidative stress in liver disease

How can FABP1 research advance personalized medicine approaches?

The prevalence of the T94A variant (26-38% minor allele frequency) provides an opportunity for personalized medicine approaches . Research methodologies should:

• Correlate T94A genotype with drug responses, particularly PPARα agonists

• Develop targeted nutritional interventions based on FABP1 variant status

• Investigate how FABP1 variants affect endocannabinoid metabolism and response to cannabinoid-based therapeutics

• Establish predictive biomarkers for NAFLD progression based on FABP1 status and function