Recombinant Human Fibroblast growth factor 1 protein (FGF1) (Active)

What is FGF1 and what are its basic biological functions?

FGF1, also known as acidic Fibroblast Growth Factor, is a 16-17 kDa nonglycosylated member of the FGF family of mitogenic peptides. It functions as a potent inducer of DNA synthesis, cell proliferation, and demonstrates chemotactic activities . FGF1 is produced by multiple cell types and stimulates the proliferation of cells of mesodermal origin and many cells of neuroectodermal, ectodermal, and endodermal origin .

Beyond its classical mitogenic role, FGF1 regulates cardiogenesis through protein kinase C signaling, functions as an insulin sensitizer, and mediates adipose tissue remodeling . It plays significant roles in development, regeneration, and angiogenesis . Recent research has also uncovered its importance in glucose homeostasis .

What are the alternative names for FGF1 in the scientific literature?

FGF1 appears in scientific literature under numerous alternative designations:

• Fibroblast Growth Factor 1

• Acidic Fibroblast Growth Factor

• HBGF-1 (Heparin-binding growth factor 1)

• β-endothelial growth factor

• ECGF (Endothelial cell growth factor)

• ECGF-β (Endothelial cell growth factor-β)

• GLIO703

• FGFA

• ECGFA

• AFGF

• Endothelial cell growth factor-α

• ECGFB

• FGF-α

• aFGF

This diversity of names reflects the protein's discovery in different contexts and its multiple biological roles across various tissues and cell types.

What is the typical structure and molecular characteristics of recombinant human FGF1?

Recombinant human FGF1 typically has the following characteristics:

The amino acid sequence of full-length human FGF1 is: MFNLPPGNYK KPKLLYCSNG GHFLRILPDG TVDGTRDRSD QHIQLQLSAE SVGEVYIKST ETGQYLAMDT DGLLYGSQTP NEECLFLERL EENHYNTYIS KKHAEKNWFV GLKKNGSCKR GPRTHYGQKA ILFLPLPVSS D .

What typical bioassays are used to confirm FGF1 activity?

FGF1 activity is commonly assessed through cell proliferation assays using specific responsive cell lines. The most frequently used methods include:

• Proliferation of BALB/c 3T3 cells: Human FGF1 stimulates proliferation with an ED50 typically less than 2 ng/ml, corresponding to an expected specific activity of 5.0 × 10^5 units/mg .

• NR6R-3T3 mouse fibroblast cell proliferation: Recombinant Human FGF1 stimulates cell proliferation with an ED50 of 0.015-0.15 ng/mL in the presence of 10 μg/mL of heparin .

• SDS-PAGE analysis: Protein quality is assessed through SDS-PAGE under reducing and non-reducing conditions, with silver staining typically showing a single band at the expected molecular weight (16-19 kDa) .

These standardized bioassays provide reliable measures of both protein quality and functional activity, essential for research applications.

How can researchers optimize FGF1 signaling in experimental systems?

Optimizing FGF1 signaling in experimental systems requires careful consideration of several parameters:

• Heparin co-administration: FGF1 activity is significantly enhanced by heparin or heparan sulfate. For optimal activity, researchers should include 10 μg/mL of heparin in their experimental systems . The heparin-binding properties of FGF1 are critical for stabilizing the FGF1-FGFR complex .

• Receptor expression profiling: Before designing experiments, characterize the FGFR expression profile of your cell system. FGF1 can bind and activate all FGFR isoforms, but the expression levels will determine sensitivity .

• Thermal stability considerations: FGF1 complexed with its receptor and heparin demonstrates increased thermal stability. In experimental setups requiring elevated temperatures, ensure the presence of stabilizing factors. The FGF1 WT-FGFR1c-HS complex shows significantly higher thermal stability (higher Tm) compared to complexes without heparin .

• Careful storage and handling: Reconstituted FGF1 should be stored at appropriate temperatures (-20°C to -80°C) and minimize freeze-thaw cycles to maintain activity. Consider adding carrier proteins for dilute solutions to prevent adsorption to surfaces .

• Signal pathway monitoring: For comprehensive analysis, monitor multiple downstream pathways as FGF1 activates diverse signaling cascades including MAPK/ERK, PI3K/AKT, and PLCγ pathways .

How can researchers engineer FGF1 variants with altered functional properties?

Engineering FGF1 variants with modified properties has become an important approach for dissecting its various functions. Key strategies include:

• Heparin-binding site modifications: Mutating key residues in the heparin-binding site (HBS) can alter the stability of FGF1-FGFR dimers and subsequently modify signaling strength. For example, the FGF1^ΔHBS triple mutant (K127D, K128Q, K133V) shows compromised heparin-binding affinity and reduced ability to promote HS-assisted FGFR dimerization .

• Structure-guided design: Using crystallographic data of FGF1-FGFR-heparin complexes to identify critical interaction residues. This approach allows for precise modifications that affect specific aspects of FGF1 function .

• Biophysical validation: Employ techniques such as surface plasmon resonance (SPR) to confirm altered binding properties, size-exclusion chromatography with multi-angle light scattering (SEC-MALS) to assess complex formation, and thermal shift assays to evaluate stability changes .

• Functional validation: Compare wild-type and variant FGF1 proteins in cell-based assays measuring both mitogenic responses (e.g., BrdU incorporation) and metabolic responses (e.g., insulin sensitization, glucose uptake) .

The utility of this approach is demonstrated by the FGF1^ΔHBS variant, which showed a ~13°C lower unfolding temperature than wild-type FGF1 when in complex with FGFR1c and heparin, confirming reduced stability of the signaling complex .

What methodologies are used to study FGF1-FGFR signaling networks?

Studying FGF1-FGFR signaling networks requires multifaceted approaches:

• Curated pathway databases: Researchers have developed resources like NetPath that document specific pathway reactions triggered by the FGF-1/FGFR system across various cell types and tissues .

• Systematic literature mining: Comprehensive literature searches using databases like NCBI PubMed to retrieve and document molecular events triggered by FGF1/FGFR signaling, including:

  • Physical associations between proteins

  • Posttranslational modifications (PTMs)

  • Changes in subcellular localization

  • Activation or inhibition of specific proteins

  • Regulation of gene expression

• Phosphoproteomics: Mass spectrometry-based approaches to identify proteins phosphorylated following FGF1 stimulation, revealing activation of signaling cascades .

• Pathway visualization tools: Software platforms that enable visualization and analysis of complex signaling networks, integrating data from multiple experimental sources .

• ERK-dependent signaling analysis: Monitoring phosphorylation of downstream targets such as DRP1 at Ser616, which mediates processes like mitochondrial fission and mitophagy in response to FGF1 stimulation .

These methodologies provide a comprehensive understanding of the complex signaling cascades initiated by FGF1, essential for both basic research and therapeutic development.

How can FGF1 be optimally used for muscle stem cell (MuSC) research?

For muscle stem cell research, FGF1 plays a crucial role in promoting proliferation while maintaining stemness. Optimal utilization involves:

• Serum-free culture conditions: Recombinant FGF1 significantly enhances the proliferation of porcine MuSCs under serum-free conditions, enabling animal component-free culture systems essential for both basic research and applications like cultured meat production .

• Mitochondrial dynamics assessment: FGF1 induces mitochondrial fission and mitophagy by activating ERK-dependent phosphorylation of DRP1 at Ser616, resulting in improved mitochondrial function and proliferation capacity in MuSCs. Researchers should monitor these parameters when studying FGF1 effects on muscle progenitors .

• Species-specific recombinant proteins: While human FGF1 shows cross-reactivity with cells from multiple species due to high sequence conservation (human FGF1 shares 92%, 96%, 96%, and 96% amino acid sequence identity with bovine, mouse, porcine, and rat FGF1, respectively), species-matched recombinant proteins may provide optimal results for specific applications .

• Dosage optimization: Determine the optimal concentration of FGF1 for MuSC proliferation without triggering premature differentiation. This typically requires dose-response experiments for each specific cell isolation and culture system .

• Combination with other factors: For long-term expansion, combining FGF1 with other growth factors and small molecules that maintain stemness can enhance outcomes .

What are the research applications of FGF1 in neural and epithelial cell systems?

FGF1 has diverse applications in neural and epithelial cell research:

For neural systems:

• Neural progenitor maintenance: FGF1's neurotrophic properties make it ideal for maintaining neural progenitors in culture .

• Glial cell support: FGF1 supports oligodendrocytes and astroglia, making it valuable for studying neuron-glia interactions .

• Remyelination studies: In multiple sclerosis research, FGF1 has shown potential to promote remyelination of neurons, making it a valuable tool for both basic and translational neuroscience .

For epithelial systems:

• Organoid development: FGF1 promotes branching of epithelial cells, making it useful for embryonic lung epithelium cultures and human iPSC-derived ureteric bud organoids .

• Endothelial cell proliferation: FGF1 is used to promote the differentiation and proliferation of endothelial cells, supporting vascular research .

• Angiogenesis models: Due to its role in blood vessel formation, FGF1 is employed in models of developmental and therapeutic angiogenesis, including potential applications for myocardial infarction treatment .

These applications highlight the versatility of FGF1 across different cell types and research areas, from basic developmental biology to disease modeling and regenerative medicine.

How can researchers utilize FGF1 for metabolic research and diabetes studies?

FGF1 has emerged as a significant factor in metabolic research, particularly for diabetes studies:

• Glucose homeostasis models: FGF1 has been discovered to play important roles in glucose regulation. In experimental models, FGF1 injections can lower glucose levels without risk of hypoglycemia through effects on glucose-sensing neuronal circuits .

• Uncoupling mitogenic and metabolic functions: Engineered FGF1 variants like FGF1^ΔHBS allow researchers to separate the protein's growth-promoting effects from its metabolic regulatory effects. This enables more precise studies of metabolic pathways without confounding effects on cell proliferation .

• Insulin sensitivity research: FGF1 functions as an insulin sensitizer, making it valuable for studying mechanisms of insulin resistance and for developing potential therapies for Type 2 diabetes .

• Adipose tissue remodeling: FGF1 mediates adipose tissue remodeling processes, offering a tool for investigating adipose tissue biology and obesity-related research .

• Central nervous system regulation: Studies suggest FGF1 affects metabolic regulation through central nervous system mechanisms, opening avenues for research into brain-peripheral tissue communication in metabolic disorders .

These diverse applications in metabolic research highlight FGF1's potential beyond its classical mitogenic role, positioning it as an important molecule for both basic and translational diabetes research.

What are common challenges in recombinant FGF1 production and how can they be addressed?

Production of high-quality recombinant FGF1 presents several challenges:

• Soluble expression: Achieving high yields of soluble FGF1 in E. coli can be challenging. Recent advances have established efficient methods for soluble expression, with reported yields of up to 48 mg of purified protein per liter of culture for porcine FGF1 . Strategies include:

  • Optimization of induction temperature (typically lower temperatures improve solubility)

  • Selection of appropriate E. coli strains

  • Use of fusion tags that enhance solubility

  • Co-expression with chaperones

• Protein stability: FGF1 can be relatively unstable in solution. Approaches to improve stability include:

  • Addition of heparin during purification and storage

  • Inclusion of stabilizing excipients

  • Careful buffer optimization

  • Storage at appropriate temperatures (-20°C to -80°C)

• Endotoxin removal: As FGF1 is typically produced in E. coli, endotoxin contamination must be minimized, especially for sensitive cell culture applications. Commercial preparations typically guarantee endotoxin levels ≤1.00 EU/μg .

• Activity verification: Ensuring consistent biological activity between batches is critical. Standardized bioassays using responsive cell lines (BALB/c 3T3 or NR6R-3T3) should be employed to verify each preparation's potency .

• Animal component-free production: For certain applications, animal component-free production is essential. This requires careful selection of all media components and purification reagents throughout the production process .

How should researchers optimize FGF1 storage and handling for maximum activity?

Proper storage and handling of FGF1 is crucial for maintaining its biological activity:

• Reconstitution recommendations:

  • Use sterile, buffered solutions (typically PBS) for reconstitution

  • For low concentration solutions, consider adding carrier proteins (e.g., BSA) to prevent adsorption to surfaces

  • Filter sterilize through 0.2 μm filters if necessary

• Storage conditions:

  • Store lyophilized FGF1 at -20°C to -80°C

  • After reconstitution, prepare single-use aliquots to avoid repeated freeze-thaw cycles

  • Short-term storage (1-2 weeks) at 4°C is possible for working solutions with appropriate preservatives

• Stability considerations:

  • FGF1 is more stable in the presence of heparin

  • Avoid repeated freeze-thaw cycles which can lead to significant loss of activity

  • Monitor pH during storage as shifts can affect protein stability

• Working solution preparation:

  • Prepare fresh working solutions when possible

  • When using FGF1 in cell culture, include heparin (typically 10 μg/mL) for maximum activity

  • Calculate ED50 based on known values (0.015-0.15 ng/mL in the presence of heparin for NR6R-3T3 cells)

• Quality control:

  • Periodically verify activity of stored FGF1 using standardized bioassays

  • Monitor protein integrity through techniques like SDS-PAGE if activity appears compromised

These recommendations will help ensure consistent experimental results when working with this sensitive protein.

What controls should be included in FGF1 signaling experiments?

Robust FGF1 signaling experiments require comprehensive controls:

• Activity controls:

  • Positive control: A standardized preparation of FGF1 with verified activity

  • Negative control: Vehicle-only treatment following identical handling procedures

  • Dose-response curve: Multiple concentrations of FGF1 to demonstrate specificity and determine optimal working concentration

• Receptor specificity controls:

  • FGFR inhibitor controls: Small molecule inhibitors of FGFR kinase activity (e.g., PD173074)

  • Heparin control: Experiments with and without heparin to demonstrate its effect on signaling

  • Heparinase treatment: To demonstrate the requirement for endogenous cell surface heparan sulfate

• Pathway validation controls:

  • Inhibitors of downstream pathways (e.g., U0126 for MEK/ERK pathway)

  • Positive controls for each pathway being investigated

  • Time-course analysis to capture both early and late signaling events

• FGF1 variant controls:

  • When studying specific aspects of FGF1 signaling, engineered variants like FGF1^ΔHBS can serve as valuable controls to distinguish between different functional outcomes

  • Wild-type comparison for any modified FGF1 protein

• Cell-specific controls:

  • Cell lines with known FGFR expression profiles

  • FGFR knockdown/knockout controls

  • For metabolic studies, insulin sensitivity controls to differentiate FGF1-specific effects from general metabolic changes

What are emerging therapeutic applications of FGF1 research?

FGF1 research is opening several promising therapeutic frontiers:

• Diabetes treatment: FGF1's ability to lower glucose levels without hypoglycemia risk makes it a promising candidate for treating Type 2 diabetes. The engineering of FGF1 variants with selective metabolic activity while minimizing mitogenic potential represents a significant advance in this direction .

• Neurodegenerative diseases: FGF1 shows potential in treating conditions like multiple sclerosis through its ability to promote remyelination of neurons. Research is exploring delivery methods and optimal dosing regimens for neurological applications .

• Cardiovascular therapies: FGF1's role in angiogenesis has potential applications for novel therapies following myocardial infarction, potentially promoting revascularization of damaged heart tissue .

• Regenerative medicine: Applications in tissue regeneration and wound healing leverage FGF1's mitogenic properties for accelerating repair processes .

• Cancer therapies: While FGF1 can promote cancer progression in some contexts, understanding its signaling has led to investigations into targeted therapies to inhibit FGF1 signaling in cancer cells .

These diverse therapeutic possibilities highlight the importance of continued fundamental research into FGF1 biology and signaling mechanisms.

How is FGF1 research contributing to sustainable food technology?

Recent advances demonstrate FGF1's emerging role in sustainable food technology:

• Cultured meat production: Recombinant FGF1 is being employed to develop animal component-free in vitro systems for muscle stem cell (MuSC) expansion. Recent research reported in January 2025 established an efficient method for producing recombinant porcine FGF1 (rpFGF1) with yields of 48 mg of purified protein per liter of bacterial culture .

• Serum-free culture systems: Treatment with rpFGF1 significantly enhanced proliferation of porcine MuSCs under serum-free conditions, addressing a key challenge in scaling cultured meat production without animal-derived components .

• Mitochondrial function enhancement: rpFGF1 was shown to induce mitochondrial fission and mitophagy by activating ERK-dependent phosphorylation of DRP1 at Ser616, resulting in improved mitochondrial function and proliferation capacity in porcine MuSCs. This mechanistic understanding enables optimization of culture conditions .

• Scalability improvements: The development of efficient bacterial expression systems for FGF1 production contributes to the economic feasibility of cultured meat by providing cost-effective growth factors .

This research addresses the challenges associated with traditional livestock farming while working toward meeting future protein demands through technological innovation.

What new methodologies might advance our understanding of FGF1 signaling specificity?

Several innovative approaches are poised to deepen our understanding of FGF1 signaling specificity:

• Single-cell signaling analysis: Applying single-cell technologies to track FGF1 responses would reveal cell-to-cell variability in signaling outcomes and potentially identify previously unrecognized subpopulations with distinct response patterns.

• Structural biology advances: Cryo-electron microscopy and advanced crystallography of FGF1-FGFR complexes in different cellular contexts could reveal subtleties in receptor conformation that dictate downstream signaling specificity .

• Systems biology integration: Comprehensive network mapping of FGF1/FGFR signaling using multi-omics approaches (transcriptomics, proteomics, metabolomics) can provide a holistic view of pathway interactions and cross-talk .

• CRISPR-based signaling perturbation: Systematic CRISPR screens targeting components of FGF1 signaling networks could identify new regulators and reveal unexpected pathway connections.

• Engineered cellular systems: Designer cell lines with controlled expression of specific FGFR isoforms and downstream effectors would allow precise dissection of signaling branch points.

• Advanced imaging approaches: Techniques such as live-cell FRET sensors for monitoring FGF1-induced conformational changes in real-time could provide dynamic insights into signaling initiation and propagation.

These methodological advances will be essential for developing the next generation of FGF1-based therapeutics and research tools.