Recombinant Human FGF R1α (IIIb)

Recombinant Human FGF R1α (IIIb) is used in research applications to study fibroblast growth factor (FGF) signaling, particularly in contexts where the specific activity, ligand binding, or inhibition of the FGF receptor 1 alpha (IIIb) isoform is relevant. This isoform is a naturally occurring, functional receptor preferentially expressed in tissues such as skin and brain.

Key scientific applications and rationale include:

• Ligand Binding and Specificity Studies: FGF R1α (IIIb) is one of several splice variants of FGFR1, differing in the third immunoglobulin-like domain, which determines ligand-binding specificity. The IIIb isoform preferentially binds certain FGFs (e.g., FGF-1, FGF-3, FGF-10), making it essential for dissecting isoform-specific FGF signaling pathways.

• Functional Assays and Inhibition Studies: Recombinant FGF R1α (IIIb) can be used as a soluble decoy receptor to inhibit FGF-mediated signaling in cell-based assays. For example, it has been shown to inhibit FGF acidic (FGF-1)-dependent proliferation of NR6R-3T3 mouse fibroblast cells, with an ED50 typically in the low ng/mL range. This allows researchers to assess the contribution of FGF signaling to cellular processes such as proliferation, differentiation, or migration.

• Neutralization and Competition Experiments: The recombinant protein can be used to neutralize endogenous or exogenous FGF activity in vitro, enabling the study of FGF-dependent biological effects and the validation of FGF pathway inhibitors.

• Receptor-Ligand Interaction Mapping: By using recombinant FGF R1α (IIIb), researchers can map the binding affinities and specificities of various FGF ligands, which is critical for understanding tissue-specific signaling and for developing targeted therapeutics.

• Assay Interference Controls: In multiplex assays (e.g., Luminex), recombinant FGF R1α (IIIb) can be used to test for potential assay interference or cross-reactivity, as it may interfere with FGF detection at higher concentrations.

• Tissue-Specific Signaling Research: Since FGF R1α (IIIb) is preferentially expressed in epithelial tissues, it is particularly relevant for studies on skin biology, wound healing, and epithelial-mesenchymal interactions.

Summary of best practices:

• Use recombinant FGF R1α (IIIb) at concentrations validated for your assay (typically low ng/mL for inhibition studies).
• Include appropriate controls to distinguish specific from non-specific effects.
• Store and handle the protein according to manufacturer and protocol recommendations to preserve activity.

In summary, recombinant human FGF R1α (IIIb) is a critical tool for dissecting FGF signaling pathways, studying receptor-ligand interactions, and modulating FGF activity in a controlled, isoform-specific manner in vitro.

Recombinant Human FGF R1α (IIIb) is generally not suitable as a standard for quantification or calibration in ELISA assays targeting FGF ligands (such as FGF1, FGF2, etc.), because it is a receptor protein, not the ligand itself. ELISA standards must match the analyte being measured in terms of structure and immunoreactivity.

Key considerations:

• ELISA standards should be either highly purified native or recombinant forms of the target analyte—in this case, the FGF ligand (e.g., FGF1, FGF2, FGF8, etc.), not the receptor (FGF R1α).
• Using a recombinant receptor (FGF R1α (IIIb)) as a standard for quantifying FGF ligands will not yield accurate results, as the antibodies in the ELISA are designed to recognize the ligand, not the receptor.
• Recombinant proteins are commonly used as standards when they are identical to the analyte being measured, and their concentration is accurately known.

Interference and specificity:

• Some assay datasheets note that recombinant human FGF R1α (IIIb) can interfere with FGF ligand detection at high concentrations, but this does not mean it can serve as a standard for quantification.
• ELISA kits for FGF ligands are calibrated against recombinant forms of the ligand, not the receptor.

Best practice:

• For quantification of FGF ligands in ELISA, use a recombinant or purified FGF ligand standard that matches the analyte of interest.
• If you wish to quantify FGF R1α (IIIb) itself, you must use an ELISA specifically designed for the receptor, with a standard curve generated using recombinant FGF R1α (IIIb).

Summary Table:

Conclusion:
Only use recombinant human FGF R1α (IIIb) as a standard for ELISA assays specifically designed to quantify FGF R1α (IIIb), not for assays targeting FGF ligands. For ligand quantification, use a standard that matches the ligand analyte.

Recombinant Human FGF R1α (IIIb) has been validated in published research primarily for applications involving receptor binding studies, cell signaling assays, and functional neutralization experiments.

Key validated applications include:

• Receptor Binding Studies: FGFR1-IIIb has been expressed in cell lines (e.g., L6 rat skeletal muscle myoblasts) and used to characterize ligand-receptor interactions, specifically demonstrating binding with FGF-1.

• Cell Signaling and Proliferation Assays: Recombinant Human FGF R1α (IIIb) Fc Chimera has been used to inhibit FGF acidic-induced proliferation in NR6R-3T3 mouse fibroblast cells, validating its role in modulating FGF signaling pathways.

• Neutralization Assays: The activity of Recombinant Human FGF R1α (IIIb) in cell proliferation assays can be neutralized by specific monoclonal antibodies, confirming its functional relevance in FGF-mediated cellular responses.

• Western Blot and ELISA: The recombinant protein has been used as a standard or target in Western blot and ELISA assays to detect and quantify FGF R1α (IIIb) and its interactions.

Supporting details:

• Specificity: The recombinant protein is validated to detect the IIIb isoform of human FGF R1, distinguishing it from IIIc isoforms and other FGF receptors.

• Functional Validation: Its ability to inhibit FGF-induced cell proliferation and be neutralized by antibodies demonstrates its biological activity and utility in mechanistic studies of FGF signaling.

• Research Utility: These applications are foundational for studies on FGF receptor biology, ligand specificity, and downstream signaling, as well as for screening potential therapeutic modulators of FGF pathways.

No published research currently validates this recombinant protein for clinical therapeutic use or in vivo disease models; its primary use is in vitro biochemical and cell-based assays. If you require protocols for a specific application (e.g., receptor binding, neutralization, or cell proliferation), please specify for more detailed guidance.

To reconstitute and prepare Recombinant Human FGF R1α (IIIb) protein for cell culture experiments, follow these general steps based on best practices for recombinant receptor proteins and available product data:

• Centrifuge the vial briefly before opening to ensure all lyophilized protein is at the bottom.
• Reconstitute the lyophilized protein in sterile, endotoxin-free phosphate-buffered saline (PBS), pH 7.2–7.3, or as specified in the product datasheet. A typical concentration for reconstitution is 0.1–1.0 mg/mL. For example, add 100–1000 μL of PBS per 0.1 mg of protein to achieve this range.
• Gently mix by pipetting up and down or swirling; do not vortex, as this may denature the protein.
• Aliquot the reconstituted solution to avoid repeated freeze-thaw cycles, which can reduce protein activity.
• Storage after reconstitution: Store aliquots at 2–8 °C for up to 1 month or at –20 °C to –70 °C for up to 6 months under sterile conditions. Avoid repeated freeze-thaw cycles.

Additional recommendations for cell culture use:

• For working solutions, dilute the reconstituted stock in cell culture medium or buffer containing a carrier protein such as 0.1% BSA to minimize adsorption and stabilize the protein.
• Confirm the absence of preservatives or additives that may affect cell viability or experimental outcomes.
• If the protein is an Fc chimera or fusion, ensure compatibility with your assay system and consider potential effects on receptor binding or signaling.

Summary protocol:

1. Spin down the vial.
2. Add sterile PBS (pH 7.2–7.3) to achieve 0.1–1.0 mg/mL.
3. Gently mix to dissolve.
4. Aliquot and store at –20 °C to –70 °C.
5. For cell culture, dilute in medium with carrier protein as needed.

Always consult the specific product datasheet or certificate of analysis for any unique instructions or formulation details, as buffer composition and concentration may vary between preparations.