Recombinant Human Activin RIB

Recombinant Human Activin RIB (also known as ALK4) is a key tool for studying TGF-β superfamily signaling, cell differentiation, and disease mechanisms, particularly in contexts such as neurobiology, development, cancer, and immunology. Its use enables precise manipulation and analysis of activin-mediated pathways in vitro and in vivo, facilitating mechanistic studies and therapeutic research.

Essential context and supporting details:

• Signal Transduction Studies: Activin RIB is the principal type I receptor for activin and inhibin molecules. It forms a receptor complex with Activin RIIB, which is essential for initiating activin signaling via phosphorylation of its cytoplasmic domain. Recombinant forms allow for controlled investigation of receptor-ligand interactions, downstream signaling, and pathway modulation.

• Functional Assays and Bioactivity: Recombinant Human Activin RIB is widely used in bioassays to study activin-dependent cellular responses, including cell proliferation, apoptosis, and differentiation. It is particularly valuable for dissecting the molecular mechanisms underlying embryonic cell fate determination, axis formation, and tissue development.

• Disease Modeling and Therapeutic Research: Activin RIB signaling is implicated in tumorigenesis, fibrosis, wound healing, and neurodegeneration. Recombinant receptor proteins enable researchers to model disease states, test inhibitors or agonists, and explore therapeutic interventions targeting the activin pathway.

• Neuroscience Applications: Activin RIB is involved in synaptic plasticity and neurogenesis. Studies using recombinant activin A and receptor constructs have demonstrated restoration of long-term potentiation (LTP) and neurotrophic effects in models of cognitive decline and neurodegeneration.

• Immunology and Cancer: Manipulation of activin receptor signaling can modulate immune cell function and tumor microenvironment, making recombinant Activin RIB a useful reagent for immunological assays and cancer research.

• Protein Engineering and Structural Studies: Recombinant forms, such as Fc chimeras, facilitate structural analysis, ligand trapping, and receptor binding studies, supporting drug discovery and protein engineering efforts.

Best practices:

• Use recombinant Activin RIB in controlled bioassays to quantify activin signaling and receptor-ligand interactions.
• Employ in cell-based assays to study differentiation, proliferation, and apoptosis in relevant cell types.
• Apply in disease models to investigate the role of activin signaling in pathology and test potential therapeutic agents.

Summary of scientific applications:

• Cell signaling research
• Developmental biology
• Neurobiology and synaptic plasticity
• Cancer and fibrosis modeling
• Immunological studies
• Protein engineering and drug discovery

Recombinant Human Activin RIB is thus a versatile reagent for elucidating activin pathway biology and advancing translational research in multiple fields.

Recombinant Human Activin RIB (also known as ALK-4 or ACVR1B) can be used as a standard for quantification or calibration in ELISA assays, but only if the ELISA is specifically designed to detect Activin RIB and the recombinant protein is validated for this purpose.

Key considerations:

• ELISA specificity: Most commercial ELISA kits for activin family proteins are designed to detect ligands such as Activin A, Activin B, or Activin AB—not the receptor Activin RIB/ALK-4. Using Activin RIB as a standard in these ligand-specific assays would not be appropriate, as the antibodies are not designed to recognize the receptor, and cross-reactivity is generally low or untested.
• Receptor-specific ELISAs: If you have an ELISA kit or have developed an assay specifically for human Activin RIB/ALK-4, then a recombinant Activin RIB protein can be used as a standard, provided it is of high purity, its concentration is accurately known, and it is compatible with the antibodies used in the assay. Some commercial ELISA kits for Activin RIB/ALK-4 do exist and include recombinant Activin RIB as the standard.
• Protein format: Recombinant proteins are often available in carrier-free or carrier-added (e.g., BSA) formulations. For ELISA standards, the carrier-added form is generally recommended for stability, unless the presence of BSA interferes with your assay.
• Validation: It is essential to validate that the recombinant Activin RIB standard produces a linear, reproducible standard curve in your specific ELISA setup. The standard should be prepared in the same matrix as your samples to minimize matrix effects.
• Bioactivity vs. immunoreactivity: Not all recombinant proteins are tested for both bioactivity and immunoreactivity. For ELISA calibration, immunoreactivity (i.e., recognition by the assay antibodies) is critical. Some recombinant proteins are not recommended for use as standards in bioassays unless specifically validated for that purpose.

Summary Table: Use of Recombinant Human Activin RIB as ELISA Standard

Best Practices:

• Confirm the specificity of your ELISA for Activin RIB/ALK-4.
• Use a recombinant standard that matches the protein detected by your assay.
• Validate the standard curve with your recombinant protein in your assay conditions.
• Use carrier-added protein for stability unless BSA interferes with your assay.

If your ELISA is not specifically for Activin RIB, using this recombinant protein as a standard will not yield accurate quantification. Always refer to your ELISA kit’s documentation and, if necessary, perform cross-reactivity and recovery experiments to confirm suitability.

Recombinant Human Activin RIB (ALK-4) has been validated for use in bioassays, ELISA standards, and surface plasmon resonance in published research.

Key validated applications include:

• Bioassay: Recombinant Human Activin RIB has been used in functional bioassays to study ligand-receptor interactions and signal transduction mechanisms, particularly in the context of the TGF-beta superfamily. This includes assays measuring its ability to bind activin and inhibin molecules and initiate downstream signaling.

• ELISA Standard: The protein is recommended as a standard in ELISA assays for quantifying activin RIB levels or for validating antibody specificity. Its use as a standard ensures accurate measurement in immunoassays.

• Surface Plasmon Resonance (SPR): Published studies have utilized recombinant Activin RIB in SPR experiments to characterize binding kinetics and affinities with ligands such as activin, inhibin, and other TGF-beta family members. This application is critical for understanding receptor-ligand interactions at a molecular level.

Additional context:

• Sample Types: Validated for use with whole cells and recombinant proteins in human and mouse models.
• Functional Studies: The protein has been employed to investigate growth, differentiation, cell fate determination, apoptosis, and tumorigenesis, reflecting its broad biological relevance.
• Blocking/Neutralizing: Recombinant Activin RIB/ALK-4 proteins are also used in blocking or neutralizing assays to dissect activin signaling pathways.

No evidence was found in the provided search results for validation in applications such as immunohistochemistry (IHC), western blot (WB), or flow cytometry for the recombinant protein itself; these are more commonly validated for antibodies targeting Activin RIB.

In summary, the main validated research applications for Recombinant Human Activin RIB are bioassays, ELISA standards, and SPR-based binding studies.

To reconstitute and prepare Recombinant Human Activin RIB protein for cell culture experiments, dissolve the lyophilized protein at a concentration of 100 μg/mL in sterile PBS. This concentration is commonly recommended for bioassays and cell culture applications.

Essential steps and best practices:

• Centrifuge the vial briefly before opening to ensure all lyophilized powder is at the bottom.
• Add sterile PBS directly to the vial to reach the desired concentration (e.g., for 100 μg protein, add 1 mL PBS for 100 μg/mL).
• Gently mix by pipetting or swirling; avoid vigorous vortexing to prevent protein denaturation.
• Aliquot the reconstituted solution if not using immediately, to avoid repeated freeze-thaw cycles.
• Storage after reconstitution:
  • Short-term: 2–8 °C for up to 1 month under sterile conditions.
  • Long-term: −20 °C to −70 °C for up to 6 months under sterile conditions.
• Avoid repeated freeze-thaw cycles to maintain protein integrity.

Additional considerations:

• If your application requires a different concentration, adjust the volume of PBS accordingly using the formula:
  [\text{Volume to add (mL)} = \frac{\text{Mass in vial (μg)}}{\text{Desired concentration (μg/mL)}}]
• For cell culture, ensure all solutions and containers are sterile to prevent contamination.
• If the protein is carrier-free, consider adding a carrier protein (e.g., BSA) if stability is a concern, unless your experiment requires carrier-free conditions.

Summary Table:

Always consult the product-specific Certificate of Analysis or datasheet for any unique instructions.