Recombinant Human Maspin (SERPINB5)

Recombinant Human Maspin (SERPINB5) offers several compelling advantages for research applications, particularly in cancer biology, cell adhesion studies, and epithelial cell biology.

Tumor Suppressor Properties

Maspin functions as a non-inhibitory serpin with potent tumor suppressor activity. Unlike classical serpins, it does not undergo the conformational transition characteristic of active serine protease inhibitors, yet it effectively blocks the growth, invasion, and metastatic properties of mammary tumors. This unique mechanism makes it valuable for investigating tumor suppression pathways independent of protease inhibition.

Cytoskeleton Interaction and Cell Morphology

One of Maspin's most distinctive features is its direct interaction with the cytoskeleton. Recombinant Maspin binds to both F-actin and stabilized microtubules in the nanomolar range, suppressing microtubule growth at physiologically relevant concentrations. This capability enables researchers to study:

• Epithelial cell shape regulation and maintenance of epithelial morphology
• Cytoskeletal dynamics and reorganization
• Cell-cell junction assembly and stability
• The interface between adhesion sites and the cytoskeleton

Cell Adhesion and Migration Modulation

When added to cell culture medium, recombinant Maspin modulates cell adhesion and motility through interaction with the uPA/uPAR/β1-integrin complex at the cell surface. This makes it particularly useful for investigating:

• Cancer cell invasion mechanisms
• Cell migration inhibition pathways
• Adhesion-dependent signaling cascades
• Epithelial plasticity and phenotypic transitions

Broad Cancer Research Applications

Clinical research has consistently linked Maspin expression to improved outcomes across multiple cancer types, including breast, prostate, pancreatic, and lung cancers. This makes recombinant Maspin valuable for studying tumor suppression mechanisms in diverse cancer models and for developing therapeutic strategies targeting these pathways.

Experimental Versatility

Recombinant Maspin is typically produced in bacterial expression systems and is available as a non-glycosylated protein of approximately 42.1 kDa containing 375 amino acid residues. Its availability in various formats (with or without affinity tags) allows for flexible experimental designs, including affinity purification studies to identify novel protein-protein interactions.

You can use recombinant human Maspin (SERPINB5) as a standard for quantification or calibration in ELISA assays if the recombinant protein is of high purity, its concentration is accurately known, and it is compatible with the antibodies used in your specific ELISA system. However, there are important caveats and best practices to consider:

• Purity and Quantification: The recombinant Maspin should be highly purified and its concentration precisely determined, ideally by methods such as HPLC or BCA assay, to ensure accurate standard curve generation.
• Epitope Compatibility: The recombinant protein must contain the same epitopes recognized by the capture and detection antibodies in your ELISA. Differences in expression systems, folding, or post-translational modifications can affect antibody recognition.
• Kit-Specific Recommendations: Many commercial ELISA kits use recombinant Maspin as their standard, but manufacturers often caution that standards from other sources may not be fully compatible due to differences in protein sequence, folding, or modifications. For example, one ELISA kit manual states:

  "We cannot guarantee that our kit will be able to detect recombinant proteins produced by other companies. We do NOT recommend using this ELISA kit for the detection of other recombinant proteins".

• Validation Required: If you are not using the standard provided with a commercial kit, you must validate that your recombinant Maspin produces a standard curve with expected sensitivity, linearity, and parallelism to native samples.

Best Practices:

• Prepare a dilution series of your recombinant Maspin in the same buffer as your samples.
• Run the standard curve in parallel with the kit’s standard (if available) and compare results for linearity and parallelism.
• Confirm that the detection range and sensitivity meet your assay requirements.

Summary Table:

In summary, recombinant human Maspin can be used as a standard in ELISA, but only if you validate its performance in your specific assay context and ensure it is recognized equivalently to the standard provided by the kit or to native Maspin in your samples.

Recombinant Human Maspin (SERPINB5) has been validated in published research for several key applications, primarily related to its roles in cell biology, cancer research, and cytoskeletal regulation. The main applications supported by the literature include:

1. Cell Adhesion and Motility Assays
   Recombinant Maspin has been used to modulate cell adhesion and motility in epithelial and cancer cell lines. Studies show that adding recombinant Maspin to the cell medium influences cell adhesion and migration, often through interaction with cell surface receptors such as the uPA/uPAR/β1-integrin complex.

2. Cytoskeletal Interaction Studies
   Recombinant Maspin has been validated for in vitro reconstitution assays to study its direct binding to cytoskeletal components, including microfilaments (F-actin) and microtubules. These assays demonstrate that Maspin interacts with both actin and tubulin, regulating microtubule dynamics and cytoskeletal organization.

3. Affinity Purification and Protein Interaction Studies
   Recombinant Maspin is used as bait in affinity purification-mass spectrometry (AP/MS) experiments to identify interacting partners, including cytoskeletal proteins such as plectin, α-actinin-4, myosin II subunits, actin, and tubulin.

4. Microtubule Growth and Dynamics Assays
   Recombinant Maspin has been shown to suppress microtubule growth in vitro and in cells, with effects observed at low (nanomolar) concentrations. It can also decorate and recruit free tubulin to microtubule seeds, further validating its role in microtubule regulation.

5. Apoptosis and Chemosensitivity Studies
   Recombinant Maspin has been used to sensitize tumor cells to drug-induced apoptosis, particularly in prostate and bladder cancer models. It enhances chemosensitivity to agents such as cisplatin.

6. Cellular Localization and Immunostaining
   Recombinant Maspin, often tagged (e.g., GFP), is used to study its subcellular localization, including its presence at the cortical cytoskeleton, lamellipodia, and mitotic spindle, as well as its nuclear accumulation under certain conditions.

7. Gene Expression and Functional Rescue Experiments
   Recombinant Maspin is used in ectopic expression studies to restore Maspin function in tumor cells that have lost its expression, allowing researchers to study its tumor-suppressive effects on cell growth, invasion, and epithelial-mesenchymal transition.

These applications highlight the versatility of recombinant Maspin in both basic research and translational studies, particularly in the context of cancer biology and cytoskeletal regulation.

To reconstitute and prepare Recombinant Human Maspin (SERPINB5) protein for cell culture experiments, dissolve the lyophilized protein in sterile, deionized water to achieve a stock concentration between 0.1–1.0 mg/mL. Mix gently to avoid foaming and ensure complete dissolution of the protein.

Detailed protocol:

• Add sterile, deionized water directly to the vial containing lyophilized Maspin protein.
• Target a final concentration of 0.1–1.0 mg/mL for your stock solution.
• Gently mix by swirling or inverting the vial; avoid vigorous shaking or vortexing, which can denature the protein.
• Allow the protein to dissolve at room temperature for 15–30 minutes with gentle agitation.
• If recommended by the datasheet, you may add 5–50% glycerol to the solution for enhanced stability, especially if you plan to store aliquots at −20°C or −80°C.
• Once fully dissolved, aliquot the stock solution to avoid repeated freeze-thaw cycles, which can degrade the protein.
• Store aliquots at −20°C to −80°C for long-term use.

Preparation for cell culture:

• Before adding to cells, dilute the stock solution into your cell culture medium (e.g., DMEM with 10% FBS) to the desired working concentration, typically in the nanomolar to low micromolar range, depending on experimental requirements.
• Ensure the final solution is sterile; filter through a 0.22 μm filter if necessary.
• Add the recombinant Maspin directly to the cell culture medium and proceed with your experiment.

Additional notes:

• Always consult the specific product datasheet for any unique requirements regarding reconstitution buffer or additives.
• Avoid repeated freeze-thaw cycles by preparing single-use aliquots.
• If the protein is tagged (e.g., His-tag), confirm compatibility with your downstream applications.

This protocol ensures optimal solubility and stability of recombinant Maspin for cell-based assays.