HMMR Antibody

What is HMMR and why is it important in research?

HMMR (Hyaluronan-Mediated Motility Receptor) is a protein that functions as a receptor for hyaluronan and mediates cell motility. It is also known as RHAMM, CD168, IHABP (intracellular hyaluronic acid-binding protein), and receptor for hyaluronan-mediated motility . The protein has a molecular weight of approximately 84.1 kilodaltons and plays crucial roles in:

• Cell migration and motility

• Cell cycle progression

• Mitotic spindle formation

• Wound repair responses

• Cancer progression mechanisms

HMMR is particularly important in research because its expression is typically low in normal tissues but significantly upregulated in various cancers and during wound repair processes . This differential expression pattern makes it a valuable target for understanding disease mechanisms and potential therapeutic interventions.

What detection methods are available for HMMR antibodies?

HMMR antibodies can be utilized across multiple detection platforms with varying sensitivity and specificity profiles:

For optimal results, most protocols recommend antigen retrieval with TE buffer pH 9.0 for IHC applications, though citrate buffer pH 6.0 can serve as an alternative .

How should HMMR antibodies be stored and handled?

Proper storage and handling are critical to maintaining antibody functionality:

• Store at -20°C for long-term preservation

• Stable for approximately one year after shipment when properly stored

• Aliquoting is unnecessary for -20°C storage of small (20μl) volumes

• Contains PBS with 0.02% sodium azide and 50% glycerol at pH 7.3

• Avoid repeated freeze-thaw cycles as this can degrade antibody quality

• Some formulations of small volume antibodies may contain 0.1% BSA as a stabilizer

How can I validate the specificity of my HMMR antibody?

Antibody validation is a critical step to ensure experimental rigor. For HMMR antibodies, consider these validation approaches:

• Knockdown/Knockout Controls: Use shRNA or siRNA-mediated HMMR depletion to confirm specificity. In neuronal studies, researchers observed significant decreases in HMMR immunofluorescence signal in the soma and neurites of HMMR-depleted neurons, confirming antibody specificity .

• Peptide Competition Assay: Pre-incubate the antibody with the immunizing peptide before application to samples. Signal reduction indicates specific binding.

• Multiple Antibody Validation: Compare staining patterns using antibodies targeting different epitopes of HMMR. Consistent patterns suggest specificity.

• Western Blot Molecular Weight Verification: Confirm that the detected band aligns with the expected molecular weight (84 kDa for full-length HMMR) .

• Positive/Negative Control Tissues: Test antibodies on tissues known to express or lack HMMR expression. Validated positive samples include HepG2 cells, K-562 cells, C6 cells, and T-47D cells for Western blotting .

What are the methodological considerations for studying HMMR in leukemic stem cells?

When investigating HMMR in leukemic stem cells (LSCs), several methodological considerations must be addressed:

• Expression Level Analysis: Research has shown that HMMR expression in leukemic stem cells does not differ significantly from expression in hematopoietic stem cells from healthy controls, complicating its use as a specific target .

• Population Purification: Careful cell sorting protocols are essential as HMMR expression varies across cell populations. CD34+ populations require specific isolation parameters.

• Proliferation Status Consideration: HMMR expression is cell cycle-dependent, with maximal expression during G2/M phase. This must be accounted for when comparing populations with different proliferation rates .

• Cross-Reactivity Controls: Include controls for proliferating CD34+ cells from healthy donors and activated T cells to account for background HMMR expression that could confound interpretation .

• Quantitative Assessment Methods: Employ both protein and mRNA level analyses, as post-transcriptional regulation may lead to discrepancies between transcript and protein abundance.

Research has suggested that despite its initial promise, HMMR may not fulfill the criteria of an ideal target antigen for immunotherapy of acute myeloid leukemia due to these expression pattern complexities .

How can HMMR antibodies be utilized to study cancer immunity and immune evasion mechanisms?

HMMR has emerged as an important factor in cancer immune evasion, particularly through its regulation of the "don't eat me" signal CD47. Researchers can leverage HMMR antibodies to investigate these pathways:

• Macrophage Phagocytosis Assays: HMMR targeting can reduce CD47 expression on cancer cells, stimulating macrophages to phagocytose tumor cells. This approach has shown promise for mitigating adverse reactions associated with direct CD47 antibody blockade .

• Signaling Pathway Analysis: HMMR interacts with FAK to activate downstream NF-κB signaling, which regulates CD47 expression. Co-immunoprecipitation with HMMR antibodies can help elucidate this non-canonical cytoplasmic regulatory pathway that functions independently of CD44 .

• T-Cell Infiltration Studies: Loss of HMMR enhances CD8+ T cell infiltration in tumors, suggesting HMMR as a target whose modulation could synergize with anti-PD-1 therapies. Immunohistochemistry with HMMR antibodies can help stratify patients who might respond better to immunotherapy .

• Non-Canonical Signaling Detection: HMMR antibodies can identify the CD44-independent recruitment and activation of FAK through HMMR's C-terminal region in the cytoplasm, explaining why patients with HMMR^high/CD44^low expression maintain higher CD47 expression .

These applications hold particular promise for hepatocellular carcinoma treatment strategies that aim to overcome antiphagocytosis mechanisms independent of directly blocking CD47.

What are the key methodological considerations when using HMMR antibodies in proximity ligation assays?

Proximity Ligation Assay (PLA) is a powerful technique for detecting protein-protein interactions that has been successfully applied to HMMR research:

• Antibody Compatibility: When performing PLA for HMMR interactions, antibody pairs must be raised in different species to allow species-specific secondary antibodies. For example, in neuronal studies, anti-HMMR and anti-β-III-tubulin antibodies from different species were used to study HMMR-microtubule interactions .

• Distance Constraints: PLA only generates signals when proteins are within ~40 nm of each other, making it ideal for confirming direct interactions. Fluorescent PLA puncta detected in neuronal soma and neurites confirmed HMMR association with microtubules .

• Controls: Both positive and negative controls are essential:

  • Omit one primary antibody to confirm signal specificity

  • Include known interacting partners as positive controls

  • Test in cells where one partner is depleted (e.g., HMMR knockdown cells)

• Signal Interpretation: Carefully distinguish between generalized background and specific punctate signals. In neuronal studies, fluorescent PLA puncta were only observed when both primary antibodies were present, confirming signal specificity .

• Subcellular Localization Analysis: PLA can reveal interaction sites within cells. HMMR-microtubule interactions were detected in both soma and along neurites in hippocampal neurons, providing spatial information about this association .

How do analytical techniques for monoclonal antibodies apply to HMMR antibody characterization and quality control?

Comprehensive characterization of HMMR antibodies requires multiple complementary analytical approaches:

For HMMR antibodies specifically, special consideration should be given to:

• Epitope Mapping: Determining which region of HMMR (e.g., C-terminus amino acids 706-724) is recognized by the antibody is crucial for understanding potential cross-reactivity with HMMR isoforms .

• Isoform Recognition: Some antibodies only detect specific HMMR isoforms. At least two alternatively spliced isoforms of HMMR exist, and some antibodies will only detect the larger isoform .

• Cross-Reactivity Profiling: Thorough testing against related proteins is essential. Some antibodies have been validated to show no cross-reactivity with other proteins .

• Post-Translational Modification Sensitivity: Assess whether antibody binding is affected by glycosylation, phosphorylation, or other modifications to HMMR that may be context-dependent .

These analytical approaches ensure that HMMR antibodies meet the rigorous standards required for research applications, particularly in complex disease models where precise target recognition is essential.

What are common issues when using HMMR antibodies in tissue samples and how can they be addressed?

Researchers may encounter several challenges when detecting HMMR in tissue samples:

• Variable Expression Levels: HMMR expression can vary significantly between tissue types and disease states. While normally poorly expressed in most normal tissues, its expression increases during wound repair in response to hypoxia and fibrogenic factors .

  Solution: Include positive control tissues (e.g., human tonsillitis tissue for IHC) and compare relative expression rather than absolute signals .

• Antigen Retrieval Challenges: Insufficient antigen retrieval can lead to false negatives.

  Solution: For HMMR detection, suggested antigen retrieval with TE buffer pH 9.0 is recommended, though citrate buffer pH 6.0 can be used as an alternative for IHC applications .

• Background Staining: Non-specific background can complicate interpretation.

  Solution: Include blocking steps with appropriate sera (based on secondary antibody species), optimize antibody concentrations (starting with 1:50-1:500 dilutions for IHC), and include appropriate negative controls .

• Cell Cycle-Dependent Expression: Since HMMR expression is maximal during G2/M phase, heterogeneous cell cycle states within tissue can create variable staining patterns .

  Solution: Consider dual staining with cell cycle markers to correlate HMMR expression with specific cell cycle phases.

• Distinguishing Isoforms: Different HMMR isoforms may have distinct functions and localization patterns.

  Solution: Use antibodies targeting specific domains and compare results with antibodies recognizing different epitopes to build a comprehensive picture of HMMR expression .

How can HMMR antibodies be effectively used to study HMMR's role in cancer progression and therapeutic resistance?

HMMR has emerged as a significant factor in cancer progression and therapeutic resistance, particularly in prostate cancer. Research approaches using HMMR antibodies include:

Research data indicates that HMMR expression is increased in advanced stages of prostate cancer and is associated with treatment resistance and poorer prognosis, making it a valuable target for both biomarker and therapeutic development studies .

What are the latest methodological advances in generating human monoclonal antibodies against HMMR?

Recent advances in generating human monoclonal antibodies (hmAbs) against targets like HMMR include:

• Antibody-Secreting Cell (ASC) Isolation: A rapid protocol utilizing antibody-secreting cells isolated from whole blood collected 7 days after vaccination can generate fully human monoclonal antibodies. This technique allows hmAbs production with as little as 20 ml of human blood in as little as 28 days under optimal conditions .

• Single-Cell Cloning Approaches: Flow cytometry-based sorting of single antibody-secreting cells into plates, followed by RT-PCR and nested PCR amplification of antibody genes, cloning into expression vectors, and transfection into human cell lines .

• Advantages Over Traditional Methods: This approach is more efficient than previous methodologies like B-cell immortalization or phage display, which although capable of isolating rare specific antibodies years after immunization, result in few relevant antibodies .

• Expression and Characterization: The expressed antibodies can be purified and assayed for binding and neutralization, enabling rapid generation of numerous antigen-specific hmAbs in a short timeframe .

This methodology is especially valuable for generating antibodies against targets like HMMR where specific epitope recognition is crucial for research and potential therapeutic applications.

How can HMMR antibodies contribute to understanding the non-mitotic roles of HMMR in neuronal function?

Recent research has revealed important non-mitotic functions of HMMR in neuronal systems that can be studied using HMMR antibodies:

• Neuronal Morphogenesis Studies: HMMR depletion in hippocampal neurons causes significant decreases in total neurite length, axon length, dendrite length, and axon branch density. HMMR antibodies can be used to track these morphological changes and protein localization .

• Subcellular Localization Analysis: Endogenous HMMR shows punctate localization along axons and dendrites, with higher abundance in the soma. Immunofluorescence with HMMR antibodies can map this distribution pattern .

• Microtubule Interaction Visualization: When overexpressed, HMMR colocalizes with microtubules and sometimes causes the formation of looped microtubules in neurons. Co-immunostaining with HMMR and tubulin antibodies can reveal these structural interactions .

• Proximity Ligation Assays: PLA using HMMR and β-III-tubulin antibodies confirms the association between HMMR and neuronal microtubules, with fluorescent puncta detected in the soma and along neurites .

• Rescue Experiment Validation: Expression of human HMMR (EGFP-hHMMR) rescues the phenotype of HMMR knockdown in hippocampal neurons. Antibodies against both endogenous and tagged HMMR can verify expression levels in these experiments .

These applications demonstrate how HMMR antibodies are essential tools for understanding HMMR's role beyond its well-characterized functions in mitotic cells.