NECTIN2 Human

What is the molecular structure of NECTIN2 and how does it relate to function?

NECTIN2, also known as CD112 and PVRL2 (Poliovirus receptor-related 2), is a type I transmembrane glycoprotein that belongs to the nectin family of cell adhesion molecules. The protein exists in multiple splice forms, with Nectin-2δ being a 65 kDa form synthesized as a 538 amino acid precursor containing a 31 amino acid signal sequence, a 329 amino acid extracellular region, a 21 amino acid transmembrane segment, and a 157 amino acid cytoplasmic domain . The extracellular portion comprises one N-terminal V-type Ig domain and two C2-type Ig domains . The V-domain mediates binding to ligands and is critical for interactions with immune receptors and viral proteins . This structure enables NECTIN2 to function as both a cell adhesion molecule in normal physiology and as a critical modulator of immune responses.

How does NECTIN2 regulate T-cell function in normal immune responses?

NECTIN2 exhibits a fascinating dual role in T-cell regulation, functioning as either a costimulator or coinhibitor depending on the receptor it engages. When NECTIN2 interacts with CD226 (DNAM-1), it stimulates T-cell proliferation and promotes cytokine production, including IL-2, IL-5, IL-10, IL-13, and IFNγ . Conversely, NECTIN2 binding to PVRIG results in inhibition of T-cell proliferation . This dual functionality creates a balanced immune response through a complex network of competing receptor interactions. TIGIT, TACTILE (CD96), and PVRIG compete for binding to NECTIN2, with each interaction triggering different signaling pathways . The expression patterns of these receptors on different immune cell populations determine how NECTIN2 influences immune homeostasis in specific contexts.

What experimental methods are most reliable for detecting NECTIN2 expression?

For accurate detection of NECTIN2 expression, flow cytometry using specific monoclonal antibodies represents the gold standard approach. The search results describe using Mouse Anti-Human Nectin-2/CD112 PE-conjugated Monoclonal Antibody (FAB2229P) for detection in K562 human leukemia cells, with appropriate isotype controls (IC002P) to validate specificity . When implementing flow cytometry protocols, researchers should follow established guidelines for membrane protein staining and protein quantification. For broader expression analysis across tissues or tumor samples, bioinformatic approaches utilizing databases such as TCGA and GTEx provide valuable comparative insights . Additional complementary techniques include immunohistochemistry for tissue localization and quantitative PCR for transcript-level analysis.

What is the evidence for differential expression of NECTIN2 across cancer types?

Comprehensive bioinformatic analysis using GEPIA2 based on TCGA data reveals a striking pattern of NECTIN2 overexpression across multiple cancer types compared to matched normal tissues. This differential expression pattern is observed in the following cancer types:

This extensive overexpression pattern suggests NECTIN2 plays a significant role in the biology of diverse cancer types .

How does NECTIN2 expression correlate with cancer progression and patient outcomes?

NECTIN2 expression demonstrates significant correlations with both cancer stage and patient survival outcomes, though these relationships vary by cancer type. Higher NECTIN2 expression correlates with advanced tumor stages in adrenocortical carcinoma (ACC), bladder urothelial carcinoma (BLCA), head and neck squamous cell carcinoma (HNSC), testicular germ cell tumors (TGCT), skin cutaneous melanoma (SKCM), and uterine corpus endometrial carcinoma (UCEC) .

The prognostic significance of NECTIN2 expression follows a complex pattern:

This divergent prognostic significance highlights the context-dependent role of NECTIN2 in cancer biology and necessitates cancer-specific approaches when considering it as a therapeutic target .

What molecular mechanisms underlie NECTIN2's role in cancer progression?

The mechanisms through which NECTIN2 influences cancer progression appear to involve complex immune regulatory pathways. NECTIN2 overexpression in tumors impacts immune surveillance through interactions with activating receptors like DNAM-1 (CD226) on NK cells and T cells, as well as inhibitory receptors including TIGIT, TACTILE, and PVRIG . These interactions create a balance of signals that modulates anti-tumor immune responses. Additionally, the wide expression pattern of NECTIN2 across tumor types suggests it may have proto-oncogenic characteristics .

Notably, while PVR (a related nectin family member) has been shown to be directly regulated by p53 at the promoter level, the transcriptional regulation of NECTIN2 remains less well characterized . NECTIN2 can be upregulated by Toll-like receptor agonists in dendritic cells and by DNA-damage response in multiple myeloma cells or activated T lymphocytes, suggesting its expression may be modulated by various cellular stress conditions relevant to the tumor microenvironment .

Which viruses utilize NECTIN2 as an entry receptor and through what mechanisms?

NECTIN2 serves as an entry receptor for multiple human herpesviruses, including herpes simplex virus 1 (HHV-1) mutant Rid1, herpes simplex virus 2 (HHV-2), pseudorabies virus (PRV), and human herpesvirus 6B (HHV-6B) . Research specifically investigating HHV-6B demonstrates that this virus can utilize NECTIN2 as an entry receptor in cells lacking CD134 (the primary HHV-6B receptor) . This represents a CD134-independent virus entry mechanism that may explain how HHV-6B can infect cells in organs where CD134 expression is absent, such as the salivary glands, nervous system, and liver .

The molecular interaction underlying viral entry involves direct binding between the virus glycoprotein B (gB) and the V-set domain of NECTIN2 . This interaction was confirmed in studies where NECTIN2 knockout in parotid-derived cells significantly reduced viral entry, and conversely, virus-insensitive T-cells transduced with NECTIN2 were transformed into virus-permissive cells . These findings highlight NECTIN2's important role in viral tropism and pathogenesis.

How can researchers experimentally investigate NECTIN2-mediated viral entry?

To investigate NECTIN2-mediated viral entry, researchers can implement several experimental approaches:

• Receptor knockout studies: Generation of NECTIN2 knockout cell lines using CRISPR-Cas9 technology to assess the impact on viral infection rates .

• Receptor transduction experiments: Transduction of virus-insensitive cells with NECTIN2 to determine if this confers susceptibility to infection .

• Protein domain interaction analysis: Investigation of specific NECTIN2 domains (particularly the V-set domain) in viral binding through mutation studies or competitive inhibition with domain-specific antibodies .

• Viral protein binding assays: Biochemical and structural studies to characterize interactions between viral glycoproteins (such as gB for HHV-6B) and NECTIN2 .

• Cell-based viral entry assays: Quantification of viral entry in various cell types expressing different levels of NECTIN2 using fluorescently labeled viruses or viral DNA quantification.

These methodological approaches provide complementary evidence for understanding the mechanisms and specificity of NECTIN2-mediated viral entry.

What immunotherapeutic approaches target the NECTIN2 axis?

The NECTIN2 axis represents a promising target for cancer immunotherapy, with several strategies under development:

• DNAM-1 chimeric receptor-engineered NK cells: This approach involves engineering natural killer cells with a chimeric receptor based on DNAM-1 (CD226) that specifically recognizes PVR and NECTIN2 ligands widely expressed on tumor cells . This strategy leverages the overexpression of NECTIN2 in multiple tumor types to enhance NK cell-mediated tumor killing.

• Immune checkpoint blockade: Given the inhibitory interactions between NECTIN2 and receptors like TIGIT and PVRIG, antibodies blocking these inhibitory pathways represent another therapeutic approach. By preventing these inhibitory interactions, such antibodies could enhance anti-tumor immune responses .

• Combined targeting approaches: The complex network of activating and inhibitory receptors interacting with NECTIN2 suggests that combination approaches might be most effective, potentially combining enhancement of DNAM-1 signaling with blockade of inhibitory receptors like TIGIT and PVRIG .

The wide expression of NECTIN2 across numerous tumor types makes these approaches potentially applicable to a broad spectrum of cancers, though the different prognostic associations across cancer types suggest the need for careful patient selection .

What technical challenges arise when developing NECTIN2-targeted therapies?

Developing NECTIN2-targeted therapies presents several technical challenges:

• Receptor competition: The shared binding of NECTIN2 to both activating (DNAM-1) and inhibitory receptors (TIGIT, PVRIG, TACTILE) creates a complex signaling environment that may affect therapeutic efficacy . Therapies must carefully consider this balance to avoid unintended activation of inhibitory pathways.

• Context-dependent prognostic significance: The divergent associations between NECTIN2 expression and patient outcomes across cancer types suggests that therapeutic approaches may need to be tailored to specific cancer contexts .

• Potential off-target effects: NECTIN2's role in normal cell adhesion and immune regulation raises concerns about possible off-target effects when targeting this molecule therapeutically. Careful assessment of toxicity profiles is essential.

• Delivery challenges for engineered cell therapies: For approaches like DNAM-1 chimeric receptor-engineered NK cells, challenges include efficient NK cell expansion, maintenance of functionality after engineering, and effective tumor infiltration .

• Heterogeneous expression within tumors: Variability in NECTIN2 expression within tumor tissues might limit therapeutic efficacy and necessitate combination approaches to address all tumor cell subpopulations.

What novel technologies are advancing NECTIN2 research?

Several cutting-edge technologies are advancing research on NECTIN2:

• Single-cell technologies: Single-cell RNA sequencing and CyTOF (mass cytometry) enable detailed characterization of NECTIN2 expression patterns and co-expression with its receptors at the single-cell level across different cell populations.

• CRISPR-based screening: Genome-wide CRISPR screens can identify genes that modulate NECTIN2 expression or function, revealing new regulatory pathways and potential therapeutic targets.

• Spatial transcriptomics: These techniques allow researchers to analyze NECTIN2 expression patterns while preserving spatial information about cellular organization and interactions within tissues.

• Organoid models: Patient-derived organoids provide three-dimensional culture systems that better recapitulate the complexity of tumors and allow for more physiologically relevant testing of NECTIN2-targeted approaches.

• High-throughput functional assays: Automated platforms for immune cell function assessment enable rapid evaluation of how manipulating the NECTIN2 axis affects various immune cell functions.

How can researchers effectively differentiate between the roles of NECTIN2 and related family members?

Differentiating between NECTIN2 and other nectin family members requires specialized experimental approaches:

• Specific antibodies: Use of highly specific monoclonal antibodies that recognize unique epitopes on NECTIN2 without cross-reactivity to other nectin family members .

• Gene-specific knockdown/knockout: Precise genetic manipulation using CRISPR-Cas9 or RNAi technologies targeting NECTIN2 specifically while monitoring for potential compensatory changes in other family members .

• Domain-specific interaction studies: Investigation of which specific domains of NECTIN2 mediate key interactions, as these may differ from those of other family members. For instance, the V-set domain of NECTIN2 is crucial for interaction with HHV-6B glycoprotein B .

• Receptor binding specificity analysis: Comprehensive analysis of receptor binding preferences, as different nectin family members show distinct patterns of interaction with immune receptors. For example, PVR binds TIGIT and TACTILE, while NECTIN2 binds TIGIT and PVRIG .

• Comparative expression analysis: Systematic comparison of expression patterns across tissues, cell types, and disease states using multiplexed approaches that simultaneously detect multiple nectin family members.

What are the most promising research directions for understanding NECTIN2 biology?

The most promising directions for advancing NECTIN2 research include:

• Regulatory mechanisms: Further investigation into the transcriptional and post-translational regulation of NECTIN2, particularly in cancer and viral infection contexts .

• Structural biology: Detailed structural characterization of NECTIN2 interactions with immune receptors and viral proteins to inform rational drug design targeting these interactions .

• Tumor microenvironment dynamics: Studies exploring how NECTIN2 expression on tumor cells shapes the immune landscape within the tumor microenvironment and influences responsiveness to various immunotherapies .

• Biomarker development: Validation of NECTIN2 as a prognostic or predictive biomarker for specific cancer subtypes and therapies, given its correlation with outcomes in multiple cancer types .

• Combination therapy approaches: Investigation of optimal combinations of NECTIN2-targeting approaches with other immunotherapies, targeted therapies, or conventional treatments to maximize therapeutic efficacy .

• Cross-talk with other signaling pathways: Exploration of how NECTIN2 signaling integrates with other key cancer and immune signaling pathways to influence disease progression and treatment response.