PVR Human

What is the human Poliovirus Receptor (PVR)?

Human Poliovirus Receptor (PVR), also known as CD155 or Nectin-like protein 5 (NECL-5), is a glycosylated single polypeptide chain protein that was initially identified as the cellular receptor for poliovirus but has since been recognized for its important roles in immune function and cell adhesion . PVR is a transmembrane glycoprotein that mediates NK cell adhesion and triggers NK cell effector functions through interactions with different NK cell receptors . The protein also plays significant roles in tumor cell invasion and migration, demonstrating its multifunctional nature in human biology .

What is the molecular structure of human PVR?

Human PVR is typically a single, glycosylated polypeptide chain containing approximately 331-343 amino acids (positions 21-343 in the full protein sequence) . The native molecular mass is approximately 36.1 kDa, though it appears at approximately 40-57 kDa on SDS-PAGE due to glycosylation patterns . The protein contains multiple functional domains that facilitate its interactions with immune cells and viral particles . When expressed recombinantly, PVR is often tagged (such as with an 8 amino acid His-tag at the C-terminus) to facilitate purification and experimental manipulation .

What are the primary biological functions of PVR?

PVR serves several critical functions in human biology:

• Immune regulation: Mediates NK cell adhesion and triggers NK cell effector functions by binding to receptors CD96 and CD226

• Immunological synapse formation: These interactions accumulate at cell-cell contact sites, leading to the formation of mature immunological synapses between NK cells and target cells

• Cytotoxicity regulation: Triggers adhesion and secretion of lytic granules and IFN-gamma, activating cytotoxicity in NK cells

• Tumor cell functions: Plays roles in tumor cell invasion and migration mechanisms

• Viral receptor: Acts as a receptor for poliovirus and pseudorabies virus, potentially facilitating viral entry into cells

• Axonal transport: May play a role in axonal transport of poliovirus by targeting virion-PVR-containing endocytic vesicles to the microtubular network through interaction with DYNLT1

What expression systems are recommended for recombinant PVR production?

Researchers can utilize several expression systems for recombinant PVR production, each with specific advantages depending on the research application:

• HEK 293 cells: This mammalian expression system produces recombinant human PVR protein (usually amino acids 27-343) with mammalian-type glycosylation patterns, resulting in ≥90% purity suitable for SDS-PAGE and functional studies

• Sf9 insect cells: This system produces glycosylated PVR (amino acids 21-343) as a single polypeptide chain, typically with a C-terminal His-tag for purification purposes

The choice between expression systems should be guided by the specific requirements of downstream applications, with HEK 293-expressed protein potentially offering glycosylation patterns more similar to native human PVR .

What are the optimal storage conditions for maintaining PVR stability?

For optimal stability of recombinant PVR preparations:

• Short-term storage (2-4 weeks): Store at 4°C if the entire vial will be used within this timeframe

• Long-term storage: Store frozen at -20°C

• For extended preservation: Addition of a carrier protein (0.1% HSA or BSA) is recommended to maintain stability during freeze-thaw cycles

• Avoid repeated freeze-thaw cycles, which can lead to protein degradation and loss of functional activity

How can researchers effectively study PVR's role in NK cell function?

To investigate PVR's role in NK cell biology, researchers should consider these methodological approaches:

• Immunological synapse analysis: Use fluorescent microscopy to visualize protein accumulation at cell-cell contact sites between NK cells and target cells

• Effector function assays: Measure secretion of lytic granules and IFN-gamma production to assess the impact of PVR on NK cell activation

• Modular exchange studies: Investigate PVR transfer from target cells to NK cells during cell-cell interactions using labeled proteins and flow cytometry

• Tumor immunoevasion models: Develop systems to study how PVR-expressing tumor cells may trigger fratricide NK cell activation as a potential immunoevasion mechanism

What experimental approaches can assess PVR's involvement in viral infection?

For studying PVR's role as a viral receptor:

• Viral binding assays: Quantify binding of labeled viral particles to cells expressing varying levels of PVR

• Axonal transport visualization: Track the interaction between PVR-containing endocytic vesicles and the microtubular network through DYNLT1

• Retrograde transport models: Develop neuronal models to study how the PVR-DYNLT1 interaction facilitates viral movement along axons

• Receptor blockade studies: Use antibodies or other blocking agents against PVR to assess the impact on viral entry and infection rates

How can contradictions in PVR functional data be addressed methodologically?

When facing contradictory findings in PVR research:

• Standardize experimental conditions: Ensure consistent cell types, protein concentrations, and assay conditions across experiments

• Multi-system validation: Validate findings across different experimental systems (cell lines, primary cells, in vivo models)

• Context assessment: Evaluate the impact of the cellular microenvironment on PVR function, particularly in immune and tumor contexts

• Apply the DECODE framework: Consider structured approaches to identifying and resolving contradictions in experimental data, similar to those used in other biological contradiction detection frameworks

What methodologies are most effective for studying PVR in proliferative vitreoretinopathy?

• Dominant negative approaches: Consider gene therapy strategies using truncated receptors (similar to the truncated PDGF α receptor approach used in PVR disease models)

• In vivo gene delivery: Utilize retroviral vectors to express receptor antagonists in appropriate disease models

• Collagen gel contraction assays: Employ these in vitro systems to test efficacy of receptor-targeting approaches on cellular responses

• Animal models: Develop and validate relevant animal models (such as rabbit models) that recapitulate key disease features

How can PVR's role in tumor progression be effectively investigated?

To study PVR's contribution to tumor biology:

• Invasion and migration assays: Quantify the impact of PVR expression on tumor cell movement and invasive capabilities

• NK cell interaction studies: Investigate how tumor-expressed PVR interacts with NK cells and potentially subverts anti-tumor immunity

• Immunoevasion mechanisms: Examine how PVR-mediated processes might provide tumors with mechanisms to escape immune recognition

• Cytomegalovirus models: Study how viral infections (such as Human cytomegalovirus) may prevent PVR from reaching the cell surface, potentially as a mechanism to escape NK cell recognition

What are the key considerations for experimental design when studying PVR interactions?

When designing PVR interaction studies, researchers should consider:

What are the comparative properties of different recombinant PVR preparations?