NRBP2 Antibody

What is NRBP2 and what cellular functions has it been associated with?

NRBP2 (Nuclear Receptor Binding Protein 2) is a conserved protein of approximately 55-60 kDa with predominantly cytoplasmic localization in neural stem/progenitor cells, brain tumor cells, and hepatocellular carcinoma cells . Initially identified during screens of neural differentiation genes, NRBP2 plays important roles in regulating apoptosis of neural progenitor cells during differentiation . It has also been characterized as a pseudokinase that participates in transport between the endoplasmic reticulum and Golgi apparatus . More recent studies have established NRBP2 as a tumor suppressor that inhibits proliferation and metastasis while promoting apoptosis across multiple cancer types .

What experimental evidence supports NRBP2's role as a tumor suppressor?

Multiple lines of experimental evidence confirm NRBP2's tumor suppressor function. In cholangiocarcinoma cell lines (RBE and CCLP), NRBP2 overexpression significantly decreased cell viability as measured by CCK-8 assays and induced G1 phase arrest, reducing expression of cell cycle regulators including CDK2, CDK4, and cyclin A2 . In breast cancer models, NRBP2 overexpression inhibited both in vitro cell proliferation and invasion, while also significantly reducing lung metastatic nodules in orthotopic breast tumor mouse models . Mechanistically, NRBP2 expression positively correlates with E-cadherin (epithelial marker) and negatively with N-cadherin (mesenchymal marker), demonstrating its role in suppressing epithelial-mesenchymal transition, a critical process in cancer progression .

What are the validated applications for NRBP2 antibodies in cancer research?

NRBP2 antibodies have been successfully applied in several experimental techniques:

• Western blotting: Successfully used at 1/2000 dilution with expected band size of 58 kDa for monitoring expression levels in cell lysates

• Immunohistochemistry (IHC-P): Effectively applied at dilutions of 1/100-1/500 on paraffin-embedded tissues including colon carcinoma and breast cancer samples

• Expression correlation studies: Used to establish relationships between NRBP2 and EMT markers (E-cadherin, N-cadherin, Snail) through dual immunostaining approaches

• Validation of genetic manipulation: Applied to confirm successful overexpression or knockdown of NRBP2 in functional studies

How does NRBP2 interact with the AMPK/mTOR signaling pathway in tumor suppression?

Research has revealed that NRBP2 exerts its tumor-suppressive effects partly through modulation of the AMPK/mTOR signaling axis. In breast cancer cells, NRBP2 overexpression increases phosphorylated AMPK (p-AMPK) levels while concurrently decreasing phosphorylated mTOR (p-mTOR) levels . This relationship was functionally validated through inhibitor studies: when AMPK signaling was blocked using Compound C in NRBP2-overexpressing breast cancer cells, the inhibitory effects of NRBP2 on EMT, cell proliferation, and invasion were partially rescued . Conversely, treatment with rapamycin (an mTOR inhibitor) eliminated the proliferative and invasive advantages conferred by NRBP2 knockdown . These findings establish that NRBP2's tumor-suppressive effects operate at least partly through positive regulation of AMPK activity and subsequent inhibition of mTOR signaling.

What methodological approaches can detect changes in NRBP2-regulated pathways?

Researchers investigating NRBP2's effects on downstream pathways should employ a multi-faceted approach:

• Phosphorylation state analysis: Western blotting with phospho-specific antibodies targeting p-AMPK, AMPK, p-mTOR, and mTOR to assess pathway activation status

• Pathway inhibitor studies: Utilize specific inhibitors (e.g., Compound C for AMPK, rapamycin for mTOR) combined with NRBP2 manipulation to establish causality in observed phenotypes

• EMT marker assessment: Monitor epithelial markers (E-cadherin) and mesenchymal markers (N-cadherin, Snail) at both protein and mRNA levels to characterize EMT regulation

• Cell cycle analysis: Flow cytometry combined with cell cycle protein expression (CDK2, CDK4, cyclin A2) to determine effects on cell cycle progression

• Apoptosis measurements: Flow cytometry and Western blot detection of apoptotic markers (caspase-3, cleaved caspase-3) to assess cell death regulation

What considerations should guide experimental design when studying NRBP2 in different cancer types?

When extending NRBP2 research across cancer types, several important considerations should guide experimental design:

• Baseline expression profiling: Quantify endogenous NRBP2 expression across candidate cell lines via Western blot and RT-PCR before selecting models for manipulation

• Context-dependent function assessment: NRBP2's effects may vary by cancer type; compare proliferation, invasion, apoptosis, and EMT markers across multiple cell lines from different tissues

• In vivo model selection: For orthotopic studies, consider tissue-specific microenvironmental factors that might influence NRBP2 function; the MDA-MB-231 breast cancer model has been validated for NRBP2 studies

• Prognostic correlation validation: Examine NRBP2 expression in patient tissues and correlate with clinicopathological parameters and survival data to establish clinical relevance

• Chemotherapy interaction studies: Assess how NRBP2 expression affects response to standard chemotherapeutic agents relevant to the cancer type under investigation

What are the optimal conditions for NRBP2 antibody use in Western blotting?

For optimal Western blot results with NRBP2 antibodies:

Sample Preparation:

• Use standard cell lysis with RIPA buffer supplemented with protease and phosphatase inhibitors

• Load 30 μg of total protein per lane as demonstrated with IMR32 whole cell lysate

• Separate proteins on 12% SDS-PAGE gels for optimal resolution around the 58 kDa mark

Antibody Application:

• Primary antibody dilution: 1/2000 has been validated for ab227480

• Incubation conditions: Typically overnight at 4°C with gentle agitation

• Secondary antibody: HRP-conjugated anti-rabbit IgG at manufacturer's recommended dilution

• Expected band size: 58 kDa for human NRBP2

Detection and Validation:

• Use enhanced chemiluminescence for signal development

• Include positive controls from cell lines with confirmed NRBP2 expression

• For validation studies, include NRBP2 overexpression and knockdown samples

What protocol modifications improve NRBP2 immunohistochemical detection in tissue samples?

For effective NRBP2 immunohistochemistry on paraffin-embedded tissues:

Pretreatment Steps:

• Deparaffinize slides completely in xylene followed by graded alcohols

• Perform antigen retrieval using citrate buffer (pH 6.2) with microwave heating for 20 minutes

• Block endogenous peroxidase activity with 0.3% hydrogen peroxide in absolute methanol for 30 minutes

Staining Protocol:

• Blocking: 5% FBS for 60 minutes at room temperature

• Primary antibody: Anti-NRBP2 at 1/100-1/500 dilution (ab172866 validated at 1/100 , ab227480 at 1/500 )

• Primary incubation: Overnight at 4°C in humidity chamber

• Secondary antibody: HRP-conjugated anti-rabbit IgG for 40 minutes at room temperature

• Visualization: Diaminobenzidine (DAB) with hematoxylin counterstain

Analysis Considerations:

• Include both tumor and adjacent normal tissue on the same slide when possible

• Use quantitative scoring systems that account for both staining intensity and percentage of positive cells

• For correlation studies, prepare serial sections for staining with NRBP2 and related markers (E-cadherin, N-cadherin)

How should researchers optimize experimental design when investigating NRBP2 functions through genetic manipulation?

When designing NRBP2 overexpression or knockdown experiments:

Overexpression Approaches:

• NRBP2 cDNA clones are commercially available (e.g., Origene SC310591)

• Construct selection should include appropriate species-specific promoters for target cell lines

• Validation requires both Western blot and RT-PCR confirmation of expression levels

• Both transient and stable expression systems have been successfully employed

Knockdown Strategies:

• siRNA targeting NRBP2 has been effective for transient knockdown

• For longer-term studies, shRNA constructs delivered via lentiviral vectors are recommended

• Always include scrambled/control siRNA or shRNA constructs as negative controls

• Validate knockdown efficiency at both protein and mRNA levels

Functional Readouts:

• Cell viability: CCK-8 assay at 24, 48, and 72 hours post-transfection

• Cell cycle: Flow cytometry with propidium iodide staining

• Apoptosis: Annexin V/PI staining and Western blot for apoptotic markers

• Cell invasion: Transwell assay with Matrigel coating

• Cell migration: Wound healing assay

• EMT markers: Western blot for E-cadherin, N-cadherin, and Snail

How can researchers address inconsistent results in NRBP2 expression analysis across different experimental platforms?

When facing discrepancies in NRBP2 expression data:

• Cross-validate with multiple detection methods:

  • Compare protein levels (Western blot) with mRNA expression (RT-PCR, qPCR)

  • Confirm localization patterns using both immunofluorescence and immunohistochemistry

  • If possible, validate with multiple antibodies targeting different NRBP2 epitopes

• Consider technical variables:

  • Antibody lot variation: Test multiple lots with known positive controls

  • Fixation effects: Compare fresh-frozen versus formalin-fixed samples

  • Cell culture conditions: Confluency and passage number can affect expression levels

  • RNA/protein extraction methods: Different lysis buffers may yield varying results

• Biological context factors:

  • Cell type-specific expression patterns: Neural-derived cells show higher baseline expression

  • Growth conditions: Serum levels and stress factors may regulate NRBP2 expression

  • Cell cycle stage: Synchronize cells when making direct comparisons

What are the key considerations when interpreting NRBP2's role in the AMPK/mTOR pathway across different experimental conditions?

When analyzing NRBP2's effects on AMPK/mTOR signaling:

• Establish baseline pathway activation:

  • Determine basal p-AMPK and p-mTOR levels in the specific cell lines under study

  • Consider the energy status of cells (glucose concentration, confluency) as this affects AMPK activity

• Temporal dynamics:

  • Monitor signaling changes at multiple time points after NRBP2 manipulation

  • Rapid changes (minutes to hours) may indicate direct regulation

  • Delayed effects (days) may suggest indirect mechanisms

• Pathway crosstalk:

  • Assess additional AMPK substrates beyond mTOR (e.g., ACC, ULK1)

  • Evaluate mTOR complex components (mTORC1 vs. mTORC2) using phospho-specific markers for S6K, 4E-BP1, and Akt

  • Consider parallel pathways that might compensate for or interact with AMPK/mTOR signaling

• Context-dependent interpretation:

  • The magnitude of effect may vary by cell type based on endogenous AMPK/mTOR activity

  • Nutrient status can alter the sensitivity of the pathway to NRBP2 manipulation

  • Cancer-specific mutations in AMPK/mTOR pathway components may impact NRBP2's effects

What experimental approaches can resolve contradictory findings regarding NRBP2's tumor suppressor functions?

To address conflicting results about NRBP2's tumor suppressor activities:

• Genetic rescue experiments:

  • Perform knockdown in NRBP2-overexpressing cells to confirm specificity of observed effects

  • Introduce mutations in functional domains to identify critical regions for tumor suppression

  • Rescue experiments with downstream effectors can establish mechanistic hierarchy

• Dose-dependent analysis:

  • Create cell lines with varying levels of NRBP2 expression

  • Determine whether effects follow a threshold or linear response model

  • Correlate expression levels with functional outcomes quantitatively

• Microenvironmental considerations:

  • Test NRBP2 function under various stress conditions (hypoxia, nutrient deprivation)

  • Evaluate effects in 3D culture systems versus 2D monolayers

  • Compare in vitro findings with in vivo tumor models to account for microenvironmental factors

• Combination with clinical data:

  • Analyze patient cohorts stratified by NRBP2 expression levels

  • Correlate with treatment responses and disease progression

  • Examine multiple cancer types to identify common versus tissue-specific functions

By implementing these rigorous experimental approaches, researchers can reconcile contradictory findings and develop a more nuanced understanding of NRBP2's role in cancer biology, potentially leading to new therapeutic strategies targeting this important tumor suppressor pathway.