Acetyl-RELA (K218) Antibody

What is RELA/p65 and what role does K218 acetylation play in its function?

RELA (p65) is a 65 kDa protein that functions as a key subunit of the NF-κB transcription factor complex. It contains a Rel homology domain (RHD) and is involved in immune responses, inflammation, and cellular stress responses . Acetylation at lysine 218 (K218) represents a critical post-translational modification that regulates NF-κB activity. Specifically, K218 acetylation has an inhibitory effect on NF-κB activation and its downstream inflammatory responses . In its inactive state, the NF-κB complex containing p65 is bound to IκB and localized in the cytoplasm. Upon cellular stimulation, IκB becomes phosphorylated and degraded, allowing the activated NF-κB complex to translocate to the nucleus where it functions as a transcription factor . K218 acetylation plays a crucial regulatory role in this process by modulating the transcriptional activity of p65.

How does acetylation at K218 differ from other acetylation sites on RELA/p65?

The p65 subunit contains multiple acetylation sites that differentially regulate its function. K218 acetylation specifically exerts an inhibitory effect on NF-κB activity. Research has shown that K218Q (acetylation-mimicking) mutation strongly decreases p65 transcriptional activity, while K79Q mutation has minimal effect . This indicates that acetylation at different sites serves distinct regulatory purposes. Other known acetylation sites include K310, K314, and K315, which are targeted by p300 . Studies comparing acetylation-deficient mutants have demonstrated that K218, along with K221, contributes significantly to p300-dependent acetylation of RelA/p65 after TNFα treatment, but to a lesser extent than K314 and K315, which appear to be the primary targets . Unlike K218, K310 acetylation has been more extensively characterized with specific antibodies confirming its TNFα-induced acetylation in vivo .

What enzymes regulate the acetylation status of K218 on RELA/p65?

The acetylation status of K218 is regulated through a balance of acetylation and deacetylation processes. Deacetylation of K218 is mediated by HDAC3 (Histone Deacetylase 3), while HIPK2 (Homeodomain-interacting protein kinase 2) counteracts this by blocking HDAC3-mediated deacetylation . Flow cytometric analysis has confirmed that HDAC3 overexpression reduces K218 acetylation levels, while its phosphorylated form (S374D mutant) fails to affect K218 acetylation . On the acetylation side, p300 appears to be involved in acetylating various lysine residues on RelA/p65, potentially including K218. Studies using acetylation-deficient point mutants suggest that p300 contributes to acetylation at K218 and K221 after TNFα stimulation . This enzymatic regulation creates a dynamic system for controlling NF-κB activity in response to various cellular signals.

What are the optimal applications for Acetyl-RELA (K218) antibodies in research?

Acetyl-RELA (K218) antibodies are valuable tools for studying NF-κB signaling regulation through post-translational modifications. Based on available literature, these antibodies can be effectively applied in several experimental techniques:

• Western blotting (WB): For detecting acetylated p65 at K218 in protein lysates, with typical working dilutions of 1:500-1:2000

• ELISA: For quantitative detection of acetylated p65, typically at dilutions of 1:20000

• Flow cytometry: For measuring acetylation levels in individual cells

• Immunoprecipitation: For isolating acetylated p65 complexes prior to analysis

It's worth noting that while antibodies against acetylated K310 have been successfully employed for in vivo detection of acetylated RelA/p65 in TNFα-stimulated cells, some antibodies raised against acetylated K314 and K315 have shown specificity issues . Researchers should therefore carefully validate antibody specificity before application.

How should samples be prepared for optimal detection of Acetyl-RELA (K218)?

Optimal detection of acetylated RELA at K218 requires careful sample preparation to preserve the acetylation state and enable accurate analysis:

• Cell treatment: Stimulate cells with appropriate activators (e.g., TNFα, LPS) to induce NF-κB signaling

• HDAC inhibitor treatment: Include HDAC inhibitors such as Trichostatin A (TSA) and Nicotinamide (NAM) to prevent deacetylation during sample preparation

• Nuclear extraction: Since activated NF-κB translocates to the nucleus, nuclear extraction protocols are often necessary for enrichment

• Protein preservation: Use phosphatase and protease inhibitors in lysis buffers to prevent degradation

• Buffer composition: Typically use phosphate-buffered solution (PBS) containing additives like 0.5% BSA and 0.02% sodium azide

For immunoprecipitation experiments, anti-p65 antibodies can be used to pull down the protein complex, followed by detection with acetylation-specific antibodies . When using flow cytometry, intracellular staining protocols are recommended, typically using 5 μl of antibody per million cells in 100 μl staining volume .

What controls should be included when using Acetyl-RELA (K218) antibodies?

Proper experimental controls are essential for reliable interpretation of results when using Acetyl-RELA (K218) antibodies:

Positive controls:

• TNFα-stimulated cells (known to induce NF-κB activation and p65 acetylation)

• Cells overexpressing wild-type p65 along with p300 (enhances acetylation)

• Cells treated with HDAC inhibitors (increases acetylation levels)

Negative controls:

• Unstimulated cells (basal acetylation levels)

• Cells expressing K218R mutant (acetylation-deficient)

• Samples treated with λ-phosphatase (to distinguish from phosphorylation signals)

Specificity controls:

• Peptide competition assays using acetylated and non-acetylated peptides

• Comparison with other acetylation site-specific antibodies (K310, K314, K315)

• Use of acetylation-mimicking mutants (K218Q) and acetylation-deficient mutants (K218R)

These controls help validate antibody specificity and ensure accurate interpretation of results across different experimental systems.

How can Acetyl-RELA (K218) antibodies be used to investigate the relationship between acetylation and NF-κB transcriptional activity?

Researchers can employ Acetyl-RELA (K218) antibodies to explore the complex relationship between acetylation and NF-κB function through several sophisticated approaches:

These methodologies allow researchers to dissect the specific contributions of K218 acetylation to the broader regulatory network controlling NF-κB function in various biological contexts.

What are the common technical challenges when working with Acetyl-RELA (K218) antibodies and how can they be addressed?

Working with Acetyl-RELA (K218) antibodies presents several technical challenges that researchers should anticipate and address:

Challenge 1: Low signal intensity

• Solution: Enrich for nuclear fractions where activated NF-κB localizes

• Solution: Pretreat samples with HDAC inhibitors to preserve acetylation

• Solution: Optimize antibody concentration and incubation conditions

Challenge 2: Non-specific binding

• Solution: Increase blocking time and concentration

• Solution: Perform peptide competition assays to confirm specificity

• Solution: Use K218R mutant-expressing cells as negative controls

Challenge 3: Variability between experiments

• Solution: Standardize stimulation protocols (duration and concentration)

• Solution: Normalize to total p65 levels

• Solution: Use internal controls consistently across experiments

Challenge 4: Distinguishing from other modifications

• Solution: Use specific inhibitors targeting distinct enzymes

• Solution: Employ mass spectrometry for unambiguous identification

• Solution: Compare with other acetylation site-specific antibodies

Challenge 5: Limited sensitivity for detecting endogenous levels

• Solution: Use immunoprecipitation to concentrate the target protein

• Solution: Apply signal amplification methods

• Solution: Consider using overexpression systems for initial optimization

Addressing these challenges requires careful experimental design and stringent validation procedures to ensure reliable and reproducible results.

How can Acetyl-RELA (K218) antibodies be used in multiplexed detection systems with other post-translational modifications?

Advanced research often requires simultaneous analysis of multiple post-translational modifications. Acetyl-RELA (K218) antibodies can be incorporated into multiplexed detection systems through several approaches:

• Multi-color Flow Cytometry: Combine antibodies against different modifications (acetylation, phosphorylation, methylation) using distinct fluorophores. For example, PE-conjugated anti-NF-κB p65 antibodies can be excited by blue (488 nm) or yellow-green (561 nm) lasers , allowing combination with antibodies conjugated to compatible fluorophores.

• Sequential Immunoprecipitation: First immunoprecipitate with one modification-specific antibody, then perform a second immunoprecipitation on the eluate using another antibody to identify proteins with multiple modifications.

• Mass Spectrometry Analysis: Use antibodies to enrich for acetylated proteins, then perform mass spectrometry to identify additional modifications. This approach has successfully identified acetylated K79 and K218 in p65 from HEK293T cells .

• Proximity Ligation Assay (PLA): Detect the co-occurrence of different modifications within close proximity (<40 nm), providing spatial information about modification patterns.

• Multiplex Western Blotting: Employ sequential probing with different modification-specific antibodies after careful stripping, or use different species antibodies with distinguishable secondary antibodies.

When designing multiplexed experiments, researchers should consider potential cross-reactivity between antibodies and ensure that epitope accessibility is not compromised by concurrent binding of multiple antibodies.

How does RELA/p65 K218 acetylation status differ across cell types and disease models?

The acetylation status of RELA/p65 at K218 exhibits significant variability across different cellular contexts and disease states:

Cell Type Variations:

• Immune Cells: In primary macrophages (PEMs), K218 acetylation increases following LPS treatment, with HIPK2 knockdown reducing this acetylation

• Fibroblasts: Primary MEFs show similar patterns of K218 acetylation as immune cells in response to LPS

• Epithelial Cells: HEK293T cells demonstrate p65 K218 acetylation that can be modulated by HIPK2 overexpression

Disease Model Variations:

These variations highlight the context-dependent nature of K218 acetylation and underscore the importance of studying this modification across diverse biological systems to fully understand its regulatory significance.

What is the relationship between RELA/p65 K218 acetylation and other post-translational modifications?

RELA/p65 undergoes multiple post-translational modifications that function in concert to fine-tune its activity. K218 acetylation exists within this complex regulatory network:

Relationship with Other Acetylation Sites:

• K218 acetylation often occurs alongside K221 acetylation

• K310, K314, and K315 acetylation represent major p300-mediated modifications that may influence K218 acetylation status

• Different acetylation sites can have opposing effects; while K218 acetylation appears inhibitory, other sites may enhance NF-κB activity

Interplay with Phosphorylation:

• HIPK2-mediated phosphorylation of HDAC3 at S374 prevents deacetylation of K218, establishing a phosphorylation-acetylation regulatory axis

• Other phosphorylation events on p65 (such as at S536) may synergize with or antagonize the effects of K218 acetylation

Connection to Ubiquitination and Degradation:

• Acetylation status may influence protein stability by affecting ubiquitination patterns

• K218 acetylation could potentially modulate the interaction between p65 and proteins involved in its degradation

Understanding these inter-relationships is essential for developing a comprehensive model of how various modifications collectively determine NF-κB signaling outcomes in different physiological and pathological contexts.

How can Acetyl-RELA (K218) antibodies be utilized in drug discovery and validation?

Acetyl-RELA (K218) antibodies offer valuable tools for drug discovery efforts targeting NF-κB signaling pathways:

Target Identification and Validation:

• Screen for compounds that modulate K218 acetylation levels as potential anti-inflammatory agents

• Validate HDAC3 inhibitors by measuring their effects on K218 acetylation

• Assess HIPK2 activators for their ability to enhance K218 acetylation and suppress inflammation

Mechanism of Action Studies:

• Determine whether candidate drugs affect K218 acetylation directly or through upstream regulators

• Distinguish between effects on acetylation versus other post-translational modifications

• Correlate changes in K218 acetylation with functional outcomes in relevant disease models

Biomarker Development:

• Use K218 acetylation status as a pharmacodynamic biomarker for drug efficacy

• Monitor K218 acetylation in clinical samples to stratify patients for targeted therapies

• Develop high-throughput assays based on K218 acetylation for drug screening campaigns

Combination Therapy Approaches:

• Identify synergistic drug combinations that maximize K218 acetylation while minimizing off-target effects

• Explore sequential treatment strategies based on temporal dynamics of K218 acetylation

This application of Acetyl-RELA (K218) antibodies extends their utility beyond basic research into translational medicine and therapeutic development.

How do different detection methods for Acetyl-RELA (K218) compare in terms of sensitivity and specificity?

Various detection methods offer distinct advantages and limitations for analyzing Acetyl-RELA (K218):

Research has demonstrated that flow cytometry provides effective detection of K218 acetylation levels, particularly when comparing wild-type and mutant conditions . Meanwhile, for rigorous confirmation of acetylation sites, mass spectrometry remains the gold standard, having successfully identified K218 acetylation in HEK293T cells with or without HIPK2 overexpression .

What are the technical considerations for developing site-specific antibodies against Acetyl-RELA (K218)?

Developing highly specific antibodies against Acetyl-RELA (K218) involves several critical considerations:

Immunogen Design:

• Use synthetic peptides containing acetylated K218 with sufficient flanking sequences for specificity

• Consider carrier protein conjugation strategies that preserve the acetyl-lysine modification

• Ensure the immunogen represents the native protein conformation around K218

Host Selection and Antibody Type:

• Rabbit hosts often yield high-affinity antibodies against post-translational modifications

• Monoclonal antibodies provide consistency across batches but may have limited epitope recognition

• Polyclonal antibodies offer broader epitope recognition but require more extensive validation

Purification Strategy:

• Employ affinity purification using the acetylated peptide to enrich specific antibodies

• Consider negative selection against the non-acetylated peptide to remove antibodies recognizing the unmodified site

• Carefully validate purification method effectiveness, as demonstrated for other antibodies

Validation Requirements:

• Test against acetylation-mimicking (K218Q) and acetylation-deficient (K218R) mutants

• Verify specificity using peptide competition assays

• Confirm reactivity in multiple applications (WB, ELISA, flow cytometry)

• Assess cross-reactivity with other acetylation sites, particularly K221 which is proximal

Storage and Handling:

• Maintain stability in appropriate buffer systems (e.g., PBS with 50% glycerol, 0.5% BSA, 0.02% sodium azide)

• Store according to manufacturer recommendations (typically -20°C to -80°C)

• Avoid repeated freeze-thaw cycles to maintain antibody integrity

These considerations are essential for developing reliable tools for investigating K218 acetylation in diverse experimental contexts.

How can researchers verify the specificity of Acetyl-RELA (K218) antibodies in their experimental systems?

Rigorous validation of Acetyl-RELA (K218) antibody specificity is crucial for experimental reliability. Researchers should implement a multi-faceted validation approach:

Genetic Approaches:

• Test antibody reactivity against wild-type p65 versus K218R (acetylation-deficient) mutant

• Compare K218Q (acetylation-mimicking) mutant patterns with wild-type under various stimulation conditions

• Use CRISPR/Cas9 to generate K218R knock-in cell lines as definitive negative controls

Biochemical Validation:

• Perform peptide competition assays using both acetylated and non-acetylated K218 peptides

• Treatment with recombinant HDAC3 should reduce signal if the antibody is specific for the acetylated form

• Mass spectrometry validation of immunoprecipitated samples to confirm acetylation at K218

Pharmacological Approaches:

• HDAC inhibitor treatment should increase signal intensity

• TNFα or LPS stimulation should induce detectable changes in K218 acetylation levels

• HIPK2 inhibition should reduce K218 acetylation in stimulated cells

Cross-Reactivity Assessment:

• Test against other acetylated lysine sites (particularly K221, K310, K314, K315)

• Evaluate specificity across species (human, mouse, rat) if claiming multi-species reactivity

• Check for non-specific binding to other acetylated proteins with similar flanking sequences

These validation steps ensure that experimental observations truly reflect K218 acetylation status rather than artifacts or cross-reactivity with other modifications or proteins.