klhl21 Antibody

What is KLHL21 and why is it significant for scientific research?

KLHL21 (kelch-like 21) is a 597 amino acid protein with a calculated molecular weight of 67 kDa that belongs to the Kelch-like gene family. Its significance spans multiple cellular processes, making it a valuable target for diverse research areas. KLHL21 functions as a negative regulator of IKKβ in the NF-κB signaling pathway, which is crucial for inflammation and immune responses . Additionally, KLHL21 plays an essential role in cell division, specifically during cytokinesis, by regulating the translocation of the chromosomal passenger complex from chromosomes to the spindle midzone during anaphase . This protein also interacts with Cul3 to form an E3 ubiquitin ligase complex that mediates the ubiquitination of aurora B kinase . These multifaceted functions position KLHL21 as a significant research target in cell biology, immunology, and potentially in disease mechanisms including cancer.

What structural domains characterize KLHL21 and how do they relate to function?

KLHL21 contains several key structural domains that enable its diverse cellular functions:

• BTB (Broad-Complex, Tramtrack, and Bric-a-brac) domain: Located in the N-terminal region, this domain mediates interaction with Cul3 for E3 ubiquitin ligase activity . Mutations in this domain (D114A/L115A/Q117A) disrupt CUL3 binding .

• Kelch domains: Located at the C-terminus, these domains are critical for protein-protein interactions, particularly with the kinase domain of IKKβ . Deletion studies have demonstrated that these domains are essential for KLHL21's ability to interact with IKKβ and regulate NF-κB signaling .

• Back domain: Connects the BTB and Kelch domains, providing structural support for the protein's tertiary configuration.

The functional separation of these domains allows KLHL21 to simultaneously interact with different proteins through distinct regions. For example, while the Kelch domains interact with IKKβ, the BTB domain can independently engage with Cul3. This architectural arrangement enables KLHL21 to perform its dual roles in cellular signaling and cell division regulation.

What species reactivity and sample types work best with commercial KLHL21 antibodies?

Commercial KLHL21 antibodies show specific reactivity patterns that researchers should consider when designing experiments:

While theoretical cross-reactivity may exist across mammalian models due to sequence conservation, validation in your specific experimental system remains essential. For example, antibody 16952-1-AP has been tested in human, mouse, and rat samples, but cited reactivity predominantly focuses on human samples . When working with less common model organisms or cell lines, preliminary validation experiments comparing positive control samples (like HeLa cells) with your experimental samples are strongly recommended to confirm antibody performance.

What are the optimal dilutions and conditions for using KLHL21 antibodies in different applications?

The optimal conditions for KLHL21 antibody applications vary by technique:

These parameters should serve as starting points for optimization. The antibody should be titrated in each specific testing system to obtain optimal results, as performance can be sample-dependent . For detection of endogenous KLHL21 in Western blots, HeLa and A431 cell lysates serve as reliable positive controls, with detection expected at approximately 67 kDa .

How should I design experiments to study KLHL21 expression changes during inflammatory responses?

KLHL21 expression demonstrates consistent down-regulation during inflammatory responses across multiple cell types. To effectively study these changes, consider this experimental design approach:

• Cell model selection: Choose relevant models such as RAW264.7 macrophages, dendritic cells, or primary monocytes, which show documented KLHL21 expression changes upon inflammatory stimulation .

• Stimulation protocol: Treat cells with appropriate inflammatory stimuli:

  • Bacterial components: LPS (100 ng/ml)

  • Viral mimetics: CpG oligonucleotides

  • Cytokines: TNFα (10-50 ng/ml)

• Time-course analysis: Collect samples at multiple time points (0, 1, 2, 4, 8, 24 hours) to capture both early and late expression changes .

• Expression analysis methods:

  • Western blot: Using KLHL21 antibody (1:500-1:1000 dilution)

  • qRT-PCR: For mRNA expression changes

  • Flow cytometry: For single-cell analysis of expression changes

• Parallel assessment of inflammatory markers: Monitor NF-κB activation markers (phospho-IKKβ, IκBα degradation) alongside KLHL21 to establish temporal relationships .

• Validation through gain/loss-of-function: Use KLHL21 overexpression or siRNA-mediated knockdown to confirm the functional relationship between KLHL21 down-regulation and enhanced inflammatory responses .

This comprehensive approach will enable detailed characterization of how KLHL21 expression changes correlate with and potentially regulate inflammatory pathway activation.

What controls should be included when using KLHL21 antibodies for immunoprecipitation studies?

A robust immunoprecipitation experiment with KLHL21 antibodies requires several critical controls:

• Input control: Reserve 5-10% of the pre-cleared lysate to verify protein expression and loading consistency.

• Isotype control: Include an irrelevant antibody of the same isotype (rabbit IgG for 16952-1-AP) to identify non-specific binding.

• Positive sample control: HeLa cells have been verified for successful KLHL21 immunoprecipitation and should be included alongside experimental samples.

• Negative depletion control: When investigating stimulus-dependent interactions (like KLHL21-IKKβ), include samples from KLHL21 siRNA-treated cells to confirm antibody specificity .

• Reciprocal IP: Perform reverse immunoprecipitation with antibodies against predicted interaction partners (e.g., IKKβ) to confirm bidirectional interaction.

• Treatment controls: For studying dynamic interactions, include appropriate time points after stimulation (e.g., 0, 5, 10, 30 minutes post-TNFα), as the KLHL21-IKKβ interaction is gradually attenuated upon TNFα treatment .

• Bead-only control: Include a sample with beads but no antibody to identify proteins that non-specifically bind to the solid support.

These controls collectively ensure that observed interactions are specific, reproducible, and biologically relevant rather than experimental artifacts.

How does KLHL21 regulate the NF-κB signaling pathway mechanistically?

KLHL21 functions as a negative regulator of NF-κB signaling through a direct physical interaction with IKKβ, the key kinase in the canonical NF-κB activation pathway. This regulatory mechanism involves several specific molecular events:

• Domain-specific interaction: KLHL21 binds to the kinase domain of IKKβ via its C-terminal Kelch domains . Deletion mutant studies have conclusively demonstrated that:

  • IKKβ mutants lacking the kinase domain fail to interact with KLHL21

  • KLHL21 mutants without Kelch domains cannot bind IKKβ

• Inhibition mechanism: When bound to IKKβ, KLHL21:

  • Suppresses IKKβ phosphorylation at Ser-177/181

  • Prevents subsequent IκBα phosphorylation and degradation

  • Inhibits p65/RelA nuclear translocation

• Stimulus-responsive regulation: Upon TNFα stimulation, the KLHL21-IKKβ interaction is gradually attenuated, with significant reduction after 10 minutes . This dissociation allows IKKβ activation to proceed.

• E3 ligase-independent function: Unlike its role in cell division, KLHL21's inhibitory effect on IKKβ does not require its E3 ubiquitin ligase activity, as demonstrated by point mutant KLHL21M (D114A/L115A/Q117A) that cannot bind CUL3 but still inhibits IKKβ .

• Expression-level regulation: KLHL21 itself is rapidly down-regulated in multiple cell types upon proinflammatory stimulation, providing an additional mechanism to enhance NF-κB activation during inflammatory responses .

This multi-layered regulatory system allows for precise control of NF-κB signaling intensity and duration in response to changing cellular conditions.

What is known about KLHL21's role in cell division and its implications for cancer research?

KLHL21 plays a critical role in cell division through its regulation of aurora B kinase, with significant implications for cancer research:

• Mitotic function: KLHL21 is essential for proper cytokinesis, specifically regulating the translocation of the chromosomal passenger complex (CPC) from chromosomes to the spindle midzone during anaphase . This process is crucial for successful cell division.

• E3 ubiquitin ligase activity: Unlike its IKKβ regulation, KLHL21's mitotic functions depend on its E3 ligase activity. KLHL21 forms a complex with Cul3 to mediate the ubiquitination of aurora B kinase , a key component of the CPC that regulates multiple aspects of mitosis.

• Cancer implications: Dysregulation of KLHL21 could potentially contribute to cancer development through several mechanisms:

  • Mitotic defects leading to genomic instability

  • Altered NF-κB signaling affecting cell survival and inflammation

  • Changes in cell cycle checkpoint control

• Tissue expression: The detection of KLHL21 in human liver cancer tissue by immunohistochemistry suggests potential relevance in hepatocellular carcinoma pathophysiology.

• Research applications: Investigating KLHL21 in cancer contexts using antibody-based approaches can include:

  • Expression analysis across tumor types and grades

  • Correlation with clinical parameters and patient outcomes

  • Co-localization with mitotic markers in tumor samples

  • Assessment of KLHL21 interaction partners in cancer cells versus normal cells

The dual functionality of KLHL21 in both cell division and inflammatory signaling positions it as a multifaceted target for cancer research, potentially linking these two cancer-relevant processes.

How do post-translational modifications affect KLHL21 function and antibody recognition?

Post-translational modifications (PTMs) of KLHL21 can significantly impact both its biological function and detectability by antibodies. Although research on KLHL21 PTMs is still emerging, several considerations are important:

• Potential phosphorylation: As a regulator of kinase activity (IKKβ) and a substrate for E3 ligase complexes, KLHL21 likely undergoes phosphorylation events that may:

  • Modulate its binding affinity to interaction partners

  • Affect its subcellular localization during cell cycle progression

  • Regulate its own stability or activity

• Ubiquitination: Given KLHL21's role in ubiquitin ligase complexes, it may itself be regulated through ubiquitination:

  • Auto-ubiquitination as a regulatory mechanism

  • Ubiquitination by other E3 ligases as feedback control

• Impact on antibody recognition:

  • Epitope masking: PTMs may alter antibody accessibility to recognition sites

  • Conformational changes: Modifications can induce structural changes affecting antibody binding

  • Cross-reactivity: Some antibodies may preferentially recognize modified or unmodified forms of KLHL21

• Experimental considerations:

  • Phosphatase treatment before immunoprecipitation or Western blot may reveal whether phosphorylation affects antibody recognition

  • Stimulus-dependent changes in PTM status may explain the gradual attenuation of KLHL21-IKKβ interaction upon TNFα treatment

  • Cell cycle synchronization may be necessary to capture cell cycle-dependent modifications

When investigating KLHL21 PTMs, researchers should consider using antibodies targeting specific modifications or combining KLHL21 immunoprecipitation with mass spectrometry to identify and characterize modification sites and their functional significance.

What are common challenges in detecting endogenous KLHL21 and how can they be overcome?

Detecting endogenous KLHL21 can present several challenges that require specific methodological solutions:

• Low expression levels: KLHL21 may be expressed at relatively low levels in some cell types or tissues.
  Solution: Enrich for KLHL21 through immunoprecipitation before Western blot analysis or use signal amplification methods like tyramide signal amplification for immunostaining.

• Stimulus-dependent expression changes: KLHL21 expression is rapidly down-regulated upon inflammatory stimulation .
  Solution: Include appropriate time-course samples and unstimulated controls when studying KLHL21 in inflammation-related contexts.

• Antibody specificity concerns: KLHL21 belongs to the Kelch-like protein family with structural similarities to other members.
  Solution: Validate antibody specificity using KLHL21 siRNA knockdown samples as negative controls . The effectiveness of siRNA knockdown should be confirmed at both mRNA and protein levels.

• Antibody sensitivity limitations: Some KLHL21 antibodies may have detection thresholds above endogenous expression levels.
  Solution: Optimize protein loading (30-50 μg per lane), use sensitive detection methods (e.g., chemiluminescence with signal enhancers), and extend exposure times cautiously.

• Sample preparation issues: Inappropriate lysis conditions may affect protein extraction or epitope availability.
  Solution: Compare different lysis buffers (RIPA vs. NP-40 vs. Triton X-100) to determine optimal extraction conditions for your sample type.

• Cell type-specific expression: KLHL21 has been successfully detected in A431 and HeLa cells , but expression may vary across cell types.
  Solution: Include positive control lysates (HeLa or A431) alongside experimental samples when first optimizing detection protocols.

By addressing these challenges systematically, researchers can achieve reliable detection of endogenous KLHL21 across various experimental contexts.

How should experiments be designed to study the dynamics of KLHL21-IKKβ interaction during inflammatory responses?

To effectively study the dynamic interaction between KLHL21 and IKKβ during inflammatory responses, a carefully designed experimental approach is required:

• Temporal analysis design:

  • Treat cells with TNFα (10-50 ng/ml) or other inflammatory stimuli

  • Collect samples at short intervals (0, 2, 5, 10, 15, 30, 60 minutes) to capture the gradual attenuation of interaction observed upon TNFα treatment

  • Process all samples simultaneously to minimize technical variation

• Co-immunoprecipitation strategy:

  • Perform bidirectional co-IPs (KLHL21 IP followed by IKKβ detection and vice versa)

  • Use gentle lysis conditions (50 mM Tris-HCl pH 7.4, 150 mM NaCl, 1% NP-40) to preserve protein-protein interactions

  • Include appropriate controls (isotype control, input, KLHL21-depleted samples)

• Parallel signaling analysis:

  • Monitor IKKβ phosphorylation status (pSer177/181)

  • Track IκBα phosphorylation and degradation

  • Assess NF-κB nuclear translocation via fractionation or imaging

• Quantitative assessment:

  • Normalize co-IP signal to input and IP efficiency

  • Calculate relative interaction strength across time points

  • Correlate interaction dynamics with downstream signaling events

• Validation approaches:

  • Fluorescence resonance energy transfer (FRET) or proximity ligation assay (PLA) to visualize the interaction in intact cells

  • Domain mutant analysis to confirm interaction interfaces

  • Structure-function analysis using point mutants at key residues

• Inhibitor studies:

  • Use pathway-specific inhibitors to determine whether the interaction attenuation requires specific signaling events

  • Test proteasome inhibitors to assess whether protein degradation contributes to interaction dynamics

This comprehensive approach will provide mechanistic insights into how inflammatory stimuli regulate the KLHL21-IKKβ interaction and subsequently NF-κB signaling activation.

What strategies can be employed for multiplexed detection of KLHL21 and its interaction partners?

Multiplexed detection of KLHL21 and its interaction partners provides comprehensive insights into its functional networks. Several methodological approaches can be employed:

• Multi-color immunofluorescence:

  • Use spectrally distinct fluorophores for KLHL21 and partners (IKKβ, aurora B, Cul3)

  • Apply sequential staining with careful antibody selection to avoid cross-reactivity

  • Perform confocal microscopy to assess subcellular co-localization patterns

  • Quantify co-localization using Pearson's or Mander's coefficients

• Proximity ligation assay (PLA):

  • Detect protein-protein interactions in situ with single-molecule sensitivity

  • Particularly valuable for transient interactions like KLHL21-IKKβ during inflammatory responses

  • Quantifiable via fluorescent dot analysis

  • Can be combined with other markers to assess cellular context

• Co-immunoprecipitation with multiplexed detection:

  • Perform KLHL21 immunoprecipitation followed by multiplexed Western blotting

  • Use differentially labeled secondary antibodies for simultaneous detection

  • Employ fluorescence-based Western detection systems for quantitative analysis

  • Strip and re-probe membranes sequentially with careful documentation

• Mass spectrometry-based approaches:

  • Immunoprecipitate KLHL21 followed by LC-MS/MS analysis

  • Implement stable isotope labeling (SILAC) to compare interaction partners under different conditions

  • Use label-free quantification to identify stimulus-dependent changes in the KLHL21 interactome

  • Apply crosslinking mass spectrometry to capture transient interactions

• Cytometric bead array:

  • Utilize matched antibody pairs for KLHL21 in combination with antibodies against interaction partners

  • Enable simultaneous quantification of multiple proteins in complex samples

  • Particularly useful for analyzing small sample volumes or precious specimens

These complementary approaches provide a comprehensive understanding of KLHL21's dynamic interactions across different cellular contexts and experimental conditions.

How might KLHL21 research contribute to therapeutic developments in inflammatory diseases?

KLHL21's role as a negative regulator of NF-κB signaling positions it as a potential therapeutic target for inflammatory diseases. Several promising research directions emerge:

• Expression profiling in disease states:

  • Compare KLHL21 expression in tissues from patients with inflammatory diseases versus healthy controls

  • Investigate correlations between KLHL21 levels and disease severity or treatment response

  • Determine whether KLHL21 expression could serve as a biomarker for inflammatory status

• Mechanism-based therapeutic strategies:

  • Develop peptide mimetics based on the KLHL21-IKKβ interaction interface to inhibit IKKβ activation

  • Design small molecules that stabilize the KLHL21-IKKβ interaction even during inflammatory stimulation

  • Explore approaches to prevent the rapid down-regulation of KLHL21 that occurs during inflammatory responses

• Genetic validation studies:

  • Investigate whether KLHL21 polymorphisms associate with inflammatory disease risk or severity

  • Develop tissue-specific KLHL21 transgenic or knockout mouse models to assess effects on inflammatory responses in vivo

  • Use CRISPR/Cas9-based approaches to modulate KLHL21 expression in primary human cells

• Pathway-specific interventions:

  • Determine whether KLHL21 regulation differs across various inflammatory pathways (TNFα, IL-1, TLR, etc.)

  • Identify stimulus-specific regulation mechanisms that could be targeted for pathway-selective anti-inflammatory effects

  • Explore the relationship between KLHL21 and existing anti-inflammatory drug mechanisms

• Cell type-specific considerations:

  • Characterize KLHL21 expression and function across immune cell subsets

  • Investigate cell type-specific regulatory mechanisms

  • Develop targeted delivery systems for KLHL21-modulating therapeutics to specific cell populations

These research directions could ultimately lead to novel anti-inflammatory therapeutics that modulate NF-κB signaling through the KLHL21 axis, potentially offering more selective approaches than direct NF-κB inhibition.

What emerging technologies might advance our understanding of KLHL21 biology?

Emerging technologies offer unprecedented opportunities to deepen our understanding of KLHL21 biology across multiple dimensions:

• Advanced imaging approaches:

  • Super-resolution microscopy to visualize KLHL21 subcellular localization with nanometer precision

  • Live-cell imaging with fluorescently tagged KLHL21 to track dynamic relocalization during cell division or inflammatory responses

  • Lattice light-sheet microscopy for long-duration 3D imaging with minimal phototoxicity

• Single-cell analysis technologies:

  • Single-cell RNA-seq to identify cell populations with distinct KLHL21 expression patterns

  • Single-cell proteomics to correlate KLHL21 protein levels with other signaling components

  • Spatial transcriptomics to map KLHL21 expression within tissue microenvironments

• Structural biology innovations:

  • Cryo-electron microscopy to determine the 3D structure of KLHL21 alone and in complex with IKKβ

  • Hydrogen-deuterium exchange mass spectrometry to map interaction interfaces dynamically

  • Integrative structural modeling to predict how KLHL21 conformational changes might regulate its function

• CRISPR-based functional genomics:

  • CRISPR activation/inhibition screens to identify regulators of KLHL21 expression

  • Base editing to introduce specific point mutations in endogenous KLHL21

  • CRISPR knock-in of fluorescent or affinity tags at the endogenous KLHL21 locus

• Protein interaction mapping technologies:

  • BioID or APEX proximity labeling to identify the KLHL21 proximal proteome in living cells

  • Reversible crosslinking coupled with mass spectrometry to capture transient interactions

  • Protein complementation assays to visualize dynamic protein-protein interactions in real-time

These technological advances will enable researchers to address previously intractable questions about KLHL21 biology, from atomic-level structural details to system-level functional networks.

How can researchers integrate KLHL21 findings across cell division and inflammatory signaling functions?

Integrating KLHL21's dual roles in cell division and inflammatory signaling presents a unique opportunity to understand crosstalk between these fundamental biological processes:

• Temporal integration approaches:

  • Synchronize cells and track KLHL21 functions across the cell cycle while simultaneously monitoring inflammatory responses

  • Develop dual-reporter systems to visualize both mitotic progression and NF-κB activation in the same cells

  • Perform time-resolved proteomics to identify condition-specific KLHL21 interaction partners

• Domain-specific functional analysis:

  • Generate domain-specific KLHL21 mutants that selectively disrupt either cell division or inflammatory signaling functions

  • For example, compare the Kelch domain mutants that cannot bind IKKβ against BTB domain mutants that cannot bind Cul3

  • Assess whether these functions can be genetically separated or are coordinately regulated

• Context-dependent regulation studies:

  • Investigate how inflammatory stimuli affect KLHL21's role in cell division

  • Determine whether cell cycle phase influences KLHL21's ability to regulate NF-κB signaling

  • Examine whether these functions compete for a limited pool of KLHL21 protein

• Disease-relevant integration:

  • Study KLHL21 in contexts where both inflammation and cell division are dysregulated, such as cancer

  • Assess whether KLHL21 serves as a molecular link between inflammation-induced cell proliferation

  • Determine if therapeutic targeting of one function inevitably affects the other

• Systems biology approaches:

  • Develop mathematical models incorporating both KLHL21 functions

  • Perform network analysis to identify common upstream regulators or downstream effectors

  • Use perturbation experiments to validate model predictions

By integrating these perspectives, researchers can develop a unified understanding of how KLHL21 coordinates cellular responses across different biological processes, potentially revealing novel regulatory principles with broader implications for cell biology and disease.