CDK2 (Ab-160) Antibody

What is CDK2 (Ab-160) Antibody and what specific epitope does it recognize?

CDK2 (Ab-160) Antibody is a rabbit polyclonal antibody designed to detect the phosphorylated threonine 160 (T160) residue of CDK2 . This antibody was developed using synthetic peptides corresponding to the region surrounding the T160 phosphorylation site in human CDK2 . Phosphorylation at T160 is a critical regulatory event that occurs in the T-loop of CDK2 and is essential for its full activation. The antibody allows researchers to specifically monitor the activated form of CDK2 in various experimental contexts, making it an invaluable tool for studying cell cycle regulation .

What experimental applications has the CDK2 (Ab-160) Antibody been validated for?

The CDK2 (Ab-160) Antibody has been validated for several research applications, including Western blot (WB) analysis and immunohistochemistry on paraffin-embedded tissues (IHC-P) . In Western blot applications, it successfully detects a band of approximately 34 kDa, corresponding to phosphorylated CDK2 . For immunohistochemistry, the antibody has been effectively used at dilutions of approximately 1/50 on human breast carcinoma tissue samples . The antibody predominantly reacts with human samples, though cross-reactivity with other species may occur due to sequence conservation in the targeted phosphorylation region .

What is the biological significance of CDK2 phosphorylation at T160?

Phosphorylation of CDK2 at threonine 160 represents a critical activation event in cell cycle regulation. This phosphorylation is catalyzed by CDK-activating kinase (CAK) and induces conformational changes that enable full kinase activity . T160 phosphorylation is essential for CDK2's role in promoting the transition from G1 to S phase of the cell cycle . Research has revealed that this phosphorylation not only enhances CDK2's catalytic activity but also influences its interaction with binding partners, including cyclins and CDK inhibitors (CKIs) . Without T160 phosphorylation, CDK2 exhibits significantly reduced kinase activity, even when bound to its cyclin partners, highlighting the central importance of this modification in cell proliferation control .

What are the optimal protocols for using CDK2 (Ab-160) Antibody in Western blot analysis?

For effective Western blot detection of phosphorylated CDK2 using the Ab-160 antibody, researchers should consider the following protocol optimizations:

• Sample preparation should include phosphatase inhibitors (sodium orthovanadate, sodium fluoride, and β-glycerophosphate) to preserve phosphorylation states .

• Use a dilution of 1/500 for the primary antibody, as this has been reported to provide optimal signal-to-noise ratio .

• Include appropriate controls: untreated cell extracts (negative control) and UV-treated cell extracts (positive control) as phosphorylation at T160 increases following certain stress stimuli .

• The expected band size is approximately 34 kDa, though higher molecular weight bands may appear due to post-translational modifications .

• For blocked membranes, BSA (5% in TBST) is preferred over milk, as milk contains phosphatases that may reduce phospho-specific signals.

• Extended washing steps (at least 3×10 minutes) are recommended to reduce background signals that could interfere with specific detection.

How can I effectively use CDK2 (Ab-160) Antibody in immunohistochemistry studies?

For optimal immunohistochemical detection of phosphorylated CDK2:

• Tissue fixation is critical—use 10% neutral buffered formalin for 24-48 hours to preserve phospho-epitopes without causing overfixation artifacts .

• Antigen retrieval is essential—heat-induced epitope retrieval using citrate buffer (pH 6.0) has shown good results with this antibody .

• Use the antibody at a dilution of approximately 1/50, which has been validated on human breast carcinoma tissues .

• Develop separate scoring systems for nuclear and cytoplasmic staining, as recent research indicates that subcellular localization of phospho-CDK2 has distinct biological significance .

• Include both positive controls (proliferating tissues known to express phospho-CDK2) and negative controls (primary antibody omitted) in each staining batch to validate results.

• When analyzing cancer specimens, correlate phospho-CDK2 staining patterns with other clinicopathological parameters for comprehensive assessment .

How can I validate the specificity of CDK2 (Ab-160) Antibody in my experimental system?

Validating antibody specificity is essential for reliable research outcomes. For CDK2 (Ab-160) Antibody, consider these approaches:

• Phosphatase treatment: Divide your sample and treat one portion with lambda phosphatase to remove phosphorylation. This should eliminate or significantly reduce the signal if the antibody is truly phospho-specific .

• Gene knockdown validation: Use siRNA to reduce CDK2 expression and confirm decreased signal intensity in both Western blot and immunostaining applications .

• Analog-sensitive CDK2 models: If available, utilize cell lines expressing analog-sensitive CDK2 (CDK2-as) and treat with specific inhibitors like 3-MB-PP1, which should modulate phosphorylation status in a predictable manner .

• Peptide competition: Pre-incubate the antibody with excess immunizing phospho-peptide, which should block specific binding and eliminate genuine signals.

• Compare with total CDK2 staining: Run parallel experiments with antibodies detecting total CDK2 to assess the proportion of phosphorylated protein and confirm signal specificity .

How can CDK2 (Ab-160) Antibody help investigate the dual functions of CDK2 in cell cycle regulation?

CDK2 possesses both catalytic (kinase) and non-catalytic (scaffold) functions in cell cycle regulation . The CDK2 (Ab-160) Antibody can help dissect these roles through:

• Chemical genetics approaches: Using analog-sensitive CDK2 mutants (F80G) in combination with the phospho-specific antibody allows researchers to differentiate between phenotypes resulting from loss of CDK2 kinase activity versus disruption of protein-protein interactions .

• Studying cyclin binding patterns: The antibody can be used to examine how T160 phosphorylation affects CDK2's competitive binding to cyclin A versus CDK1. Under normal conditions, cyclin A complexes contain approximately 2-fold more CDK2 than CDK1, and this ratio can be monitored following various perturbations .

• Time-course experiments: Following synchronization, researchers can track T160 phosphorylation throughout the cell cycle to correlate activation states with specific cell cycle transitions .

• Inhibitor studies: The antibody can monitor T-loop phosphorylation following treatment with ATP-competitive inhibitors versus protein degraders, revealing different requirements for catalytic and scaffold functions .

Research has demonstrated that both the catalytic and scaffold functions of CDK2 are required for normal timing of restriction point passage and S-phase entry .

What insights can CDK2 (Ab-160) Antibody provide about subcellular localization of active CDK2 in cancer?

Recent research indicates that subcellular localization of phosphorylated CDK2 has important implications in cancer biology . Using CDK2 (Ab-160) Antibody:

• Distinct scoring systems can be implemented for nuclear versus cytoplasmic phospho-CDK2 staining in tumor samples, revealing previously overlooked patterns .

• Data from 1676 breast carcinoma patients showed that cytoplasmic localization of phospho-CDK2 correlates strongly with cytoplasmic cyclin E, suggesting coordinated mislocalization of the active complex .

• Cytoplasmic phospho-CDK2 expression correlates with high tumor grade, negative estrogen/progesterone receptor status, and HER2 positivity in breast cancer, potentially serving as a biomarker for aggressive disease .

• The strong correlation between cytoplasmic phospho-CDK2 and poor clinical outcomes suggests altered subcellular localization may contribute to oncogenic activity through non-canonical functions or substrates .

This application represents an emerging area where phospho-specific antibodies can provide insights beyond simple activity measurements, potentially revealing mechanisms of oncogenic dysregulation.

How can the relationship between CDK2 phosphorylation status and cyclin binding be studied using this antibody?

The interaction between CDK2 phosphorylation and cyclin binding is complex and critical for proper cell cycle control . Using CDK2 (Ab-160) Antibody:

• Sequential immunoprecipitation can be performed—first precipitating specific cyclins (E or A), then detecting the proportion of bound CDK2 that is phosphorylated at T160 .

• Analysis of mutant CDK2 models revealed that phosphorylation status affects competitive binding between CDK2 and CDK1 for cyclin A. While wild-type cyclin A complexes contained ~2-fold more CDK2 than CDK1, this ratio was inverted in certain mutants .

• Treatment with specific chemical compounds (like 3-MB-PP1) can modulate both T-loop phosphorylation and cyclin binding patterns, allowing researchers to study the interrelationship between these events .

• Time-course experiments following cell synchronization can reveal how the temporal coordination of T160 phosphorylation relates to sequential binding of cyclin E and cyclin A during cell cycle progression .

This approach provides insights into how phosphorylation at T160 influences not only CDK2 activity but also its preference for specific cyclin partners at different cell cycle stages.

How should researchers interpret discrepancies between phospho-CDK2 levels and measured CDK2 kinase activity?

Researchers may encounter situations where phospho-CDK2 (T160) levels do not directly correlate with measured CDK2 kinase activity. Consider these factors when interpreting such discrepancies:

• CDK inhibitor binding: Proteins like p21^Cip1 can bind to phosphorylated CDK2-cyclin complexes, inhibiting activity despite T160 phosphorylation being present .

• Inhibitory phosphorylations: CDK2 can simultaneously contain activating (T160) and inhibitory (T14, Y15) phosphorylations, with the latter overriding the former's activating effect .

• Cyclin availability: T160 phosphorylation alone is insufficient for full activation; the appropriate cyclin partner must also be present in stoichiometric amounts .

• Subcellular sequestration: Phosphorylated CDK2 may be sequestered away from its substrates through compartmentalization or binding to scaffold proteins .

• Phosphorylation dynamics: Rapid turnover of phosphorylation can create discrepancies between static measurements and dynamic activity.

To resolve these discrepancies, combine phospho-CDK2 detection with direct kinase activity assays, and assess the levels of CDK inhibitors and inhibitory phosphorylations to obtain a complete picture of CDK2 regulation.

What factors can influence staining patterns in immunohistochemistry using CDK2 (Ab-160) Antibody?

When performing immunohistochemistry with phospho-specific antibodies like CDK2 (Ab-160), several factors can influence staining patterns:

• Fixation conditions: Phospho-epitopes are particularly sensitive to fixation variables; overfixation can mask epitopes while underfixation may allow phosphatase activity to remove the modification .

• Tissue processing time: Delays between tissue removal and fixation can lead to dephosphorylation and false-negative results.

• Antigen retrieval method: Heat-induced versus enzymatic retrieval methods may yield different results with phospho-specific antibodies .

• Antibody concentration: Optimal dilution (typically around 1/50 for this antibody) must be determined empirically for each tissue type .

• Detection system sensitivity: Amplification systems may be required for tissues with low expression levels.

• Phosphatase activity in tissues: Endogenous phosphatase activity can vary between tissue types and pathological states.

A comprehensive study of breast carcinoma tissues demonstrated that separate evaluation of nuclear versus cytoplasmic staining provides more meaningful results than traditional aggregate scoring systems .

How can researchers distinguish between specific and non-specific signals when using CDK2 (Ab-160) Antibody?

Distinguishing genuine signals from artifacts is critical for reliable research. For CDK2 (Ab-160) Antibody:

• Include proper controls:

  • Phosphatase-treated samples as negative controls

  • Mitotic cell populations as positive controls (high CDK activity)

  • Peptide competition controls to identify specific binding

• Verify expected molecular weight (34 kDa) in Western blot applications .

• Compare staining patterns with total CDK2 antibodies to confirm overlap of signal distribution .

• Implement double staining with cell cycle markers (e.g., Ki-67, PCNA) to confirm expected co-expression patterns.

• Use analog-sensitive CDK2 models with specific inhibitors to demonstrate predictable changes in phosphorylation patterns .

• Apply functional tests such as CDK2 knockdown or inhibition to confirm decreases in signal intensity that correlate with functional outcomes.

These approaches collectively strengthen confidence in signal specificity and enable reliable interpretation of experimental results.

What is the relationship between CDK2 phosphorylation at T160 and the cell cycle restriction point?

CDK2 plays a crucial role in the restriction point, which represents the commitment to cell cycle progression . Analysis with CDK2 (Ab-160) Antibody reveals:

• Both catalytic and scaffold functions of CDK2 are required for normal timing of restriction point passage, with T160 phosphorylation being essential for the catalytic component .

• In normal cells, T-loop phosphorylation increases after growth factor stimulation, correlating with restriction point passage and commitment to cell cycle entry .

• Using chemical genetics approaches with analog-sensitive CDK2, researchers demonstrated that specific inhibition of CDK2 activity impeded cell proliferation, establishing a non-redundant requirement for CDK2 catalytic activity in cell cycle commitment .

• Time-course experiments show coordinated T160 phosphorylation with other restriction point events such as Rb phosphorylation and E2F activation, indicating an orchestrated sequence of phosphorylation events .

• Mathematical modeling incorporating phospho-CDK2 data has helped elucidate how the timing of restriction point passage is fine-tuned by the balance between activating phosphorylation and cyclin availability .

How does CDK2 phosphorylation status influence the interplay between CDK2 and CDK1 in cell cycle control?

The relationship between CDK2 and CDK1 is complex and regulated in part through phosphorylation . Studies using CDK2 (Ab-160) Antibody have revealed:

• Under physiological conditions, there is a specific ratio of CDK2:CDK1 bound to cyclin A (approximately 2:1), which is maintained through preferential binding of CDK2 .

• An important non-catalytic function of CDK2 appears to be excluding CDK1 from cyclin complexes until DNA replication has commenced, potentially preventing premature firing of late replication origins .

• Mutations affecting CDK2 can disrupt this balance, inverting the ratio and allowing increased CDK1-cyclin A complex formation .

• T160 phosphorylation affects not only CDK2's kinase activity but also influences its competitive advantage over CDK1 in forming complexes with cyclin A .

• Chemical modulation of CDK2 phosphorylation (using small molecule inhibitors with analog-sensitive CDK2) can restore normal cyclin binding patterns, demonstrating the regulatory importance of this phosphorylation .

This data suggests a sophisticated regulatory mechanism where phosphorylation status influences not just enzymatic activity but also protein-protein interaction networks that control cell cycle progression.

What is the significance of CDK2 phosphorylation patterns in cancer research and potential therapeutic applications?

CDK2 phosphorylation has emerging importance in cancer biology and therapeutics :

• A comprehensive study of 1676 breast carcinoma cases revealed that cytoplasmic localization of phospho-CDK2 correlates with aggressive tumor characteristics, including high grade, negative hormone receptor status, and HER2 positivity .

• The table below summarizes the distribution of cyclin E and CDK2 phosphorylation patterns in breast cancer samples:

What methodological advances would enhance the utility of CDK2 (Ab-160) Antibody in studying cell cycle regulation?

Several methodological advances could expand the research applications of CDK2 (Ab-160) Antibody:

• Development of phospho-specific antibodies that simultaneously recognize T160 phosphorylation while discriminating between inhibitory phosphorylations (T14/Y15) would provide greater insight into the balance of activating and inhibitory modifications.

• Creation of conformation-specific antibodies that recognize the unique structural changes induced by T160 phosphorylation could distinguish between phosphorylated but inactive (inhibitor-bound) and fully active CDK2.

• Implementation of multiplex immunofluorescence techniques to simultaneously detect phospho-CDK2, specific cyclins, and CDK inhibitors at the single-cell level would reveal complex regulatory relationships.

• Adaptation of the antibody for proximity ligation assays would enable visualization of specific CDK2-substrate interactions dependent on T160 phosphorylation in intact cells.

• Integration with live-cell imaging using complementary fluorescent biosensors for CDK2 activity would correlate phosphorylation status with real-time kinase activity measurements.

These approaches would expand our understanding of how T160 phosphorylation integrates with other regulatory mechanisms to control CDK2 function in different cellular contexts.

How might CDK2 phosphorylation analysis contribute to precision medicine approaches in cancer treatment?

CDK2 phosphorylation analysis holds promise for advancing precision medicine in oncology:

• Stratification biomarker: Cytoplasmic phospho-CDK2 detection could identify patient subgroups most likely to benefit from CDK inhibitor therapies, particularly in breast cancer where its expression correlates with aggressive disease features .

• Resistance mechanisms: Monitoring changes in CDK2 phosphorylation patterns in tumors developing resistance to CDK4/6 inhibitors could reveal compensatory activation mechanisms and inform sequential treatment strategies.

• Combinatorial therapy approaches: Identifying tumors with high levels of phospho-CDK2 might guide rational drug combinations, potentially pairing CDK2 inhibitors with drugs targeting pathways that regulate CDK2 activation.

• Treatment response monitoring: Sequential biopsies analyzed for phospho-CDK2 could provide early indications of treatment efficacy before clinical response is evident.

• Development of novel CDK2-directed therapies: Understanding the relationship between phosphorylation, localization, and oncogenic activity could inspire new therapeutic approaches beyond traditional ATP-competitive inhibitors.

Research using phospho-specific antibodies has already established cytoplasmic CDK2 activation as a prognostic biomarker in breast cancer , providing a foundation for these translational applications.