CREB1 (Ab-133) Antibody

What is CREB1 and what role does phosphorylation at Ser133 play in its function?

CREB1 (cAMP responsive element binding protein 1) is a bZIP transcription factor that homo- or hetero-dimerizes to activate target genes through cAMP response elements (CRE). CREB1 binds constitutively to CREs in open chromatin and is activated primarily through phosphorylation at Ser133 by numerous kinases, including PKA, AMPK, MAPK, and AKT .

Upon phosphorylation at Ser133, pCREB1 can specifically recruit the coactivator CREB binding protein (CBP) and its paralog p300, which is essential for transcriptional activation . This phosphorylation is a critical regulatory event that transforms CREB1 from a DNA-bound but inactive transcription factor to an active one capable of driving gene expression of various downstream targets involved in cell differentiation, proliferation, survival, and other cellular processes.

Which experimental applications are suitable for CREB1 (Ab-133) antibody?

CREB1 (Ab-133) antibody can be utilized in multiple experimental techniques:

For optimal results, always validate the antibody in your specific experimental system and include appropriate positive and negative controls .

How can I optimize western blot protocols for detecting phosphorylated CREB1?

For optimal detection of phosphorylated CREB1:

• Sample preparation: Lyse cells directly in phosphatase inhibitor-containing buffer to prevent dephosphorylation during processing. Add protease inhibitors to prevent degradation.

• Protein loading and separation: Load 20-40 μg of total protein per lane. Use 10-12% SDS-PAGE gels for optimal separation around the 43-46 kDa range where phosphorylated CREB1 migrates .

• Transfer conditions: Use wet transfer for best results with PVDF membranes (0.45 μm pore size).

• Blocking and antibody incubation:

  • Block with 5% BSA in TBST (not milk, as it contains phosphatases)

  • Dilute primary antibody 1:500-1:1000 in blocking buffer

  • Incubate overnight at 4°C with gentle agitation

  • Wash thoroughly with TBST (at least 3 × 10 minutes)

  • Use appropriate HRP-conjugated secondary antibody

• Signal generation: Use enhanced chemiluminescence detection with exposure times optimized for your sample.

• Controls: Include both phosphatase-treated negative controls and forskolin-treated positive controls (forskolin activates adenylyl cyclase, increasing cAMP levels and PKA activity, resulting in CREB1 phosphorylation) .

The expected molecular weight for phosphorylated CREB1 is 43-46 kDa, though a band at 35 kDa may also be observed .

What are the critical considerations for immunohistochemical detection of phosphorylated CREB1?

When performing IHC for phosphorylated CREB1:

• Tissue fixation: Use 10% neutral buffered formalin; overfixation may mask epitopes.

• Antigen retrieval: Two options are recommended:

  • Heat-induced epitope retrieval with TE buffer pH 9.0 (preferred method)

  • Alternative: citrate buffer pH 6.0

• Blocking: Use 10% normal serum from the same species as the secondary antibody plus 1% BSA.

• Antibody dilution: Start with 1:50-1:200 dilution for primary antibody .

• Detection system: Use a polymer-based detection system for increased sensitivity.

• Counterstaining: Use hematoxylin for nuclear contrast; phosphorylated CREB1 shows nuclear localization.

• Positive controls: Include tissues known to express phosphorylated CREB1 such as:

  • Forskolin-treated cell lines

  • Cervix carcinoma tissue

  • Neuronal tissue (ganglion cell and inner nuclear layers of retina)

• Negative controls: Include primary antibody omission and tissue sections known to lack phosphorylated CREB1.

Remember that signal intensity may vary based on the level of CREB1 phosphorylation in different tissue types and cellular states.

How can I differentiate between CREB1 and ATF1 phosphorylation in my experiments?

Distinguishing between phosphorylated CREB1 and ATF1 is challenging as they share significant sequence homology, particularly around the phosphorylation site:

• Antibody selection: Many phospho-specific antibodies against CREB1 (Ser133) cross-react with phosphorylated ATF1 due to sequence similarity. The search results indicate that CREB1 (Ab-133) antibody detects both phosphorylated CREB1 and the related ATF1 protein .

• Molecular weight discrimination:

  • Phosphorylated CREB1: 43-46 kDa

  • Phosphorylated ATF1: ~35-38 kDa

  Use appropriate molecular weight markers and run samples long enough to resolve these close bands .

• Activation kinetics: Research shows that CREB1 and ATF1 are activated with different kinetics during cellular processes. For example, in prostate luminal cell differentiation, ATF1 is transiently activated at day 12 and decreases by day 14, while CREB1 activation peaks at day 14 .

• Knockdown validation: Use siRNA/shRNA knockdown of either CREB1 or ATF1 to confirm band identity in Western blots.

• Functional studies: ATF1 and CREB1 have different biological roles despite their structural similarities. For instance, knockdown of ATF1 blocked suprabasal induction in prostate epithelial cells while CREB1 knockdown did not prevent differentiation but affected cell survival .

For definitive identification, consider using tandem approaches like immunoprecipitation followed by Western blotting with isoform-specific antibodies or mass spectrometry analysis.

What is the significance of CREB1 phosphorylation in prostate cancer models and what methods best detect these changes?

CREB1 phosphorylation plays a crucial role in prostate cancer progression:

This research demonstrates how the same transcription factor can promote normal differentiation or oncogenesis depending on cellular context and targeting different gene sets .

How is CREB1 phosphorylation implicated in immune responses and HIV vaccination efficacy?

Research has established CREB1 as a critical factor in immune responses, particularly in HIV vaccination efficacy:

• CREB1 as immunogenicity driver: The transcription factor CREB1 and its target genes were shown to be induced by the recombinant canarypox vector ALVAC+Alum, augmenting immunogenicity in Non-human primates (NHPs) .

• Correlation with HIV-1 acquisition protection:

  • The average expression of CREB1 target genes (CREB1 z-score) was significantly elevated in RV144 trial participants who remained uninfected compared to those who became infected post-vaccination.

  • Kaplan-Meier analysis showed significantly reduced risk of HIV-1 acquisition in individuals with medium and high CREB1 z-scores, with the high z-score group maintaining lower acquisition risk for up to three years post-vaccination .

• Methodological approaches to study this connection:

  • Gene Set Enrichment Analysis (GSEA) to identify CREB1 pathway activation

  • Transcriptomic profiling of vaccine recipients

  • Correlation of CREB1 target gene expression with protective immunity markers

  • Analysis of cytokine/chemokine expression patterns

• Mechanism of action: CREB1 gene expression likely results from direct cGAMP (STING agonist) modulated p-CREB1 activity, which drives the recruitment of CD4+ T cells and B cells to the site of antigen presentation .

• Adjuvant effects on CREB1 signaling:

  Vaccine Formulation	CREB1 Target Gene Expression	Protection Outcome
  ALVAC+Alum (RV144 trial)	Significantly increased	Showed partial protection
  ALVAC+MF59 (HVTN702 trial)	Significantly reduced	No protection observed

This research highlights CREB1 as a potential biomarker for vaccine efficacy and suggests that adjuvants triggering CREB1 signaling may be critical for developing efficacious HIV-1 vaccines .

What is the relationship between CREB1 phosphorylation and renal cell carcinoma progression?

Research has uncovered important connections between phosphorylated CREB1 and renal cell carcinoma (RCC):

• p-CREB1 as a prognostic marker: Studies have shown that phosphorylated CREB1 at Ser133 (p-CREB1) protein levels correlate with poor prognosis in clear cell renal cell carcinoma (ccRCC), the most prevalent subtype of renal cancer .

• Mechanistic role: Activated CREB1 (p-CREB1) binds to the promoter region of downstream genes containing cAMP-responsive elements and regulates tumor invasion and proliferation .

• Experimental approaches for studying p-CREB1 in RCC:

  • Immunohistochemical staining of tissue microarrays to assess p-CREB1 levels in ccRCC specimens

  • Correlation of staining intensity with clinicopathological variables

  • Survival analysis based on p-CREB1 expression levels

  • In vitro functional studies using RCC cell lines with CREB1 overexpression or knockdown

• Key findings:

  • p-CREB1 is frequently overexpressed in ccRCC compared to normal kidney tissue

  • Higher p-CREB1 levels are associated with unfavorable outcomes including tumor recurrence, metastasis, and death

  • p-CREB1 regulates the expression of proto-oncogenes such as cyclin A and Bcl-2, which are associated with cell differentiation, proliferation, cell cycle regulation, and apoptosis

• Signaling pathways: p-CREB1 in RCC may be activated through multiple pathways:

  • ERK1/2 signaling

  • PKA pathway

  • PKC pathway

  • CaMKII signaling pathway

These findings suggest that p-CREB1 could be a valuable prognostic biomarker and potential therapeutic target in renal cell carcinoma.

Why might I observe variable or unexpected band patterns when using CREB1 (Ab-133) antibody in Western blots?

Several factors can contribute to variable or unexpected band patterns:

• Cross-reactivity with related proteins:

  • CREB1 (Ab-133) antibody detects both CREB1 and the related protein ATF1 due to sequence similarity around the phosphorylation site .

  • Expected molecular weights:

    • Phosphorylated CREB1: 43-46 kDa

    • Phosphorylated ATF1: ~35-38 kDa

• Post-translational modifications:

  • Besides phosphorylation at Ser133, CREB1 undergoes other modifications including sumoylation on Lys-304 and Lys-285 .

  • These modifications can alter migration patterns on SDS-PAGE.

• Isoform detection:

  • Multiple CREB1 isoforms exist (α, β, γ) with different molecular weights.

  • The antibody may detect multiple isoforms depending on tissue/cell type.

• Sample preparation issues:

  • Inadequate phosphatase inhibition during sample preparation can lead to dephosphorylation.

  • Use fresh phosphatase inhibitor cocktails and keep samples cold.

  • Avoid freeze-thaw cycles that can affect phosphorylation status.

• Technical considerations:

  • Use positive controls like forskolin-treated cells that show strong CREB1 phosphorylation .

  • Include phosphatase-treated negative controls.

  • Verify antibody specificity with siRNA/shRNA knockdown.

  • Consider using a monoclonal antibody like p-CREB1 (10E9) that may provide stronger signal and more consistent results .

For optimal results, follow manufacturer's recommendations for blocking buffer (BSA rather than milk, which contains phosphatases) and incubation conditions.

How can I validate CREB1 (Ab-133) antibody specificity in my experimental system?

Proper validation of antibody specificity is critical for reliable research results:

• Positive and negative controls:

  • Positive control: Use cell lines or tissues known to express phosphorylated CREB1 (forskolin-treated cell lines, brain tissue) .

  • Negative control: Include samples treated with lambda phosphatase to remove phosphorylation.

  • Tissue-specific controls: For example, in adult mammalian retina, p-CREB1 is normally limited to the ganglion cell and inner nuclear layers .

• Knockdown/knockout validation:

  • Use siRNA/shRNA targeting CREB1 to demonstrate decreased signal.

  • If available, use CREB1 knockout cells or tissues from CREB1 knockout models.

  • Note: Unlike total CREB knockout which is perinatally lethal, mice with a Ser133 to alanine mutation in the endogenous Creb gene are viable (though born at less than Mendelian frequency) .

• Stimulation experiments:

  • Treat cells with agents known to increase CREB1 phosphorylation:

    • Forskolin (activates adenylyl cyclase)

    • Growth factors (activate MAPK pathway)

    • Calcium ionophores (activate CaMK)

  • Compare signal before and after treatment.

• Peptide competition:

  • Pre-incubate antibody with the immunizing peptide (phospho-peptide containing Ser133).

  • This should abolish specific signal.

• Multi-technique validation:

  • Confirm results using different techniques (WB, IHC, IF).

  • Use antibodies from different vendors or that recognize different epitopes.

  • Consider orthogonal methods like mass spectrometry to confirm identity.

• Documentation:

  • Record all validation experiments in detail.

  • Include validation data when publishing research using this antibody.

Following these validation steps ensures that your observations truly reflect CREB1 phosphorylation status rather than non-specific binding or artifacts.

How do different CREB1 phosphorylation pathways affect gene expression programs in development and disease?

Research has revealed that CREB1 phosphorylation occurs through multiple pathways with distinct outcomes:

• PKA vs. MAPK/MSK pathways:

  • PKA pathway: In response to cAMP elevation, PKA phosphorylates CREB1 at Ser133, promoting recruitment of co-activators CBP and p300 .

  • MAPK/MSK pathway: MSK1/2 phosphorylates CREB1 at Ser133 downstream of MAPK signaling, but this does not strongly promote CBP/p300 recruitment despite being critical for CREB-dependent gene induction .

• Context-dependent gene regulation:

  • The requirement of Ser133 phosphorylation for gene induction is promoter-specific.

  • Studies using S133A-knockin mice revealed that phosphorylation dependence varies by gene and cellular context .

• Developmental programs:

  • In prostate epithelium, CREB1 activation is essential for differentiated luminal cell survival but not differentiation itself.

  • CREB1 regulates different target genes during development:

    Cell Type	CREB1 Targets	Function
    Prostate luminal cells	PRDM1, PLK2, CLDN1	Differentiation, cell cycle suppression
    Cardiac progenitors	PLK2	Early lineage commitment
    Keratinocytes	BLIMP1	Terminal differentiation

• Disease contexts:

  • In cancer, CREB1 targets completely different gene sets than in normal development.

  • In prostate cancer models, CREB1 regulates genes like GATA2 and TWIST1 rather than differentiation-associated genes .

  • In HIV vaccination, CREB1 activation correlates with protective immune responses .

  • In renal cell carcinoma, p-CREB1 is associated with poor prognosis .

• Integration with other signaling pathways:

  • CREB1 interacts with nuclear receptors such as glucocorticoid receptor and ERα in a cell-context dependent manner.

  • CREB1 and ERα share chromatin binding sites upon stimulation by estrogen and cAMP .

This research highlights how the same phosphorylation event (Ser133) can lead to vastly different outcomes depending on cellular context, additional modifications, binding partners, and integration with other signaling pathways.

What emerging technologies are enhancing our ability to study CREB1 phosphorylation dynamics in live cells?

Recent technological advances have revolutionized the study of CREB1 phosphorylation:

• Phospho-specific biosensors:

  • FRET-based biosensors that change conformation upon CREB1 phosphorylation, allowing real-time monitoring in live cells

  • These biosensors can detect subtle spatiotemporal differences in CREB1 phosphorylation in different subcellular compartments

• Optogenetic approaches:

  • Light-activated kinases that can induce CREB1 phosphorylation with precise spatial and temporal control

  • Enables studies of immediate early gene activation following CREB1 phosphorylation in specific cell populations

• Single-cell phosphoproteomics:

  • Mass cytometry (CyTOF) with phospho-CREB1 antibodies allows quantification across heterogeneous cell populations

  • Single-cell Western blotting technologies enable analysis of phospho-CREB1 levels in individual cells

• Genome editing for endogenous tagging:

  • CRISPR/Cas9-mediated knock-in of fluorescent or epitope tags to endogenous CREB1

  • Creation of phospho-mimetic (S133D) or phospho-dead (S133A) CREB1 mutations in endogenous loci

• Advanced microscopy techniques:

  • Super-resolution microscopy to visualize CREB1 binding to individual CRE elements

  • Lattice light-sheet microscopy for long-term imaging of CREB1 dynamics with minimal phototoxicity

  • Fluorescence lifetime imaging microscopy (FLIM) to detect CREB1 interactions with co-activators

• Multiomics integration:

  • Combined ChIP-seq, RNA-seq, and phosphoproteomics approaches to correlate CREB1 phosphorylation with genomic binding and transcriptional outcomes

  • Machine learning algorithms to predict CREB1-dependent gene expression from multiple data types

These technologies are providing unprecedented insights into how CREB1 phosphorylation regulates gene expression in real-time across diverse physiological and pathological contexts, moving beyond traditional end-point assays to dynamic, systems-level understanding.

How should I design experiments to investigate CREB1's dual roles in both normal development and disease progression?

To effectively study CREB1's context-dependent functions, consider this comprehensive experimental design:

• Cell and tissue model selection:

  • Paired normal/disease models: Use matched normal and disease cell lines (e.g., normal prostate epithelial cells vs. prostate cancer cells)

  • Developmental systems: Select models with well-characterized differentiation protocols

  • Patient-derived samples: Include tissues representing disease progression stages

• Temporal dynamics characterization:

  • Time-course experiments: Monitor CREB1 phosphorylation and target gene expression throughout differentiation or disease progression

  • Inducible systems: Use systems allowing controlled activation of signaling pathways

  • Synchronization methods: When appropriate, synchronize cells to capture specific stages

• Comprehensive target identification:

  • ChIP-seq: Map CREB1 binding sites in normal vs. disease states

  • RNA-seq: Identify differentially expressed genes following CREB1 activation

  • Comparison analysis: Use computational approaches to identify context-specific vs. shared targets

• Genetic manipulation strategies:

  • Acute vs. chronic perturbation: Compare short-term (siRNA) vs. long-term (shRNA, CRISPR) CREB1 depletion

  • Phosphorylation mutants: Use S133A (phospho-dead) and S133D (phospho-mimetic) mutants

  • Domain-specific mutants: Target other functional domains besides phosphorylation sites

• Signaling pathway dissection:

  • Pathway-specific activators/inhibitors: Use forskolin (PKA), growth factors (MAPK), etc.

  • Pathway component knockdowns: Target upstream regulators separately

  • Combinatorial approaches: Test pathway interactions using multiple manipulations

• Functional outcome assessment:

  • Cell-specific phenotypes: Measure differentiation, proliferation, survival, etc.

  • In vivo models: Use xenografts, genetically engineered models with tissue-specific manipulation

  • Rescue experiments: Attempt to rescue disease phenotypes by normalizing CREB1 activity

• Data integration strategy:

  • Multi-omics integration: Combine phosphoproteomics, transcriptomics, and epigenomics data

  • Network analysis: Identify key nodes connecting CREB1 to phenotypic outcomes

  • Single-cell approaches: Characterize heterogeneity in CREB1 activity within populations

This comprehensive approach will help uncover how the same transcription factor can regulate distinct gene sets and cellular processes in normal development versus disease states.

What are the critical controls needed when measuring CREB1 phosphorylation in complex biological samples?

Proper controls are essential for accurate assessment of CREB1 phosphorylation:

• Phosphorylation status controls:

  • Positive control: Include samples with known high p-CREB1 levels (forskolin-treated cells)

  • Negative control: Pre-treat sample aliquots with lambda phosphatase to remove phosphorylation

  • Basal control: Include unstimulated samples to establish baseline phosphorylation

• Antibody validation controls:

  • Peptide competition: Pre-incubate antibody with phospho-peptide to confirm specificity

  • Multiple antibodies: Use antibodies from different vendors or clones recognizing the same epitope

  • Non-specific IgG control: For immunoprecipitation experiments

• Sample processing controls:

  • Phosphatase inhibitor controls: Compare samples processed with and without phosphatase inhibitors

  • Time-course collection: Process samples at different time points after collection to assess phosphorylation stability

  • Subcellular fractionation quality: Use markers for different compartments (e.g., HDAC1 for nucleus)

• Stimulation paradigm controls:

  • Dose-response: Test multiple concentrations of stimulating agent

  • Kinetic analysis: Include multiple time points to capture phosphorylation dynamics

  • Pathway inhibitor controls: Use specific inhibitors of upstream kinases (e.g., H89 for PKA, U0126 for MEK/ERK)

• Genetic controls:

  • CREB1 knockdown/knockout: Verify signal disappearance in CREB1-depleted samples

  • S133A mutant: Use cells expressing CREB1 with Ser133 mutated to alanine as negative control

  • Closely related proteins: Control for ATF1 contribution to observed signal

• Tissue/context-specific controls:

  • Tissue-specific expression patterns: Include tissues with known p-CREB1 distribution (e.g., specific retinal layers)

  • Developmental stage controls: Include samples from different developmental stages

  • Loading controls: Use total CREB1 antibodies and housekeeping proteins appropriate for the tissue

• Quantification controls:

  • Standard curve: Include recombinant phosphorylated CREB1 standards when possible

  • Normalization strategy: Test multiple normalization approaches (to total CREB1, to housekeeping proteins)

  • Technical replicates: Include multiple technical replicates to assess measurement variability

Implementing these controls will substantially increase confidence in p-CREB1 measurements and ensure biological findings are robust and reproducible.

How might CREB1 phosphorylation status serve as a biomarker for disease progression or treatment response?

CREB1 phosphorylation shows considerable promise as a biomarker in multiple disease contexts:

• Cancer prognostication:

  • In clear cell renal cell carcinoma, increased p-CREB1 correlates with poor prognosis

  • Phosphorylated CREB1 could serve as a tissue-based biomarker to stratify patients for more aggressive treatment

  • Quantitative IHC scoring systems for p-CREB1 nuclear staining could be standardized for clinical application

• Immunological response prediction:

  • In HIV vaccine trials, CREB1 target gene expression (CREB1 z-score) significantly predicted reduced HIV-1 acquisition

  • Transcriptomic profiling of CREB1 target genes could serve as a surrogate marker for vaccine efficacy

  • This approach could be expanded to other vaccine development efforts

• Therapeutic response monitoring:

  • Changes in p-CREB1 levels could indicate response to therapies targeting upstream signaling pathways

  • Serial liquid biopsies might allow non-invasive monitoring of p-CREB1 in circulating tumor cells

  • Significant research is needed to establish standardized methodologies

• Implementation strategies:

  Disease Context	Biomarker Approach	Clinical Application
  Cancer	Tissue IHC for p-CREB1	Prognostication, treatment selection
  Vaccine response	CREB1 target gene signature	Efficacy prediction, correlate of protection
  Neurological disorders	CSF p-CREB1 levels	Disease activity monitoring
  Treatment monitoring	Sequential p-CREB1 measurement	Response assessment

• Technical considerations for biomarker development:

  • Standardization of assays across laboratories

  • Establishment of clinically relevant thresholds

  • Integration with other biomarkers for improved predictive power

  • Rigorous validation in prospective clinical trials

• Challenges to overcome:

  • Tissue heterogeneity and effect on p-CREB1 measurement

  • Pre-analytical variables affecting phosphorylation status

  • Distinguishing disease-specific from general stress-induced CREB1 activation

  • Need for prospective studies to establish clinical utility

With continued research into standardization and clinical validation, p-CREB1 could transition from a research tool to a clinically useful biomarker for multiple diseases.

What is the relationship between CREB1 phosphorylation and epigenetic regulation in long-term cellular memory?

The intersection of CREB1 phosphorylation and epigenetic regulation represents a fascinating frontier:

• Mechanistic connection:

  • Phosphorylated CREB1 recruits the histone acetyltransferases CBP/p300, creating a direct link to histone acetylation

  • This recruitment establishes an active chromatin state at CREB1 target genes

  • The persistence of these epigenetic marks may outlast the initial CREB1 phosphorylation event

• Temporal dynamics:

  • CREB1 phosphorylation is typically transient, lasting minutes to hours

  • The epigenetic changes induced by p-CREB1 (histone modifications, DNA methylation changes) can persist for days, weeks, or longer

  • This creates a mechanism for converting short-term signals into long-term cellular memory

• Contextual effects:

  • The epigenetic outcomes of CREB1 phosphorylation depend on:

    • Pre-existing chromatin state at target genes

    • Presence of other transcription factors and co-regulators

    • Cell type-specific factors

  • This explains why the same phosphorylation event leads to different outcomes in different contexts

• Experimental approaches to study this relationship:

  • ChIP-seq for p-CREB1 and various histone modifications

  • ATAC-seq to assess chromatin accessibility changes

  • CUT&RUN or CUT&Tag for higher resolution mapping

  • Time-course experiments to track the sequence of events

  • Targeted epigenetic editing to test causal relationships

• Biological contexts where this relationship is critical:

  • Neuronal plasticity and memory formation

  • Cellular differentiation and identity maintenance

  • Adaptation to environmental stressors

  • Transgenerational epigenetic inheritance

• Potential therapeutic implications:

  • Targeting the p-CREB1-epigenetic axis could provide more durable therapeutic effects

  • Combined targeting of signaling pathways and epigenetic modifiers

  • Development of drugs that specifically disrupt p-CREB1 interaction with epigenetic machinery