cypE Antibody

What is Cyclophilin E (CypE) and what cellular functions does it perform?

Cyclophilin E (CypE) is a member of the cyclophilin family that exhibits peptidyl-prolyl cis-trans isomerase (PPIase) activity, catalyzing the cis-trans isomerization of proline imidic peptide bonds in proteins . CypE performs several key cellular functions:

• Pre-mRNA splicing: Functions as a component of the spliceosome

• RNA binding: Shows preference for single-stranded RNA molecules with poly-A and poly-U stretches, suggesting it binds to the poly(A)-region in the 3'-UTR of mRNA molecules

• Isomerase activity: Catalyzes the cis-trans isomerization of proline imidic peptide bonds in proteins, affecting protein folding and function

• Transcriptional regulation: Inhibits KMT2A activity through its proline isomerase activity

• Viral interactions: Interacts with nucleoprotein (NP) of influenza virus and potentially with other viral proteins

• Bone formation: Acts as a positive regulator in osteoblast differentiation by enhancing the transcriptional activity of Runx2 through its PPIase activity

What experimental applications are CypE antibodies most suitable for?

CypE antibodies have been validated for multiple experimental applications in molecular and cellular biology research:

Common Applications:

• Western blotting: For protein expression analysis and quantification

• Immunoprecipitation: To study protein-protein interactions involving CypE

• Immunofluorescence: For subcellular localization studies

• Co-immunoprecipitation: For investigating binding partners such as viral proteins or transcription factors

• GST pull-down assays: For in vitro analysis of protein interactions

Application-specific considerations:

When designing experiments, researchers should note that the antibody concentration and detection methodology must be optimized for each application. For instance, typical antibody dilutions range from 1:1000 for western blotting to 1:100-1:500 for immunofluorescence studies .

How can I validate the specificity of a CypE antibody for my research?

Antibody validation is critical for ensuring experimental reproducibility. Based on established protocols from the literature, consider these methodological approaches:

Comprehensive validation strategy:

• Positive and negative controls: Use cell lines with known CypE expression levels; include CypE knockout/knockdown samples as negative controls

• Multiple detection methods: Validate using different techniques (western blot, immunoprecipitation, immunofluorescence) to ensure consistent results

• Peptide competition assay: Pre-incubate the antibody with purified CypE protein or peptide before application to demonstrate binding specificity

• siRNA knockdown validation: Perform siRNA-mediated knockdown of CypE (example sequence: 5′-ATTGTGGTTTGTGAAATCACCGCCC-3′) and confirm reduced antibody signal

• Cross-reactivity assessment: Test for reactivity against other cyclophilin family members (particularly CypA) due to sequence homology

The consensus criteria developed by the research community emphasize that antibodies should be validated across multiple applications they'll be used for, not just a single technique .

What role does CypE play in viral infection mechanisms, particularly with influenza and coronaviruses?

CypE has emerged as an important host factor in viral infection processes:

Influenza virus:

CypE functions as a negative regulator to influenza virus replication by interacting with the viral nucleoprotein (NP) . Experimental evidence shows:

• CypE directly interacts with NP but not with other components of the viral ribonucleoprotein complex (vRNP): PB1, PB2, and PA

• This interaction can be demonstrated through GST pull-down assays and co-immunoprecipitation

• CypE knockdown using siRNA results in increased virus titers, confirming its inhibitory role

Coronaviruses:

While CypE-specific data is limited for coronaviruses, the related cyclophilin family member Cyclophilin A (CypA) has been extensively studied:

• Human CypA interacts strongly with SARS-CoV-2 receptor-binding domain (RBD) with a binding affinity of 6.85 × 10⁻⁸ M

• CypA can block the binding of RBD to the ACE2 receptor, suggesting therapeutic potential

• Cyclophilin inhibitors like cyclosporine A (CsA) and non-immunosuppressive analogs can suppress coronavirus replication

This suggests related cyclophilins may have similar interactions with viral proteins, making CypE an important target for further investigation in coronavirus research.

What technical considerations are important when using CypE antibodies for immunoprecipitation?

Successful immunoprecipitation (IP) with CypE antibodies requires careful optimization:

Optimized IP protocol for CypE:

• Cell lysis conditions: Use a binding buffer containing 1% NP-40, 150 mM NaCl, 20 mM HEPES (pH 7.4), 10% glycerol, and 1 mM EDTA with protease inhibitor cocktail

• Antibody amount: For standard IP from mammalian cells, use 2-5 μg of antibody per 500 μg of total protein lysate

• Washing conditions: After binding, wash beads 5 times with washing buffer containing 1% NP-40, 300 mM NaCl, 20 mM HEPES (pH 7.4), 10% glycerol, and 1 mM EDTA with protease inhibitor cocktail

• Bead selection: For epitope-tagged CypE constructs, consider using specific agarose conjugates (e.g., anti-FLAG M2 affinity gel for FLAG-tagged CypE)

• Detection method: For detecting co-immunoprecipitated proteins, optimize the western blot protocol for each specific binding partner

For investigating endogenous CypE interactions during viral infection, infect cells with the virus of interest (e.g., MOI = 1), collect lysates at appropriate time points (12h post-infection for influenza virus), and perform co-immunoprecipitation using anti-CypE antibody .

How can I investigate CypE-protein interactions in my research?

To study CypE interactions with target proteins, multiple complementary approaches can be employed:

Experimental approaches for investigating CypE interactions:

• GST pull-down assays:

  • Express GST-fused CypE and its truncations

  • Purify using Sepharose 4B-glutathione

  • Incubate with His-tagged target protein or cell lysates

  • Analyze binding by western blotting with appropriate antibodies

• Co-immunoprecipitation:

  • Transfect cells with CypE and target protein constructs (or use endogenous proteins)

  • Lyse cells in appropriate buffer (1% NP-40, 150 mM NaCl, 20 mM HEPES pH 7.4, 10% glycerol, 1 mM EDTA)

  • Immunoprecipitate using anti-CypE antibody or epitope tag antibody

  • Detect interacting proteins by western blotting

• Confocal microscopy for co-localization:

  • Fix cells with 4% paraformaldehyde

  • Permeabilize with 0.5% Triton X-100

  • Perform dual immunostaining with CypE antibody and antibody against target protein

  • Analyze co-localization using confocal microscopy

• Functional validation through knockout/knockdown:

  • Use siRNA targeting CypE (e.g., 5′-ATTGTGGTTTGTGAAATCACCGCCC-3′)

  • Assess impact on target protein function or localization

  • Perform rescue experiments with wild-type or mutant CypE to confirm specificity

For protein domain mapping, truncated constructs of CypE can be generated to identify specific interaction regions with target proteins .

What is the relationship between CypE and Runx2 in osteoblast differentiation?

Recent research has elucidated a previously unknown role for CypE in bone formation:

CypE's role in osteoblast differentiation:

• CypE positively regulates osteoblast differentiation by enhancing the transcriptional activity of Runx2 through its PPIase activity

• This regulatory function involves the Akt signaling pathway

Experimental evidence:

• Gain or loss of function experiments demonstrate CypE's positive impact on osteoblast differentiation

• CypE physically interacts with Runx2, as shown through co-immunoprecipitation experiments

• The interaction can be studied by transfecting HEK 293 cells with HA-CypE, Myc-Runx2, and Myc-Runx2 deletion mutants (N, R, C)

• The protein complex can be isolated by incubating cell lysates with appropriate antibodies (HA or Myc) and Protein A Sepharose CL-4B

This discovery positions CypE as a potential therapeutic target for bone disorders, warranting further investigation of this molecular mechanism.

How does the PPIase activity of CypE influence its various biological functions?

The peptidyl-prolyl isomerase (PPIase) activity is central to CypE's diverse biological functions:

PPIase activity and functional implications:

• Protein folding regulation: CypE catalyzes the cis-trans isomerization of proline imidic peptide bonds, which can be rate-limiting steps in protein folding

• Transcriptional regulation: CypE inhibits KMT2A activity through its PPIase activity, affecting gene expression patterns

• RNA processing: CypE's role in pre-mRNA splicing may depend on its ability to induce conformational changes in spliceosome components

• Osteoblast differentiation: The PPIase activity of CypE enhances Runx2 transcriptional activity, promoting bone formation

• Viral interactions: The isomerase activity may affect the conformation of viral proteins, potentially explaining its regulatory role in viral replication

To experimentally distinguish PPIase-dependent from PPIase-independent functions, researchers often employ:

• Point mutations that abolish PPIase activity but maintain protein-protein interactions

• PPIase inhibitors like cyclosporine A (CsA) or non-immunosuppressive analogs

• Structure-function analysis with truncated versions of CypE that lack specific domains

How can neutralizing antibodies against viral targets inform our understanding of CypE's role in viral infections?

While not directly about CypE antibodies, understanding neutralizing antibody mechanisms provides valuable insights for investigating CypE's role in viral infections:

Lessons from neutralizing antibody research:

• Epitope identification strategies: The "coldspot-guided antibody discovery" approach, which focuses on conserved viral regions that are functionally important but averse to change, can be applied to identify key interaction sites between CypE and viral proteins

• Cross-reactive antibody mechanisms: Studies of broadly reactive antibodies against coronaviruses reveal that targeting conserved regions (like fusion peptide and HR2) provides cross-protection , suggesting that CypE might interact with conserved viral protein domains

• Structure-based prediction: Computational methods that predict antibody structures with similar functions despite sequence differences could be applied to predict CypE interactions with viral proteins

• Experimental validation approaches: Techniques used for validating neutralizing antibodies, such as:

  • Flow cytometry to isolate specific B cells

  • Far-western blotting and surface plasmon resonance (SPR) to measure binding affinity

  • Molecular interaction lateral flow (MILF) strip assay for immunochromatographic signal read-outs

These approaches can be adapted to study CypE-viral protein interactions and develop potential therapeutics that target these interactions.

What methods can be used to modify or engineer CypE's functions in experimental systems?

For researchers interested in manipulating CypE function to investigate its biological roles:

Experimental strategies to modify CypE function:

• RNA interference:

  • siRNA-mediated knockdown using validated sequences (e.g., 5′-ATTGTGGTTTGTGAAATCACCGCCC-3′)

  • shRNA for stable knockdown in long-term studies

  • Assessment of functional consequences through viral titers, protein expression, or cellular phenotypes

• CRISPR-Cas9 gene editing:

  • Complete knockout of CypE to study loss-of-function effects

  • Introduction of point mutations to disrupt specific functions (e.g., PPIase activity)

  • Domain deletion to identify critical regions for different cellular functions

• Overexpression systems:

  • Transfection with CypE expression constructs (wild-type or mutant)

  • Use of inducible expression systems to control timing and level of expression

  • Assessment of gain-of-function phenotypes

• Domain swapping and chimeric proteins:

  • Creation of hybrid cyclophilins by swapping domains between CypE and other cyclophilins

  • Analysis of functional changes to identify domain-specific activities

  • Example from cyclophilin research: grafting the 81-Asn 149 fragment of a cyclophilin onto another to create a hybrid with altered function

• Small molecule inhibitors:

  • Cyclosporine A (CsA) or non-immunosuppressive analogs like alisporivir to inhibit PPIase activity

  • Analysis of biological consequences to distinguish PPIase-dependent from PPIase-independent functions

These methodological approaches provide a comprehensive toolkit for investigating CypE's roles in various biological processes and potential therapeutic interventions.

How do different types of vaccines affect antibody responses to conserved viral epitopes, and what might this tell us about CypE-viral interactions?

Research on SARS-CoV-2 vaccines reveals important insights about antibody responses that could inform CypE research:

Implications for CypE research:

• When studying CypE interactions with viral proteins, consider that different experimental systems may expose different protein conformations

• The stabilization of viral proteins in vaccines may reduce accessibility of certain epitopes, which could also affect CypE binding sites

• Research on CypE-viral interactions should include multiple approaches to account for potential conformational differences

This knowledge could guide the design of experiments investigating CypE's interactions with viral proteins and inform potential therapeutic approaches targeting these interactions.

What are the best practices for characterizing CypE antibodies according to modern antibody validation standards?

Modern antibody characterization requires rigorous validation. Based on consensus principles from the research community:

Comprehensive antibody validation framework:

• Genetic strategies:

  • Test antibody on samples from CypE knockout/knockdown models

  • Compare signal in cells with normal versus reduced CypE expression

  • Document complete loss of signal in knockout samples

• Independent antibody validation:

  • Use multiple antibodies targeting different epitopes on CypE

  • Compare staining/binding patterns across techniques

  • Consistent results across different antibodies increase confidence

• Expression of tagged proteins:

  • Express epitope-tagged CypE (HA, FLAG, Myc)

  • Compare detection pattern between anti-tag and anti-CypE antibodies

  • Co-localization confirms antibody specificity

• Immunoprecipitation-mass spectrometry:

  • Immunoprecipitate using anti-CypE antibody

  • Identify pulled-down proteins by mass spectrometry

  • Confirm presence of CypE and known interaction partners

• Orthogonal strategies:

  • Compare protein levels detected by antibody with mRNA levels

  • Correlate antibody signal with functional readouts

  • Document concordance between different measurement approaches

• Application-specific validation:

  • Validate for each specific application (WB, IP, IF, IHC)

  • Document optimal conditions and dilutions for each method

  • Provide representative images showing positive and negative results