sh3rf1 Antibody

What is SH3RF1 and what are its primary functions in cellular processes?

SH3RF1 (SH3 domain containing ring finger 1), also known as POSH, RNF142, or SH3MD2, is a multifunctional protein that contains an N-terminus RING-finger domain, four SH3 domains, and a region implicated in binding the Rho GTPase Rac . It functions primarily as:

• An E3 ubiquitin-protein ligase involved in protein sorting at the trans-Golgi network

• A scaffold for the c-Jun N-terminal kinase (JNK) signaling pathway

• A negative post-translational regulator of FAT1 cadherin levels

The protein serves as a pro-apoptotic factor, working in coordination with SH3RF2 to regulate programmed cell death through the JNK signaling cascade . This dynamic regulatory mechanism is essential for maintaining cellular homeostasis in various tissues.

How does SH3RF1 interact with other proteins to regulate cellular functions?

SH3RF1 engages in several critical protein-protein interactions:

• It interacts with the cytoplasmic tail of FAT1 cadherin at the juxtamembrane region, as revealed by yeast two-hybrid library screens

• It forms complexes with components of the JNK signaling pathway, facilitating formation of functional signaling modules

• It appears to have interactions with SH3RF2, with which it forms a dynamic regulatory mechanism controlling apoptosis

These interactions allow SH3RF1 to influence diverse cellular processes including cell death, protein degradation, and signaling cascades.

What criteria should be considered when selecting an SH3RF1 antibody for specific research applications?

When selecting an SH3RF1 antibody, researchers should evaluate several critical parameters:

For advanced applications like proximity ligation assays or super-resolution microscopy, additional validation may be necessary beyond manufacturer specifications.

How can researchers validate the specificity of SH3RF1 antibodies?

A multi-step validation approach is recommended:

• Positive controls: Use cell lines with known SH3RF1 expression (e.g., U87-MG has been recommended)

• Western blot analysis: Confirm single band of appropriate molecular weight

• siRNA knockdown: Compare signal in cells with normal versus reduced SH3RF1 expression

• Overexpression studies: Test antibody against overexpressed SH3RF1

• Peptide competition assay: Pre-incubation with immunizing peptide should abolish specific signal

• Cross-species reactivity testing: Validate predicted reactivity against multiple species as needed

Remember that different applications may require different validation protocols. For instance, antibodies performing well in Western blot may not always work in immunohistochemistry.

What are optimal conditions for using SH3RF1 antibodies in Western blot analyses?

Based on validated protocols in the literature:

• Dilution ranges: Typically 1:500-1:5000 for Western blot applications

• Sample preparation: Mouse brain tissue often serves as a positive control

• Blocking solution: 5% non-fat milk or BSA in TBST is generally effective

• Incubation conditions: Primary antibody incubation at 4°C overnight often yields best results

• Detection systems: Both chemiluminescence and fluorescence-based systems are compatible

For particularly challenging samples, a more concentrated primary antibody application (1:200-1:500) may be necessary. When working with tissue lysates, thorough homogenization and effective protein extraction are crucial for detecting SH3RF1 .

What methodologies are effective for studying SH3RF1's role in protein-protein interactions?

Several complementary approaches can reveal SH3RF1's interaction network:

• Co-immunoprecipitation: SH3RF1 antibodies can pull down interacting partners like FAT1

• Yeast two-hybrid screening: This method successfully identified SH3RF1 as an interacting partner for FAT1's juxtamembrane region

• Proximity ligation assay: Detect in situ protein interactions with spatial resolution

• FRET/BRET analyses: For studying dynamic interactions in living cells

• Mass spectrometry following immunoprecipitation: For unbiased identification of interaction partners

When designing experiments, consider that SH3RF1 contains multiple protein-interaction domains (RING-finger, four SH3 domains) that can engage different partners simultaneously .

How can researchers investigate SH3RF1's function as an E3 ubiquitin ligase?

To study SH3RF1's E3 ligase activity, researchers should consider these methodological approaches:

• In vitro ubiquitination assays: Reconstitute ubiquitination using purified components

  • Requires: Recombinant SH3RF1, E1, E2 enzymes, ubiquitin, ATP, potential substrates

  • Readout: Detection of ubiquitinated products via Western blot

• Cellular ubiquitination assays:

  • Overexpress tagged ubiquitin and SH3RF1 in cells

  • Immunoprecipitate potential substrates (e.g., FAT1)

  • Detect ubiquitin chains by Western blot

• RING domain mutant studies:

  • Generate catalytically inactive SH3RF1 via RING domain mutations

  • Compare effects of wild-type vs. mutant on substrate levels

• Proteasome inhibition:

  • Treat cells with MG132 or bortezomib

  • Monitor accumulation of SH3RF1 substrates

This multi-faceted approach can reveal both the mechanism and specificity of SH3RF1's E3 ligase activity, particularly in the context of its regulation of FAT1 protein levels .

What experimental designs effectively explore the relationship between SH3RF1 and FAT1 regulation?

Based on published research, effective experimental designs include:

• Gene silencing approach:

  • Transfect cells with SH3RF1-specific siRNAs

  • Monitor FAT1 protein levels by Western blot

  • Expected outcome: Increased FAT1 levels following SH3RF1 knockdown

• Overexpression studies:

  • Transfect cells with SH3RF1 expression constructs

  • Quantify FAT1 protein levels

  • Expected outcome: Decreased FAT1 levels

• Protein stability assays:

  • Perform cycloheximide chase experiments in control vs. SH3RF1-depleted cells

  • Monitor FAT1 degradation kinetics

  • Expected outcome: Prolonged FAT1 half-life in SH3RF1-depleted cells

• Cell surface biotinylation:

  • Label surface proteins with biotin

  • Compare FAT1 internalization/degradation rates with/without SH3RF1

  • Expected outcome: Stabilized surface expression in absence of SH3RF1

These approaches collectively demonstrate SH3RF1's role as a negative post-translational regulator of FAT1, with potential implications for diseases where FAT1 dysregulation occurs.

How does SH3RF1 expression change during physiological adaptation processes?

Research in exercise physiology has provided insights into SH3RF1 expression patterns:

• Studies in Arabian horses showed a decrease in SH3RF1 gene expression following training periods, though this change was not statistically significant

• This contrasted with the significant decrease observed in the anti-apoptotic SH3RF2 gene

• The expression patterns suggest a potential role in exercise-induced adaptation of muscle tissue

These findings imply that the balance between pro-apoptotic SH3RF1 and anti-apoptotic SH3RF2 may be physiologically regulated during adaptation to physical stress . The regulation appears to be tissue-specific and responsive to environmental changes.

What methods are recommended for quantifying SH3RF1 expression in tissue samples?

Several complementary approaches are recommended:

• Real-time PCR (qPCR) for mRNA quantification:

  • Has been successfully employed in muscle biopsies from horses

  • Requires careful selection of reference genes for normalization

  • Provides information about transcriptional regulation

• Western blot analysis for protein quantification:

  • Recommended antibody dilutions range from 1:500-1:5000

  • Positive controls include mouse brain tissue

  • Enables assessment of post-transcriptional regulation

• Immunohistochemistry/Immunofluorescence for spatial distribution:

  • Optimal dilutions range from 1:20-1:200 for IHC

  • Has been validated in human gliomas

  • Provides information about cell-type specific expression

• Flow cytometry for population analysis:

  • Allows quantification at single-cell resolution

  • Requires careful optimization of fixation and permeabilization protocols

When interpreting results, researchers should consider that SH3RF1 expression may be subject to both transcriptional and post-transcriptional regulation mechanisms.

What are common challenges in detecting SH3RF1 and how can they be addressed?

Researchers may encounter several technical challenges when working with SH3RF1:

For particularly challenging applications, consider using epitope-tagged constructs as an alternative approach to detection with validated tag-specific antibodies.

How should SH3RF1 antibodies be stored and handled to maintain optimal performance?

Proper storage and handling are crucial for antibody performance:

• Long-term storage: Most SH3RF1 antibodies should be stored at -20°C

• Working solutions: Aliquot to avoid repeated freeze-thaw cycles

• Short-term storage: Some formulations can be stored at 4°C for limited periods

• Buffer composition: Many are supplied in PBS with glycerol (50%) and preservatives like sodium azide (0.02-0.09%)

• Handling: Centrifuge briefly before opening; avoid contamination

• Shipping: Typically shipped on wet ice or with cold packs

Following manufacturer-specific recommendations is essential, as formulations vary between suppliers. For example, the SH3RF1 monoclonal antibody K1E030_5E8 is recommended to be stored at 4°C for short-term use but at -20°C for long-term storage to avoid freeze/thaw cycles .

How is SH3RF1 being studied in the context of disease pathogenesis?

SH3RF1's roles in several disease contexts are being actively investigated:

• Cancer research:

  • SH3RF1 antibodies are being used to study its expression in various cancer types including gliomas

  • Research focuses on its pro-apoptotic function and potential as a therapeutic target

• Neurological disorders:

  • Studies examine SH3RF1's role in neuronal apoptosis and JNK signaling

  • SH3RF1 antibodies enable detection in brain tissue samples

• Developmental disorders:

  • Investigation of its interaction with FAT1, which is implicated in developmental abnormalities

  • This interaction may contribute to glomerular nephropathy and other FAT1-associated conditions

• Muscle-related disorders:

  • Research on the balance between SH3RF1 and SH3RF2 in muscle homeostasis

  • Potential implications for muscle adaptation and disease

These diverse applications highlight the importance of having well-validated SH3RF1 antibodies for examining its expression and interactions in various disease models.

What experimental systems are most suitable for studying SH3RF1's role in apoptotic pathways?

Several experimental systems have proven effective:

• Cell culture models:

  • HeLa cells have been successfully used for immunofluorescence studies of SH3RF1

  • U87-MG cells serve as recommended positive controls for certain antibodies

• Animal models:

  • Horse muscle biopsies have demonstrated dynamic regulation of SH3RF1/SH3RF2 during training

  • Mouse brain tissue shows detectable levels of SH3RF1 protein

• In vitro reconstitution:

  • Recombinant SH3RF1 protein systems allow study of direct biochemical activities

  • Particularly useful for investigating E3 ligase function

• Genetic manipulation approaches:

  • siRNA knockdown effectively reduces SH3RF1 levels and can reveal downstream effects

  • Overexpression systems demonstrate dose-dependent effects on targets like FAT1

When designing experiments, researchers should select systems that best model the specific aspect of SH3RF1 function under investigation, with appropriate positive and negative controls.