ARHGAP35 Antibody

What is ARHGAP35 and why is it significant in cancer research?

ARHGAP35 (also known as p190RhoGAP, p190A, GRF-1, or GRLF1) is a Rho GTPase-activating protein that plays crucial roles in cell adhesion, migration, and cytoskeletal organization. It has gained significant attention in cancer research because:

• The ARHGAP35 gene is one of the most frequently mutated genes in human cancers, ranking among the top 30 significantly mutated genes

• It functions predominantly as a tumor suppressor, with its decreased expression associated with metastatic status in cancers like gastric cancer

• The mutation spectrum and loss of heterozygosity patterns in ARHGAP35 are consistent with a tumor suppressor function

• ARHGAP35 regulates contact inhibition of proliferation (CIP) through activation of LATS kinases and phosphorylation of YAP

What forms of ARHGAP35 antibodies are commercially available for research?

Several types of ARHGAP35 antibodies are available for research applications:

Most commercial antibodies are available as rabbit polyclonal antibodies that react with human, mouse, and rat species .

What are the key applications of ARHGAP35 antibodies in research?

ARHGAP35 antibodies have multiple research applications:

• Western blotting: For detecting protein expression levels and phosphorylation states of ARHGAP35 (typically at 1:500-1:2000 dilution)

• Immunohistochemistry (IHC): For examining ARHGAP35 expression in tissue sections (typically at 1:100-1:300 dilution)

• Immunofluorescence (IF): For studying subcellular localization and co-localization with other proteins (typically at 1:50-1:200 dilution)

• ELISA: For quantitative detection of ARHGAP35 protein (typically at 1:5000 dilution)

These applications have been crucial in establishing ARHGAP35's role in cancer progression and its value as a potential prognostic marker .

How should I optimize ARHGAP35 antibody conditions for Western blot analysis?

For optimal Western blot results with ARHGAP35 antibodies:

• Sample preparation: Use RIPA buffer supplemented with protease and phosphatase inhibitors for total protein extraction

• Protein loading: Load 20-50 μg of total protein per lane, as ARHGAP35 is a large protein (170 kDa) that may require higher protein concentrations for clear detection

• Transfer conditions: Use low percentage gels (6-8%) and extend transfer time for this high molecular weight protein

• Antibody dilution: Start with a 1:1000 dilution for total ARHGAP35 antibody and 1:500 for phospho-specific antibodies

• Blocking conditions: 5% BSA in TBST is often preferred over milk for phospho-specific antibodies

• Positive controls: Consider using lysates from cells known to express ARHGAP35 (many epithelial cell lines have detectable levels)

• Detection method: For this large protein, enhanced chemiluminescence with longer exposure times may be necessary

Standard β-actin can be used as a loading control, though researchers should note the significant size difference between ARHGAP35 (170 kDa) and β-actin (42 kDa) .

How can I distinguish between ARHGAP35 and its paralog ARHGAP5 (p190B) in experimental settings?

Distinguishing between these closely related proteins requires careful experimental design:

• Antibody selection: Choose antibodies raised against non-conserved regions. Antibodies targeting amino acids 1071-1120 of ARHGAP35 are often specific to this paralog

• Validation approaches:

  • Perform knockdown experiments with siRNAs specific to each paralog to confirm antibody specificity

  • Use CRISPR/Cas9 cell lines with targeted knockout of either paralog as controls

  • Employ recombinant proteins as positive controls

• Western blot analysis: Though similar in size, careful gel resolution can sometimes separate the two proteins

• RNA analysis: Complement protein detection with RT-PCR or RNA-seq to confirm expression patterns of both paralogs

• Functional assays: Assess RhoGAP activity specifically attributable to each paralog using pull-down assays for active RhoA

What is the significance of detecting phosphorylated ARHGAP35 in cancer research?

Phosphorylation of ARHGAP35 at specific residues has significant functional consequences that are relevant to cancer research:

• Y1105 phosphorylation:

  • Promotes association with p120RasGAP (RASA1)

  • Inactivates RhoA while simultaneously activating RAS signaling

  • Serves as a critical regulatory mechanism at cell-cell junctions

• Y1087 phosphorylation:

  • Affects interaction with cytoskeletal components and may influence cell migration

• Other phosphorylation sites:

  • Phosphorylation by PRKCA at S1221 and T1226 affects subcellular localization

  • Phosphorylation by MAPK1/3 at the C-terminal region inhibits GAP function

Detecting these phosphorylation states can provide insights into:

• The activation status of ARHGAP35 in tumor samples

• Potential dysregulation of upstream kinases in cancer cells

• Mechanisms of altered cell migration and invasion in metastatic cancer

• Potential therapeutic targets aimed at modulating ARHGAP35 function

How can I assess ARHGAP35 function in relation to the RhoA signaling pathway?

To assess ARHGAP35's GAP activity toward RhoA:

• RhoA activity assays:

  • Use pull-down assays with GST-tagged Rhotekin-RBD to capture active GTP-bound RhoA

  • Compare RhoA activation in cells with normal, depleted, or overexpressed ARHGAP35

  • Analyze by Western blot using anti-RhoA (total) and anti-GTP-RhoA antibodies

• Cytoskeletal organization analysis:

  • Perform phalloidin staining to visualize F-actin structures

  • Use immunofluorescence with anti-paxillin antibodies to examine focal adhesions

  • Quantify stress fiber formation and focal adhesion size/number in relation to ARHGAP35 expression levels

• Functional readouts:

  • Cell migration assays (Transwell, wound healing) to assess the functional consequences of altered RhoA signaling

  • Spreading assays to evaluate cytoskeletal dynamics

  • Cell contractility assays using deformable substrates

• Rescue experiments:

  • Express ARHGAP35 mutants lacking GAP activity to determine if phenotypes are dependent on RhoA regulation

  • Co-express constitutively active or dominant-negative RhoA to bypass ARHGAP35 regulation

These approaches can establish causality between ARHGAP35, RhoA signaling, and cellular phenotypes relevant to cancer progression.

What strategies can resolve conflicting data regarding ARHGAP35's role in cancer progression?

While ARHGAP35 is generally considered a tumor suppressor, some studies report context-dependent oncogenic functions. To resolve such conflicts:

• Cell type considerations:

  • Compare epithelial versus mesenchymal cell backgrounds

  • Assess expression in primary versus metastatic tissues

  • Consider tissue-specific microenvironments that may influence function

• Isoform analysis:

  • Distinguish between linear ARHGAP35 mRNA and circARHGAP35

  • The circARHGAP35 can produce a truncated protein with oncogenic properties, contrasting with the tumor-suppressive function of linear ARHGAP35

  • Use specific primers/antibodies that distinguish between these forms

• Pathway context:

  • Examine the status of the Hippo pathway components (LATS, YAP)

  • Assess E-cadherin expression and adherens junction integrity

  • Consider RhoA-independent functions of ARHGAP35

• Mutation analyses:

  • Catalog the specific mutations in your model system

  • Distinguish between loss-of-function, gain-of-function, and dominant-negative mutations

  • Consider allele-specific effects on ARHGAP35 function

• Mechanistic depth:

  • Perform immunoprecipitation to identify context-specific interaction partners

  • Use chromatin immunoprecipitation to examine transcriptional effects

  • Consider post-translational modifications beyond phosphorylation

These approaches can help reconcile apparently contradictory findings regarding ARHGAP35's role in cancer.

What are the technical challenges in studying ARHGAP35 phosphorylation dynamics and how can they be overcome?

Studying ARHGAP35 phosphorylation dynamics presents several technical challenges:

• Phosphorylation site specificity:

  • Challenge: Multiple phosphorylation sites with distinct functions

  • Solution: Use phospho-specific antibodies for key sites (Y1087, Y1105)

  • Validation: Employ phosphatase treatments and phospho-mimetic/dead mutants as controls

• Low abundance of phosphorylated forms:

  • Challenge: Phosphorylated species may represent a small fraction of total protein

  • Solution: Enrich phosphoproteins using titanium dioxide or phospho-tyrosine antibodies before detection

  • Amplification: Consider proximity ligation assays for increased sensitivity in tissue sections

• Temporal dynamics:

  • Challenge: Phosphorylation events may be transient

  • Solution: Perform time-course studies after stimulation (e.g., growth factors, cell adhesion)

  • Stabilization: Include phosphatase inhibitors at all steps during sample preparation

• Spatial regulation:

  • Challenge: Phosphorylation may occur in specific subcellular compartments

  • Solution: Combine immunofluorescence with phospho-specific antibodies

  • Resolution: Consider super-resolution microscopy techniques for precise localization

• Functional relevance:

  • Challenge: Correlating phosphorylation with functional outcomes

  • Solution: Generate phospho-mimetic (Y→D/E) and phospho-dead (Y→F) mutants for functional studies

  • Integration: Combine phosphorylation analysis with RhoA activity assays and cytoskeletal readouts

These approaches can generate more reliable and informative data on ARHGAP35 phosphorylation dynamics.

How can ARHGAP35 antibodies be used to explore the connection between this protein and the Hippo signaling pathway?

Recent research has revealed an important connection between ARHGAP35 and the Hippo pathway that can be explored using antibodies:

• Co-immunoprecipitation studies:

  • Use ARHGAP35 antibodies to pull down protein complexes

  • Probe for Hippo pathway components (LATS1/2, MST1/2, YAP/TAZ)

  • Determine how ARHGAP35 physically interacts with or influences these proteins

• Phosphorylation cascade analysis:

  • Examine how ARHGAP35 expression affects LATS and YAP phosphorylation

  • Use phospho-specific antibodies to monitor YAP (S127) and LATS (T1079/S909) phosphorylation

  • Assess nuclear/cytoplasmic distribution of YAP using immunofluorescence

• Transcriptional readouts:

  • Combine ARHGAP35 manipulation with analysis of YAP/TEAD target genes

  • Use chromatin immunoprecipitation to examine YAP/TEAD binding to target promoters

  • Correlate ARHGAP35 levels with YAP-dependent transcription

• 3D culture systems:

  • Examine ARHGAP35 and YAP localization in 3D epithelial cultures (e.g., MDCK cells in Matrigel)

  • Assess how ARHGAP35 knockdown affects architecture and YAP localization

  • Correlate with contact inhibition of proliferation and cell polarity

This research direction is particularly promising as it links ARHGAP35's tumor suppressor function to the well-established Hippo pathway, potentially revealing new therapeutic targets.

What role does ARHGAP35 play in epithelial-to-mesenchymal transition (EMT) and how can this be studied?

ARHGAP35 has emerged as a regulator of EMT in cancer, which can be studied using these approaches:

• Expression correlation studies:

  • Analyze correlation between ARHGAP35 and E-cadherin expression in cancer tissues

  • Use immunohistochemistry with both antibodies on serial sections

  • Perform double immunofluorescence to examine co-expression patterns

• Functional interrogation:

  • Manipulate ARHGAP35 expression (knockdown/overexpression) and monitor EMT markers

  • Examine E-cadherin, N-cadherin, vimentin, and Snail/Slug/ZEB1 expression changes

  • Assess cell morphology and invasive capacity in parallel

• Mechanistic studies:

  • Determine if ARHGAP35 effects on EMT are RhoA-dependent

  • Use RhoA inhibitors or constitutively active RhoA to bypass ARHGAP35

  • Investigate whether ARHGAP35 regulates E-cadherin at transcriptional or post-translational levels

• Clinical correlations:

  • Stratify patient outcomes based on ARHGAP35 and E-cadherin co-expression

  • Develop scoring systems that integrate both markers for prognostic value

  • Assess whether ARHGAP35/E-cadherin status predicts metastatic potential

Studies have shown that ARHGAP35 upregulates E-cadherin and attenuates EMT in gastric cancer cells, suggesting that the ARHGAP35/RhoA/E-cadherin axis could be a potential therapeutic target .

How can researchers distinguish between functions of linear ARHGAP35 and circular ARHGAP35 (circARHGAP35) in experimental settings?

Recent research has revealed that circARHGAP35 can encode an oncogenic protein that contrasts with the tumor suppressor role of linear ARHGAP35 . To distinguish their functions:

• Expression analysis:

  • Design divergent primers that specifically amplify circular junctions for RT-PCR

  • Use northern blotting with probes spanning back-splice junctions

  • Perform RNase R treatment (which degrades linear but not circular RNA) before analysis

• Protein detection:

  • Develop antibodies against the unique C-terminal sequence of circARHGAP35-encoded protein

  • Use immunoprecipitation followed by mass spectrometry to confirm protein identity

  • Perform size fractionation to separate the circARHGAP35 protein (smaller) from linear ARHGAP35

• Functional discrimination:

  • Design siRNAs targeting the back-splice junction to specifically deplete circARHGAP35

  • Use CRISPR strategies to selectively eliminate circRNA formation without affecting linear mRNA

  • Employ rescue experiments with specific expression constructs for each form

• Subcellular localization:

  • Determine if circARHGAP35-encoded protein localizes differently from linear ARHGAP35

  • Use immunofluorescence with antibodies that can distinguish the forms

  • Perform subcellular fractionation followed by Western blotting

• Translational regulation:

  • Investigate m6A modification of circARHGAP35 at the start codon

  • Use m6A-specific antibodies for RNA immunoprecipitation

  • Test the effect of m6A demethylase FTO on translation efficiency

Understanding the distinct and potentially opposing functions of these two forms may resolve conflicting data in the literature and provide new therapeutic approaches.

What are the latest developments in targeting the ARHGAP35 pathway for cancer therapy?

While direct ARHGAP35-targeted therapies are still in early stages, several approaches show promise:

• RhoA pathway modulation:

  • Small molecule inhibitors of RhoA or ROCK could potentially mimic ARHGAP35 activity

  • Testing established RhoA/ROCK inhibitors in ARHGAP35-deficient models

  • Developing compounds that enhance residual ARHGAP35 GAP activity

• YAP-TEAD interaction targeting:

  • Since ARHGAP35 regulates the Hippo pathway, targeting YAP-TEAD interaction may be effective

  • Compounds like verteporfin that disrupt YAP-TEAD binding could be particularly effective in ARHGAP35-deficient tumors

  • Evaluating sensitivity of ARHGAP35-mutant cancers to YAP inhibition

• Synthetic lethality approaches:

  • Identifying genes that, when inhibited, cause selective lethality in ARHGAP35-deficient cells

  • Screening for compounds that exhibit synthetic lethality with ARHGAP35 mutation

  • Exploring dependencies on parallel pathways regulating cytoskeletal dynamics

• CircARHGAP35 targeting:

  • Developing strategies to selectively inhibit circARHGAP35 without affecting linear ARHGAP35

  • Designing antisense oligonucleotides targeting the back-splice junction

  • Exploring inhibitors of HNRNPL, which facilitates circARHGAP35 formation

• Biomarker development:

  • Using ARHGAP35 mutation status to guide treatment decisions

  • Developing IHC protocols for ARHGAP35 and associated markers (E-cadherin, phospho-YAP)

  • Creating multi-marker panels to predict therapeutic response